Question of 87
Q.(a) Differentiate between Methanoic acid and Ethanoic acid. [3]
(b) Write IUPAC names of the following compounds: [2]
(i) CH3-CH2-N(CH3)-CH3
(ii) CH3-CH(Br)-CONH2
Bihar BsebBihar Board Intermediate 2025Subjective· 5mImportance★★★★★
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Start your 14-day free trial to unlock the full solution →(a) HCOOH has an aldehyde-like H so it is reducing and a stronger acid; CH3COOH is non-reducing and weaker. (b) N,N-dimethylethanamine and 2-bromopropanamide.
Part (a) — Methanoic acid vs Ethanoic acid:
| Property | Methanoic acid (HCOOH) | Ethanoic acid (CH3COOH) |
|---|---|---|
| Structure | H-COOH — a hydrogen atom attached to -COOH | CH3-COOH — a methyl group attached to -COOH |
| Aldehyde character | Contains a -CHO-like grouping (H-C=O), so it acts as a reducing agent | No aldehyde grouping; not a reducing agent |
| Tollens' reagent | Reduces it, giving a silver mirror | No reaction |
| Fehling's solution | Reduces it, giving red Cu2O | No reaction |
| Acid strength | Stronger acid (Ka larger; no electron-donating group) | Weaker acid (the +I effect of CH3 destabilises the anion) |
Thus formic acid is unique among carboxylic acids in also behaving like an aldehyde (reducing Tollens' and Fehling's reagents), while acetic acid does not.
Part (b) — IUPAC names: …
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