Given below are two statements: In the light of the above statements, choose the most appropriate answer from the options given below:
- Statement I is incorrect but Statement II is correct
- Both Statement I and Statement II are correct
- Statement I is correct but Statement II is incorrect
- Both Statement I and Statement II are incorrect
Answer
(2) Both Statement I and Statement II are correct
Solution
Statement I: In neopentane, C(CH3)4, all twelve H atoms are equivalent (each is a 1° H on one of four identical -CH3 groups attached to the same quaternary carbon).
Replacing any one H gives the same product, e.g. only one monochloro derivative, (CH3)3C-CH2Cl. Statement I is correct.
Statement II: Melting point depends on how well the molecules pack in the crystal lattice. Neopentane is nearly spherical and highly symmetrical, so it packs far better than the zig-zag n-pentane.
m.p. of neopentane (256.5 K) > m.p. of n-pentane (143.3 K). Statement II is correct.
(Boiling point shows the opposite order, because branching reduces surface area.)
Answer: (2)