Problem

Compound X (molecular formula C7H6O) shows the following:

1. Gives orange precipitate with 2,4-DNP
2. Gives silver mirror with Tollens' test
3. Does NOT give yellow precipitate with I2/NaOH
4. With concentrated NaOH, gives two products: Y and Z. Y gives effervescence with Na (–OH group confirmed), and Z is an ionic compound (sodium salt).

Identify X, Y, and Z. Name all reactions involved.

Step-by-Step Solution

Step 1 — Determine functional group from test 1: Positive 2,4-DNP → C=O group present (aldehyde or ketone).

Step 2 — Distinguish aldehyde from ketone using test 2: Positive Tollens' test → X is an aldehyde (RCHO).

Step 3 — Identify the type of aldehyde from test 3: Negative iodoform → X does NOT have the CH3CO- group. So X is NOT acetaldehyde (CH3CHO). X is an aldehyde without a methyl group adjacent to C=O.

Step 4 — Determine from molecular formula: C7H6O with degree of unsaturation = (2×7 + 2 - 6)/2 = (16-6)/2 = 5. Five degrees of unsaturation = benzene ring (4 from ring + pi) + C=O (1) = 5. Therefore X contains a benzene ring + aldehyde group. X = benzaldehyde (C6H5CHO).

Step 5 — Reaction with concentrated NaOH: Benzaldehyde has no alpha-H → Cannizzaro reaction: $2\text{C}_6\text{H}_5\text{CHO} \xrightarrow{\text{conc. NaOH}} \text{C}_6\text{H}_5\text{COO}^-\text{Na}^+ + \text{C}_6\text{H}_5\text{CH}_2\text{OH}$

Y = Benzyl alcohol (C6H5CH2OH) — gives effervescence with Na (–OH group, alcoholic). Z = Sodium benzoate (C6H5COONa) — ionic, soluble salt.

Reactions involved: (i) Nucleophilic addition with 2,4-DNP (condensation), (ii) Oxidation by Tollens' (Tollens' test), (iii) Cannizzaro reaction with conc. NaOH.