Comparative NMR Spectra of Metronidazole and Ornidazole

We successfully built structures of metronidazole and ornidazole on Gaussian, both of which we calculated the NMR spectra in chloroform. Additionally, we obtained this data using experimental spectroscopic techniques; this was then compared to the theoretical spectra from Gaussian.

Theoretical proton NMR of metronidazole indicated five different types of hydrogens; Gaussian was unable to differentiate between the hydrogens of the methylene group attached to the imidazole ring, both of which were depicted in two different peaks yet with a degeneracy of one. In comparison, our experimental proton spectra depicted these five peaks more downfield. Gaussian predicted six carbon peaks while experimental NMR resulted in five carbon peaks, three of which were shifted more downfield and two of which were very similar in chemical shifts with Gaussian. The missing peak was the carbon with the nitro group on the imidazole ring.

Gaussian provided a more complex proton NMR for ornidazole, in which the hydrogens on the methyl group and the hydrogen on the hydroxide group were reflected in similar peaks. The hydrogens on the methylene group were also reflected in two peaks. Experimental spectra provided one more hydrogen peak. In contrast to theoretical data, the methyl group was more upfield than the hydroxyl group. Seven different carbons were predicted by Gaussian; experimental spectra indicated some similarities in the chemical shifts of three carbons. The carbon with the nitro attachment on the imidazole ring was reflected in a small peak this time.

With these results we were able to adjust our objectives for the future. Gaussian provided a reasonable theoretical analysis of structural information, and in utilization with experimental spectroscopy, we can determine the reaction mechanism of metronidazole and ornidazole. We want to investigate what the activated complex in the interaction between the drug and the microbe looks like, as well as how it forms. This is particularly an area of interest for ornidazole, which has been verified as more potent than metronidazole because of the smaller amount of drug required to kill a larger number of microbes.

 

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