The Wittig reaction employs which reagent to convert aldehydes or ketones into alkenes?

Prepare for the AIChE Chemical Engineering Jeopardy Exam. Enhance your skills with challenging questions, detailed explanations, and exam-ready strategies. Be confident on exam day!

Multiple Choice

The Wittig reaction employs which reagent to convert aldehydes or ketones into alkenes?

Explanation:
In the Wittig reaction the reagent that converts aldehydes or ketones into alkenes is a phosphonium ylide. This ylide, formed from a phosphonium salt and a strong base, reacts with the carbonyl group to form a betaine that cyclizes to an oxaphosphetane intermediate, which then fragments to give the desired alkene and triphenylphosphine oxide. The nature of the ylide influences the alkene’s geometry, with stabilized ylides tending to give one stereoisomer and unstabilized ylides offering different selectivity. Other options correspond to different reactions: Grignard reagents add to carbonyls to yield alcohols after workup, hydrogen gas with a catalyst reduces carbonyls or other unsaturations, and Grubbs catalysts catalyze olefin metathesis, not the carbonyl-to-alkene transformation seen in the Wittig reaction.

In the Wittig reaction the reagent that converts aldehydes or ketones into alkenes is a phosphonium ylide. This ylide, formed from a phosphonium salt and a strong base, reacts with the carbonyl group to form a betaine that cyclizes to an oxaphosphetane intermediate, which then fragments to give the desired alkene and triphenylphosphine oxide. The nature of the ylide influences the alkene’s geometry, with stabilized ylides tending to give one stereoisomer and unstabilized ylides offering different selectivity.

Other options correspond to different reactions: Grignard reagents add to carbonyls to yield alcohols after workup, hydrogen gas with a catalyst reduces carbonyls or other unsaturations, and Grubbs catalysts catalyze olefin metathesis, not the carbonyl-to-alkene transformation seen in the Wittig reaction.

Subscribe

Get the latest from Examzify

You can unsubscribe at any time. Read our privacy policy