Purification Methods
Recrystallisation of the borohydride from H2O three times yields ca 94% pure compound. Dry in high vacuum at 100o for 3hours. The solubility in H2O is 48% (20o), 61% (40o), and in EtOH 0.5% (25o) and MeCN 0.4% (25o). It decomposes slowly in a vacuum at 150o, but rapidly at 250o. The rate of hydrolysis of Me4N.BH4 (5.8M) in H2O at 40o is constant over a period of 100hours at 0.04% of original wt/hour. The rate decreases to 0.02%/hour in the presence of Me4NOH (5% of the wt of Me4N.BH4). [Banus et al. J Am Chem Soc 74 2346 1952, Beilstein 4 IV 148.]
