[friedpork]

For my lab, we have homework questions about the grignard reaction

1) If I start with 2-pentyl bromide, what would be the structure and name of the "impurity that could have formed during the preparation of the Grignard reagent.

I believe that the chief impurity would be 4,5-dimethyloctane.

2) Provide methods for synthesizing the following compounds using only a Grignard reaction, plus any necessary workup. In each case the Grignard reagent, propylmagnesium bromide, must be used in the synthesis. Express these syntheses in the form of balanced equations, using structural formulae, showing all reagents any specific conditions required

a) butanoic acid
b)1-pentanol
c)propane
d)4-ethyl-4-heptanol
e)4-ethyl-4-heptanol (different from d)

butanoic acid can be made from the grignard reagent as the starting material and then treating it with carbon dioxide and then having an acidic workup

1-pentanol can be made from an epoxide then use the reagents 1)PrMgBr, anh diethyl ether
2)H2O

for propane, I can just treat the grignard reagent with water to make propane

For 4-ethyl-4-heptanol, I can only think of one method and that is to use 3-hexanone as the starting material, use the grignard reagent to attack the 3-hexanone and then have an acidic workup.

Is this all correct so far? What other method could I use to make 4-ethyl-4-heptanol?

[zhangcarlin]

think about an ester

[discodermolide]

Do you mean heptan-4-one as the ketone?

[zhangcarlin]

No, I mean you can use an ester as your SM

[discodermolide]

I was responding to the original poster.

[friedpork]

No its 4-ethyl-4-heptanol

[discodermolide]

You said "For 4-ethyl-4-heptanol, I can only think of one method and that is to use 3-hexanone as the starting material, use the grignard reagent to attack the 3-hexanone and then have an acidic workup."
I think the ketone should be heptan-4-one!!!

[friedpork]

But if I use 4-heptanone, don't I end up with 4-propyl-4-heptanol instead of 4-ethyl-4-heptanol?

[discodermolide]

I apologise I didn't see the requirement for propyl Grignard reagent

[discodermolide]

No its 4-ethyl-4-heptanol

You are correct it is hexan-3-one. I apologise again for my error.
As the other poster suggested think of an ester.

[friedpork]

I could use methyl propanoate with excess propyl magnesium bromide to make 4-ethyl-4-heptanol I believe, is that correct?

[discodermolide]

Yes that is OK.

[zhangcarlin]

Yes that is OK.

You score.

[friedpork]

For these questions I'm not entirely sure how to espress these syntehsis in the form of balanced equations..

For question 1 can i express it in these way?

CH3CH2CH2MgBr + CO2 ---> CH3CH2CH2CO2H

[discodermolide]

No, not really, that is not the product, it is ultimately but you must do something to it first to get the acid, what?