It has been shown that active prototropy of the propyne-allene type does not occur in these compounds, and that the 1, 3-diarylpropynes exhibit low proton mobility. Comparison with benzyl cyanide and 3-phenyl-1-propyne indicates that the phenylethynyl group has less activating effect than-C= N or-C= CH, which is in agreement with the anticipated order.
