Lab 10: Phenacetin From Acetaminophen Via Williamson Ether

Question 1

Ether

Answer 1

O with two R groups

Question 2

Williamson ether synthesis steps

Answer 2

1. Depronation of alcohol by a suitable base to from an alkoxide ion
2. is an SN2 reaction where alkoxide acts as the nucleophile and alkyl halide acts as the electrophile

Question 3

Limits of Williamson ether is step 1

Answer 3

• acid-base reaction
• alcohols are not highly acidic species, so it is important to choose a base that is strong enough to facilitate the deprotonation
• otherwise alcohol is not a sufficient nucleophile to proceed with step 2 reaction

Question 4

Limits of step 2 of Williamson ether synthesis

Answer 4

-limits from SN2 apply

• choice of alkyl halide
• occur best with sterically unhindered alkyl halides, because nucleophile has to attack the electrophile carbon at the same time LG leaves.
• competition of elimination products
• alkoxide are good bases they can perform elimination reactions to convert alkyl halide to Alkene , more sterically hindered the more likely elimination favored
• secondary and tertiary do not yield ether products

Question 5

Factors that increase rate of SN2 Williamson ether

Answer 5

• reaction rate dependent on strength of nucleophile and substrate/leaving group
• weaker bases make better leaving groups
• so, alkyl iodides>alkyl bromides>alkyl chlorides

-solvent choice:polar aprotic b/c
-polar protic hydrogen bond and solvated the nucleophile, thus hindering its approach to the electrophile.
DMSO, DMF, ACN are good solvents

Question 6

Rotary evaporator

Answer 6

1. Solution under vacuum: lowering pressure above the liquid which decreases its boiling point and evaporates faster
2. Hot water bath: heats liquid brining it closer to the boiling point

Other advantages:
1.centrifugal and frictional forces created by rotating cause the solution to spread out over the flask= increase surface area for evaporation

2. Rotation helps prevent bumping