NMR Applications: Bench Chemistry

NMR spectroscopy is the method of choice for many organic chemists because of its versatility in elucidating molecular structure, optimizing reaction dynamics, measuring reaction kinetics, monitoring reaction content and controlling product purity. NMR spectroscopy provides a wealth of information on physical, electronic, chemical and structural aspects of molecular systems. It is a nondestructive technique ideally suited for measuring and recovering small sample quantities. NMR complements other techniques, such as FTIR, UV-Vis spectroscopy and mass spectrometry, providing a wealth of molecular-scale information. Now, instead of relying on limited access to an expensive central NMR facility, you can have an inexpensive, compact and reliable NMR spectrometer right in your own lab.

The spectrum below demonstrates the capability of the Thermo Scientific picoSpin NMR spectrometer, revealing the characteristic triplet-quartet splitting pattern of the ethyl group in ethanol. High signal-to-noise ratio and high resolution marks the picoSpin 45 as a true spectrometer, providing quality spectra at a small fraction of the cost of conventional NMR spectrometers.

Figure 1. NMR Spectrum of Ethanol (neat, 16 scans)

Often chemists need to establish the current state of their reaction – perhaps a reaction isn't proceeding as expected. Is the stoichiometry off, or is an impurity present? NMR could tell us right away what may be the problem, but the NMR lab is booked, and you need results immediately. With a picoSpin-45 spectrometer, you can obtain results in a matter of minutes, and make adjustments to your reaction pot today, not next week.

The NMR spectrum of ethanol above indicates the presence of an impurity signal at 4.3 ppm in what should have been a sample of pure compound. Preliminary analysis of this sample of ethanol would have prompted the chemist to dry the solvent prior to use, saving valuable time. The spectrum of ethyl acetate below indicates a samples free of impurities.

Figure 2. NMR Spectrum of Ethyl Acetate (neat; 4 scans)

Bench chemistry applications

Pharmaceuticals

Below are several examples of spectra of prescription and over-the-counter (OTC) medications obtained using the Thermo Scientific™ picoSpin™ NMR spectrometer.

Figure 1. NMR Spectrum of Aspirin (0.4 M in DMSO-d6)

Figure 2. NMR Spectrum of Naproxen (50% (v/v) in CDCl3)

Figure 3. NMR Spectrum of trans-chalcone (0.99 M in Ac-d6)

Figure 4. NMR Spectrum of Benzocaine (0.52 M in CDCl3)

Figure 5. NMR Spectrum of Lidocaine (0.68 M in CDCl3)

Figure 6. NMR Spectrum of Procainamide (0.52 M in D2O)

Figure 7. NMR Spectrum of Procaine (1.5 M in D2O)

Solvents

Below are several examples of some common chemical solvents. All spectra were acquired from pure samples, except where noted, and used without further purification. Thermo Scientific™ picoSpin™ 45 NMR spectra were acquired using a 90-degree pulse angle, 750 ms acquisition time, 10 s recovery delay, and are an average of 16, 24, 48, 64, or 72 scans.

Figure 1. NMR Spectrum of Tributyl Phosphate (neat, 16 scans)

Figure 2. NMR Spectrum of Acetone-free Nail Polish Remover (neat, 16 scans), containing Ethyl Acetate, Ethanol, and Water

Figure 3. NMR Spectrum of Acetone (neat, 16 scans)

Figure 4. NMR Spectrum of Anhydrous Tetrahydrofuran (neat, 16 scans)

Figure 5. NMR Spectrum of Anhydrous Pyridine (neat, 25 scans)

Figure 6. NMR Spectrum of Store-Brand 99% Isopropyl Alcohol (neat, 16 scans)

Figure 7. NMR Spectrum of Anhydrous Ethyl Acetate (neat, 72 scans)

Figure 8. NMR Spectrum of Anhydrous Ethyl Benzene (neat, 72 scans)

Figure 9. NMR Spectrum of Anhydrous Ethanol (neat, 72 scans, * impurity). Hydroxyl and methylene proton coupling resolved

Figure 10. NMR Spectrum of Ethanol with water impurity (neat, 72 scans). Resolution of hydroxyl-methylene proton coupling diminishes as rapid proton exchange with water protons increases

Figure 11. NMR Spectrum of Ethanol with water impurity (neat, 72 scans). Hydroxyl-methylene proton coupling no longer visible

Figure 12. NMR Spectrum of Anhydrous p-Xylene (neat, 24 scans)

Figure 13. NMR Spectrum of Anhydrous Toluene (neat, 24 scans)

Figure 14. NMR Spectrum of Anhydrous p-Xylene/Toluene solution (50/50 v/v, 48 scans)

Figure 15. NMR Spectrum of Hardware Store Xylol (neat, 16 scans). Stated content: 75-90% o-, m-, p-Xylene; 10-25% Ethyl Benzene

Customer testimonials

Metro State University

Sarah Dimick Gray
Assistant Professor
picoSpin 45 NMR Spectrometer Customer

Loma Linda University

Dr. David Weldon
Assistant Professor, Pharm Sci
picoSpin 45 NMR Spectrometer Customer

Red Rocks Community College

Dr. Brandon English
Chemistry Instructor
picoSpin-45 NMR Spectrometer Customer

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Bench chemistry applications

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