In an SN2 substitution reaction of the type which 
one of the followings has the highest relative rate?
CH3-CH2-CH2Br
CH3-CH(CH2)-CH2Br
CH3C(CH3)2CH2Br
CH3CH2Br
D.
CH3CH2Br
The relative reactivity of alkyl halide towards SN N reactions is as follows;
Primary > secondary > Tertiary
However, if the primary alkyl halide or the nucleophile/base is sterically hindered the nucleophile will have difficulty to getting the back side of the alpha carbon as a result of this elimination product will be predominant. Here CH3CH2Br is the least hindered, hence it has the highest relative rate towards SN2 reaction.
Benzene reacts with CH3Cl in the presence of anhydrous AlCl3 to form
toluene
chlorobenzene
benzylchloride
benzylchloride
A.
toluene
CH3Cl in the presence of anhydrous AlCl3 acts as alkylation agent and introduces an alkyl group.
This reaction is known as Friedel-Craft's alkylation of benzene.
B.
The mechanism of electrophilic addition reaction is consistent with the occurrence of rearrangement leading to more stable carbocation.
The order of stability of carbocation is as;
T > S> P > CH3
Switch
