ester lecture notes
TRANSCRIPT
Esterification of Vanillin
Expt 24.1A1
Esters
Esterifications
• What will you be doing:
– convert a phenol (vanillin) to an ester (vanillin acetate) and recrystallize it.
Fischer Esterification
+ CH3CH2OHCH3C
O
OH CH3C
O
OCH2CH3 + H2OH3O+
acetic acid ethanol ethyl acetate
Fischer Esterification
RCO2H + R’OH RCO2R’
CH3CH2CH2C
O
OH
CH3CH2C
O
OH
CH3C
O
OH
CH3OH
CH3CH2OH
OH
OH
OH
Mechanism
Acetylation of Vanillin (Expt 24.1A1)
C
O
H
OCH3
OH
C
O
H
OCH3
O C CH3
O
NaOH(aq)
O
O O
vanillin vanillin acetate
Acetylation with Anhydrides
Pre-lab Preparation
• Read Expt 24.1A1– General background – Procedures: p. 483-484 for 24.1A1 (preparation of vanillin
acetate)
• Notebook (preparative lab)– All the usual sections– Table of reagents and products – Balanced Reaction– LR/TY– Procedures
• Two column format
• Synthesize vanillin acetate. – Get crude mp and mass. – Solvent pair recrystallization. – After it air-dries for at least 24 hours, get a
weight and melting point.
In Lab
After Lab
• Calculations– Actual yield of vanillin acetate– Theoretical yield recalculation if your quantities
of reagents changed from the pre-lab– % yield of vanillin acetate– % recovery recrystallization– % error in the melting point – crude and
recrystallized
After lab• Results and Discussion
– Comment on the synthesis of vanillin acetate (yield, purity, recovery).
Vanillin Acetate Procedures• Procedural summary:
• Put vanillin and NaOH in flask.• Heat if necessary.• Cool to RT.• Add ice and acetic anhydride.• Swirl periodically.• Filter and wash with cold water.• Crude mass and mp • Recrystallize from ethanol-water solvent pair.• Get MP
Procedural Considerations
• Purpose of NaOH.• Heat.• Purpose of crushed ice.• Swirling.• Cold water wash.• Solvent pair recrystallization
Quiz Considerations
1. Equations and stoichiometry
2. Purpose of all reagents
3. Pre-lab questions 2c, 4 - 6 on page 483
4. R&C 4 on page 485
5. Critical thinking questions 2 and 3, on page 488
Experimental Recap
Overall Reaction equation – Stoichiometry?
Setup (HW and glassware) –
Synthesis -Starting materialsSolventsReaction conditions
Isolation -
Purification -
Characterization -