Hi everyone, in my notes there is a secondary N reacting with an alpha beta unsaturated ketone at the beta position. Would it ever react at the carbonyl instead?
Secondary NitrogenNitrogen reacting with double bond O or alpha beta unsaturated ketone?
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Um, I don't think it is possible for the nucleophiles to attack the carbonyl carbon. The carbonyl oxygen will withdraw electron density through pi bonds. If you draw the resonance forms, you will see both carbonyl and alpha carbons become electron rich and only beta carbon is electron deficient with a positive charge. In other words, beta carbon is the most electrophilic site in your examples.
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This is a classical Michael reaction. When dealing with an alpha-beta unsaturated system only strong nucleophiles such as Grignards, alkyl lithium reagents and hydrides would react with the carbonyl. Nucleophiles other than this usually react at the beta position. Essentially, the reactions that hit the beta carbon are orbital controlled reactions, and reactions hitting the carbonyl carbon are charged controlled reactions. In advanced Organic Chemistry we deal with this when studying hard acid-hard base,and soft acid-base theory. The explanation is beyond the scope of what you need for the DAT, but use this as a general rule and you will be fine.
Hope this helps!
Dr. Romano
