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JEE Main levelSingle correct optionDifficulty 2 of 3el175

Two synthetic detergents have the same sulphonate head. One has an unbranched dodecyl chain, the other a highly branched chain. Which statement is correct?

  1. AThe unbranched one is not degradable because it is a straight hydrocarbon
  2. BBoth are equally biodegradable because the head group is the same
  3. CThe branched one is degraded faster because it has more tertiary carbons
  4. DThe unbranched one is degraded faster by bacteria, so the branched one leaves persistent foam in rivers

Answer: D

Microorganisms degrade unbranched chains efficiently, whereas branched chains resist degradation. Non-degraded detergent accumulates and produces foam and water pollution. Hence the unbranched isomer is the biodegradable one.
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