Eft Spectrometer User Publications
Eft spectrometer users have published several journal articles to inform our existing and potential users how the Eft might be used in the undergraduate teaching laboratory.
A Discovery-Based Experiment Involving Rearrangement in the Conversion of Alcohols to Alkyl Halides
Richard A. Kjonaas; Ryand J.F. Tucker J. Chem. Educ. 2008 85, 100
The use of permanent magnet 13C NMR in large-section first-semester organic chemistry lab courses is limited by the availability of experiments that not only hinge on first-semester lecture topics, but which also produce at least 0.5 mL of neat liquid sample. This article reports a discovery-based experiment that meets both of these criteria. Students convert three alcohols to alkyl halides under acidic conditions and record the 13C NMR spectrum in each case. By comparing the number of resonances observed with the number of resonances predicted for each possible product, they conclude that (i) with 1-propanol there is no carbocation rearrangement, (ii) with 2-pentanol there is a considerable degree of secondary-to-secondary carbocation rearrangement, and (iii) with 2,4-dimethyl-3-pentanol all of the alkyl halide formed is the result of a secondary-to-tertiary carbocation rearrangement.
Peer Mentoring in the General Chemistry and Organic Chemistry Laboratories
Arrington, Caleb A.; Hill, Jameica B.; Radfar, Ramin; Whisnant, David M.; Bass, Charles G. J. Chem. Educ. 2008, 85, 288
This article describes a discovery experiment for general chemistry and organic chemistry labs. Although the pinacol rearrangement has been employed in undergraduate organic laboratories before, in this application organic chemistry students act as mentors to students of general chemistry. Students work together using distillation—a new technique for the general chemistry students and a basic one for the organic students—to isolate an unknown compound. Then, using spectroscopy (IR and NMR), the students collaborate to determine the structure of the product of the reaction. This application of a standard experiment allows general chemistry students to gain exposure to modern spectroscopic instrumentation and to enhance their problem-solving skills. Organic chemistry students improve their understandings of laboratory techniques and spectroscopic interpretation by acting as the resident experts for the team.
Imidazole as a pH Probe: An NMR Experiment for the General Chemistry Laboratory
William J. Hagan, Jr., Dennis L. Edie, and Linda B. Cooley J. Chem. Educ. 2007 84, 1188
An experiment is described that employs the 1H-NMR signal of aqueous imidazole to determine the pH of an unknown solution. The procedure involves the preparation of a calibration curve, which is then used for the analysis of the unknown(s). The advantages of imidazole as a pH probe for near-neutral solutions are briefly discussed. The exercise is primarily intended for general chemistry students, but could also be employed in a course on instrumental analysis.
Acid-Catalyzed Isomerization of Carvone to Carvacrol
Richard A. Kjonaas and Shawn P. Mattingly J. Chem. Educ. 2005 82, 1813
The acid-catalyzed isomerization of carvone (oil of spearmint) to carvacrol (oil of origanum) in the sophomore organic chemistry laboratory is discussed. The experiment demonstrates several important concepts including (i) formation of a carbocation by protonation of an alkene, (ii) rearrangement of a carbocation, (iii) deprotonation of a carbocation, (iv) acid-catalyzed enolization, and (v) aromaticity. The experiment is especially suitable for use with low-field permanent-magnet FT–NMR for two important reasons: (i) even the 60 MHz proton spectrum is interpretable by the students and (ii) the product is a liquid that is obtained from an inexpensive starting material in sufficiently high yield and purity so that a neat or highly concentrated NMR sample can be prepared for 13C NMR analysis.
Implementation and Use of Selective Shaped Pulses on Lower-end NMR Spectrometers
Daniel Lim* and Guillermo Moyna Journal of Undergraduate Chemistry Research 2004, 3, 96-102.
The implementation of selective shaped pulses as pulse-width modulated DANTE pulse trains on an Anasazi Eft-90 NMR spectrometer, an extremely popular instrument among institutions with modest research programs, is presented. The excitation frequency profiles obtained for several types of shaped DANTE pulse trains, including square, triangular, trapezoidal, Gaussian, and half-Gaussian, are presented and compared to theoretical calculations, and their usefulness is further showcased in a series of selective population inversion (SPI) experiments. Comparison of these results to those obtained from analogous experiments recorded using conventional shaped pulses on a state-of-the-art NMR spectrometer indicates that the shaped DANTE pulse trains perform remarkably well. Their practical and theoretical limitations, as well as general guidelines for their implementation in other spectrometers, are discussed.
Measurement of the Isotopic Ratio of 10B/11B in NaBH4 by 1H NMR
Murray Zanger and Guillermo Moyna . J. Chem. Educ. 2005 82, 1390.
A simple and remarkably accurate method for estimating the isotopic ratio between 10B and 11B through the use of 1H nuclear magnetic resonance (NMR) spectroscopy is presented. The experiment relies on the splitting caused by 10B (I = 3) and 11B (I = 3/2) on the 1H signal of a proton directly bound to boron, a phenomenon readily observed on an aqueous sample of NaBH4. In combination with a brief lecture or prelaboratory presentation, this laboratory can serve to introduce students to magnetic properties as well as theoretical and experimental aspects of NMR spectroscopy as early as the freshman-level chemistry.