[C:1](=[O:6])([O-:5])[O:2][CH2:3][CH3:4].[Na+:7].C(OC([O-])=O)(=O)[O-].[O-]CC.[Na+].[Na].C(=O)=O.[Cl:23][C:24]([O:26][CH2:27][CH3:28])=[O:25]>C1(C)C=CC=CC=1.C(O)C>[C:1]([O:5][C:24]([O:26][CH2:27][CH3:28])=[O:25])(=[O:6])[O:2][CH2:3][CH3:4].[Cl-:23].[Na+:7]The dialkyl pyrocarbonates may be prepared by reacting alkali metal alkyl carbonate, e.g., sodium ethyl carbonate, with alkyl halocarbonate, e.g., ethyl chlorocarbonate (ethyl chloroformate). The alkyl groups of the alkyl carbonate and halocarbonate are chosen to correspond to the alkyl group desired for the pyrocarbonate. For example, sodium ethoxide, which can be prepared by dissolving sodium metal in toluene solution of ethyl alcohol, is carbonated with carbon dioxide to prepare sodium ethyl carbonate. Thereafter, the sodium ethyl carbonate is reacted with ethyl chloroformate to form diethyl pyrocarbonate and sodium chloride. The chloride salt is filtered and the pyrocarbonate recovered by distillation.
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