Answer to Question #153361 in Organic Chemistry for Rashinda

Question

Distinguish between the following pairs of organic comounds including a chemical test.

(i) CH3C≡CCH3 and CH3CH2C≡CCH3

(ii) C6H5COCH3 and C6H5CHO

Answer 1

(i) Hydrogenate the substance on Pd/C. If the product is liquid at room temperature, it was pent-2-yne, but if it is a gas, than it was but-2-yne.

C₄H₆ + 2H₂ = C₄H₁₀ (gas)

C₅H₈ + 2H₂ = C₅H₁₂ (liquid)

(ii) Add KMnO₄ + H₂SO₄ solution. If you notice bubbles (CO₂) occuring, that will mean that it is a ketone, otherwise it is an aldehyde.

5PhCOCH₃ + 8KMnO₄ + 12H₂SO₄ $\to$ 5PhCOOH + 8MnSO₄ + 17H₂O + 4K₂SO₄ + 5CO₂ (gas)

5PhCHO + 2KMnO₄ + 3H₂SO₄ $\to$ 5PhCOOH + 2MnSO₄ + 3H₂O + K₂SO₄