The use of appropriately prepared silica gel and alumina has been found to mediate the addition of hydrogen halides to alkynes. The technique has been rendered even more convenient by the use of various organic and inorganic acid halides that react in the presence of silica gel or alumina to generate hydrogen halides in situ. Treatment in this fashion of 1-propynylbenzene (I), which underwent no reaction in CHzClz solution ...