Page "Alkyne" Paragraph 26

In addition to undergoing the reactions characteristic of internal alkynes, terminal alkynes are reactive as weak acids, with pK < sub > a </ sub > values ( 25 ) between that of ammonia ( 35 ) and ethanol ( 16 ).

The acetylide conjugate base is stabilized as a result of the high s character of the sp orbital, in which the electron pair resides.

Electrons in an s orbital benefit from closer proximity to the positively charged atom nucleus, and are therefore lower in energy.

Treatment of terminal alkynes with a strong base gives the corresponding metal acetylides: