Prediction of proton and carbon-13 NMR chemical shifts using chemical shift prediction programs

• Main Author: Dyosi, Zolani
• Other Authors: Jackson, Graham Ellis
• Format: Dissertation
• Language: English
• Published: University of Cape Town 2014
• Subjects: Chemistry
• Online Access: http://hdl.handle.net/11427/7413

Includes bibliographical references. === Ab-initio, semi-empirical, and empirical calculations are used in computer programs separately or in conjunction with one another to calculate predicted chemical shifts for a wide range of chemical compounds. 1H-spectra for several flexible and rigid organic compounds were acquired on Oxford-Broker spectrometer and interpreted using two-dimensional NMR techniques. ACD-V 4 and CHARGE-V7 programs were used to predict 1H chemical shifts for these compounds. 1H and 13C_spectra for alkaloids were also collected using a Varian spectrometer and also interpreted with the use of multi-pulse techniques. CHARGE-V7, ACD-V4 (1H and 13C) predictor programs together with SpecInfo-V3.2 (1H and 13C) predictor program were used in the prediction of chemical shifts for alkaloids. The results obtained for flexible and rigid organic compounds indicate good calculation of 1H-chemical shifts by both CHARGE-V7 and ACD-V4 programs. These results are contrary to the poor chemical shifts generated by these programs for a1kaloids. The poor prediction of alkaloids could be due to the absence of similar fragments in ACD-V4 and SpecInfo-V3.2 program's databases. Poor parameterisation of CHARGE-V7 program coupled with complex spectra of a1kaloids could be contributing to the inaccurate predicted chemical shifts. Increasing the size of the user database for SpecInfo and ACD programs would improve the accuracy in prediction of both 1H and 13C chemical shifts. Improvement in the accuracy of parameterisation of CHARGE-V7 to cater for rare compounds such as natural products is also required.