Organic Spectroscopy

Chem 203
Professor James S. Nowick

Problems from Previous Years' Exams

This archive includes six types of problems from the midterm and final exams of my Chem 203 Organic Spectroscopy class. The first three focus on infrared spectroscopy, mass spectrometry, and 1D NMR spectroscopy. The next focuses on using these three techniques together to determine the structures of organic compounds. The last two categories incorporate 2D NMR spectroscopy and are thus considered "advanced." The advanced spectral analysis problems focusing on analyzing 1- and 2D NMR spectra to address questions of stereochemistry. The advanced structure determination problems focus on using all of these techniques to determine the structures of organic compounds.

INFRARED (IR) SPECTROSCOPY PROBLEMS

2014 Midterm Exam Part I.1. (2014-MT-I.1.pdf)
Problem Type: Match aromatic compounds with IR spectra.
Techniques: IR spectroscopy.
Notes: A set of compounds with unusual functional groups. One of my favorites.

2013 Midterm Exam Part I.1. (2013-MT-I.1.pdf)
Problem Type: Match aromatic compounds with IR spectra.
Techniques: IR spectroscopy.
Notes: A set of aromatic compounds with similar structures but different functional groups.

2012 Midterm Exam Part I.1. (2012-MT-I.1.pdf)
Problem Type: Match aromatic compounds with IR spectra.
Techniques: IR spectroscopy.
Notes: A set of aromatic compounds with carbonyl and other functional groups.

2011 (fall) Midterm Exam Part I.1. (2011f-MT-I.1.pdf)
Problem Type: Match aromatic compounds with IR spectra.
Techniques: IR spectroscopy.
Notes: A set of aromatic compounds bearing different functional groups.

MASS SPECTROMETRY (MS) PROBLEMS

2014 Midterm Exam Part I.2. (2014-MT-I.2.pdf)
Problem Type: Interpret peaks of a large molecule, maitotoxin, in negative and positive ion modes
Techniques: Negative ion FAB and ESI mass spectrometry.
Notes: Concepts in mass, charge, and isotopomers. One of my favorites

2013 Midterm Exam Part I.2. (2013-MT-I.2.pdf)
Problem Type: Interpret peaks in an ESI mass spectrum.
Techniques: ESI mass spectrometry.
Notes: This is modern ESI MS problem that focuses on the concepts of mass, charge, and molecular formula.

2012 Midterm Exam Part I.2. (2012-MT-I.2.pdf)
Problem Type: Interpret peaks in EI and ESI mass spectra.
Techniques: EI and ESI mass spectrometry.
Notes: Concepts in fragmentation, isotope patterns, and molecular ions.

2011 (fall) Midterm Exam Part I.3. (2011f-MT-I.3.pdf)
Problem Type: Identify the transition metal complex from the isotope pattern.
Techniques: EI mass spectrometry.
Notes: Electron ionization (EI) mass spectra are shown for five transition metal acetylacetonate (acac) complexes.

NUCLEAR MAGNETIC RESONANCE (NMR) SPECTROSCOPY PROBLEMS

2014 Midterm Exam Part I.3. (2014-MT-I.3.pdf)
Problem Type: Interpret the 1H NMR spectrum of (S)-glycidyl benzyl ether.
Techniques: 1H NMR spectroscopy.
Notes: This problem gets to the heart of coupling and diastereotopicity. It is one of my all-time favorites.

2013 Midterm Exam Part I.3. (2013-MT-I.3.pdf)
Problem Type: Match regioisomeric aromatic compounds with 1H NMR spectra.
Techniques: 1H NMR spectroscopy.
Notes: This is a great little matching problem that gets to the heart of pattern recognition, coupling, and symmetry in 1H NMR spectroscopy.

2013 Midterm Exam Part I.4. (2013-MT-I.4.pdf)
Problem Type: Stereochemical determination by 1H NMR spectroscopy.
Techniques: 1H NMR spectroscopy.
Notes: This problem builds on some of my favorite concepts in sterochemical determination in a cyclohexane ring system (2-phenyl-1-cyclohexanol) from the coupling pattern.

2012 Midterm Exam Part I.3. (2012-MT-I.3.pdf)
Problem Type: Match the eight constitutional isomeric alcohols C5H12O with 1H NMR and 13C NMR spectra.
Techniques: 1H NMR and 13C NMR spectroscopy.
Notes: A challenging matching problem that probes concepts of chemical equivalence and symmetry in 1H NMR spectroscopy. One of my favorites.

2011 (fall) Midterm Exam Part I.2a. (2011f-MT-I.2a.pdf)
Problem Type: Match the regioisomers of dinitrophenol with 1H NMR spectra.
Techniques: 1H NMR and 13C NMR spectroscopy.
Notes: A matching problem that probes concepts of chemical equivalence and symmetry in 1H NMR spectroscopy.

2011 (fall) Midterm Exam Part I.2b. (2011f-MT-I.2b.pdf)
Problem Type: Match the regioisomers of methylpyridine with 1H NMR spectra.
Techniques: 1H NMR and 13C NMR spectroscopy.
Notes: A matching problem that probes concepts of chemical equivalence and symmetry in 1H NMR spectroscopy.

BASIC STRUCTURE DETERMINATION PROBLEMS

2014 Midterm Exam Part II.1. (2014-MT-II.1.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: EI-MS; IR (thin film on NaCl plates); 500 MHz 1H NMR in CDCl3; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in CDCl3.
Notes: A small but challenging molecule. One of my favorites.

2014 Midterm Exam Part II.2. (2014-MT-II.2.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: EI-MS; IR (thin film on NaCl plates); 500 MHz 1H NMR in CDCl3; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in CDCl3.
Notes: This problem was designed to build on concepts of 1H NMR non-first-order coupling pattern recogntion and symmetry.

2014 Midterm Exam Part II.3. (2014-MT-II.3.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: EI-MS; IR (thin film on NaCl plates); 500 MHz 1H NMR in CDCl3; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in CDCl3.
Notes: A simple but challenging molecule with a rich 1H NMR spectrum.

2014 Midterm Exam Part II.4. (2014-MT-II.4.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: EI-MS; IR (KBr pellet); 500 MHz 1H NMR in CD3SOCD3; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in CD3SOCD3.
Notes: This problem was designed to build on concepts of 1H NMR coupling pattern recogntion and symmetry.

2013 Midterm Exam Part II.1. (2013-MT-II.1.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: Exact mass; CI-MS (low resolution/accuracy); IR (solution in CHCl3 in a 0.1 mm CaF2 cell); 500 MHz 1H NMR in C6D6; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in C6D6.
Notes: We designed this molecule to illustrate principles of coupling patterns in the 1H NMR spectrum and isotope patterns in the mass spectrum.

2013 Midterm Exam Part II.2. (2013-MT-II.2.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: EI-MS and CI-MS (low resolution/accuracy); IR (solution in CHCl3 in a 0.1 mm CaF2 cell); 500 MHz 1H NMR in C6D6; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in C6D6.

2013 Midterm Exam Part II.3. (2013-MT-II.3.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: EI-MS (low resolution/accuracy); IR (solution in CHCl3 in a 0.1 mm CaF2 cell); 500 MHz 1H NMR in C6D6; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in C6D6.
Notes: A pretty spectrum with interesting coupling patterns. One of my favorites.

2013 Midterm Exam Part II.4. (2013-MT-II.4.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: EI-MS (low resolution/accuracy); IR (solution in CHCl3 in a 0.1 mm CaF2 cell); 500 MHz 1H NMR in CDCl3; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in CDCl3.
Notes: A small but challenging molecule. One of my favorites.

2012 Midterm Exam Part II.1. (2012-MT-II.1.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: Exact mass; EI-MS (low resolution/accuracy); IR (solution in CHCl3 in a 0.1 mm CaF2 cell); 500 MHz 1H NMR in CDCl3; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in CDCl3.
Notes: Concepts in pattern recognition, symmetry, and diastereotopicity.

2012 Midterm Exam Part II.2. (2012-MT-II.2.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: Exact mass; EI-MS (low resolution/accuracy); IR (solution in CHCl3 in a 0.1 mm CaF2 cell); 500 MHz 1H NMR in CD3SOCD3; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in CD3SOCD3.
Notes: We designed this molecule to illustrate principles of coupling patterns in the 1H NMR spectrum and isotope patterns in the mass spectrum.

2012 Midterm Exam Part II.3. (2012-MT-II.3.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: Exact mass; EI-MS (low resolution/accuracy); IR (solution in CHCl3 in a 0.1 mm CaF2 cell); 500 MHz 1H NMR in CDCl3; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in CDCl3.
Notes: A small but challenging molecule.

2012 Midterm Exam Part II.4. (2012-MT-II.4.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: Exact mass; EI-MS (low resolution/accuracy); IR (thin film on NaCl plates); 500 MHz 1H NMR in CDCl3; 125.8 MHz 13C NMR, DEPT 90, and DEPT 135 in CDCl3.
Notes: Concepts in pattern recognition, symmetry, and diastereotopicity.

2011 (fall) Midterm Exam Part II.1. (2011f-MT-II.1.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: Exact mass; EI-MS (low resolution/accuracy); IR (thin film on salt plates); 500 MHz 1H NMR in CDCl3; 125.6 MHz 13C NMR, DEPT 90, and DEPT 135 in CDCl3.
Notes: Concepts in pattern recognition and spin-spin coupling.

2011 (fall) Midterm Exam Part II.2. (2011f-MT-II.2.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: Exact mass; ESI-MS (low resolution/accuracy); IR (solution in CH2Cl2 in a 0.1 mm CaF2 cell); 400 MHz 1H NMR in CDCl3; 100.6 MHz 13C NMR, DEPT 90, and DEPT 135 in CDCl3.
Notes: Concepts in pattern recognition and spin-spin coupling.

2011 (fall) Midterm Exam Part II.3. (2011f-MT-II.3.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Techniques: EI-MS (low resolution/accuracy); IR (thin film on salt plates); 500 MHz 1H NMR in CDCl3; 125.6 MHz 13C NMR, DEPT 90, and DEPT 135 in CDCl3.
Notes: A small molecule with interesting IR and NMR spectra.

ADVANCED SPECTRAL ANALYSIS PROBLEMS

2014 Final Exam Part I. (2014-F-I.pdf)
Problem Type: Assignment of NMR resonances and stereochemical analysis.
Compound Information: Two diastereomeric L-hexopyranose pentaacetates.
Techniques: 500 MHz 1H NMR, 125.8 MHz 13C NMR, DEPT, COSY, HMQC, NOESY, and a 1D NOE experiment.
Notes: This problem focuses on conformational and stereochemical analysis in two diastereomeric L-hexopyranose pentaacetates.

2013 Final Exam Part I. (2013-F-I.pdf)
Problem Type: Assignment of NMR resonances and stereochemical analysis.
Compound Information: A pentacyclic compound.
Techniques: 500 MHz 1H NMR, 125.8 MHz 13C NMR, DEPT, COSY, TOCSY (20 ms mixing time), HMQC, HMBC, NOESY, and HSQC-TOCSY spectra with 5-, 10-, 25-, and 50-ms mixing times.
Notes: This problem focuses on conformational and stereochemical analysis in a system of fused cyclohexane rings.

2012 Final Exam Part I. (2012-F-I.pdf)
Problem Type: Assignment of NMR resonances and stereochemical analysis.
Compound Information: A tricyclic compound.
Techniques: 500 MHz 1H NMR, 125.8 MHz 13C NMR, DEPT, COSY, TOCSY, HMQC, HMBC, NOESY, and HSQC-TOCSY spectra with 5-, 10-, 20-, and 100-ms mixing times.
Notes: This problem focuses on conformational and stereochemical analysis in a fused 5,6 ring system. It is a great showcase for HSQC-TOCSY, which helps tremendously in assignment of the resonances.

2011 (fall) Final Exam Part I. (2011-F-I.pdf)
Problem Type: Assignment of NMR resonances and stereochemical analysis.
Compound Information: A tricyclic compound.
Techniques: 500 MHz 1H NMR, 125.8 MHz 13C NMR, DEPT, COSY, TOCSY, HMQC, HMBC, NOESY, and HSQC-TOCSY spectra with 5-, 10-, 20-, and 100-ms mixing times..
Notes: This problem focuses on conformational and stereochemical analysis in a fused 5,6 ring system. It is a great showcase for HSQC-TOCSY, which helps tremendously in assignment of the resonances.

ADVANCED STRUCTURE DETERMINATION PROBLEMS

2014 Final Exam Part II.1. (2014-F-II.1.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C10H17NO2.
Techniques: IR (thin film from CHCl3 on salt plates), 500 MHz 1H NMR, 125.8 MHz 13C NMR, DEPT-90, DEPT-135, COSY, TOCSY (100 ms mixing time), HMQC, HMBC, and NOESY, and a 1D NOE experiment.
Notes: This problem proved surprisingly challenging in spite of the small size of the molecule. It was the most popular problem of the 2014 final exam Part II problems.

2014 Final Exam Part II.2. (2014-F-II.2.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C18H21NO4.
Techniques: IR (KBr pellet), 500 MHz 1H NMR, 125.8 MHz 13C NMR, DEPT-90, DEPT-135, COSY, TOCSY (60 ms mixing time), HMQC, HMBC, NOESY, and HSQC-TOCSY spectra with increasing mixing times (5, 10, 25, and 50 ms).
Notes: This was the hardest and least popular of the 2014 final exam Part II problems. It is an beautiful and complex molecule with a disperse 1H NMR spectrum with interesting resonances.

2014 Final Exam Part II.3. (2014-F-II.3.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C17H22O3.
Techniques: IR (KBr pellet), 500 MHz 1H NMR, 125.8 MHz 13C NMR, DEPT-90, DEPT-135, COSY, TOCSY (150 ms mixing time), HMQC, HMBC, NOESY, and select regions of the HSQC-TOCSY spectra with increasing mixing times (5, 10, 25, and 50 ms).
Notes: This problem was the second most popular of the 2014 final exam Part II problems. There is moderate overlap of the 1H NMR resonances. The TOCSY and 50-ms HSQC-TOCSY spectra nicely illuminate the major spin systems.

2013 Final Exam Part II.1. (2013-F-II.1.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C18H25NO. Related to codeine.
Techniques: IR (solution in CHCl3), 500 MHz 1H NMR, 125.8 MHz 13C NMR, DEPT-90, DEPT-135, COSY, HMQC, HMBC, TOCSY (150 ms mixing time) and NOESY.
Notes: The easiest of the 2013 final exam Part II problems. It is also my favorite. Although the molecule is large the problem is very workable and satisfying. I had been wanting to introduce it for a number of years, but it was only in 2013 that we were able implement it.

2013 Final Exam Part II.2. (2013-F-II.2.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C16H25NO2. Related to codeine.
Techniques: IR (solution in CHCl3), 500 MHz 1H NMR, 125.8 MHz 13C NMR, DEPT-90, DEPT-135, COSY, HMQC, HMBC, TOCSY (150 ms mixing time) and NOESY. Also included are select regions of the HSQC-TOCSY spectra with increasing mixing times.
Notes: The hardest and least popular of the 2013 final exam Part II problems.

2013 Final Exam Part II.3. (2013-F-II.3.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C16H24O.
Techniques: IR (solution in CHCl3), 500 MHz 1H NMR, 125.8 MHz 13C NMR, DEPT-90, DEPT-135, COSY, TOCSY (20 ms mixing time), HMQC, HMBC, 1D NOE (irradiation at 3.36 ppm), and NOESY.
Notes: This problem was the most popular of the 2013 final exam Part II problems.

2012 Final Exam Part II.1. (2012-F-II.1.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C17H19ClO.
Techniques: IR (solution in CHCl3), 600 MHz 1H NMR, 150.9 MHz 13C NMR, DEPT-90, DEPT-135, COSY, HMQC, HMBC, TOCSY and NOESY.
Notes: This was the second most popular of the 2012 final exam Part II problems. In spite of the larger size of the molecule (compared to the other two problems) it is manageable.

2012 Final Exam Part II.2. (2012-F-II.2.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C9H10O4.
Techniques: IR (thin film from CHCl3 solution on NaCl plates), 500 MHz 1H NMR, 125.7 MHz 13C NMR, DEPT-90, DEPT-135, COSY, HMQC, HMBC, TOCSY and NOESY.
Notes: The hardest and least popular of the 2012 final exam Part II problems. Although the molecule is small, it is challenging.

2012 Final Exam Part II.3. (2012-F-II.3.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C10H19N.
Techniques: IR (thin film on NaCl plates), 500 MHz 1H NMR, 125.7 MHz 13C NMR, DEPT-90, DEPT-135, COSY, HMQC, HMBC, TOCSY and NOESY.
Notes: This was the most popular of the 2012 final exam Part II problems. In spite of the small size of the molecule, its structure is actually quite challenging, in part due to W-coupling seen in the COSY.

2011 (fall) Final Exam Part II.1. (2011f-F-II.1.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C15H22O2.
Techniques: IR (Thin Film on NaCl), 500 MHz 1H NMR, 125.7 MHz 13C NMR, DEPT-90, DEPT-135, COSY, HMQC, HMBC, TOCSY and NOESY.
Notes: This was the easiest and most popular of the 2011 fall final exam Part II problems.

2011 (fall) Final Exam Part II.2. (2011f-F-II.2.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C16H22O.
Techniques: IR (Thin film on NaCl), 400 and 500 MHz 1H NMR, 125.7 MHz 13C NMR, DEPT-90, DEPT-135, COSY, HMQC, HMBC, TOCSY, and NOESY.
Notes: This was my favorite among the 2011 fall final exam Part II problems.

2011 (fall) Final Exam Part II.3. (2011f-F-II.3.pdf)
Problem Type: Structure determination and assignment of NMR resonances.
Compound Information: Molecular formula C10H16O.
Techniques: IR (Thin Film on NaCl), 500 MHz 1H NMR, 125.7 MHz 13C NMR, DEPT-90, DEPT-135, COSY, HMQC, HMBC, TOCSY, and NOESY.
Notes: In spite of the small size of this molecule, it was the hardest and most frustrating of the 2011 fall final exam Part II problems Only a few of those who attempted it got the correct structure and stereochemistry.