Ethylene glycol (HOCH \(\left._{2} \mathrm{CH}_{2} \mathrm{OH}\right)\), the
major substance in antifreeze, has a normal boiling point of \(198^{\circ}
\mathrm{C}\). By comparison, ethyl alcohol \(\left(\mathrm{CH}_{3}
\mathrm{CH}_{2} \mathrm{OH}\right)\) boils at \(78^{\circ} \mathrm{C}\) at
atmospheric pressure. Ethylene glycol dimethyl ether \(\left(\mathrm{CH}_{3}
\mathrm{OCH}_{2} \mathrm{CH}_{2} \mathrm{O} \mathrm{CH}_{3}\right)\) has a
normal boiling point of \(83{ }^{\circ} \mathrm{C},\) and ethyl methyl ether
\(\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OCH}_{3}\right)\) has a normal
boiling point of \(11^{\circ} \mathrm{C}\). (a) Explain why replacement of a
hydrogen on the oxygen by a \(\mathrm{CH}_{3}\) group generally results in a
lower boiling point. (b) What are the major factors responsible for the
difference in boiling points of the two ethers?