Cycloalkanes cyclopentane

Cycloalkanes. Cyclopentane and cyclohexane, the two most common cycloalkanes. 

When cycloalkanes (cyclopentane, cyclohexane) alkylate benzene, cycloalkylben-zenes, as well as bicyclic compounds (indan and tetralin derivatives) and products of destructive alkylation, are formed.191192 Cyclohexane reacts with the highest selectivity in the presence of HF—SbF5 to yield 79% cyclohexylbenzene and 20—21% isomeric methylcyclopentylbenzenes.191... 

The third class of organic donor molecules are a-donors, viz., alkanes and cycloalkanes. These substrates have inherently high ionization and oxidation potentials. Therefore, their radical cations are not readily available by photoinduced electron transfer, but typically require radiolysis and electron impact in the condensed phases or the gas phase, respectively. Thus, radical cations of simple alkanes (methane [206], ethane [207]) or unstrained cycloalkanes (cyclopentane, cyclohexane) [208] were identified and characterized following radiolysis in frozen matrices. In contrast, strained ring compounds have significantly lower oxidation potentials so that the radical cations of appropriate derivatives can be generated by photoinduced electron transfer. 

Letcher and coworkers investigated the excess heat of mixing of alkynes with different solvents such as cycloalkanes(cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane) with an -alkyne (n-hexyne or n-heptyne or -octyne) bicyclic compounds[decahydronaphthalene (CioHig), bicyclohexyl (CnHii) L2,3,4-tetrahydronaphthalene (C10H12), cyclohexylbenzene (C12H16)] with -hexyne or n-heptyne benzene with n-hexyne , w-heptyne or -octyne and finally, 1,3,5-trimethylbenzene with n-hexyne -heptyne or w-octyne. ... 

Cycloalkanes Cyclopentane Methylcyclopentane Cyclohexane Methylcyclohexane Pentylcyclohexane Hexylcyclohexane Heptylcyclohexane Octylcyclohexane Nonylcyclohexane Decylcyclohexane U ndecylcyclohexane Dodecylcyclohexane Tridecylcyclohexane Tetradecylcyclohexane Pentadecylcyclohexane Hexadecylcyclohexane Heptadecylcyclohexane Octadecylcyclohexane N onadecylcyclohexane... 

Cyclopentane and cyclohexane are present m petroleum but as a rule unsubsti tuted cycloalkanes are rarely found m natural sources Compounds that contain rings of various types however are quite abundant... 

At one time all cycloalkanes were believed to be planar It was expected that cyclopentane would be the least strained cycloalkane because the angles of a regular pentagon (108°) are closest to the tetrahedral angle of 109 5° Heats of combustion established that this is not so With the exception of cyclopropane the rings of all cycloalkanes are nonplanar... 

The name naphthenic acid is derived from the early discovery of monobasic carboxyUc acids in petroleum, with these acids being based on a saturated single-ring stmcture. The low molecular weight naphthenic acids contain alkylated cyclopentane carboxyUc acids, with smaller amounts of cyclohexane derivatives occurring. The carboxyl group is usually attached to a side chain rather than direcdy attached to the cycloalkane. The simplest naphthenic acid is cyclopentane acetic acid [1123-00-8] (1, n = 1). 

In addition to the ahphatic (chain) molecules, the saturates contain cycloalkanes, called naphthenes, having mainly five or six carbons in the ring (Fig. 5). Methyl derivatives of cyclopentane and cyclohexane ate commonly found in greater quantity than the parent unsubstituted stmctures and can be present at levels above 2% (2). Fused-ting dicycloalkanes such as decahydronaphthalenes (decalins) and hexahydroindans are also common, but nonfused bicyhc naphthenes, eg, cyclohexyl cyclohexane, are not. 

Physical properties of cycloalkanes [49, p. 284 50, p. 31] show reasonably gradual changes, but unlike most homologous series, different members exhibit different degrees of chemical reactivity. For example, cyclohexane is the least reactive member in this family, whereas both cyclopropane and cyclobutane are more reactive than cyclopentane. Thus, hydrocarbons containing cyclopentane and cyclohexane rings are quite abundant in nature. 

The data in Figure 4.3 show that Baeyer s theory is only partially correct. Cyclopropane and cyclobutane are indeed strained, just as predicted, but cyclopentane is more strained than predicted, and cyclohexane is strain-free. Cycloalkanes of intermediate size have only modest strain, and rings of 14 carbons or more are strain-free. Why is Baeyer s theory wrong ... 

Petroleum contains hydrocarbons other than the open-chain alkanes considered to this point. These include cycloalkanes in which 3 to 30 CH2 groups are bonded into closed rings. The structures of the two most common hydrocarbons of this type are shown in Figure 22.5 (p. 585). Cyclopentane and cyclohexane, where the bond angles are close to the ideal tetrahedral angle of 109.5°, are stable liquids with boiling points of 49°C and 81°C, respectively. 

Cycloalkane A saturated hydrocarbon containing a closed ring. General formula = C H2 , 584-585 Cyclopentane, 584 Cysteine, 622t... 

A conformational effect was detected for the H-transfer reactions from cycloalkanes to a series of attacking radicals. The data of Table 6 show that cyclopentane is generally a better H-donor than cyclohexane. The rate ratio is generally largest for the least reactive radicals because the change in hybridization at transition state... 

Compounds called cycloalkanes, having molecules with no double bonds but having a cyclic or ring structure, are isomeric with alkenes whose molecules contain the same number of carbon atoms. For example, cyclopentane and 2-pentene have the same molecular formula, C5H, but have completely... 

In a similar way the potential constant method as described here allows the simultaneous vibrational analysis of systems which differ in other strain factors. Furthermore, conformations and enthalpies (and other properties see Section 6.5. for examples) may be calculated with the same force field. For instance, vibrational, conformational, and energetic properties of cyclopentane, cyclohexane and cyclodecane can be analysed simultaneously with a single common force field, despite the fact that these cycloalkanes involve different distributions of angle and torsional strain, and of nonbonded interactions 8, 17). This is not possible by means of conventional vibrational spectroscopic calculations. 

Cyclopentane and cycloheptane have almost equal ring strains (6.5 and 6.4) and a 15 membered cycloalkane again has a very slight amount of ring strain. 

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