Question

Question: Which of the following molecules can hydrogen bond to another molecule of itself? Which can hydrogen bond with water?

a.

b.

c.

d.

Short answer

Answer

a. 1,1,1-tribromoethane does not form any hydrogen bond with another molecule or itself. It does not form a hydrogen bond with water.

b. Triethylamine can form a hydrogen bond with water.

c. Propanamide can form a hydrogen bond with another molecule of itself.

d. Methyl propionate can form a hydrogen bond with water.

Step-by-step solution

Hydrogen bonding

A hydrogen bond’s dissociation energy is based on its electronegativity. Two common kinds of hydrogen bonding are:

• intermolecular hydrogen bonding, and
• intramolecular hydrogen bonding.

Hydrogen bonding in compound a

The condition necessary for a compound to form a hydrogen bond to itself or another compound is that the molecule must comprise hydrogen bonded to oxygen, nitrogen, or fluoride.

1,1,1-tribromoethane does not contain such atoms, which makes it impossible to form any hydrogen bonding.

Hydrogen bonding in compound b

The hydrogen bonding in triethylamine is small as the hydrogen atom is not directly attached to the electronegative nitrogen atom.

The hydrogen atoms of the terminal methyl group interact with the oxygen atom of the water molecule via intermolecular hydrogen bonding.

The hydrogen bonding in triethylamine can be given as follows:

Hydrogen bonding in compound b

Hence, triethylamine can form a hydrogen bond with water.

Hydrogen bonding in compound c

The hydrogen atom connected to the nitrogen atom in propanamide interacts with the oxygen of another propanamide molecule, leading to the formation of intramolecular hydrogen bonding.

This kind of hydrogen bonding is stronger than intermolecular hydrogen bonding as it takes place within the molecule.

The hydrogen bonding in propanamide can be given as follows:

Hydrogen bonding in compound c

Hence, propanamide forms hydrogen bonding with another molecule of itself.

Hydrogen bonding in compound d

The oxygen atom of methyl propionate interacts with the hydrogen atom of the water molecule to form intermolecular hydrogen bonding. The hydrogen bonding in methyl propionate can be given as follows:

Hydrogen bonding in compound d

Hence, methyl propionate forms hydrogen bonding with water.