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SolutionsReactivity

1. Why don’t they react?

Ethyl bromide reacts with NaI in acetone, but ethanol does not. Why?

Because hydroxide, HO−, is a very strong base and hence a very bad leaving group, whereas bromide is a very weak base and a good leaving group.

2. How to activate the OH

Give three ways of turning the OH into a good leaving group.

  1. Protonate it with a strong acid: water leaves.
  2. Turn it into a sulfonate (tosylate, mesylate).
  3. Turn it into an ester of an inorganic acid with SOCl2 or PBr3.

3. The four reactions

Match each transformation of 1-propanol with the type of reaction:

  1. → propanal
  2. → propene
  3. → 1-bromopropane
  4. → propyl acetate
  1. Oxidation (with PCC).
  2. Elimination (dehydration with acid and heat).
  3. Substitution (with PBr3 or HBr).
  4. Esterification (with acetic acid or acetyl chloride).

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