IIT JEE , AIEEE Forum - Chemistry , Organic Chemistry

srini

Hi....

Acording to a book it is given that the energy of the comp.cyclohexane is less than benzene indicating that cyclohexane is more stable than benzene.....how come it is this way.........

srini

Hi..

do you have any idea

beck2ham

The book is absolutely right . This is because cyclohexane exists in the form of chair and boat conformation( of which chair is more stable than boat) and not as a planar cyclic like benzene. This is why cyclohexane has less energy than benzene.

LastMinuteGenius

hi beckham,
banzene has resonance stabilization, which contributes to stability more than the conformation of cyclohexane.
so i think benzene is more stable (also i have done a sum in thermochemistry where , 1st u give energy to benzene to overcome resonance energy, and then u hydrogenate it where you give energy to break the 3 double bonds, then energy is liberated when the 6 C-H bonds form and conformation is obtained... if i remember right the energy given is more than energy liberated - so, benzene is stabler)

srini

Hi.. still not sure....

srini

Hi..

hey beck2am....could you illustrate more on that.thank s....alot

beck2ham

Ageed that benzene has resonance stablisation and that contributes to its extra stability. But mate, if u would have gone through the NCERT of 11th class(2006 edition), u would have found y i was right. And srini, for info. about the conformations I refered to, please do the same as I cant draw their figures coz my comp. doesnt have paint.

srini

Hi.

Thanks.........then why does resonance .........more preference......is this boat conformation true for others also?

beck2ham

Resonace is given more preference coz, it operates through pi-onds, which are weak and thus are easily broken. Hence, they contribue a lot more than any other factor.

No, this conformation isn't present in any other thing.

Please do rate me if u found my reason beneficial.

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