Grignard reagent...?

Question

If you are forming a compound using a Grignard reagent and you are considering steric effects, which must be bulkier: the Grignard reagent, or the molecule to which it is being added?

Example:You want to form a tertiary alcohol by using a Grignard reagent and a ketone. Should the reagents used be (the C in parentheses is also double bonded to an O):

CH3CH2(C)CH3 + CH2CH2MgBr
and then add H3O+
(Such that the Grignard reagent is the more sterically hindered one)

OR

CH3CH2(C)CH2CH3 + CH3MgBr, then add H3O+
(Such that the Grignard is the less sterically hindered reagent)
?

Thanks so much!!

Answer 1

You're not really talking about a great difference in steric bulk here. However, if you want a faster reaction, I would suggest that the Grignard be less sterically hindered.

And I'm not sure what the other guy is talking about, as the tertiary alcohol you'd get from the reaction you're describing (3-methyl-3-pentanol) is not chiral.