What hinders SN2 more: geminal alkyl group or alkyl group on the aromatic ring? Which among these two (1-chloro-1-phenyl-ethane and 2-(chloromethyl)-1,3-dimethylbenzene) is more reactive towards SN2?


I strongly believe that it should be Y because of lesser hindrance on the electrophilic carbon.
However, the answer key of my exercise book states that X &gt; Y. What's the reason behind that?
The correct answer is X because the 2 methyl groups on the Y are bulky enough to cause steric hindrance. Surprisingly, from what I have seen, if you only had one methyl group on Y, the SN2 reaction would proceed.