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|Title: ||NMR spectra of molecules oriented in a lyotropic mesophase I. The spectra of pyridazine, pyrimidine and pyrazine|
|Authors: ||Khetrapal, C.L.|
|Issue Date: ||1975 |
|Publisher: ||Indian Academy of Sciences, Bangalore, India.|
|Citation: ||Pramana Supplement, 1975, Vol. 1, p471-481.|
|Abstract: ||A lyotropic mesophase formed by a 14 : 1 : 1 : 20 mixture (by weight) of sodium dodecyl sulphate, sodium sulphate, decanol and heavy water is used to study the PMR spectra of pyridazine, pyrimidine and pyrazine. Since the ordering of the molecules is much lower in this case compared to that in a thermotropic mesophase, analysis of the spectra was considerably simplified. Some of the dipolar couplings could be guessed fairly accurately even from the first order analysis. The geometry information and the order parameters arc derived in each case. Ratios of interproton distances thus determined are compared with those obtained from the studies in the thermotropic mesophase. For pyrimidine and pyrazine they are found to agree. However, in pyridazine a deviation of about 5% in one of the distance ratios is observed. This may be attributed to a hydrogen bonded complex formed between pyridazine and water in the lyotrophic phase. In pyridazine, the S-value along the C, axis of symmetry is found positive and that perpendicular to the plane of the ring negative as in thermotropics. The order parameter in the ring plane along an. axis perpendicular to the symmetry axis has the largest positive value. In pyrimidine, the $value of the axis perpendicular to the plane of the ring is negative Bnd its magnitude decreases with the increase of temperature such that at 45°C it is nearly zero. The order parameter of the symmetry axis has the largest positive value.
For pyrazine it was possible to determine the signs of the order parameters in this phase by assuming the signs of the indirect spin-spin couplings. This was not possible in thermotropic liquid crystal solvents. The S-value of an axis perpendicular to the ring plane was found positive as for most of the aromatics in a lyotropic mesophase.|
|Description: ||Proceedings of the international liquid crystal conference, Bangalore, 1973.|
|Copyright: ||Indian Academy of Sciences, Bangalore, India.|
|Appears in Collections:||Research Papers (SCM)|
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