Greater the electronegative atom attached to the carbon chain, greater will be its acidic nature, i.e. F3C−C≡CH is the most acidic compound. Alkyl group (−CH3) decreases the acidic nature hence, lesser the alkyl group in carbon chain, greater will be its acidic nature. i.e. ‌ Less ‌−CH3‌‌‌ two ‌−CH3‌ groups ‌ Order of acidic nature depends on alkyne > alkene > alkane (≡)‌‌(=)‌‌(−) Hence, order of acidity is More electronegative (II) >CH3−C≡CH>CH3C≡CCH3 Only one −CH3 (I) ‌‌ two CH3 groups (III) >CH3CH=CHCH3 i.e II>I>III>IV.