R " is a replaceable function, e. g. acetoxy, methoxy, their acyloxy and alkoxy homologs or halo. 是取化基,如乙氧基、甲氧基及它们的环氧和烷氧同系物或卤基。
the cutting part of a drill; usually pointed and threaded and is replaceable in a brace or bitstock or drill press . 钻机的切割部分;通常是尖头的有螺旋状图案并且可以更换,用在钻柱钻柄或钻床上。