All GRE Subject Test: Chemistry Resources
Example Questions
Example Question #1 : Carboxylic Acid Chemistry
Which of the following reactions would NOT produce a carboxylic acid?
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 #2 : Carboxylic Acid Chemistry
Which one of the following compounds can produce a carboxylic acid only when reacted with sodium dichromate and sulfuric acid?
1-pentanol
2-pentanone
2-pentanol
Pentanal
2-methylpentan-2-ol
1-pentanol
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 #1 : Help With Carboxylic Acid Synthesis
When 3-chloroheptane undergoes malonic ester synthesis, the final product is __________.
3-ethylheptanoic acid
malonic ester
None of the other answers
a ten-carbon ketone
nonanoic acid
3-ethylheptanoic acid
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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