cyclohexa-1,3-diene is more stable than cyclohexa-1,4-diene because the c=c bonds are in closer proximity to each other, this means that there is an overlap of p orbitals, and therefore extra stability
how do you use data to state and explain the stability in benzene compared with the hypothetical cyclohexatriene?
benzene is more stable than cyclohexatriene
the expected ΔH hydrogenation of benzene is 3 x (-120)= -360kJmol^-1
the actual ΔH hydrogenation is -208kJmol^-1, which is 152kJmol^-1 LESS exothermic
this is because of delocalisation
compounds with a ring of delocalised electrons are weak bases, as they do not readily donate electrons
the reagents for electrophilic substitution of benzene are conc HNO3 and conc H2SO4
formation of the NO2+ ion?
HNO + 2H2SO4 ----> NO2+ + 2HSO4- + H3O+
which base is weaker, ammonia or phenylamine?
phenylamine is a weaker base because the lone pair on the N atom is less available, as it is delocalised into the ring
nucleophiles are repelled by the ring of delocalised electrons
