[fenor]

1-the major resonance structures of the carbocation  from  1-chloro-2-butene
(crotyl chloride) and  benzyl chloride when chloride leaves.

2- What does the resonance in part (1) have to do with the rate of the reactions of benzyl chloride?

i know that for crotyl chloride, it goes fast under SN1 and SN2 since it forms resonance stabilized cations. but i dont know how would the structure look like.

[Hanlon]

1. dont know what your talking about

2. Carbocations with resonance structures are more stable since the charge is delocalized and therefore spread out more. They effect the rate of SN1 reactions because the resonance structure stabilizes the transition state of the rate determining step thereby decreaseing the energy of the transition state and increasing the reaction rate.

for Benzyl Chloride its a ring structure with a chlorine attached I believe, therefore the positive+ charge on the carbocation can move around with the double bonds in the ring structure

[cupid.callin]

1) i posted a pic of resonance of chlorobut-2-ene. You can draw same for benzyl carbocation.

i dont know what you mean by "the major resonance structures of the carbocation" but if you mean the most stable structure then structure to extreme right is most stable.

to judge stability of resonating structure:
a. structure with max. covalent bonds are more stable.
b. -ve charge on electonegative atom
c. +ve charge on electopositive atom

2) stable the product meams more the rate of reaction. not only for resulting carbocation but for any rxn.

[Hanlon]

I believe the major resonance structure of the carbocation is the most significant structure and the one that the molecule spends most of its time in

for benzyl carbocation its just a ring structure with 3 alternating double bonds so it doesn't have a major resonance structure. also the molecule is symmetrical therefore there is no regioselectivity

[cupid.callin]

Why isnt "venor" replying???