Carboxylic acids: acidic strength
- The correct order of decreasing acidity of the following aliphatic acids is : Answer: 3. HCOOH > CH₃COOH > (CH₃)₂CHCOOH > (CH₃)₃CCOOH Key idea: alkyl groups are electron-donating (+I) and destabilise the carboxylate io... 1
- The major product of the following reaction is :phthalic acid (benzene-1,2-dicarboxylic acid) + NH_3 strong\ heating Answer: 2. phthalimide (see figure) Phthalic acid reacts with ammonia to give the ammonium salt; strong heating removes water in two steps (... 1
- A mixture of 2.3 g formic acid and 4.5 g oxalic acid is treated with conc. H_2SO_4. The evolved gaseous mixture is passed through KOH pellets. Weight (in g) of the remaining product at STP will be Answer: 2. 2.8 Conc. H₂SO₄ dehydrates both acids. KOH absorbs CO₂ , so only CO remains. HCOOH→ CO+H₂O : 2.3 g / 46 = 0.05 mol, gives 0.05 mo... 1
- Carboxylic acids have higher boiling points than aldehydes, ketones and even alcohols of comparable molecular mass. It is due to their Answer: 4. formation of intermolecular H-bonding Carboxylic acids form strong intermolecular hydrogen-bonded dimers, so more energy is neede... 1
- The correct order of strengths of the carboxylic acids [I, II, III shown] is Answer: 1. II > III > I Key idea: an electron-withdrawing atom near COOH stabilises the carboxylate and raises acidity; the effect weakens w... 1