81Br/79Br-Induced 13C Isotope Shifts and Line Broadening in the 13C NMR Spectrum of Methyl Bromide
✍ Scribed by William T. Raynes; Nickolai M. Sergeyev; Peter Sandor; Martin Grayson
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 194 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
NMR studies of the 13C isotope shift between and and of the linewidths of the two resolved CH 3 79Br CH 3 81Br resonances were carried out as part of a wider study of the NMR properties of methyl halide molecules. The isotope shift of 1.12 ppb can be readily accounted for in terms of the very slight shortening of the CÈBr bond (0.000 008 which occurs upon replacing 79Br by 81Br. From the isotope shift it is shown that the CÈBr bond A ) length derivative of the carbon-13 shielding is Ô140 ppm There is no need to involve the change in bromine A -1. nuclear quadrupole moment to explain the isotope shift. The linewidths are inÑuenced by scalar relaxation of the second kind and, from the observed values of 0.084 and 0.100 Hz for and respectively, it is CH 3 79Br CH 3 81Br, possible to deduce that J(13C 79Br) = 48 Hz and J(13C 81Br) is 45 Hz. These results are in accordance with extrapolation from previously measured results for and 1997 by John Wiley & Sons, CBr 4 , CHBr 3 CH 2 Br 2 . ( Ltd.