Manufacture, Handling, and Uses of Sodium Hydride

Two types of sodium hydride are available commercially: a dry, granular material about 8 to 200 mesh in size, and a semidispersion of micron-sized crystals in mineral oil. The oil-dispersed sodium hydride is the safer and easier to handle, as the high reactivity of the hydride is protected by the oil. The principal use of sodium hydride is to carry out condensation and alkylation reactions which proceed through the formation of a carbanion (base-catalyzed). The sodium hydride dispersion has been evaluated in comparison with dry sodium hydride, sodium metal, sodamide, and sodium methylate. Yields and reaction rates in the self-condensation of esters, ester-keto condensations, and the Dieckmann condensation have been outstandingly superior. Amines can be successfully alkylated by a new technique employing polar solvents. Dehalogenations do not occur, nor does reduction unless there is no α-hydrogen present. Acyloin formation and reduction side reactions do not interfere when sodium hydride is used.