solvolysis question

[evangela7]

I do not understand why I am getting this problem wrong on my homework.

 

Rank the compounds in the following group in order of decreasing rate of solvolysis in aqueous acetone.

a) 2-methyl-4-chloro-butane

b) 2-methyl-3-chloro-butane

c) 2-methyl-2-chloro-butane

 

I know acetone is polar aprotic so it favors Sn2 reactions. Therefore, wouldn't it be in the following order: primary > secondary > tertiary or a>b>c?

Please correct me if I'm wrong...

[hypervalent_iodine]

Looks good to me.

 

Although it should be noted that the tertiary alkyl halide won't undergo S_N2.