Tetrafluoroethane (a haloalkane) is a clear liquid which boils well below room temperature (as seen here) and can be extracted from common canned air canisters by simply inverting them during use. A gas duster, also erroneously referred to as canned air, is a product consisting of liquefied Difluoroethane, trifluoroethane, or Tetrafluoroethane

The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of chemical compounds, consisting of alkanes, such as methane or ethane, with one or more halogens linked, such as chlorine or fluorine, making them a type of organic halide. A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Halocarbon compounds are Chemicals in which one or more Carbon Atoms are linked by Covalent bonds with one or more Halogen Atoms They are known under many chemical and commercial names. As flame retardants, fire extinguishants, refrigerants, propellants and solvents they have or had wide use. Flame retardants are materials that inhibit or resist the spread of Fire. A fire extinguisher is an Active fire protection device used to extinguish or control small fires often in emergency situations A refrigerant is a compound used in a heat cycle that undergoes a Phase change from a Gas to a Liquid and back A propellant is a material that is used to move ("propel" an object A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution. Some haloalkanes (those containing chlorine or bromine) have been shown to have negative effects on the environment such as ozone depletion. See also Nature The natural environment, commonly referred to simply as the environment, is a terminology that is comprised of all living and Ozone depletion describes two distinct but related observations a slow steady decline of about 4 percent per decade in the total amount of Ozone in Earth's The most widely known family within this group are the chlorofluorocarbons (CFCs).

General

A haloalkane also known as alkyl halogenide, halogenalkane or halogenoalkane, and alkyl halide is a chemical compound derived from an alkane by substituting one or more hydrogen atoms with halogen atoms. A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i In a substitution reaction, a Functional group in a particular Chemical compound is replaced by another group Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions Substitution with fluorine, chlorine, bromine, and iodine results in fluoroalkanes, chloroalkanes, bromoalkanes and iodoalkanes, respectively. Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Iodine (ˈaɪədaɪn ˈaɪədɪn or /ˈaɪədiːn/ from ιώδης iodes "violet" is a Chemical element that has the symbol I and Atomic Mixed compounds are also possible, the best-known examples being the chlorofluorocarbons (CFCs) which are mainly responsible for ozone depletion. OZONE is an object oriented Operating system written in the C programming language. Haloalkanes are used in semiconductor device fabrication, as refrigerants, foam blowing agents, solvents, aerosol spray propellants, fire extinguishing agents, and chemical reagents. Semiconductor device fabrication is the process used to create chips the Integrated circuits that are present in everyday Electrical and electronic A refrigerant is a compound used in a heat cycle that undergoes a Phase change from a Gas to a Liquid and back The most general definition of foam is a substance that is formed by trapping many gas Bubbles in a Liquid or Solid. A foaming agent is a surfactant which when present in small amounts facilitates the formation of a Foam, or enhances its colloidal stability by inhibiting the coalescence of A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution. Aerosol spray is a type of dispensing system which creates an aerosol mist of liquid particles A fire extinguisher is an Active fire protection device used to extinguish or control small fires often in emergency situations A reagent or reactant is a substance or compound consumed during a Chemical reaction.

Freon is a trade name for a group of chlorofluorocarbons used primarily as a refrigerant. Freon is DuPont 's trade name for its odorless colorless nonflammable and noncorrosive Chlorofluorocarbon and Hydrochlorofluorocarbon Refrigerants Refrigeration is the process of removing Heat from an enclosed space or from a substance and moving it to a place where it is unobjectionable The word Freon is a registered trademark belonging to DuPont. A trademark or trade mark, represented by the symbols ™ and ®, or mark is a distinctive sign or indicator used by an individual E I du Pont de Nemours and Company (,) is an American chemical company that was founded in July 1802 as a Gunpowder mill by Eleuthère Irénée

There are 3 types of haloalkanes. In primary (1°) haloalkanes the carbon which carries the halogen atom is only attached to one other alkyl group. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 However CH₃Br is also a primary haloalkane, even though there is no alkyl group. The Chemical compound bromomethane, commonly known as methyl bromide, is an organic Halogen compound with formula C[[Hydrogen In secondary (2°) haloalkanes the carbon that carries the halogen atom is attached to 2 alkyl groups. In tertiary (3°) haloalkanes the carbon that carries the halogen atom is attached to 3 alkyl groups.

Chloro fluoro carbon compounds (CFC, HCFC)

CFC molecules

Chlorofluorocarbons (CFC) are compounds containing chlorine, fluorine and carbon only, that is they contain no hydrogen. In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 They were formerly used widely in industry, for example as refrigerants, propellants, and cleaning solvents. A refrigerant is a compound used in a heat cycle that undergoes a Phase change from a Gas to a Liquid and back Their use has been regularly prohibited by the Montreal Protocol, because of effects on the ozone layer (see ozone depletion). For other similarly-named agreements see Montreal Convention (disambiguation. The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930 Ozone depletion describes two distinct but related observations a slow steady decline of about 4 percent per decade in the total amount of Ozone in Earth's They are also powerful greenhouse gases, in terms of carbon dioxide equivalence (over a time period of one hundred years) between 5000 and 8100 per kg. Carbon dioxide equivalent ( CDE) and Equivalent carbon dioxide (or CO2e) are two related but distinct measures for describing how much Global ^[1] CFCs have half-lives between 50-100 years, so their presence in the atmosphere and reactivity with ozone is long lived. One CFC molecule typically degrades around 10,000 ozone molecules before its removal, but this number can sometimes be in the millions.

Hydrochlorofluorocarbons (HCFCs) are of a class of haloalkanes where not all hydrogen has been replaced by chlorine or fluorine. They are used primarily as chlorofluorocarbon (CFC) substitutes, as the ozone depleting effects are only about 10% of the CFCs.

Hydro fluoro compounds (HFC)

Hydrofluorocarbons (HFCs) contain no chlorine. They are composed entirely of carbon, hydrogen, and fluorine. They have no known effects at all on the ozone layer. Only compounds containing chlorine and bromine are thought to harm the ozone layer. Fluorine itself is not ozone-toxic. [2] However, HFCs and perfluorocarbons do have activity in the entirely different realm of greenhouse gases, which do not destroy ozone, but do cause global warming. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared Global warming is the increase in the average measured temperature of the Two groups of haloalkanes, hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs), are targets of the Kyoto Protocol. The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing Greenhouse gases in an effort ^[2] Allan Thornton, President of Environmental Investigation Agency, an environmental watchdog, says that HFCs are up to 12,500 times as potent as carbon dioxide in global warming. Wealthy countries are clamping down on these gases. Thornton says that many countries are needlessly producing these chemicals just to get the carbon credits. Thus, as a result of carbon trading rules under the Kyoto Protocol, nearly half the credits from developing countries are from HFCs, with China scoring billions of dollars from catching and destroying HFCs that would be in the atmosphere as industrial byproducts. ^[3]

Polymer haloalkanes

Teflon structure

Chlorinated or fluorinated alkenes can be used for polymerization, resulting in polymer haloalkanes with notable chemical resistance properties. Important examples include polychloroethene (polyvinyl chloride, PVC), and polytetrafluoroethene (PTFE, or Teflon), but many more halogenated polymers exist. In Chemistry, poly(tetrafluoroethene or poly(tetrafluoroethylene ( PTFE) is a synthetic Fluoropolymer which finds numerous applications

History

Original development

Carbon tetrachloride was used in fire extinguishers and glass "anti-fire grenades" from the late nineteenth century until around the end of World War II. Carbon tetrachloride, also known by many other names (see Table is the Organic compound with the formula CCl4 World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including Experimentation with chloroalkanes for fire suppression on military aircraft began at least as early as the 1920s.

American engineer Thomas Midgley developed chlorofluorocarbons (CFC) in 1928 as a replacement for ammonia (NH₃), chloromethane (CH₃Cl), and sulfur dioxide (SO₂), which are toxic but were in common use at the time as refrigerants. Thomas Midgley Jr ( May 18, 1889 – November 2, 1944) was an American mechanical engineer turned Chemist Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Chloromethane, also called Methyl chloride, R-40 or HCC 40 is a Chemical compound of the group of Organic compounds called Haloalkanes. The new compound developed had to have a low boiling point and be non-toxic and generally non-reactive. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid In a demonstration for the American Chemical Society, Midgley flamboyantly demonstrated all these properties by inhaling a breath of the gas and using it to blow out a candle. The American Chemical Society ( ACS) is a Learned society ( Professional association) based in the United States that supports scientific inquiry ^[4]

Midgley specifically developed CCl₂F₂. However, one of the attractive features is that there exists a whole family of the compounds, each having a unique boiling point which can suit different applications. In addition to their original application as refrigerants, chlorofluoroalkanes have been used as propellants in aerosol cans, cleaning solvents for circuit boards, and blowing agents for making expanded plastics (such as the expanded polystyrene used in packaging materials and disposable coffee cups). Polystyrene ˌpɒliˈstaɪriːn ( IUPAC Polyphenylethene is an aromatic Polymer made from the aromatic Monomer Styrene

Commercial development and use

During World War II, various early chloroalkanes were in standard use in military aircraft by some combatants, but these early halons suffered from excessive toxicity. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including Nevertheless, after the war they slowly became more common in civil aviation as well.

In the 1960s, fluoroalkanes and bromofluoroalkanes became available and were quickly recognized as being among the most effective fire-fighting materials discovered. Much early research with Halon 1301 was conducted under the auspices of the US Armed Forces, while Halon 1211 was, initially, mainly developed in the UK. Bromotrifluoromethane, also known by the trade name Halon 1301 is an Organic halide with the chemical formula C[[bromine Br]] F 3 Bromochlorodifluoromethane, also known by the trade name Halon 1211 or BCF, or Halon 1211 BCF, or Freon 12B1, is a Haloalkane By the late 1960s they were standard in many applications where water and dry-powder extinguishers posed a threat of damage to the protected property, including computer rooms, telecommunications switches, laboratories, museums and art collections. Beginning with warships, in the 1970s, bromofluoroalkanes also progressively came to be associated with rapid knockdown of severe fires in confined spaces with minimal risk to personnel. A warship is a Ship that is built and primarily intended for Combat.

Work on alternatives for chlorofluorocarbons in refrigerants began in the late 1970s after the first warnings of damage to stratospheric ozone were published in the journal Nature in 1974 by Molina and Rowland (who shared the 1995 Nobel Prize in Chemistry for their work). The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere. Nature is a prominent Scientific journal, first published on 4 November 1869 José Mario Molina-Pasquel Henríquez (born March 19, 1943 in Mexico City) is a Mexican -born U Frank Sherwood Rowland (born June 28, 1927) is an American Nobel laureate and a professor of Chemistry at the University of California The Nobel Prize in Chemistry (Nobelpriset i kemi is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of Chemistry. Adding hydrogen and thus creating hydrochlorofluorocarbons (HCFC), chemists made the compounds less stable in the lower atmosphere, enabling them to break down before reaching the ozone layer. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Later alternatives dispense with the chlorine, creating hydrofluorocarbons (HFC) with even shorter lifetimes in the lower atmosphere.

By the early 1980s, bromofluoroalkanes were in common use on aircraft, ships and large vehicles as well as in computer facilities and galleries. However, concern was beginning to be felt about the impact of chloroalkanes and bromoalkanes on the ozone layer. The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930 The Vienna Convention on Ozone Layer Protection did not cover bromofluoroalkanes as it was thought, at the time, that emergency discharge of extinguishing systems was too small in volume to produce a significant impact, and too important to human safety for restriction.

However, by the time of the Montreal Protocol it was realised that deliberate and accidental discharges during system tests and maintenance accounted for substantially larger volumes than emergency discharges, and consequently halons were brought into the treaty, albeit with many exceptions. For other similarly-named agreements see Montreal Convention (disambiguation.

Phase out

Use of certain chloroalkanes as solvents for large scale application, such as dry cleaning, have been phased out, for example, by the IPPC directive on greenhouse gases in 1994 and by the Volatile Organic Compounds (VOC) directive of the EU in 1997. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared The European Union ( EU) is a political and economic union of twenty-seven member states, located primarily in Permitted chlorofluoroalkane uses are medicinal only.

Finally, bromofluoroalkanes have been largely phased out and the possession of such equipment is prohibited in some countries like the Netherlands and Belgium, from 1 January 2004, based on the Montreal Protocol and guidelines of the European Union. For other similarly-named agreements see Montreal Convention (disambiguation.

Production of new stocks ceased in most (probably all) countries as of 1994. However many countries still require aircraft to be fitted with halon fire suppression systems because no safe and completely satisfactory alternative has been discovered for this application. There are also a few other, highly specialised, uses. These programs recycle halon through "halon banks" coordinated by the Halon Recycling Corporation^[5] to ensure that discharge to the atmosphere occurs only in a genuine emergency and to conserve remaining stocks.

In the U. S. technicians and others who buy or work with CFC, HCFC, of HFC gases must pass licensing examinations set by the Environmental Protection Agency. There is one test for the Part 609 license, which allows a person to work on automobile air conditioners. This can be taken on line. There are four examinations for a full Part 608 license, which allows the holder to work on all other types of refrigeration and air conditioning equipment. These tests are given by private groups approved by the EPA. ^[6] The venting of freon, failure to be licensed, or not using approved recovery equipment, can result in substantial fines.

On September 21, 2007, approximately 200 countries agreed to accelerate the elimination of hydrochlorofluorocarbons entirely by 2020 in a United Nations-sponsored Montreal summit. Events 1217 - The Estonian tribal leader Lembitu of Lehola was killed in a battle against Teutonic Knights. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. The United Nations ( UN) is an International organization whose stated aims are to facilitate cooperation in International law, International security Montreal, or Montréal in French ( pronounced in French, in English) is the largest city in the Canadian province of Quebec Developing nations were given until 2030. Many nations, such as the United States and China, who had previously resisted such efforts, signed the treaty. The United States of America —commonly referred to as the Talk People's Republic of China) PEOPLE'S REPUBLIC OF CHINA ARTICLE GUIDELINES The global warming controversy is a dispute regarding the nature and consequences of Global warming. ^[7]

Development of alternatives

PhostrEx is a fire suppresion agent developed for use in aviation applications to replace halon. PhostrEx is a Fire suppresion agent developed for use in aviation applications to replace Halon, a Greenhouse gas (GHG Gaseous fire suppression is a term to describe the use of inert Gases and chemical agents to extinguish a Fire. It was developed by Eclipse Aviation for use aboard their Eclipse 500 very light jets as an engine fire suppression system, and is now being marketed to other aviation manufacturers. Eclipse Aviation Corporation is the manufacturer of the Eclipse 500 and Eclipse 400 Very light jets (VLJs The Eclipse Aviation 500 is a small six-seat Business jet aircraft manufactured by Eclipse Aviation. see also List of very light jets A very light jet ( VLJ) previously known as a microjet, is by convention a small Jet aircraft Fire suppression systems are used in conjunction with Smoke detectors and Fire alarm systems to improve and increase public safety Types

PhostrEx meets the requirements of both the Montreal Protocol and the Clean Air Act, and is the first commercially viable FAA & EPA certified halon replacement fire extinguishing agent. For other similarly-named agreements see Montreal Convention (disambiguation. A Clean Air Act describes one of a number of pieces of legislation relating to the reduction of Smog and Air pollution in general The Federal Aviation Administration ( FAA) is an agency of the United States Department of Transportation with authority to regulate and oversee all aspects of It reacts very quickly with atmospheric moisture, breaking down into phosphorus acid and hydrogen bromide. Phosphorus acid are Oxoacids of Phosphorus; examples include H3PO2 Hypophosphorous acid. Hydrogen bromide is the diatomic molecule H[[Bromine Br]] Under standard conditions HBr is a gas but it can be liquified

Various other solvents and methods have replaced the use of CFCs in laboratory analytics^[8].

Nomenclature

IUPAC nomenclature

The formal naming of haloalkanes should follow IUPAC nomenclature, which put the halogen as a prefix to the alkane. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general An affix is a Morpheme that is attached to a stem to form a word For example, ethane with bromine becomes bromoethane, methane with four chlorine groups becomes tetrachloromethane. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where Bromoethane, also known as ethyl bromide is a Chemical compound of the Haloalkanes group Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Carbon tetrachloride, also known by many other names (see Table is the Organic compound with the formula CCl4 However, many of these compounds have already an established trivial name, which is endorsed by the IUPAC nomenclature, for example chloroform (trichloromethane) and methylene chloride (dichloromethane). Chloroform, also known as trichloromethane and methyl trichloride, is a Chemical compound with formula C[[Hydrogen H]] Cl Dichloromethane ( DCM) or methylene chloride is the Chemical compound with the formula CH2Cl2 For unambiguity, this article follows the systematic naming scheme throughout.

Alternative nomenclature for refrigerants

The refrigerant naming system is mainly used for fluorinated and chlorinated short alkanes for refrigerant use. In the US the standard is specified in ANSI/ASHRAE Standard 34-1992, with additional annual supplements. ^[9] The specified ANSI/ASHRAE prefixes were FC (fluorocarbon) or R (refrigerant), but today most are prefixed by a more specific classification:

• CFC—list of chlorofluorocarbons
• HCFC—list of hydrochlorofluorocarbons
• HFC—list of hydrofluorocarbons
• FC—list of fluorocarbons
• PFC—list of perfluorocarbons (completely fluorinated)

The decoding system for CFC-01234a is:

• 0 = Number of double bonds (omitted if zero)
• 1 = Carbon atoms -1 (omitted if zero)
• 2 = Hydrogen atoms +1
• 3 = Fluorine atoms
• 4 = Replaced by Bromine ("B" prefix added)
• a = Letter added to identify isomers, the "normal" isomer in any number has the smallest mass difference on each carbon, and a, b, or c are added as the masses diverge from normal. Fluorocarbons are chemical compounds that contain Carbon - Fluorine bonds The relatively low reactivity and high polarity of the carbon-fluorine bond imparts Perfluorocarbons (PFCs are compounds derived from Hydrocarbons by replacement of Hydrogen Atoms by Fluorine atoms

Other coding systems are in use as well.

Overview of named compounds

Synthesis

Alkyl halides can be synthesized from alkanes, alkenes, alcohols or carboxylic acids. Halomethane compounds are molecules of Methane ( C[[hydrogen H]]4 with one or more of the Hydrogen atoms replaced with Halogen atoms Chloromethane, also called Methyl chloride, R-40 or HCC 40 is a Chemical compound of the group of Organic compounds called Haloalkanes. Dichloromethane ( DCM) or methylene chloride is the Chemical compound with the formula CH2Cl2 Chloroform, also known as trichloromethane and methyl trichloride, is a Chemical compound with formula C[[Hydrogen H]] Cl Carbon tetrachloride, also known by many other names (see Table is the Organic compound with the formula CCl4 Tetrafluoromethane, also known as carbon tetrafluoride, Freon-14 and R 14, is a Carbon Fluoride (CF4 Trichlorofluoromethane also called freon-11, CFC-11, or R-11, is a Chlorofluorocarbon. Dichlorodifluoromethane ( R-12) usually sold under the Brand name Freon-12, is a Chlorofluorocarbon Halomethane, commonly known Chlorotrifluoromethane, R-13 CFC-13 or Freon 13 is a non-flammable non-corrosive Chlorofluorocarbon (CFC and also a mixed Halomethane. Chlorodifluoromethane or difluoromonochloromethane is a Hydrochlorofluorocarbon (HCFC Fluoroform is the Chemical compound with the formula CHF3 It is one of the " haloforms " a class of compounds with the formula CHX3 Chlorofluoromethane or Freon 31 is a gaseous mixed Halomethane ( Hydrochlorofluorocarbon - HCFC Difluoromethane, also called HFC-32 or R-32, is an Organic compound of the dihalogenoalkane variety Fluoromethane, also known as methyl fluoride, Freon 41, Halocarbon-41 and HFC-41, is a non-toxic liquefiable and flammable Dibromomethane or methylene bromide, or methylene dibromide is a Halomethane. Bromoform (CHBr3 is a pale yellowish liquid with a sweet odor similar to chloroform a Halomethane or haloform Bromochloromethane or methylene bromochloride and Halon 1011 is a mixed Halomethane. Bromochlorodifluoromethane, also known by the trade name Halon 1211 or BCF, or Halon 1211 BCF, or Freon 12B1, is a Haloalkane Bromotrifluoromethane, also known by the trade name Halon 1301 is an Organic halide with the chemical formula C[[bromine Br]] F 3 Trifluoroiodomethane, also referred to as trifluoromethyl iodide is a Halomethane with the formula CF3I 2-Chloro-1112-tetrafluoroethane, C2[[hydrogen H]] Cl[[fluorine F4]] also called R-124, is a Hydrochlorofluorocarbon In Chemistry, poly(tetrafluoroethene or poly(tetrafluoroethylene ( PTFE) is a synthetic Fluoropolymer which finds numerous applications

From alkanes

Main article: free radical halogenation

Alkanes react with halogens by free radical halogenation. In Organic chemistry, free radical halogenation is a type of Halogenation. In Organic chemistry, free radical halogenation is a type of Halogenation. In this reaction a hydrogen atom is removed from the alkane, then replaced by a halogen atom by reaction with a diatomic halogen molecule. The reactive intermediate in this reaction is a free radical and the reaction is called a radical chain reaction. A reaction intermediate or an intermediate is a Molecular entity that is formed from the reactants (or preceding intermediates and reacts further to give the directly In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell

From alkenes

• In hydrohalogenation, an alkene reacts with a dry hydrogen halide (HX) like hydrogen chloride (HCl) or hydrogen bromide (HBr) to form a haloalkane. A hydrohalogenation reaction is the Electrophilic addition of Hydrohalic acids like Hydrogen chloride or Hydrogen bromide to Alkenes In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon Hydrogen bromide is the diatomic molecule H[[Bromine Br]] Under standard conditions HBr is a gas but it can be liquified The double bond of the alkene is replaced by two new bonds, one with the halogen and one with the hydrogen atom of the hydrohalic acid. Markovnikov's rule states that in this reaction, the halogen is more likely to become attached to the more substituted carbon. In Chemistry, Markovnikov's rule or Markownikoff's rule is an Observation based on Zaitsev's rule. This is a electrophilic addition reaction. In Organic chemistry, an electrophilic addition reaction is an Addition reaction where in a Chemical compound, a Pi bond is removed by the creation Water must be absent otherwise there will be a side product(water). A by-product is a secondary or incidental product deriving from a Manufacturing process a Chemical reaction or a biochemical pathway and is not the primary product The reaction is necessarily to be carried out in a dry inert solvent such as CCl₄ or directly in the gaseous phase.
• Alkenes also react with halogens (X₂) to form haloalkanes with two neighboring halogen atoms in a halogen addition reaction. A halogen addition reaction is a simple Organic reaction where a Halogen Molecule is added to the Carbon-carbon double bond of an Alkene This is sometimes known as "decolorizing" the halogen, since the reagent X₂ is colored and the product is usually colorless.

From alcohols

• Tertiary alkanol reacts with hydrochloric acid directly to produce tertiary chloroalkane, but if primary or secondary alkanol is used, an activator such as zinc chloride is needed. Hydrochloric acid is the Solution of Hydrogen chloride ( H[[Chlorine Cl]] in water Zinc chloride is the name of Chemical compound with the formula Zn[[chlorine Cl]]2 and its hydrates Alternatively the conversion may be performed directly using thionyl chloride which is called the Darzen's process. Thionyl chloride (or thionyl dichloride) is an Inorganic compound with the formula S[[Oxygen O]] Cl 2 The Darzen's process is one of the most convenient methods known because the byproducts are gaseous and thus escape, leaving behind pure alkyl chloride. Alkanol may likewise be converted to bromoalkane using hydrobromic acid or phosphorus tribromide or iodoalkane using red phosphorus and iodine (equivalent to phosphorus triiodide). Hydrobromic Acid is formed by dissolving the diatomic molecule Hydrogen bromide in water Phosphorus tribromide is a colourless liquid with the formula P[[Bromine Br]]3 Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 Iodine (ˈaɪədaɪn ˈaɪədɪn or /ˈaɪədiːn/ from ιώδης iodes "violet" is a Chemical element that has the symbol I and Atomic Phosphorus triiodide (PI3 is an unstable red solid which reacts violently with water Other halogenating agents are phosphorus pentachloride, Phosphorus with Bromine or Phosphorus with Iodine. "Fluorination" redirects here For the addition of fluoride to drinking water see Water fluoridation. Phosphorus pentachloride is the Chemical compound with the formula PCl5 Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 Iodine (ˈaɪədaɪn ˈaɪədɪn or /ˈaɪədiːn/ from ιώδης iodes "violet" is a Chemical element that has the symbol I and Atomic

From Carboxylic acids

• Two methods for the synthesis of alkyl halides from carboxylic acids are the Hunsdiecker reaction and the Kochi reaction

Reactions of haloalkanes

Haloalkanes are reactive towards nucleophiles. Carboxylic acids are Organic acids characterized by the presence of a Carboxyl group, which has the formula -C(=OOH usually written -COOH or -CO2H The Hunsdiecker reaction (also called the Borodin reaction after Alexander Borodin) is the Organic reaction of Silver salts of Carboxylic acids The Kochi reaction is an Organic reaction for the Decarboxylation of Carboxylic acids to Alkyl halides with Lead tetraacetate and a In Chemistry, a nucleophile (literally nucleus lover as in nucleus and phile) is a Reagent that forms a Chemical bond to They are polar molecules: the carbon to which the halogen is attached is slightly electropositive where the halogen is slightly electronegative. Electropositivity is a measure of an element's ability to donate Electrons, and therefore form positive Ions. " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons This results in an electron deficient (electrophilic) carbon which, inevitably, attracts nucleophiles. Electron deficiency occurs when a compound has too few Valence electrons for the connections between atoms to be described as Covalent bonds Electron deficient bonds In Chemistry, a nucleophile (literally nucleus lover as in nucleus and phile) is a Reagent that forms a Chemical bond to

Substitution reactions

Substitution reactions involve the replacement of the halogen with another molecule - thus leaving saturated hydrocarbons, as well as the halogen product. In a substitution reaction, a Functional group in a particular Chemical compound is replaced by another group Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i

Hydrolysis - a reaction in which water breaks a bond--is a good example of the nucleophilic nature of halogenoalkanes. Hydrolysis is a Chemical reaction during which one or more water molecules are split into hydrogen and hydroxide ions which may go on to participate in further reactions Water ( H2[[oxygen O]] H OH) is the most abundant Molecule on Earth 's surface composing of about 70% of the Earth's surface as The polar bond attracts a hydroxide ion, OH^-. In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen (NaOH_(aq) being a common source of this ion). This OH^- is a nucleophile with a clearly negative charge, as it has excess electrons it donates them to the carbon, which results in a covalent bond between the two. Thus C-X is broken by heterolytic fission resulting in a halide ion, X^-. In Chemistry, heterolysis or heterolytic fission (from Greek ἑτερος heteros "different" and λυσις lusis "loosening" As can be seen, the OH is now attached to the alkyl group, creating an alcohol. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon (Hydrolysis of bromoethane, for example, yields ethanol).

One should note that within the halogen series, the C-X bond weakens as one goes to heavier halogens, and this affects the rate of reaction. Thus, the C-I of an iodoalkane generally reacts faster than the C-F of a fluoroalkane.

Apart from hydrolysis, there are a few other isolated examples of nucleophilic substitution:

• Ammonia (NH₃) and bromoethane yields a mixture of ethylamine, diethylamine, and triethylamine (as their bromide salts), and tetraethylammonium bromide. In organic and Inorganic chemistry, nucleophilic substitution is a fundamental class of Substitution reaction in which an "electron rich" Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Ethylamine is a Chemical compound with the formula CH3CH2NH2 It has a strong Ammonia -like odor Diethylamine is a Secondary amine with the molecular structure CH3CH2NHCH2CH3 Triethylamine is the Chemical compound with the formula N(CH2CH33 commonly abbreviated Et 3N Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants Tetraethylammonium bromide is a Quaternary ammonium salt. It is a common source for the Tetraethylammonium cation
• Cyanide (CN^-) added to bromoethane will form propionitrile (CH₃CH₂CN), a nitrile, and Br^-. A cyanide is any Chemical compound that contains the cyano group (C≡N which consists of a Carbon Atom triple-bonded to a Propionitrile, or ethyl cyanide, is a low-molecular weight Nitrile with the molecular formula C2H5CN A nitrile is any Organic compound which has a - C ≡ N Functional group. Nitriles can be further hydrolyzed into carboxylic acids. Carboxylic acids are Organic acids characterized by the presence of a Carboxyl group, which has the formula -C(=OOH usually written -COOH or -CO2H

Elimination reactions

Rather than creating a molecule with the halogen substituted with something else, one can completely eliminate both the halogen and a nearby hydrogen, thus forming an alkene. An elimination reaction is a type of Organic reaction in which two Substituents are removed from a molecule in either a one or two-step mechanism. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon For example, with bromoethane and NaOH in ethanol, the hydroxide ion OH^- attracts a hydrogen atom - thus removing a hydrogen and bromine from bromoethane. In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen This results in C₂H₄ (ethene), H₂O and Br^-. Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond.

Applications

Propellant

One major use of CFCs has been as propellants in aerosol inhalers for drugs used to treat asthma. Aerosol spray is a type of dispensing system which creates an aerosol mist of liquid particles Asthma is a chronic Condition involving the Respiratory system in which the airways occasionally constrict become inflamed, and are The conversion of these devices and treatments from CFC to halocarbons that do not have the same effect on the ozone layer is well under way. The hydrofluoroalkane propellant's ability to solubilize medications and excipients is markedly different from CFCs and as a result requires a considerable amount of effort to reformulate (a significant amount of development effort has also been required to develop non-CFC alternatives to CFC-based refrigerants, particularly for applications where the refrigeration mechanism cannot be modified or replaced). An excipient is an inactive substance used as a carrier for the Active ingredients of a Medication. They have now been outlawed universally in all 50 U. S. states .

Fire extinguishing

At high temperatures, halons decompose to release halogen atoms that combine readily with active hydrogen atoms, quenching the flame propagation reaction even when adequate fuel, oxygen and heat remains. The chemical reaction in a flame proceeds as a free radical chain reaction; by sequestering the radicals which propagate the reaction, halons are able to "poison" the fire at much lower concentrations than are required by fire suppressants using the more traditional methods of cooling, oxygen deprivation, or fuel dilution. A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called A flame is often defined as the visible (light-emitting part of a Fire. In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell A chain reaction is a sequence of Reactions where a reactive product or by-product causes additional reactions to take place In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance

For example, Halon 1301 total flooding systems are typically used at concentrations no higher than 7% v/v in air, and can suppress many fires at 2. 9% v/v. By contrast, carbon dioxide fire suppression flood systems are operated from 34% concentration by volume (surface-only combustion of liquid fuels) up to 75% (dust traps). Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Carbon dioxide can cause severe distress at concentrations of 3 to 6%, and has caused death by respiratory paralysis in a few minutes at 10% concentration. Halon 1301 causes only slight giddiness at its effective concentration of 5%, and even at 15% persons remain conscious but impaired and suffer no long term effects. (Experimental animals have also been exposed to 2% concentrations of Halon 1301 for 30 hours per week for 4 months, with no discernible health effects at all. ) Halon 1211 also has low toxicity, although it is more toxic than Halon 1301, and thus considered unsuitable for flooding systems.

However, Halon 1301 fire suppression is not completely non-toxic; very high temperature flame, or contact with red-hot metal, can cause decomposition of Halon 1301 to toxic byproducts. The presence of such byproducts is readily detected because they include hydrobromic acid and hydrofluoric acid, which are intensely irritating. Hydrobromic Acid is formed by dissolving the diatomic molecule Hydrogen bromide in water Hydrofluoric acid is a Solution of Hydrogen fluoride in Water. Halons are very effective on Class A (organic solids), B (flammable liquids and gases) and C (electrical) fires, but they are totally unsuitable for Class D (metal) fires, as they will not only produce toxic gas and fail to halt the fire, but in some cases pose a risk of explosion. Halons can be used on Class K (kitchen oils and greases) fires, but offer no advantages over specialised foams.

Halon 1211 is typically used in hand-held extinguishers, in which a stream of liquid halon is directed at a smaller fire by a user. The stream evaporates under reduced pressure, producing strong local cooling, as well as a high concentration of halon in the immediate vicinity of the fire. In this mode, extinguishment is achieved by cooling and oxygen deprivation at the core of the fire, as well as radical quenching over a larger area. After fire suppression, the halon moves away with the surrounding air, leaving no residue.

Halon 1301 is more usually employed in total flooding systems. In these systems, banks of halon cylinders are kept pressurised to about 4 MPa (600 PSI) with compressed nitrogen, and a fixed piping network leads to the protected enclosure. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 On triggering, the entire measured contents of one or more cylinders are discharged into the enclosure in a few seconds, through nozzles designed to ensure uniform mixing throughout the room. A nozzle is a mechanical device or Orifice designed to control the characteristics of a Fluid flow as it exits (or enters an enclosed chamber or Pipe. The quantity dumped is pre-calculated to achieve the desired concentration, typically 3-7% v/v. This level is maintained for some time, typically with a minimum of ten minutes and sometimes up to a twenty minute 'soak' time, to ensure all items have cooled so reignition is unlikely to occur, then the air in the enclosure is purged, generally via a fixed purge system that is activated by the proper authorities. During this time the enclosure may be entered by persons wearing SCBA. self contained breathing apparatus, or SCBA, sometimes referred to as a Compressed Air Breathing Apparatus (CABA or simply Breathing Apparatus (BA is (There exists a common myth that this is because halon is highly toxic; in fact it is because it can cause giddiness and mildly impaired perception, and also due to the risk of combustion byproducts. )

Flooding systems may be manually operated or automatically triggered by a VESDA or other automatic detection system. A smoke detector is a device that detects Smoke and issues an Alarm. In the latter case, a warning siren and strobe lamp will first be activated for a few seconds to warn personnel to evacuate the area. The rapid discharge of halon and consequent rapid cooling fills the air with fog, and is accompanied by a loud, disorienting noise. Fog is a cloud that is in contact with the ground Stratus clouds are usually the only clouds that touch the ground

Due to environmental concerns, alternatives are being deployed. ^[10]

Halon 1301 is also used in the F-16 fighters to prevent the fuel vapors in the fuel tanks from becoming explosive; when the aircraft enters area with the possibility of unfriendly fire, Halon 1301 is injected into the fuel tanks for one-time use. A fuel tank is safe container for flammable liquids and typically part of an Engine system in which the Fuel is stored and propelled (fuel pump or released (pressurized Due to environmental concerns, trifluoroiodomethane (CF₃I) is being considered as an alternative. Trifluoroiodomethane, also referred to as trifluoromethyl iodide is a Halomethane with the formula CF3I ^[11]

Environmental issues

Since the late 1970s the use of CFCs has been heavily regulated because of their destructive effects on the ozone layer. Pollution is the introduction of contaminants into an environment that causes instability disorder harm or discomfort to the physical systems or living organisms they are in Air pollution is the human introduction into the atmosphere of Chemicals Particulate matter, or Biological materials that cause harm or discomfort Acid rain is Rain or any other form of precipitation that is unusually Acidic It has harmful effects on plants aquatic animals and infastructure The Air Quality Index ( AQI) is a standardized indicator of the Air Quality in a given location Atmospheric dispersion modeling is the mathematical simulation of how air pollutants disperse in the ambient atmosphere. The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of Chemical compounds consisting of Alkanes such as Methane Global dimming is the gradual reduction in the amount of global direct Irradiance at the Earth 's surface that was observed for several decades after the start of systematic Global warming is the increase in the average measured temperature of the Haze is traditionally an atmospheric phenomenon where dust smoke and other dry particles obscure the clarity of the sky Indoor Air Quality (IAQ deals with the content of interior air that could affect health and comfort of building occupants Ozone depletion describes two distinct but related observations a slow steady decline of about 4 percent per decade in the total amount of Ozone in Earth's Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas Smog is a kind of Air pollution; the word "smog" is a Portmanteau of Smoke and Fog. Water pollution is the contamination of Water bodies such as Lakes Rivers Oceans and Groundwater caused by human activities Eutrophication is an increase in chemical Nutrients -- typically compounds containing Nitrogen or Phosphorus -- in an Ecosystem, and may occur For other uses of the term "hypoxia" see Hypoxia. Hypoxia or oxygen depletion is a phenomenon that occurs in aquatic environments Marine pollution is the harmful effect caused by the entry into the ocean of chemicals particles, or Plastic debris. For the fictional character see Oil Slick (Transformers. An oil spill is the release of a Liquid Petroleum Hydrocarbon into Ship pollution is the pollution of air and Water by Shipping. Surface runoff is a term used to describe when soil is infiltrated to full capacity and excess Water, from Rain, Snowmelt, or other sources flows Thermal pollution is a Temperature change in natural bodies of water caused by human influence Distinguish from Wastwater (a lake in the Lake District in northwest England Waterborne diseases are caused by Pathogenic Microorganisms which are directly transmitted when contaminated Drinking water is consumed Water quality is the physical chemical and biological characteristics of Water in relationship to a set of standards Water stagnation occurs when Water stops flowing Stagnant water can be a major Environmental hazard. Soil contamination is caused by the presence of man-made chemicals or other alteration in the natural soil environment Bioremediation can be defined as any process that uses Microorganisms Fungi, green plants or their Enzymes to return the natural environment altered A herbicide is used to kill unwanted Plants Selective herbicides kill specific targets while leaving the desired Crop relatively unharmed A pesticide is a substance or mixture of substances used to kill a pest. Radioactive contamination is the uncontrolled distribution of radioactive material in a given environment Actinides in the environment refer to the sources environmental behaviour and effects of Actinides in the environment. Environmental Radioactivity is the study of radioactive materials in the Human environment. Fission products are the atomic fragments left after a large nucleus fissions. Fallout is the residual radiation hazard from a Nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion Plutonium in the environment is an article which is part of the Actinides in the environment series Radiation poisoning, also called " radiation sickness " or a " creeping dose " is a form of damage to organ tissue due to excessive exposure to This is a subpage of Environmental radioactivity. Radium Radium in quack medicine See the story of Eben Byers for details of one very nasty case Uranium in the environment, this page is about the Science of Uranium in the environment and in animals (including humans Introduced species|Weed Invasive species is a phrase with several definitions Light pollution, also known as photopollution or luminous pollution, is excess or obtrusive Light created mainly by Humans Among other effects Noise pollution (or environmental noise) is displeasing human- or machine-created sound that disrupts the activity or balance of human or animal life Radio spectrum pollution is the straying of waves in the radio and Electromagnetic spectrums outside their allocations that cause problems for some activities Visual pollution is the term given to unattractive or unnatural (human-made visual elements of a vista a Landscape, or any other thing that a person might not want to For other similarly-named agreements see Montreal Convention (disambiguation. Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution Concerning the Control of Emissions of Nitrogen Oxides or Their Transboundary Fluxes, opened for signature on The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing Greenhouse gases in an effort The Convention on Long-Range Transboundary Air Pollution, often abbreviated as Air Pollution or CLRTAP, is intended to protect the human environment against Air This is a list of environmental organizations. See also Environmental organization Intergovernmental organizations International organizations The Department for Environment Food and Rural Affairs ( Defra) is the United Kingdom government department responsible for environmental protection The Global Atmosphere Watch (GAW is a worldwide system established by the World Meteorological Organization a United Nations agency to monitor trends in the Greenpeace, originally known as the Greenpeace Foundation, was founded in Vancouver, British Columbia, Canada in 1972 The National Ambient Air Quality Standards (NAAQS are standards established by the United States Environmental Protection Agency that apply for outdoor Air Environmental science is the study of interactions among physical chemical and biological components of the environment. See also Nature The natural environment, commonly referred to simply as the environment, is a terminology that is comprised of all living and After the development of his electron capture detector, James Lovelock was the first to detect the widespread presence of CFCs in the air, finding a concentration of 60 parts per trillion of CFC-11 over Ireland. The electron capture detector (ECD was invented in 1957, by Dr Dr James Ephraim Lovelock, CH, CBE, FRS (born 26 July 1919) is an independent scientist author researcher environmentalist and Ireland (pronounced /ˈaɾlənd/ Éire) is the third largest island in Europe, and the twentieth-largest island in the world In a self-funded research expedition ending in 1973, Lovelock went on to measure the concentration of CFC-11 in both the Arctic and Antarctic, finding the presence of the gas in each of 50 air samples collected, but incorrectly concluding that CFCs are not hazardous to the environment. The experiment did however provide the first useful data on the presence of CFCs in the atmosphere. The damage caused by CFCs discovered by Sherry Rowland and Mario Molina who, after hearing a lecture on the subject of Lovelock's work, embarked on research resulting in the first published paper suggesting the connection in 1974. Frank Sherwood Rowland (born June 28, 1927) is an American Nobel laureate and a professor of Chemistry at the University of California José Mario Molina-Pasquel Henríquez (born March 19, 1943 in Mexico City) is a Mexican -born U It turns out that one of CFCs' most attractive features—their unreactivity—has been instrumental in making them one of the most significant pollutants. CFCs' lack of reactivity gives them a lifespan which can exceed 100 years in some cases. This gives them time to diffuse into the upper stratosphere. The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere. Here, the sun's ultraviolet radiation is strong enough to break off the chlorine atom, which on its own is a highly reactive free radical. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell This catalyzes the break up of ozone into oxygen by means of a variety of mechanisms, of which the simplest is:

Cl· + O₃ → ClO· + O₂

ClO· + O₃ → Cl· + 2 O₂

Since the chlorine is regenerated at the end of these reactions, a single Cl atom can destroy many thousands of ozone molecules. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Reaction schemes similar to this one (but more complicated) are believed to be the cause of the ozone hole observed over the poles and upper latitudes of the Earth. Ozone depletion describes two distinct but related observations a slow steady decline of about 4 percent per decade in the total amount of Ozone in Earth's Decreases in stratospheric ozone may lead to increases in skin cancer. Skin cancer is a Malignant growth on the Skin which can have many causes

In 1975, the US state of Oregon enacted the world's first ban of CFCs (legislation introduced by Walter F. Brown). The United States of America —commonly referred to as the A US state is any one of the fifty subnational entities of the United States of America that share Sovereignty with the federal government Oregon ( is a state in the Pacific Northwest region of the United States. Walter Frederick Brown (born July 28, 1926) is an American politician and was the presidential candidate of the Socialist Party USA The United States and several European countries banned the use of CFCs in aerosol spray cans in 1978, but continued to use them in refrigeration, foam blowing, and as solvents for cleaning electronic equipment. By 1985, scientists observed a dramatic seasonal depletion of the ozone layer over Antarctica. International attention to CFCs resulted in a meeting of world diplomats in Montreal in 1987. Montreal, or Montréal in French ( pronounced in French, in English) is the largest city in the Canadian province of Quebec They forged a treaty, the Montreal Protocol, which called for drastic reductions in the production of CFCs. For other similarly-named agreements see Montreal Convention (disambiguation. On March 2, 1989, 12 European Community nations agreed to ban the production of all CFCs by the end of the century. Events 986 - Louis V becomes King of the Franks. 1127 - Assassination of Charles the Good Year 1989 ( MCMLXXXIX) was a Common year starting on Sunday (link displays 1989 Gregorian calendar) The European Community (EC is one of the Three pillars of the European Union (EU created under the Maastricht Treaty (1992 In 1990, diplomats met in London and voted to significantly strengthen the Montreal Protocol by calling for a complete elimination of CFCs by the year 2000. London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. By the year 2010 CFCs should be completely eliminated from developing countries as well.

Ozone-depleting gas trends

Because the only available CFC gases in countries adhering to the treaty is from recycling, their prices have gone up considerably. A worldwide end to production should also terminate the smuggling of this material, such as from Mexico to the United States.

A number of substitutes for CFCs have been introduced. Hydrochlorofluorocarbons (HCFCs) are much more reactive than CFCs, so a large fraction of the HCFCs emitted break down in the troposphere, and hence are removed before they have a chance to affect the ozone layer. Nevertheless, a significant fraction of the HCFCs do break down in the stratosphere and they have contributed to more chlorine buildup there than originally predicted. The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere. Development of non-chlorine based chemical compounds as a substitute for CFCs and HCFCs continues. Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and One such class are the hydrofluorocarbons (HFCs), which contain only hydrogen and fluorine. One of these compounds, HFC-134a, is now used in place of CFC-12 in automobile air conditioners; which itself may contribute to global warming (see HFC-134a).

There is concern that halons are being broken down in the atmosphere to bromine, which reacts with ozone, leading to depletion of the ozone layer (this is similar to the case of chlorofluorocarbons such as freon). Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five OZONE is an object oriented Operating system written in the C programming language. Ozone depletion describes two distinct but related observations a slow steady decline of about 4 percent per decade in the total amount of Ozone in Earth's The photochemical mechanisms that give rise to the ozone layer were worked out by the British physicist Sidney Chapman in 1930 These issues are complicated: the kinds of fires that require halon extinguishers to be put out will typically cause more damage to the ozone layer than the halon itself, not to mention human and property damage. However, fire extinguisher systems must be tested regularly, and these tests may lead to damage. As a result, some regulatory measures have been taken, and halons are being phased out in most of the world.

In the United States, purchase and use of freon gases is regulated by the Environmental Protection Agency, and substantial fines have been levied for their careless venting. Also, licenses, good for life, are required to buy or use these chemicals. The EPA website discusses these rules in great detail, and also lists numerous private companies that are approved to give examinations for these certificates.

There are two kinds of licenses. Obtaining a "Section 609" license to use CFCs to recharge old (pre-1993 model year) car air conditioners is fairly easy and requires only an online multiple choice test offered by several companies. Companies that use unlicensed technicians for CFC recharge operations are subject to a US$15,000 fine per technician by the EPA.

The "Section 608" license, needed to recharge CFC-using stationary and non-automobile mobile units, is also multiple choice but more difficult. A general knowledge test is required, plus separate exams for small size (such as home refrigerator) units, and for high and low pressure systems. These are respectively called Parts I, II, and III. A person who takes and passes all tests receives a "Universal" license; otherwise, one that is endorsed only for the respectively passed Parts. While the general knowledge and Part I exams can be taken online, taking them before a proctor (which has to be done for Parts II and III) lets the applicant pass these tests with lower scores.

Safety

Haloalkanes in copper tubing open to the environment can turn into phosgene gas after coming in contact with extreme heat, such as while brazing or in a fire situation. Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Phosgene is the Chemical compound with the formula COCl2 This colorless gas gained infamy as a Chemical weapon during World War I Brazing is a joining process whereby a Filler metal or Alloy is heated to melting temperature above - or by the traditional definition in the United States Other ways that phosgene can be created is by passing the haloalkane through an internal combustion engine, or by inhaling it through a lit cigarette, cigar or pipe. Phosgene is a substance that was used as a chemical weapon in World War I. Chemical warfare involves using the toxic properties of Chemical substances to kill injure or incapacitate an enemy. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All Low exposure can cause irritation, but high levels cause fluid to collect in the lungs, possibly resulting in death. lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive

See also

• Halogenation
• Halomethane
• Halogenoarene

References

1. ^ Protection of Stratospheric Ozone: Listing of Global Warming Potential for Ozone-Depleting Substances | Federal Register Environmental Documents | USEPA
2. ^ Lerner & K. "Fluorination" redirects here For the addition of fluoride to drinking water see Water fluoridation. Halomethane compounds are molecules of Methane ( C[[hydrogen H]]4 with one or more of the Hydrogen atoms replaced with Halogen atoms In Organic chemistry, a halogenoarene, haloarene, or aryl halide, is an organic compound in which a Halogen atom is bonded to a Carbon Lee Lerner, Brenda Wilmoth (2006). Environmental issues : essential primary sources.". Thomson Gale. Retrieved on 2006-09-11. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 9 - The Battle of the Teutoburg Forest ends 506 - The Bishops of Visigothic Gaul
3. ^ All Things Considered, NPR News, 5:24 p. m. , December 11, 2007.
4. ^ McNeill, J. R. Something New Under the Sun: An Environmental History of the Twentieth-Century World (2001) New York: Norton, xxvi, 421 pp. (as reviewed in the Journal of Political Ecology)
5. ^ Welcome to the Halon Coprporation
6. ^ Regulatory Programs | Ozone Depletion | US EPA
7. ^ HCFC Phaseout Schedule
8. ^ Use of Ozone Depleting Substances in Laboratories. TemaNord 516/2003. [1]
9. ^ ASHRAE Bookstore
10. ^ 3-III-2 HALON 1301 REPLACEMENTS
11. ^ Defense Tech Briefs

• [3] Fluorocarbons and Sulphur Hexafluoride, proposed by the European Fluorocarbons Technical Committee (EFCTC)
• B. S. Furnell et al. , Vogel's Textbook of Practical Organic Chemistry, 5th edition, Longman/Wiley, New York, 1989.
• Nomenclature FAQ
• Numbering Scheme for Ozone-Depleting Substances and their Substitutes
• Class I Ozone-Depleting Substances
• CFC Smuggling
• CFC Illegal Trade
• Numbering Scheme for Ozone-Depleting Substances and their Substitutes
• Class I Ozone-Depleting Substances
• Class II Ozone-Depleting Substances (HCFC's)
• History of Halon use by the US Navy
• Ozone Loss: The Chemical Culprits