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Ketones

Ketones

Background:


Ketones are very closely related to aldehydes in that they both consist of an alkyl chain with a double bonded oxygen attached to one of the carbons atoms in the chain.

In the case of aldehydes that oxygen atom is double bonded to the primary carbon, or end of chain carbon. In ketones the oxygen is bonded to a secondary, or middle of the chain carbon.

A diketone is a compound containing two ketone groups.

Physical Properties:


Ketones are polar compounds making them soluble in water. Ketones are more volatile than alcohols and carboxylic acids of similar molecular weight.

Chemical Properties:


Ketones tend to be less chemically active than aldehydes of a similar molecular size.

Uses and Applications:


Ketones are often used in perfumes and paints to stabilize the other ingredients so that they don't degrade as quickly over time. They also have other uses in surface coatings, adhesives, thinners, printing inks and cleaning agents, in tanning, as solvents, as preservatives, in hydraulic fluids and as intermediates in the chemical industry.

In our bodies acetone, acetoacetate and beta-hydroxybutyrate are ketones (or ketone bodies) generated from carbohydrates, fatty acids and amino acids. Ketones are elevated in blood after fasting including a night of sleep, and in both blood and urine during starvation. The brain relies heavily on ketone bodies as a substrate for lipid synthesis and for energy during times of reduced food intake.

Laboratory Preparation:


Ketones can be prepared by the oxidation of secondary alcohols using strong oxidizing agents such as potassium dichromate or potassium permanganate.

CH3(CH-OH)CH3 + O ---> CH3(C=0)CH3 + H2O

Naming Conventions:


The common name for a ketone is constructed by adding ketone to the names of the two alkyl groups on the C=O double bond, listed in alphabetical order. The following is ethyl methyl ketone.

CH3(C=0)CH2CH3

Using the IUPAC nomencature this same molecule would be referred to as 2-propanone. Note that the name is derive from alkane name for the longest carbon chain with the final "e" in the alkane name being replaced by the suffix "one". The "2" indetifies the location of the oxygen double bond.

Bibliography:


Perdue University article on aldehydes and ketones
Wikipedia article on ketones
Britanica Online - keytone article
Michigan State U. Article of Aldehydes and Ketones

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