The compounds below are base pairs used to form supramolecular polymers (Org. Lett. 2011, 240). They are held together by three intermolecular hydrogen bonds and each contains one intramolecular hydrogen bond. Which atom in structure B forms a hydrogen bond with the circled hydrogen in structure A?
A) 1
B) 2
C) 3
D) 4

Question

The compounds below are base pairs used to form supramolecular polymers (Org. Lett. 2011, 240). They are held together by three intermolecular hydrogen bonds and each contains one intramolecular hydrogen bond. Which atom in structure B forms a hydrogen bond with the circled hydrogen in structure A? 
A) 1 
B) 2 
C) 3 
D) 4

Quizplus · Accepted Answer

The circled hydrogen in structure A is the hydrogen on the nitrogen atom. In structure B, the nitrogen atom forms an intramolecular hydrogen bond with the oxygen atom with a lone pair of electrons. Therefore, the only available hydrogen atom for intermolecular hydrogen bonding is the one on the carbon atom attached to the nitrogen atom. This makes choice C the correct answer.

The Compounds Below Are Base Pairs Used to Form Supramolecular