Arrange (a) cis-1,2-dimethylcyclopentane, (b) methylcyclohexane and (c) 1,1,2,2-tetramethylcyclopropane in decreasing order of heat of combustion.
(a)
(b)
(c)

Question

Arrange (a) cis-1,2-dimethylcyclopentane, (b) methylcyclohexane and (c) 1,1,2,2-tetramethylcyclopropane in decreasing order of heat of combustion. (a) (b) (c)

TestHub · Accepted Answer

All three are C 7 ​ H 14 ​ isomers, so the comparison reflects stability. 1,1,2,2-Tetramethylcyclopropane has a strained three-membered ring plus steric crowding, so it has the largest value. Cis-1,2-dimethylcyclopentane has some ring and eclipsing strain, and methylcyclohexane is strain free and the most stable. Order : c > a > b. Because the formulae are equal, this comparison can be used to assess relative stability.

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