Question

Choose the correct order of acidic strength:
1. Propane
2. Prop-1-ene
3. Prop-1-yne

• A. Propane > Prop-1-ene > Prop-1-yne
• B. Prop-1-yne > Prop-1-ene > Propane
• C. Prop-1-ene> Propane > Prop-1-yne
• D. Propane = Prop-1-ene = Prop-1-yne

Answer 1

The correct option is B Prop-1-yne > Prop-1-ene > Propane

Conjugate bases for the given compounds :

More the s-character more is the electronegativity, and stable is the conjugate base, or in other words, that compound is more acidic.
For prop-1-yne, the s character is 50%
For prop-1-ene, the $s{p}^3$ hybridised carbon is more acidic because conjugate base formed is stabilised by resonance effect.
For propane, the anion is destablised by $+I$ effect, it is least acidic.
Since, terminal alkyne is more acidic than alkene.
So, acidic character follows the order :
Alkyne> Alkene> Alkane
The correct option is (b)