1,4-Diacetoxy-2-butyne 1573-17-7 2-Butyne-1,4-diol diacetate 2-Butyne-1,4-diol, diacetate AI3-26931 But-2-yne-1,4-diyl diacetate Butynediol diacetate EINECS 216-394-4 NSC 76565