ERIC Number: EJ1188406
Record Type: Journal
Publication Date: 2018-Aug
Pages: 5
Abstractor: As Provided
ISBN: N/A
ISSN: ISSN-0021-9584
EISSN: N/A
Ammonia Borane Acid-Base Complex: An Experiment Involving [superscript 1]H and [superscript 11]B NMR Spectroscopy and the Gas Laws
Arulsamy, Navamoney
Journal of Chemical Education, v95 n8 p1381-1385 Aug 2018
An experiment involving a moisture-sensitive synthesis and spectroscopic characterization suitable for the advanced inorganic laboratory course is presented. The acid-base complex ammonia borane (AB) is synthesized from the heterogeneous reaction between sodium borohydride and finely ground ammonium sulfate in tetrahydrofuran solvent. AB is isolated as a fluffy white solid. The [superscript 1]H and [superscript 11]B NMR spectra of AB, separately measured in the solvents D[subscript 2]O and CD[subscript 3]CN, provide an excellent opportunity to introduce some of the basic concepts of multinuclear NMR spectroscopy. The triplet and quartet peaks observed for the NH[subscript 3] and BH[subscript 3] groups in the [superscript 1]H spectrum measured in CD[subscript 3]CN can be used to discuss the nature of J[subscript NH] and J[subscript BH] coupling. The former coupling is rarely observed because the quadrupolar [superscript 14]N in nonspherical structures experiences rapid relaxation and large J coupling, leading to broad peaks for -NH and -NH[subscript 2] protons. Although such coupling due to [superscript 11]B is more commonly observed, a comparison of the [superscript 1]H NMR spectra of AB and NaBH[subscript 4] further illustrates the effect of spherical symmetry on the NMR behavior of quadrupolar nuclei. AB is also valued in the field of energy research as a potential chemical H[subscript 2] storage material and has assumed new significance as a potential portable energy source. The efficacy of H[subscript 2] generation from AB is examined, and the purity of student-synthesized samples is determined by applying the gas laws. The experiment can be performed in two 3-hour lab periods.
Descriptors: Science Instruction, Science Experiments, Spectroscopy, College Science, Undergraduate Study, Inorganic Chemistry, Laboratory Experiments, Scientific Concepts, Concept Formation
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
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A
Grant or Contract Numbers: N/A