Hydroxy acids Gamma, Anhydrides

In this case we have formed an inner anhydride which will be explained presently, when we consider the hydroxy acids. These differences in the reaction of alpha-y beta- and gamma-hdXogtn acids are characteristic of alpha-y beta-.y and ga/w/wo-substituted acids in general and will be more clearly shown when we consider them in connection with the hydroxy acids (p. 241). 

Anhydrides.—(7) The most striking reactions of the hydroxy acids are those in which the alpha- beta- and gamma-hydioxy acids react differently. These reactions involve the loss of water and the formation of anhydrides. The reaction takes place simply under the influence of heat, and shows the different effect which is produced by a difference in the position of the hydroxyl group in relation to the carboxyl. 

A reaction analogous with that of cyclic-anhydride-formation is the formation of lactones from 7-hydroxy acids and from 7-halogen acids. (Cf. page 39.) A related reaction is the dehydration of acids possessing a carbonyl group in the gamma position. 

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