Show how you would accomplish the following synthetic conversions by adding an organolithium reagent to an acid.
(c) pentanoic acid 
(d) phenylacetic acid 
Solution 7P
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Dianion is protonated in presence of
to form hydrate and followed by removal of water to form target product.
(b)
Bromocyclopentane reacts with two equivalents of lithium to form one equivalent of cyclopentyl lithium.
Here one equivalent of cyclopentyl lithium is formed. So, in order to react with one equivalent of cyclopentyl lithium 0.5 equivalent of acetic acid is required.
One equivalent of cyclopentyl lithium reacts with 0.5 equivalent of acetic acid to form a dianion.
Dianion is protonated in presence of to form hydrate and followed by removal of water to form target product.
(c)
Ethyl lithium is commercially available (inexpensive). So, the carboxylic acid reacts with two equivalents of ethyl lithium.
Pentanoic acid reacts with two equivalents of ethyl lithium and followed by protonation in presence of to form heptan-3-one.
Step by step reaction is as follows:
One equivalent of ethyl lithium abstracts ion pentanoic acid to form lithium pentanoate.
Another molecule of ethyl lithium attacks the lithium pentanoate to form a dianion.
Dianion is protonated in presence of to form hydrate and followed by removal of water to form target product.
(d)
