?Ethylene glycol \(\left(\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}\right)\), the

Chapter 11, Problem 11.27

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Ethylene glycol \(\left(\mathrm{HOCH}_{2} \mathrm{CH}_{2} \mathrm{OH}\right)\), 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 \(\left(\mathrm{CH}_{3} \mathrm{OCH}_{2} \mathrm{CH}_{2} \mathrm{OCH}_{3}\right)\) 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?

Text Transcription:

 (HOCH_2CH_2OH)

198^{\circ} C

(CH_3CH_2OH)

78^{\circ} C

(CH_3OCH_2CH_2OCH_3)

83^{\circ} C

(CH_3CH_2OCH_3)

11^{\circ} C

CH_3