Question

Which among the following are the correct statements?
Statement 1: Ethylamine is soluble in water, whereas aniline is not.
Statement 2: Ethylamine forms hydrogen bonds with water molecules.
a.) Assertion is correct, reason is incorrect.
b.) Assertion is incorrect, reason is correct.
c.) Both assertion and reason are correct, reason is correct for assertion.
d.) Both assertion and reason are correct but reason is not correct for assertion.

Answer 1

Hint: Lower aliphatic amines are soluble in water because they can form hydrogen bonds with water molecules. Aniline has a presence in the benzene group. Benzene group is hydrophobic. Solubility is dependent on formation of hydrogen bonds. When small alkyl groups like methyl are present, there is no steric hindrance in formation of hydrogen bonds.

Complete step by step answer:
-Intermolecular forces are forces of attraction and repulsion between neighboring molecules.
-Hydrogen bond is a type of intermolecular force. It exists in molecules in which highly polar bonds such as N-H, O-H, H-F are present.

-Strength of hydrogen bond is determined by interaction between lone pairs of electronegative atoms and hydrogen atoms.
-In primary amines, intermolecular associations are more as there are two hydrogen atoms available for hydrogen bonds.
-Steric hindrance plays an important role in formation of hydrogen bonds. When small alkyl groups like methyl are present, there is no steric hindrance in formation of hydrogen bonds. In case of a bigger alkyl group like ethyl, there will be steric hindrance to hydrogen bonding.
-As in ethylamine, there is no steric hindrance, it can form hydrogen bonds with water molecules and is soluble in water. In Aniline, a hydrophobic group like benzene is present so it is moderately soluble in water.
So, the correct answer is “Option C”.

Note: primary and secondary amines are involved in intermolecular association due to hydrogen bond. In secondary amines, there are hydrogen atoms available for hydrogen bonds. In tertiary amine, no hydrogen atom is available for hydrogen bonds so there is no intermolecular association.