Question

Question: Classify each solvent as protic or aprotic.

1. (CH₃)₂CHOH
2. CH₃NO₂
3. CH₂Cl₂
4. NH₃
5. N(CH₃)₃
6. HCONH₂

Short answer

Answer

1. Protic solvent.
2. Aprotic solvent.
3. Aprotic solvent.
4. Protic solvent.
5. Aprotic solvent.
6. Protic solvent.

Step-by-step solution

Protic solvents

The solvents are classified as polar solvents if they have a hydrogen atom bonded to an electronegative atom such as nitrogen, oxygen, or fluoride.

The polar solvents are able to donate protons very easily to the solute molecules.

The polar solvents result in the formation of hydrogen bonds with the solute molecules. Water is a very commonly used polar solvent.

Aprotic solvents

The aprotic solvents are not able to donate a hydrogen atom. They do not contain any hydrogen atom which is dissociable.

The aprotic solvents are incapable of forming hydrogen bonds.

The classification of the given compounds as protic and aprotic solvents

a. (CH₃)₂CHOH

The given compound is a secondary alcohol. It contains one polar O-H bond and is able to donate a proton. (CH₃)₂CHOH is, therefore, a protic solvent.

b. CH₃NO₂

The given compound is nitromethane. It is a polar solvent due to the presence of a nitro group. It is an aprotic solvent because of its inability to lose a proton. This compound does not have any O-H or N-H bond in it.

c. CH₂Cl₂

The name of this compound is dichloromethane. It is a polar compound due to the presence of highly electronegative chlorine atoms. It is an aprotic solvent because it cannot lose a proton. There are no C-H and N-H bonds in this compound.

d.NH₃

This compound is known as ammonia. It is a polar solvent due to the presence of lone pair of electrons on the nitrogen atom. Due to the high electronegativity of nitrogen and the presence of lone pair of electrons, it has a very strong dipole moment.

Ammonia molecule does have an N-H bond, and it can lose a proton; hence, it is a protic solvent. It is also capable of forming hydrogen bonds.

e. N(CH₃)₃

This compound is known as trimethylamine. This molecule has methyl groups HCONH₂ attached to the highly electronegative nitrogen atom. It cannot release a proton; hence, N(CH₃)₃ is an aprotic solvent.

f. HCONH₂

This compound is known as formamide. It is polar in nature. It contains one N-H bond and is able to lose a proton; therefore, it is a polar protic solvent.