Alcohols with short carbon chains are soluble in water, but solubility falls sharply as the chain lengthens because
Correct answer: C. the growing non polar hydrocarbon chain cannot form hydrogen bonds with water and dominates the molecule
- A. the hydroxyl group disappears in longer molecules
- B. long chain alcohols are gases
- C. the growing non polar hydrocarbon chain cannot form hydrogen bonds with water and dominates the molecule
- D. longer alcohols react with water
Explanation
Methanol, ethanol and propan-1-ol mix with water in all proportions because the hydroxyl group hydrogen bonds effectively, but as the chain grows the hydrophobic portion outweighs it and solubility falls until the higher alcohols are essentially insoluble. Branching increases solubility slightly by making the molecule more compact. The same principle explains why soaps need a hydrophilic head on a long tail.
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About Alcohols
Alcohols contain a hydroxyl group attached to a saturated carbon atom and are classified as primary, secondary or tertiary. Their nomenclature, hydrogen bonding, acidity, oxidation, dehydration, reaction with sodium and conversion to haloalkanes are covered, along with the distinction between alcohols and phenols, where the hydroxyl group is attached directly to an aromatic ring.
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535 free Alcohols and Phenols MCQs from Chemistry, each with the correct answer and an explanation. Unlimited attempts, no account needed.
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