Question

Arrange the following three alcohols according to the rising boiling point, find the answer based on the forces that work between the molecules (London forces, polarities, hydrogen bonds).

I)       1-propanol, CH3CH2CH2OH;

II)     1,2-propanediol, CH3CH(OH)CH2OH;

III)    1,2,3-propanetriol, (glycerol), HOCH2CH(OH)CH2OH.

choose one

a. I, II, III

b. III,II, I

c. II, I, III

d. I, III, II

e. III, I, II

Answer 1

1,2,3 tripropanol has highest boiling point followed by 1,2 propanediol and propanol.

answer is option a.

Explanation- This is because in 1,2,3 propanetriol there are 3 hydroxyl groups which undergoes Hydrogen bonding with other molecules and hence makes the interaction stronger whereas in 1,2 propanediol there are two hydroxyl (OH) groups and in propanol there is one OH group.

These OH groups are responsible for hydrogen bonding , more the Hydrogen bonding, more stronger the interactions and high will be the boiling point .

Hydrogen bonding- Hydrogen bond is the interaction between two atoms, one of the atom is hydrogen and other is the electronegative atom such as Oxygen, Fluorine, Nitrogen.