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Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
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Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development

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Residues of volatile halocarbons in margarines

R C Entz1, G W Diachenko

  • 1Division of Food Chemistry and Technology, Food and Drug Administration, Washington, DC 20204.

Food Additives and Contaminants
|July 1, 1988
PubMed

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A method involving the transformation of methyl ketones to carboxylic acids using excess base and halogen is called the haloform reaction. It begins with the deprotonation of α hydrogen to form an enolate ion which reacts with the electrophilic halogen to give an α-halo ketone. The step continues until all the α protons are substituted to form a trihalomethyl ketone. The resulting molecule is unstable, and in the presence of a hydroxide base, it readily undergoes nucleophilic acyl substitution.
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Unlike aldehydes and ketones, carboxylic acids do not readily participate in α halogenation reactions via enols or enolate intermediates. However, α-halogenated acids are obtained through other methods. One of the approaches is the Hell–Volhard–Zelinsky (HVZ) reaction, wherein the carboxylic acid is treated with halogen in the presence of PBr3. It involves the conversion of acid to acid halide, which exists in equilibrium with its enol form. The enol attacks the electrophilic halogen to produce...
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