Sodium borohydride reacts slowly with water ultimately to liberate 4 moles of hydrogen per mole of the compound at room temperature, or 2.4 1. per gram. The reaction is greatly accelerated by rise of temperature or by the addition of acidic substances, for which latter purpose boric oxide is convenient and effective when the objective is the generation of hydrogen. Particularly striking is the catalytic effect of certain metal salts, especially that of eobalt(II) chloride. Thus pellets of sodium borohydride containing only 5% of the cobalt salt react as rapidly as those containing 10 times that amount of boric oxide. The effect of the cobalt salt is ascribed to the catalytic action of a material of empirical composition, Co2B, which is formed in the initial stages o'f the reaction.

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The concept of free rotation about the single bond has been a basic postulate of the stereochemist. This belief is based upon the failure of II Reaction proceeds to right: R = CHS < (CHS)2CH < (CH3)3C.

On account of its position in the periodic system and the composition of its most widely known compounds, boron has generally been regarded as a trivalent element; its hydrides therefore might have been expected to have the "normal" formulas BH3, B2H4, B3H6, etc. Actually, however, the simplest known hydride of boron is diborane (B2H6), a substance whose

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As has already been described in a brief preliminary communication, trimethylaluminum and diborane react to form the compound AIB~Hu, according to the equation Ala(CHs)s + 4B2Hs + 2B(CH& f 2AlBaHin (6) Burg and Schlesinger, ibid., 59, 780 11937). (6) Burg and Schlesinger, ibid., 62, 3425 (1940).