AAMC FL1 CP #4

[663697]

By having a carbocation intermediate this would mean the reaction is E1. As far as I'm aware, the passage didn't mention the solvent or base that was used for the dehydration, so I am assuming it is just water. For future reference, how would we distinguish whether this is an E1 or E2 reaction? Does it have to do with it being a secondary alcohol?

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[theonlytycrane]

This is one of those questions where you're just looking for a clearly incorrect answer choice. Since the question stem mentions that the dehydration of malic acid results in the formation of two isomers (fumaric and maleic acid), the reaction can't be stereospecific (or else only one isomer would be produced).

Choice (B) can be ruled out because it's a true statement. There isn't enough information to rule out choices (A) and (C).

 

[aldol16]

I agree with the above poster. Don't make the question harder than it is. The strategy here should be looking for the odd answer out - three of those fit with one reaction mechanism and they can't all be wrong so it must be that reaction mechanism. With secondary carbons, it's hard to tell when they would proceed via E1 or E2 because they can really do both depending on the circumstances.