how to know if a nucleophile will attack the carbonyl carbon or beta carbon

[wall1two]

or the beta carbon of a Michael addition acceptor?

when i see Cu-R2 i know to attack the beta carbon and when we have di-ketones.

but a grinyard aklyne : C (tripplebond) C Mg Br attacks the carbonyl even if it is conjugated, but NH2R attacks the beta carbon. How can i know the difference?

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[FredDurst]

or the beta carbon of a Michael addition acceptor?

when i see Cu-R2 i know to attack the beta carbon and when we have di-ketones.

but a grinyard aklyne : C (tripplebond) C Mg Br attacks the carbonyl even if it is conjugated, but NH2R attacks the beta carbon. How can i know the difference?

The harder nucleophiles attack the carbonyl carbon while soft nucleophiles attack at the beta-position.

 

[RCLEE]

delete?

 

[RCLEE]

Doesn't primary Amine (RNH2) also attacks the carbonyl carbon to form an amide?

I don't understand/don't remember what hard and soft nu:- are. Normally, if there's a catalyst that's involved to form an alpha,beta-unsaturated carbonyl from an a,b-saturated, then it would attack the beta carbon. So you have to look at your reagents for a strong base. If not, I normally would go with the attack on the carbonyl carbon.

When is your test? Good luck!

 

[wall1two]

thanks fred, keep rollin. and reclee thanks too. yeah when i see LDA it is a give away but ill just work with the strong vs soft idea. here si the example. there is no metal involved so i should have assumed the nitrogen isnt as strong as it could be. (the nucleophile is MeNH2)

i take it tomorrow, yippie 👎