The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

This discussion is now closed.

Check out other Related discussions

Enthalpy thing in Benzene Unit5 Edexcel

Was just confused over what the book's point is when they talk about the enthalpy changes to explain Benzene?!! Do we need to know this...or is it safe to skip? Cos the NAS book goes into detail to explain...but i dnt get it! :frown:

Thanks for any help!
the point is that the stabilising effect of the delocalised ring is 360-208 = +152kJ, hence benzene undergoes substitution rather than addition reactions. but i don't think you need to know the enthalpy stuff in detail; only what i mentioned above. hope this helps.
Reply 2
Avatar for cujo
cujo
pretty simple ill explain it to you.

It was assumed that benzene and cyclohexatriene had the same structure. IE that benzene consisted of 3 single and 3 double bonds. When hydrogen was added to cyclohexatriene it was assumed that the enthalpy value obtained would be the same if hydrogen was added to benezene as i stated before kekule assumed it was the same structure. In fact the enthalpy of benzene was 150kjmol-1 less. This is known as the delocalisation stabilisation energy and the reason for this is because of benzene delocalised pi electron structure. I hope this helps.
Reply 3
Avatar for hopefulloser
hopefulloser
OP
thanks for the help! So the enthalpy stuff is just to prove that benzene is not the same as cyclohexatriene..? So thats it, no need to understand anything further. Its just there to prove the structure of benzene?

The book went thru alot to explain just that!
Reply 4
Avatar for sufiankane
sufiankane
2
you do need to understanfd it further, some exam questions ask this and you need to say that from this, benzene has a delooclised pi electron cloud which helps stabilise it, it prefers not to undergo addition reactions, as it destroys the electron cloud and this is less stable enthalpy wise, so undergoes subsitution and it does not have any localised c=c bonds. they are all delocalised.

Related discussions

Latest

Trending

Trending

Articles for you