Question

hoq to distinguish
1. 2-pentanone and 3-pentanone
​2.oxalic acid and benzoic acid

Answer 1

1. 2-pentanone and 3-pentanone can be distinguished by iodoform test. Iodoform test is shown by methyl ketone (CH₃CO) group. 2-pentanone has methylketone and it forms iodoform whereas 3-pentanone show negative iodoform test.

CH₃COCH₂CH₂CH₃ + I₂ -------------​ CHI₃ + NaOOCCH₂CH₂CH₃
NaOH

2. Oxalic acid (aliphatic) and aromatic acid is distinguished by treating the neutral solution of the acid (by adding ammonium hydroxide) with neutral FeCl​₃. Oxalic acid gives yellow precipitate and benzoic acid gives buff precipitate.
Another test to distinguish is add dil. H₂SO₄ to oxalic acid, warm the solution and add few drops of Potassium permanganate, the permanganate colour is decolourised. Whereas benzoic acid give negative answer for this.