GRE Subject Test: Chemistry : Carboxylic Acid Chemistry

Study concepts, example questions & explanations for GRE Subject Test: Chemistry

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Example Questions

Example Question #24 : Reactions By Product

Which of the following reactions would NOT produce a carboxylic acid?

Possible Answers:

Correct answer:

Explanation:

PCC is considered a weak oxidizing agent. The reaction of a primary alcohol with PCC would only yield an aldehyde, while reaction with a secondary alcohol will yield a ketone. PCC will not be used to generate carboxylic acids.

A stronger oxidation, like or , is required to oxidize up to the carboxylic acid. Treatment of an ester with a base or treatment of carbon dioxide with a Grignard reagent are other ways of making carboxylic acids.

Example Question #25 : Reactions By Product

Which one of the following compounds can produce a carboxylic acid only when reacted with sodium dichromate and sulfuric acid?

Possible Answers:

2-pentanone

Pentanal

2-pentanol

1-pentanol

2-methylpentan-2-ol

Correct answer:

1-pentanol

Explanation:

After recognizing the reagents given, we know we need to begin with an alcohol. The alcohol choices differ only by how substituted they are.

For a carboxylic acid to form from a reaction with sodium dichromate and sulfuric acid, a primary alcohol needs to be available. Therefore, 1-pentanol is the correct answer.

Example Question #3 : Carboxylic Acid Chemistry

When 3-chloroheptane undergoes malonic ester synthesis, the final product is __________.

Possible Answers:

3-ethylheptanoic acid

nonanoic acid

a ten-carbon ketone

malonic ester

None of the other answers

Correct answer:

3-ethylheptanoic acid

Explanation:

The malonic ester is deprotonated at the most acidic hydrogen, the one on the carbon between the two oxygens. The electrons from that bond to the hydrogen form a carbon-carbon double bond while electrons from the oxygen-carbon double bond go to the oxygen atom. This is the enolate form. The chlorine leaves the 3-chloroheptane and the electrons from the carbon-carbon double bond bond to the carbon that the chlorine left. At the same time, the carbonyl is reformed. After deesterfication, 3-ethylheptanoic acid is formed.

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