Raymond C. Ferguson

Computer Analysis of NMR Spectra: Magnetic Equivalence Factoring

An extension of the NMR analysis method of Swalen and Reilly is described. The Hamiltonian matrix is factored to reduce it to minimal dimension by taking advantage of magnetic equivalence. Significant improvements are obtained in computation speed, computer program capacity, and convenience of use. Other extensions of the method provide a thorough statistical assessment of the resulting parameter estimates, and permit a solution even when some of the energy levels do not participate in any of the assigned transitions. The method has been tested by analyzing the 60‐Mc/sec proton resonance spectra of propane (A6B2) and isobutane (A9B). The chemical shifts, downfield from internal tetramethylsilane, and the coupling constants are: CH3CH2CH3; δ(CH3) = 0.912±0.005 ppm, δ(CH2) = 1.350±0.005 ppm, J = 7.35±0.02 cps: (CH3)3CH; δ(CH3) = 0.900±0.005 ppm, δ(CH) = 1.738±0.005 ppm, J = 6.73±0.05 cps.

A computer program for simulating many-spin NMR spectra

Abstract A digital computer program has been developed for simulating spectra arising from many coupled nuclear spins. It is particularly designed for the analysis of polymer spectra. The input is any set of transition lists, preferably the output transition frequencies and intensities from one of the conventional spin simulation programs. The transition lists are combined with appropriate statistical weights to simulate the spectra of synthetic polymers. Use of the program is illustrated by tests of various models for quantitatively estimating the tacticity of polypropylene from high resolution 1H-NMR spectra.