Four pairs of compounds (A) - (D) are given below. Indicate, in each pair, which compound can be more effectively hydrogen bonded. (a) \(\mathrm{CH}_{3} \underset{(\mathrm{I})}{\mathrm{CH}_{2}} \mathrm{OH}\) and \(\mathrm{CH}_{3}-\underset{(\mathrm{IH})}{\mathrm{O}-\mathrm{CH}_{3}}\) (b) \(\underset{\text { (I) }}{\left(\mathrm{CH}_{3}\right)}_{3} \mathrm{~N}\) and \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\) (c) \(\mathrm{HOCH}_{2}-\left(\mathrm{CH}_{2}\right)_{4}-\mathrm{CH}_{2} \mathrm{OH}\) and \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}_{\text {(II) }}{\mathrm{C}} \mathrm{HOHCH}_{3}\) (d) \(\mathrm{CH}_{3} \underset{\text { (I) }}{\mathrm{CH}_{2}} \mathrm{OH}\) and \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{SH}\) (a) \((\mathrm{A})-(\mathrm{I}),(\mathrm{B})-(\mathrm{I}),(\mathrm{C})-(\mathrm{I}),(\mathrm{D})-(\mathrm{I})\) (b) (A) - (I), (B) - (II), (C) - (I), (D) - (II) (c) \((\mathrm{A})-(\mathrm{I}),(\mathrm{B})-(\mathrm{I}),(\mathrm{C})-(\mathrm{II}),(\mathrm{D})-(\mathrm{II})\) (d) (A) - (I), (B) - (II), (C) - (I), (D) - (I)

Step by step solution

01

Pair (a) - comparison

For the first pair, \(\mathrm{CH}_{3} \underset{(\mathrm{I})}{\mathrm{CH}_{2}} \mathrm{OH}\) [compound (I)] has an OH group that can readily form hydrogen bonds with other molecules, while the ether \(\mathrm{CH}_{3}-\underset{(\mathrm{IH})}{\mathrm{O}-\mathrm{CH}_{3}}\) [compound (IH)] has an oxygen atom with lone pairs but no hydrogens bound to it, making it less effective at forming hydrogen bonds.

02

Pair (a) - Answer

Compound (I) can form more effective hydrogen bonds in the pair (a).

03

Pair (b) - comparison

In the given pair, compound (I) \(\underset{\text { (I) }}{\left(\mathrm{CH}_{3}\right)}_{3} \mathrm{~N}\) has a nitrogen atom with a lone pair, but no hydrogens covalently bound to it (tertiary amine). On the other hand, compound (II) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\) has an amino group with two hydrogens covalently bound to nitrogen, making it an effective hydrogen bond donor.

04

Pair (b) - Answer

Compound (II) can form more effective hydrogen bonds in the pair (b).

05

Pair (c) - comparison

In this pair, compound (I) \(\mathrm{HOCH}_{2}-\left(\mathrm{CH}_{2}\right)_{4}-\mathrm{CH}_{2} \mathrm{OH}\) has two OH groups on the ends, which make it an effective hydrogen bond donor. In comparison, compound (II) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}_{\text {(II) }}{\mathrm{C}} \mathrm{HOHCH}_{3}\) has only one OH group but has more steric hindrance due to the large tertiary carbon group. This steric hindrance prevents it from forming effective hydrogen bonds.

06

Pair (c) - Answer

Compound (I) can form more effective hydrogen bonds in the pair (c).

07

Pair (d) - comparison

Comparing the last pair, compound (I) \(\mathrm{CH}_{3} \underset{\text { (I) }}{\mathrm{CH}_{2}} \mathrm{OH}\) has an OH group, which makes it a good hydrogen bond donor, while compound (II) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{SH}\) has an SH group, which is weaker at forming hydrogen bonds compared to the OH group.

08

Pair (d) - Answer

Compound (I) can form more effective hydrogen bonds in the pair (d).

09

Summary of Answers

(a) Compound (I) (b) Compound (II) (c) Compound (I) (d) Compound (I)

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