HO–CH₂–CH₂–OH + HIO₄ → 2 HCHO (formaldehyde) + HIO₃ + H₂O

Explanation (2–3 marks)

• Periodic acid cleaves –CHOH–CHOH (vicinal diol)
• C–C bond breaks
• Each carbon forms a carbonyl compound
• Since both carbons are –CH₂OH → gives 2 molecules of formaldehyde

A. CH₃(CH₂)₃NH₂ → (i) Alkaline hydrolysis

B. CH₃C≡CH → (ii) With KOH (alcohol) and CHCl₃ produces bad smell

C. CH₃CH₂COOCH₃ → (iii) Gives white ppt. with ammoniacal AgNO₃

D. CH₃CH(OH)CH₃ → (iv) With Lucas reagent cloudiness

Glycerol + excess HI → 2-iodopropane (isopropyl iodide) + I₂ + H₂O

Explanation

• First, –OH groups are replaced by –I
• Then elimination and rearrangement occur
• Finally, the most stable secondary alkyl iodide is formed

Ethylene glycol (ethane-1,2-diol)

• Ethylene glycol has two –OH groups, so it forms strong hydrogen bonding.
• It lowers the freezing point of water (freezing point depression).
• It also raises the boiling point, preventing overheating.

✔ Used as antifreeze because it prevents water from freezing in cold conditions.

Other than ethylene glycol, there are a few compounds used as antifreeze:

Other Antifreeze Compounds

1. Propylene glycol (propane-1,2-diol)

• Less toxic than ethylene glycol
• Used in safer antifreeze formulations (food-grade systems)

2. Glycerol (glycerine, propane-1,2,3-triol)

• Has three –OH groups → strong H-bonding
• Good freezing point depression
• Used in older or special applications

3. Methanol / Ethanol

• Also lower freezing point
• But ❌ not preferred because:
  • Highly volatile
  • Flammable
  • Evaporate easily

Step 1: Calculate DU

Formula:$$DU = \frac{2C + 2 – H}{2}$$

For C₆H₁₄O (ignore O in DU):$$DU = \frac{2(6) + 2 – 14}{2} = \frac{12 + 2 – 14}{2} = 0$$

Meaning of DU = 0

• No double bond
• No triple bond
• No ring

So, all structures are open-chain saturated alcohols

1. Picric acid has three –NO₂ groups which are strong electron-withdrawing groups.
2. These groups stabilize the conjugate base (picrate ion) by resonance and –I effect.
3. Formic acid has only one –COOH group, so its conjugate base is less stabilized.
4. Greater stabilization of conjugate base ⇒ higher acidity, so picric acid is stronger.

HCOOH (Picric Acid)

Picric acid is soluble in NaHCO₃ solution?

Picric acid (2,4,6-trinitrophenol) is a strong acid due to the presence of three –NO₂ groups, which strongly withdraw electrons and stabilize the phenoxide ion. Because of this high acidity, it can react even with a weak base like NaHCO₃.

Reaction:
Picric acid + NaHCO₃ → Sodium picrate (soluble) + CO₂ + H₂O

So, it dissolves in NaHCO₃ with effervescence of CO₂ gas.