When 3,3-dichloropentane is treated with excess sodium amide in liquid ammonia, the initial product is 2-pentyne:

However, under these conditions, this internal alkyne quickly isomerizes to form a terminal alkyne that is subsequently deprotonated to form an alkynide ion:

The isomerization process is believed to occur via a mechanism with the following four steps: 

(1) Deprotonate

(2) Protonate

(3) Deprotonate

(4) Protonate.

Using these four steps as a guide, try to draw the mechanism for isomerization using resonance structures whenever possible. Explain why the equilibrium favors formation of the terminal alkyne.

CI xs NANH2 ---- CI 2-Pentyne IICIH XS NaNH2 XS NaNH, - ---- Alkynide ion 1-Pentyne 2-Pentyne