[kapital]

Whic anion is more stable: CH2=CH- or CH≡C-? Why?

[Schrödinger]

The 2nd one is more stable because the 2nd one is sp hybridized while the former is sp2. sp C being more electronegative, the 2nd one is more stable

[marcal]

Schrödinger is very right.

The sp bond is quite strong and electronegative. Very much so that the proton can be removed by not-so-strong bases and you can use the anion as a nucleophile in many reactions. It´s very common practice and a easy way to create C-C bonds.

As an exercise, check out the acidity of that proton. If I remember correctly it was something like 21 or something like this. Damn, I couldn´t resist and i had to check it out. the alkyne has a pKA of 25 whereas, as comparison, alkenes have a pKa of around 44.


Hope it helps!