O-chem: Which one of the following statements does not correctly describe Sn1 reactions of alkyl halides?

A)

Because SN1 reactions are one-step reactions, so there are no intermediates. On SN2 however, A would be true.

statement - 'd) The rate of an Sn1 reactions depends on the concentration of the nucleophile' is incorrect regarding SN1 reaction


a) is correct because carbocations are intermediates in SN1 reaction....

see this link---
http://www.chem.ucalgary.ca/courses/351/Carey/Ch08/ch8-2.html


b) is correct because as carbocations are the intermediates so more stable the carbocation ,more easily it is formed from alkyl halide and faster is the reaction...
now as we know that stability of carbocations are in the order :
tertiary > secondary > primary > methyl
so rate of reaction of alkyl halides also follows the same order :
tertiary > secondary > primary > methyl

in this case the halide is bromide so reactivity order will be :
R3CBr (tertiary) > R2CBr(secondary) > RCHBr(primary) > CH3Br (methyl)

(c) is true ...see the link i gave

so  (d) is false ....

a) Carbocations are intermediates in Sn1 reactions..