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SolutionsEsterification of Alcohols

1. Name the esters

  1. CH3COOCH2CH3
  2. HCOOCH3
  3. CH3CH2COOCH(CH3)2
  1. Ethyl acetate (ethyl ethanoate).
  2. Methyl formate (methyl methanoate).
  3. Isopropyl propanoate.

2. Tosylates

What is obtained when 1-butanol is treated with p-toluenesulfonyl chloride in pyridine and then with NaCN?

First butyl tosylate, CH3CH2CH2CH2OTs; then cyanide displaces the tosylate (an excellent leaving group) by SN2, giving pentanenitrile, CH3CH2CH2CH2CN.

3. Configuration

When the tosylate of (R)-2-butanol is formed, does the configuration of the carbon change? And in the subsequent substitution with NaI?

Not when the tosylate is formed: the O–H bond is broken, not the C–O bond. In the SN2 with iodide it does: inversion takes place and (S)-2-iodobutane is obtained.

4. Why pyridine?

Why is pyridine added in the formation of tosylates?

To neutralize the HCl formed (as pyridinium chloride), which drives the reaction and avoids side reactions in acidic medium.

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