12-Crown-4 binds with the alkali metal ions in the following order : $\mathrm{Li}^{+} \gg \mathrm{Na}^{+}>\mathrm{K}^{+}>\mathrm{Cs}^{+}$. It is due to the
(a)Right size of cation crown ether
(b)Change in entropy being positive
(c)Conformational flexibility of crown ether
(d)Hydrophobicity of crown ether
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
The 12-crown-4 cavity (≈1.2–1.5 Å) matches Li⁺ best; selectivity in crown ethers is governed by the size match between cation and cavity.