Photochemistry, a sub-discipline of chemistry, is the study of the interactions between atoms, small molecules, and light (or electromagnetic radiation). Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny 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 Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. [1]
Like most scientific disciplines, photochemistry utilizes the SI or metric measurement system. Important units and constants that show up regularly include the meter (and variants such as centimeter, millimeter, micrometer, nanometer, etc. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International ), seconds, hertz, joules, moles, the gas constant R, and the Boltzmann constant. Relationship with the Boltzmann constant The Boltzmann constant kB (often abbreviated k) may be used in place of the gas constant by working Bridge from macroscopic to microscopic physics Boltzmann's constant k is a bridge between Macroscopic and microscopic physics These units and constants are also integral to the field of physical chemistry. Physical chemistry, is the application of Physics to macroscopic microscopic atomic subatomic and particulate phenomena in chemical systems It is mostly defined as a large
The first law of photochemistry, known as the Grotthuss-Draper law (for chemists Theodor Grotthuss and John W. Draper), states that light must be absorbed by a chemical substance in order for a photochemical reaction to take place. Freiherr Christian Johann Dietrich Theodor von Grotthuss (20 January 1785 &ndash 26 March 1822 was the originator of the first law of Photochemistry in 1817 but is likely John William Draper ( May 5, 1811, &ndash January 4, 1882) was an American ( English -born Scientist, Philosopher See also Photochemistry A photochemical reaction is a Chemical reaction which is induced by light.
The second law of photochemistry, the Stark-Einstein law, states that for each photon of light absorbed by a chemical system, only one molecule is activated for a photochemical reaction. The Stark–Einstein law is named after the German-born physicists Johannes Stark and Albert Einstein, who independently formulated the law between 1908 and 1913 This is also known as the photoequivalence law and was derived by Albert Einstein at the time when the quantum (photon) theory of light was being developed. The Stark–Einstein law is named after the German-born physicists Johannes Stark and Albert Einstein, who independently formulated the law between 1908 and 1913 Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons
Photochemistry may also be introduced to laymen as a reaction that proceeds with the absorption of light. 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 Normally a reaction (not just a photochemical reaction) occurs when a molecule gains the necessary activation energy to undergo change. In Chemistry, activation energy, also called midnight energy, is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined A simple example can be the combustion of gasoline (a hydrocarbon) into carbon dioxide and water. Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. This is a chemical reaction where one or more molecules/chemical species are converted into others. Chemical species are Atoms Molecules molecular fragments Ions etc For this reaction to take place activation energy should be supplied. In Chemistry, activation energy, also called midnight energy, is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined The activation energy is provided in the form of heat or a spark. In Chemistry, activation energy, also called midnight energy, is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined In case of photochemical reactions light provides the activation energy. In Chemistry, activation energy, also called midnight energy, is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined
The absorption of a photon of light by a reactant molecule may also permit a reaction to occur not just by bringing the molecule to the necessary activation energy, but also by changing the symmetry of the molecule's electronic configuration, enabling an otherwise inaccessible reaction path, as described by the Woodward-Hoffmann selection rules. A 2+2 cycloaddition reaction is one example of a pericyclic reaction that can be analyzed using these rules or by the related frontier molecular orbital theory. In Organic chemistry, a pericyclic reaction is a type of Organic reaction wherein the Transition state of the molecule has a cyclic geometry and the reaction In Chemistry, a molecular orbital (or MO) is a region in which an Electron may be found in a Molecule.
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Main concepts
The pillars of photochemistry are UV/VIS spectroscopy, photochemical reactions in organic chemistry and photosynthesis in biochemistry. Ultraviolet-visible spectroscopy or ultraviolet-visible spectrophotometry ( UV/ VIS) involves the Spectroscopy of Photons in the UV-visible See also Photochemistry A photochemical reaction is a Chemical reaction which is induced by light. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy.
Regions of the electromagnetic spectrum
The electromagnetic spectrum is broad, however, a photochemist will find themselves working with several key regions. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies Some of the most widely used sections of the electromagnetic spectrum include:
- Visible Light: 400–700 nm wavelengths
- Ultraviolet: 100–400 nm wavelengths
- Near Infrared: 700–1000 nm wavelengths
- Far infrared: 15–1000 µm wavelengths
Applications
There are important processes based in the photochemistry principles. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of One case is photosynthesis, which some plants use light to create glucose in their chloroplasts to contribute to cell metabolism. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. The glucose is used by the plant's mitochondria to produce Adenosine Triphosphate. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy Medicine bottles are made with darkened glass to prevent the medicine itself from reacting chemically with light. In fireflies, an enzyme in the abdomen works to produce bioluminescence. FireFly is the second single by Essex Alternative rock band InMe. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Bioluminescence' is the production and emission of Light by a living Organism as the result of a chemical reaction during which chemical energy is converted The mercaptans or thiols produced by Chevron Phillips Chemical Company are produced by photochemical addition of hydrogen sulfide (H2S) to alfa olefins. In Organic chemistry, a thiol is a compound that contains the functional group composed of a Sulfur atom and a Hydrogen atom (-SH In Organic chemistry, a thiol is a compound that contains the functional group composed of a Sulfur atom and a Hydrogen atom (-SH Chevron Phillips is a chemical producer jointly owned by Chevron Corporation and ConocoPhillips. Hydrogen sulfide (or hydrogen sulphide) is the Chemical compound with the formula H 2 S. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon Among their many uses as a chemical reagent these mercaptans are used to provide a distinctive odor (an odorant) to otherwise odorless natural gas. Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, Many polymerizations are started by photoinitiatiors which decompose upon absorbing light to produce the necessary free radicals for Radical polymerization. Radical polymerization is a type of Polymerization in which the Reactive center of a polymer chain consists of a radical.
See also
References
- ^ International Union of Pure and Applied Chemistry. Photoelectrochemical cells or PECs are Solar cells and extract electrical energy from light including Visible light. A photochemical logic gate is based on the Photochemical Intersystem crossing and Molecular electronic transition between photochemically active molecules Photochemical & Photobiological Sciences (PPS is a peer-reviewed Scientific journal publishing original (primary research and review articles from all areas The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization "photochemistry". Compendium of Chemical Terminology Internet edition. Compendium of Chemical Terminology (ISBN 0-86542-684-8 is a book published by IUPAC containing internationally accepted definitions for terms in Chemistry.
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