There's a subtle question within a question here. With 1-butanol, even upon protonation of the hydroxyl group, it is highly unlikely that the water will leave carbon and form a primary carbocation. It's the same reasoning we use to say that primary carbons substitute exclusively by SN2 mechanisms and not the SN1 pathway.Princeton Passage 11:
Q1: When 1-butanol is dehydrated, the new compound's heat of hydrogenation is most likely:
A. less than 27 kcal/mol
B. Between 27 and 30 kcal/mol
C. Between 30 and 33 kcal/mol
D. greater than 33 kcal/mol
answer: C) when 1-butanol is dehydrated, one obtains 1-butene, whose heat of hydrogenation is given in table 1 as 30.3 kcal/mol
**If it was 2-butene, the answer would have been B according to the table. Dehydration should form both products but shouldn't 2-butene be the answer since it is more stable?
I was wondering this same thing, but maybe the passage is asking about the minimal alkene side product. I have to believe they weren't really thinking at too much depth beyond losing an OH from C1 and H from C2, without stopping to think about the mechanism. I have a feeling we are all looking at this question at a depth beyond what the test writer was doing when they wrote it.Did the passage mention anything about the reagent being sterically hindered? If not, it's hard to see E2 beating out SN2.