See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Concept: Periodate (HIO4) cleaves vicinal diol units (adjacent OH groups). Each cleavage of one C–C bond between two carbons bearing OH groups consumes one equivalent of HIO4. Terminal CHOH gives an aldehyde (or HCHO if it is –CH2OH), internal CHOH gives a formic acid (HCO2H) fragment when it has OH on both neighboring carbons (i.e., it is a middle carbon), and a terminal CH3–CHOH gives acetaldehyde (CH3CHO). Step 1: Draw 1,2,3-butanetriol. The structure is: CH3–CH(OH)–CH(OH)–CH2(OH), i.e., carbons C1 through C4 where C2, C3, and C4 (using the numbering 1,2,3-butanetriol meaning OH at C1, C2, C3) — actually 1,2,3-butanetriol is: HO–CH2–CH(OH)–CH(OH)–CH3. So: C1 = CH2OH, C2 = CH(OH), C3 = CH(OH), C4 = CH3. Step 2: Identify vicinal diol pairs. Pair 1: C1(OH)–C2(OH) → one cleavage, consumes 1 eq. HIO4. Pair 2: C2(OH)–C3(OH) → one cleavage, consumes 1 eq. HIO4. Total: 2 equivalents of HIO4 consumed. Step 3: Determine cleavage products. Cleavage of C1–C2: C1 (–CH2OH, terminal) → HCHO (formaldehyde, HCH=O); C2 contributes to the other fragment. Cleavage of C2–C3: C2 (internal, between two OH-bearing carbons) → HCO2H (formic acid); C3 (–CH(OH)– adjacent to C4=CH3, terminal) → CH3CHO (acetaldehyde). Wait — C2 is cleaved on both sides (C1–C2 and C2–C3), so C2 gives HCO2H. C1 (terminal –CH2OH) gives HCHO. C3 (terminal –CH(OH)–CH3) gives CH3CHO. So products: HCHO (formaldehyde = HCH=O), HCO2H (formic acid), and CH3CHO (acetaldehyde = CH3–CH=O). HIO4 consumed: 2 equivalents. Step 4: Match to options. Option (b): 2 equivalents of HIO4 consumed & HCO2H, HCH=O & CH3–CH=O are formed. ✓ This matches exactly. Why other options fail: (a) Only 1 eq. HIO4 and gives a keto-acid — incorrect, both vicinal diol pairs are cleaved. (c) 3 eq. HIO4 and acetic acid — incorrect, there are only 2 vicinal diol pairs and acetic acid is not formed. (d) 2 eq. HIO4 but gives 2 eq. HCO2H and CH3CHO — incorrect, only 1 eq. formic acid is formed; the terminal CH2OH gives HCHO not formic acid. Therefore, the correct answer is B.