Discussion
The major product formed in the following reaction
is:
Answer: A
The product is non-6-yn-2-one.
This is the Eschenmoser fragmentation of an alpha,beta-epoxy ketone tosylhydrazone. Base removes the N-H proton; the epoxide opens as the tosyl group leaves, and the ring bond between the two former epoxide carbons breaks, releasing N2 and Ts−.
The carbon bearing Et and the former C=N carbon become the two ends of a C≡C bond, and the carbon bearing Me and the epoxide oxygen becomes a ketone. Opening the six-membered ring gives a straight chain:
\[ \mathrm{CH_{3}CH_{2}C{\equiv}C(CH_{2})_{3}COCH_{3}} \]
Numbering from the ketone end gives the carbonyl at C2 and the triple bond at C6: non-6-yn-2-one, nine carbons. non-3-yn-8-one is the same chain numbered from the wrong end, non-2-yn-6-one puts the alkyne and ketone in the wrong places, and an alkene product would need hydrogen that the fragmentation does not supply.
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