Q.Alkanes and alkenes do not react with lithium amide. Give reason.

Step 1. Recall why terminal alkynes ARE acidic. Section 15.3.4 explains that a terminal alkyne's C-H sits on an sp-hybridised carbon (50% s-character), and because s-orbital electrons sit close to the nucleus and are held tightly, this makes the carbon relatively electronegative, so its hydrogen can be given up as a proton to a strong enough base like lithium amide.

Step 2. Compare with alkanes and alkenes. An alkane's C-H sits on an sp3 carbon (25% s-character) and an alkene's C-H sits on an sp2 carbon (33% s-character) -- both have lower s-character, and correspondingly lower electronegativity at the carbon, than the sp carbon of a terminal alkyne. Their C-H bonds are therefore far less acidic. …

Comparing the s-character (and hence acidity) of sp3, sp2 and sp carbon-hydrogen bonds to explain why only terminal …

• Saying lithium amide 'isn't strong enough' -- the real issue is on the OTHER side of the acid-base reaction: alkane/alkene C-H bonds simply aren't acidic enough, regardless of how strong the base is. …