CHEM 344 Summer 2024 Final Exam (200 pts)
Name:
TA Name:
Exam Length = 120 min
DO NOT REMOVE ANY PAGES FROM THIS EXAM PACKET.
Directions for drawing molecules, reactions, and electron-pushing mechanisms:
Draw all lone pairs, bonds, arrows, formal charges, and stereochemistry explicitly in all molecular
structures.
Take care when drawing molecules and labeling them with NMR assignments that you do not change the
chemical formula. Examples for 2-methyl-2-butanol are shown below.
acceptable acceptable acceptable unacceptable unacceptable
Directions for all calculations:
Explicitly show all work on all calculations and include all important labels.
1
, 1) Methyl salicylate (oil of wintergreen) can be synthesized from acetylsalicylic acid (aspirin) via
transesterification and a Fischer esterification at two different sites in the molecule by reflux in methanol
and sulfuric acid. For this transesterification, use the procedure and accompanying spectra to answer
the associated questions below. (90 pts total)
Experimental procedure: Acetylsalicylic acid (1.129 g, 6.27 mmol) is dissolved in methanol (3.5 mL, 86.5
mmol) and conc. H2SO4 (0.3 mL) in a 10-mL round bottom flask. The reaction mixture is refluxed for 90
minutes, allowed to cool to room temperature, and transferred to a separatory funnel. Saturated aqueous
sodium bicarbonate solution (5 mL) is added to the reaction mixture and the funnel vented until bubbling
subsides. The aqueous layer is extracted twice with dicholoromethane (2 × 5 mL, = 1.33 g/cm3). The
combined organic layers are dried with solid anhydrous MgSO4. After gravity filtration and evaporation
of solvent, 0.256 g white solid are isolated. A sample of the crude material is submitted for 1H-NMR, 13C-
NMR and GC-MS analysis.
a) The desired product, methyl salicylate, exists as an equilibrium mixture of conformational isomers. The
four lowest conformational isomers are shown below. Rationalize the stability of conformers A and D
compared to conformers B and C, making specific reference to relevant conjugation, steric repulsions,
hydrogen-bonding, etc. (8 pts)
A B C D
2.3 kcal/mol 8.0 kcal/mol 7.9 kcal/mol 0.0 kcal/mol
2
Name:
TA Name:
Exam Length = 120 min
DO NOT REMOVE ANY PAGES FROM THIS EXAM PACKET.
Directions for drawing molecules, reactions, and electron-pushing mechanisms:
Draw all lone pairs, bonds, arrows, formal charges, and stereochemistry explicitly in all molecular
structures.
Take care when drawing molecules and labeling them with NMR assignments that you do not change the
chemical formula. Examples for 2-methyl-2-butanol are shown below.
acceptable acceptable acceptable unacceptable unacceptable
Directions for all calculations:
Explicitly show all work on all calculations and include all important labels.
1
, 1) Methyl salicylate (oil of wintergreen) can be synthesized from acetylsalicylic acid (aspirin) via
transesterification and a Fischer esterification at two different sites in the molecule by reflux in methanol
and sulfuric acid. For this transesterification, use the procedure and accompanying spectra to answer
the associated questions below. (90 pts total)
Experimental procedure: Acetylsalicylic acid (1.129 g, 6.27 mmol) is dissolved in methanol (3.5 mL, 86.5
mmol) and conc. H2SO4 (0.3 mL) in a 10-mL round bottom flask. The reaction mixture is refluxed for 90
minutes, allowed to cool to room temperature, and transferred to a separatory funnel. Saturated aqueous
sodium bicarbonate solution (5 mL) is added to the reaction mixture and the funnel vented until bubbling
subsides. The aqueous layer is extracted twice with dicholoromethane (2 × 5 mL, = 1.33 g/cm3). The
combined organic layers are dried with solid anhydrous MgSO4. After gravity filtration and evaporation
of solvent, 0.256 g white solid are isolated. A sample of the crude material is submitted for 1H-NMR, 13C-
NMR and GC-MS analysis.
a) The desired product, methyl salicylate, exists as an equilibrium mixture of conformational isomers. The
four lowest conformational isomers are shown below. Rationalize the stability of conformers A and D
compared to conformers B and C, making specific reference to relevant conjugation, steric repulsions,
hydrogen-bonding, etc. (8 pts)
A B C D
2.3 kcal/mol 8.0 kcal/mol 7.9 kcal/mol 0.0 kcal/mol
2
