Question

Whichofacrylaldehyde(propenal)andbut-3-en-2-onewouldundergo1,2-additionor

20

1,4-addition with isobutylmagnesium chloride? Explain your answer in detail.

Answer 1

1-4 addition or conjugate addition takes place when the carbonyl group is less electrophilic . If the carbonyl center is heighly electrophilic center the nucliophile will prefere directly attack to the carbonyl center . Generally aldehydes are more electrophilic than ketone hence but-3ene ,2-one will gives conjugate addition or 1,4 addition with isobutyl magnesium chloride in presence of CuCl Generally the hard nucliophile attacks directly to the hard carbonyl center and soft nucliophile gives conjugate addition grignard reagent are hard nucliophiles and gives direct addition . If reaction of grignard reagent carried out in presence of CuCl which makes it soft center it will gives conjugate addition . Hence in given problem there should be some amount of CuCl as mentioned that it will gives conjugate addition