Cycloalkane
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Cycloalkanes are chemical compounds with a one or more rings of carbons to which hydrogens are attached according to the formula CnH2n. Cycloalkanes with a single ring are named analogously to their normal alkane counterpart of the same carbon count: cyclopropane, cyclobutane, cyclopentane, cyclohexane, etc. 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
The naming of polycyclic alkanes is more complex, with the base name indicating the number of carbons in the ring system, a prefix indicating the number of rings (eg, "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 which consists of a six-member ring and a four member ring, which share two adjacent carbon atoms which 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.
Reactions
The normal and the bigger cycloalkanes are very stable, like alkanes, and their reactions (cf. radicalic chain reactions) are like alkanes.
The small cycloalkanes - particularly cyclopropane - have a lower stability due to the Baeyer-tension and ring strain. They react similar to alkenes, though they don't react with the EA (cf. electrophilic addition), but with the SN2 (cf. nucleophilic substitution) reaction mechanism. These reactions are ring opening reactions or cleavage reactions of alkyl cycloalkanes.
External links
- http://chipo.chem.uic.edu/web1/ocol/SB/2-2.htm
- ExxonMobil's Exxsol product FAQ. Exxsol is mostly cycloalkanes (http://www.exxonmobilchemical.com/Public_Products/Fluids/Aliphatics/Worldwide/FAQs/Fluids_Aliphatics_FAQ_Exxsol.asp)de:Cycloalkane