Advices For Studying Organic Chemistry

2) If the substrate is 3°, elimination is the exclusive result.

3) Substitution is favored over elimination at lower temperatures.

3. Example of Williamson ether synthesis:

CH 3 CH 2 CH 2 O O −Na

O

H NaH +

Propyl alcohol Sodium propoxide

CH 3 CH 2 I

+ I−

Ethyl propyl ether

70%

CH 3 CH 2 CH 2 + H H

CH 3 CH 2 CH 2 CH 2 CH 3 Na+

11.15C TERT-BUTYL ETHERS BY ALKTLATION OF ALCOHOLS.

PROTECTING GROUPS

1. 1° alcohols can be converted to tert-butyl ethers by dissolving them in a strong
   acid such as sulfuric acid and then adding isobutylene to the mixture (to minimize
   dimerization and polymerization of the isobutylene).

RCH 2 OH + H 2 C CCH 3

CH 3

H 2 SO (^4) CCH
3
CH 3
CH 3
RCH 2 O
tert-butyl
protecting
group

1. The tert-butyl protecting group can be removed easily by treating the ether with
   dilute aqueous acid.

2. Preparation of 4-pentyn-1-ol from 3-bromo-1-propanol and sodium acetylide:
   
   
   1. The strongly basic sodium acetylide will react first with the hydroxyl group.
      HOCH 2 CH 2 CH 2 Br +NaCCH NaOCH 2 CH 2 CH 2 Br + HCCH
      3-Bromo-1-proponal
   
   
   
   

2. The –OH group has to be protected first.