Alcohols, Phenols and ethers:-Important and conceptual questions.

1. Boiling points of alcohols are higher than aldehydes , ketones of corresponding/ comparable molecular mass.

2. Phenol is acidic whereas ethanol ( alcohols) are neutral. Explain why?

3. Arrange the followings in increasing order of their acidic strength and give the reason.

CH₃-CH₂-CH₂-OH, (CH₃)₃ C-OH, (CH₃)₂CH-OH

4. Arrange the followings in increasing order of their acidic strength and give the reason.

5. Both Phenol and phenoxide ions stabilize by resonance than why is phenol basic?

Answer-

1. Due to presence of intermolecular hydrogen bonding in alcohols which is stronger than dipole -dipole attraction forces in carbonyl compounds( aldehydes and ketones)

2. Phenoxide ion stabilizes by resonance( mesomeric effect) whereas alcoxide ion destabilized by + I (Inductive) effect of alkyl group.

3. (CH₃)₃ C-OH  <  (CH₃)₂CH-OH  < CH₃-CH₂-CH₂-OH

Reason – Due to decrease in number of alkyl groups on Carbon attached to OH group the stability of alkoxide ion increases.

4.The phenoxide ion is stabilized by electron withdrawing nitro group by delocalising negative charge whereas phenoxide ion is destabilised by electron releasing methyl group, which increases negative charge.

5. Resonating structure of phenol is less stable because forming bipolar resonating (Unstable ) structure whereas in resonating structure of phenoxide , negative charge delocalizes to stabilize it.