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Sektor404 Sektor404
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Posts: 125
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11 years ago
Hey  Slight Smile

I've had to upload a picture for the question as I can't really structure it via text. Can somebody please help me answer these questions? If somebody could maybe draw the structures via Paint or another drawing program so I can visualise the steps in the answer that would be great as I can't seem to understand what is going on in these questions.

Any help is appreciated, thank you Slight Smile
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wrote...
Donated
Valued Member
11 years ago
Looking at the reactions that esters normally undergo, we see that esters can undergo reduction to alcohols in the presence of Lithium Aluminum Hydride (in an acidic environment):
methyl-2-methylpentanoate + LiAlH4 -> 2-methyl-1-pentanol (image 1)

Next, an alcohol will undergo nucleophilic substitution with Thionyl Chloride (SOCl2) to form the corresponding alkyl halide:
2-methyl-1-pentanol + SOCl2 + heat -> 1-chloro-2-methylpentane (image 2)

I worked a bit on this question.  Don't know how to get the Cl on the 2nd carbon.  I might have made a mistake.  Just wanted to give you what I had done.  I hope this helps.
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Pretty fly for a SciGuy
Sektor404 Author
wrote...
11 years ago
You definitely helped me Doctor-2-B although I'm still not 100% on understanding this completely...but thank you very much it definitely gave me an insight as to a possible mechanism!!! Slight Smile
wrote...
Donated
Valued Member
10 years ago
I believe I might've missed a carbocation rearrangement or methyl shift but maybe not?
Pretty fly for a SciGuy
wrote...
Subject Expert
10 years ago
Hi,

I was thinking about the first step is the reduction of carboxylic acid by using 1)LiAlH4, then 2) water to get the primary alcohol product. Then on the 2nd step, i would add acid to promote elimination product, making 2-methyl-1-pentene. Then I would use HCl, so that the Cl would be added to the more substituted carbon (carbon #2).

Hope this helps,
Laser
wrote...
Donated
Valued Member
10 years ago
That sounds completely reasonable.  I thought esters reduced to alcohols in Lithium Aluminum Hydride, though?
Pretty fly for a SciGuy
wrote...
Subject Expert
10 years ago
Hi Doctor-2-B,

You're right, it would; that's why we both used it in the first step. The water is just to protonate the alcohol. I did 1) and 2) on the first step, because the Lithium Aluminum Hydride violently reacts with water.

Best,
Laser
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