Ketones are a class of organic compounds. In ketones the central carbonyl group forms two additional bonds with other carbon-containing compounds. Ketones play a role in everything from human biology to heavy industry. Hopefully this guide will help bond the knowledge of ketones to your memory!
By analyzing questions, you can see patterns emerge, patterns that will help you answer questions. Qwiz5 is all about those patterns. In each installment of Qwiz5, we take an answer line and look at its five most common clues. Here we explore five clues that will help you answer a tossup on ketones.
CARBONYL GROUP
If you’ve read our previous guide on aldehydes you may remember that carbonyls are a functional group consisting of carbon atoms double-bonded to oxygen atoms. In ketones this carbonyl group is bonded to two other carbon atoms or carbon-containing compounds. Ketones can be categorized into different classes based on the type of their carbon-containing substituents. Some of these classes include unsaturated and cyclic ketones.
CONTRAST WITH ALDEHYDES
When listening to a question on ketones it’s important to pay attention to clues distinguishing them from aldehydes. Unlike ketones, the functional group in an aldehyde is bonded on one end to a hydrogen atom. Aldehydes also oxidize much more easily than ketones, which means that Tollens’ Test does not produce a silver mirror when performed on ketones. Note that an exception to this is a class of ketones known as acyloins. Acyloins will produce a positive Tollens’ Test.
WITTIG REACTION
The Wittig reaction is a common chemical reaction involving aldehydes or ketones. In the Wittig reaction an aldehyde or a ketone reacts with a triphenyl phosphonium ylide. Ylides are molecules wherein adjacent atoms have the opposite formal charge but the net formal charge of the molecule remains at zero. The Wittig reaction will convert a carbonyl compound to an alkene, a hydrocarbon containing a carbon-carbon double bond. If you hear a clue about the Wittig Reaction, remember to listen for additional information to differentiate between ketones and aldehydes.
AMINO ACID SYNTHESIS
There are several different chemical reactions that can be used to synthesize amino acids from ketones and vice-versa. One process, also applied to aldehydes, is known as Strecker amino acid synthesis and reacts a ketone or aldehyde with ammonia and potassium cyanide. The Dakin-West Reaction runs the opposite way, converting an amino acid into a keto-amide.
ACETONE
Acetone is one of the best-known ketones, and it is also the simplest. It is most commonly used as a solvent.
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Quizbowl is about learning, not rote memorization, so we encourage you to use this as a springboard for further reading rather than as an endpoint. Here are a few things to check out:
The answer to this “Guess the Chemist” quiz is Adolph Strecker, namesake of the Strecker Amino Acid Synthesis. Check out some of the other “Guess the Chemist” quizzes if you want to test your chem knowledge!
Many readers may be familiar with ketones through exposure to the Keto Diet.
Not all ketones are ketone bodies, but all ketone bodies are ketones. Looking for a handy mnemonic to remember what ketone bodies are? Check out this video.
This video offers a deeper discussion on the difference between aldehydes and ketones.
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