ERIC Number: EJ1460212
Record Type: Journal
Publication Date: 2024-Mar
Pages: 6
Abstractor: As Provided
ISBN: N/A
ISSN: ISSN-0021-9584
EISSN: EISSN-1938-1328
Available Date: 0000-00-00
NMR in the Advanced Inorganic Lab. II. Introduction to Quadrupolar Coupling: What to Do When the "n + 1" Rule and Pascal's Triangle Fail
Journal of Chemical Education, v101 n3 p1274-1279 2024
As an introduction to quadrupolar effects in NMR spectroscopy, students use low field ([superscript 1]H, 60 MHz), benchtop [superscript 13]C NMR spectroscopy to contrast the spin-spin coupling behavior of [superscript 13]C to the dipolar [superscript 1]H and quadrupolar [superscript 2]D in familiar solvents C(H/D)Cl[subscript 3], C(H/D)[subscript 2]Cl[subscript 2], and (C(H/D)[subscript 3])[subscript 2]CO. To explain the observations, students are introduced to the spin magnetic quantum number, I, and its use in predicting first order coupling patterns. To explain the multiplets, both the number of lines and the relative intensities, students must expand their understanding of coupling beyond the mnemonics "n + 1" and Pascal's triangle for binomial expansion and instead utilize the nuclear spin magnetic quantum number, I, for the quadrupolar nucleus [superscript 2]D. The exercise is a useful prelude to the introduction of NMR spectroscopy involving quadrupolar nuclei (e.g., [superscript 14]N (I = 1); [superscript 11]B (I = 3/2)) in upper-level inorganic chemistry courses or as a fundamental description of coupling in physical chemistry courses. An advantage of the low field spectrum ([superscript 13]C, 15 MHz) is the observation of magnetic nonequivalence of the two methyl groups in (CH[subscript 3])[subscript 2]CO in which the [superscript 13]C resonance for the methyl group is readily observed as a quartet of quartets.
Descriptors: Inorganic Chemistry, Science Laboratories, Scientific Concepts, Spectroscopy, Prediction, Science Process Skills, Magnets, Quantum Mechanics, Undergraduate Students, Laboratory Training
Division of Chemical Education, Inc. and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail: eic@jce.acs.org; Web site: http://pubs.acs.org/jchemeduc
Publication Type: Journal Articles; Reports - Research
Education Level: Higher Education; Postsecondary Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A
Grant or Contract Numbers: N/A
Author Affiliations: N/A