Isomerism in alkynes

Alkynes show position isomerism, which is a form of structural isomerism: the same molecular formula can place its carbon-carbon triple bond at different points along an identical carbon chain. But-1-yne and but-2-yne, both C4H6, are the standard example -- in but-1-yne the triple bond sits at the very end of the four-carbon chain (between C1 and C2), while in but-2-yne it sits in the middle (between C2 and C3). Alkynes whose triple bond sits at C1, such as but-1-yne, are additionally given the special name terminal alkynes, precisely because the triple-bond carbon at that end still carries a hydrogen atom directly attached to it -- a structural feature that turns out to matter a great deal chemically, since that …