NMR analysis of Fischer Esterification. 3, Draw the chemicalstructures of the ma

Question

NMR analysis of Fischer Esterification. 3, Draw the chemicalstructures of the main reaction of an esterification (pg. 1014 Kein)reaction using the folowing. Acetic Acid, 3methybutanol. Amberlyst 15, Ether (the solvent) and the Acetate Ester product. 4. After 30 minutes ofrenux using a 50% mole ratio of s an aliquot was assessed by HNMR. Use the following hydrogen labels to comelate with the appropriate HNMR peaks in the spectrum shown below. Explain the potential impurities which comespond with a Impurity triplet at 358 ppm b. Impurity singlet at 1.95 ppm c. Impurity doublet overlapping with the 6H doublet of the product at 0.85 ppm

Explanation / Answer

3. The reaction is shown below

                                                          catalyst  

CH3COOH + (CH3)2CHCH2CH2OH ---------> CH3COOCH2CH2CH(CH3)2 + H2O

4. Given the crude NMR for the reaction mixture after 30 min

5. The peaks shows are for,

a. Triplet at 3.58 ppm for the -CH2 protons of 3-methylbutanol protons between oxygen and CH2 group

b. singlet at 1.95 ppm for the -CH3 protons of acetic acid next to C=O group

c. doublet at 0.85 ppm for the CH3's of 3-methylbutanol next to CH group

6. From the given NMR

a. peaks for ester are at 0.9 ppm (2CH3's), 1.5 ppm (CH2 next to CH3), 1.7 ppm (CH2 between CH2's), 2.1 ppm (CH3 next to C=O), 4.1 ppm (CH2 next to oxygen)

b. overlaping peaks is at 0.9 ppm with that of CH3's os the strating material

c. integration of protons associated with C-5 is 3

d. For alcohol the integration is 6

e. Integration for 0.9 ppm peak is 6

f. Impurity is starting alcohol integrating for 6H

g. the reaction has gone to 30% (approx) completion

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