Aldehydes And Ketones

1. Definition: Rosenmund reduction is a chemical reaction used to convert acid chlorides (acyl chlorides) into aldehydes.
2. Reagents: Hydrogen gas (H ) is passed through the solution in the presence of a catalyst, which is Palladium (Pd) deposited on Barium Sulphate (BaSO ). The catalyst is often poisoned with sulfur or quinoline to prevent further reduction to alcohols.
3. Reaction:
R-COCl + H R-CHO + HCl
4. Example: Benzoyl chloride is reduced to Benzaldehyde.
C H COCl + H C H CHO + HCl

We compare the acid strengths based on the stability of their conjugate bases and pK values.
Acetic acid (CH COOH) has a pK of 4.76. Propanoic acid (CH CH COOH) has a pK of 4.88.
Benzoic acid (C H COOH) has a pK of 4.20. The phenyl group exerts an electron-withdrawing effect (due to sp carbons) which stabilizes the carboxylate ion relative to alkyl groups.
Phenylacetic acid (C H CH COOH) has a pK of 4.31. The -I effect of the phenyl ring is diminished by the intervening CH group compared to direct attachment in Benzoic acid.
Since a lower pK indicates a stronger acid, Benzoic acid (pK 4.20) is the strongest among the given options.

Lithium Aluminium Hydride (LiAlH ) is a strong reducing agent.
It reduces carboxylic acids (-COOH) directly to primary alcohols (-CH OH).
The reaction is: C H COOH C H CH OH.
The product C H CH OH is named Benzyl Alcohol.

Vinegar is a common household item used for cooking and preservation.
Chemically, it consists of a dilute solution of acetic acid in water (typically 5-8%).
The IUPAC name for acetic acid is Ethanoic acid.

1. Lower carboxylic acids (like Methanoic acid, Ethanoic acid) have a polar carboxyl group (-COOH).
2. The oxygen atoms in the carboxyl group and the hydrogen atom of the -OH group can form hydrogen bonds with water molecules.
(R-COOH OH )
3. This extensive hydrogen bonding allows the acid molecules to mix freely with water.
4. As the size of the hydrophobic alkyl chain (R) increases, the solubility decreases because the hydrophobic interaction overcomes the hydrogen bonding.