Cycloalkanes (also called naphthenes, especially if from petroleum sources) are types of alkanes which have one or more rings of carbon atoms in the chemical structure of their molecules. Petroleum ( L petroleum, from Greek πετρέλαιον, lit Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny Chemical structure refers to Molecular geometry, Electronic structure and Crystal structure. 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 Alkanes are types of organic hydrocarbon compounds which have only single chemical bonds in their chemical structure. An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic Cycloalkanes consist of only carbon (C) and hydrogen (H) atoms and are saturated because there are no multiple C-C bonds to hydrogenate (add more hydrogen to). Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Hydrogenation is the Chemical reaction that results in addition of Hydrogen (H2 A general chemical formula for cycloalkanes would be CnH2(n+1-g) where n = number of C atoms and g = number of rings in the molecule. A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Cycloalkanes with a single ring are named analogously to their normal alkane counterpart of the same carbon count: cyclopropane, cyclobutane, cyclopentane, cyclohexane, etc. Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i Cyclopropane is a Cycloalkane Molecule with the molecular formula C3H6 consisting of three Carbon Atoms linked to Cyclobutane, C4H8 with a molecular mass of 56107g/mol is a four Carbon Alkane in which all the Carbon Atoms are arranged Cyclopentane is a highly Flammable alicyclic Hydrocarbon with Chemical formula 510 and CAS number 287-92-3 Cyclohexane is a Cycloalkane with the Molecular formula C 6 H 12 The larger cycloalkanes, with greater than 20 carbon atoms are typically called cycloparaffins.
Cycloalkanes are classified into small, normal and bigger cycloalkanes, where cyclopropane and cyclobutane are the small ones, cyclopentane, cyclohexane, cycloheptane are the normal ones, and the rest are the bigger ones.
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Nomenclature
- See also: IUPAC nomenclature
![bicyclo[2,2,1]heptane](http://upload.wikimedia.org/wikipedia/commons/thumb/1/16/Bicyclo2-1-1heptane.gif/180px-Bicyclo2-1-1heptane.gif)
The naming of polycyclic alkanes such as bicyclic alkanes and spiro alkanes is more complex, with the base name indicating the number of carbons in the ring system, a prefix indicating the number of rings (e. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general bicyclic molecule contains two fused Aliphatic rings. Fusion can occur in three ways At two mutually bonded atoms or Across a sequence of atoms A spiro compound is a Bicyclic Organic compound with rings connected through just one atom g. , "bicyclo"), and a numeric prefix before that indicating the number of carbons in each part of each ring, exclusive of vertices. For instance, a bicyclooctane that consists of a six-member ring and a four-member ring, which share two adjacent carbon atoms that form a shared edge, is [4. 2. 0]-bicyclooctane. That part of the six-member ring, exclusive of the shared edge has 4 carbons. That part of the four-member ring, exclusive of the shared edge, has 2 carbons. The edge itself, exclusive of the two vertices that define it, has 0 carbons.
The group of cycloalkanes are also known as naphthenes, as they are compounds of petroleum or naphtha. Petroleum ( L petroleum, from Greek πετρέλαιον, lit Naphtha normally refers to a number of different flammable liquid mixtures of hydrocarbons i
Properties
Cycloalkanes are similar to alkanes in their general physical properties, but they have higher boiling points, melting points, and densities than alkanes. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid The melting point of a solid is the temperature range at which it changes state from solid to Liquid. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different This is due to stronger London forces because the ring shape allows for a larger area of contact. The Van der Waals equation is an Equation of state that can be derived from a special form of the potential between a pair of molecules (hard-sphere repulsion Cycloalkanes exhibit almost the same degree of unreactivity as alkanes, due to their containing only unreactive C-C and C-H bonds; however, the ring strain (see below) can cause cycloalkanes to be more reactive.
Ring strain
The carbon atoms in cycloalkanes are sp3 hybridized and are therefore a deviation from the ideal tetrahedral bond angles of 109. -->In Chemistry 47 degrees. This causes an increase in potential energy and an overall destabilizing effect. Eclipsing of hydrogen atoms is an important destabilizing effect, as well. The strain energy of a cycloalkane is the theoretical increase in energy caused by the compound's geometry, and is calculated by comparing the experimental standard enthalpy change of combustion of the cycloalkane with the value calculated using average bond energies. The standard enthalpy of combustion is the Enthalpy change when one mole of a substance completely reacts with oxygen under standard thermodynamic conditions (although
Ring strain is highest for cyclopropane, in which the carbon atoms form a triangle and therefore have 60 degree C-C-C bond angles. Cyclopropane is a Cycloalkane Molecule with the molecular formula C3H6 consisting of three Carbon Atoms linked to There are also three pairs of eclipsed hydrogens. The ring strain is calculated to be around 120 kJ/mol.
Cyclobutane has the carbon atoms in a puckered square with approximately 90-degree bond angles; "puckering" reduces the eclipsing interactions between hydrogen atoms. Cyclobutane, C4H8 with a molecular mass of 56107g/mol is a four Carbon Alkane in which all the Carbon Atoms are arranged Its ring strain is therefore slightly less, at around 110 kJ/mol.
For a theoretical planar cyclopentane the C-C-C bond angles would be 108 degrees, very close to the measure of the tetrahedral angle. Cyclopentane is a highly Flammable alicyclic Hydrocarbon with Chemical formula 510 and CAS number 287-92-3 Actual cyclopentane molecules are puckered, but this changes only the bond angles slightly so that angle strain is relatively small. The eclipsing interactions are also reduced, leaving a ring strain of about 25 kJ/mol.
In cyclohexane the ring strain and eclipsing interactions are negligible because the puckering of the ring allows ideal tetrahedral bond angles to be achieved. Cyclohexane is a Cycloalkane with the Molecular formula C 6 H 12 As well, in the most stable chair form of cyclohexane, axial hydrogens on adjacent carbon atoms are pointed in opposite directions, virtually eliminating eclipsing strain.
After cyclohexane, the molecules are unable to take a structure with no ring strain, resulting in an increase in strain energy, which peaks at 9 carbons (around 50 kJ/mol). After that, strain energy slowly decreases until 12 carbon atoms, where it drops significantly; at 14, another significant drop occurs and the strain is on a level comparable with 10 kJ/mol. After 14 carbon atoms, sources disagree on what happens to ring strain, some indicating that it increases steadily, others saying that it disappears entirely.
Reactions
The simple and the bigger cycloalkanes are very stable, like alkanes, and their reactions, for example, radical chain reactions, are like alkanes. Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i In Organic chemistry, a radical substitution reaction is a Substitution reaction involving free radicals as a Reactive intermediate.
The small cycloalkanes - particularly cyclopropane - have a lower stability due to Baeyer strain and ring strain. Baeyer strain theory or strain theory explains specific behaviour of Chemical compounds in terms of bond Angle strain. Ring strain is an Organic chemistry term that describes the destabilization of a cyclic Molecule —such as a Cycloalkane —due to the non-favorable high They react similarly to alkenes, though they do not react in electrophilic addition, but in nucleophilic aliphatic substitution. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon In Organic chemistry, an electrophilic addition reaction is an Addition reaction where in a Chemical compound, a Pi bond is removed by the creation In organic and Inorganic chemistry, nucleophilic substitution is a fundamental class of Substitution reaction in which an "electron rich" These reactions are ring-opening reactions or ring-cleavage reactions of alkyl cycloalkanes. Alkyl cycloalkanes are Chemical compounds with an Alkyl group with a single ring of Carbons to which Hydrogens are attached according to the formula Cycloalkanes can be formed in a Diels-Alder reaction followed by a catalytic hydrogenation. The Diels-Alder reaction is an Organic chemical reaction (specifically a Cycloaddition) between a conjugated Diene and a substituted Alkene, Hydrogenation is the Chemical reaction that results in addition of Hydrogen (H2
References
International Union of Pure and Applied Chemistry (1995). The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization "Cycloalkanes". 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.
External links
- "Cycloalkanes" at the online Encyclopædia Britannica
- "Cycloalkanes" by the Chemistry staff at Westminster College
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