Hydrogen 3-nitrophthalates, from alcohols

The derivative selected in any particular instance should be one which clearly singles out one compound from among all the possibilities and thus enables an unequivocal choice to be made. The melting points of the derivatives to be compared should differ by at least 5-10°. Whenever possible, a derivative should be selected which has a neutralisation equivalent as well as a melting point (e.g., an aryloxyacetic acid derivative of a phenol. Section IV,114,4, or a hydrogen S nitrophthalate of an alcohol. Section 111,25,5). 

Phthalic anhydrides readily form hydrogen phthalate esters on reaction with alcohols the derivatives from 3-nitrophthalic anhydride are usually nicely crystalline compounds and are hence suitable for purposes of characterisation. Hydrogen phthalate esters are also useful in appropriate instances for the resolution of racemic alcohols (Section 5.19). 

If, when the product is cooled, the hydrogen 3-nitrophthalate does not crystallize, extract it with saturated sodium bicarbonate solution and acidify the extract with 2N hydrochloric acid. Recrystallize from aqueous alcohol. 

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See also in sourсe #XX -- [ , ]

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