Elimination/Substitution question

[DatRav27]

Hey SDN,

Today for the DAT quesiton of the day the following question was presented:

"Which reaction mechanism predominates in the reaction below?"

A. E1
B. E2
C. SN1
D. SN2
E. SN1 with rearrangement.

The answer has not been revealed yet but I am pretty confident that it is B: E2.
Strong, small base and and antiperiplanar position on the Cl and H make this possible.

Suppose the ethyl group was wedged (coming out of the page) rather than dashed as it is now. Would E2 still be the predominant reaction (not antiperiplanar anymore)? What about SN2, the Cl is on a secondary carbon which makes both E2 and SN2 favorable.

Any advice on how to differentiate these reactions quicker?

Thanks in advance!

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[discensdentibus]

I think your reasoning is sound. secondaries are a fuzzy area. Keep in mind that the ethyl still has free rotation and really messes with backside attack as well. Its good to consider both sides of the coin (or in this case cycloalkane)

 

[KineticFlow603]

I doubt we will have any questions like this where we have to choose either E2 or Sn2 with strong base/nucleophiles

 

[discensdentibus]

I doubt we will have any questions like this where we have to choose either E2 or Sn2 with strong base/nucleophiles

Not entirely true; the key takeaway from this sort of thing is considering all your factors in sub/elim. This problem, which you pointed out, is hitting the idea of anticoplanar/antiperiplanar, and you have the right mindset on trying to keep all your bases covered. Its a good habit to reason why answers are wrong!

 

[shyfox9p]

is the answer B? That's my first choice.

 

[DatRav27]

Thanks for the input everyone. Yes the answer is B for the original question