Grignard reactions help

[prncess23]

hello.

Please help me with this question.

Give the products of the reaction of methylmagnesium chloride (Grignard reagent) with:
a.   acetaldehyde
b.   acetone
c.   ethyl acetate (1 equivalent per Grignard)
d.   ethanol
e.   propylene oxide

[chrisf]

A) propan-2-olate
B) 2-methylpropan-2-olate
C) 2-methylpropan-2-olate + ethanolate
D) I'm not sure this would work...
E) butan-2-olate

Keep in mind that these reactions are forming ions - if you follow the Grignard up with an acid/water, you'll get the corresponding alcohol (really, the whole point of these reactions - in my opinion).

[chrisf]

After protonation:

A) propan-2-ol
B) 2-methylpropan-2-ol
C) 2-methylpropan-2-ol + ethanol
D) ?
E) butan-2-ol

[prncess23]

thanks so much. how did u get to those results though and the end product is the protonated one right?

[chrisf]

Without doing the whole mechanism... the carbanion of the Grignard attacks the carbon of the carbonyl. The electrons forming the double-bond move to the oxygen giving it a negative charge. The resulting ion is a great base to deprotonate acid or water.. making the alcohol.

Unless your professor indicates a source of protonation, the answers are the ions.

[chrisf]

Here's a visual representation of the acetone reaction.

The product in blue is what you get by only adding the Grignard. The product in red is what you'd get after acidification.

[prncess23]

thank you.

[chrisf]

thank you.

Does it make sense to you?

[prncess23]

thank you.

Does it make sense to you?

yes it does. thanks.

i have a quick question though...i am having a hard time determining alpha carbons... in the following example:

benzaldehyde + acetophenone

[prncess23]

wait for d...isnt the answer ethanol + methane?

why wouldn't that work?

[chrisf]

Well, the carbanion is a strong base.. so it may abstract a hydrogen from the alcohol - but even that, I'm not sure. I just don't think there would be a significant reaction occuring there.