End of the Year Report

In this study ten different sulfonamide derivatives were studied. Sulfa drugs are commonly used in aquaculture as agricultural herbicides and in the treatment of respiratory and urinary tract infections in humans. The aim of the work was to use Raman spectroscopy as well as density functional (DFT) calculations to characterize ten sulfa drugs. The ten derivatives were sulfisoxazole, sulfamethizole, sulfamethoxazole, sulfathiazole, sulfachloropyridazine, sulfadimethoxine, sulfamerzine, sulfameter, sulamethazine and sulfadiazine. The first four mentioned sulfa drugs have a five membered ring attached to a sulfonamide group while the last six mentioned have a six membered ring attached to a sulfonamide group. This difference and the functional group each of the sulfa drug possesses were analyzed in terms of vibrational bands that are both unique and common to the sulfa drugs. Once the results were obtained experimentally through Raman Spectroscopy and theoretical using the program Gaussian, they were compared and it was observed that the experimental data was very similar to the theoretical data. The ten different derivatives exhibited peaks at common areas and unique areas, which I will discuss further in detail.

When observing the graphs of the Raman spectra it was observed that there were similar peaks in the 10 different drugs. At about the wave region of 630 cm-1 – 790 cm-1 where the carbon-sulfur bond exhibits stretching there was a peak in all ten derivatives. They all exhibited peaks at the 800 cm-1 – 1300 cm-1 wave region as well that is characteristically due to the carbon-nitrogen bond stretching. Another feature they had in common is the fact that they all exhibit ring stretching in the wave region of 900 cm-1 – 1100 cm-1. This is supported by the theoretical data that was obtained and is expected due to the fact that all of the derivatives contain a ring. Due to the fact that they are all sulfonamide derivatives, they all contain sulfonamide groups and therefore all showed peaks in the wave region 1000 cm-1 – 1200 cm-1. This is typically where sulfonamides exhibit symmetrical stretching. These peaks were also present in the theoretical data. All of the experimental spectra showed peaks at about 1600 cm-1. which was concluded to have been caused by the stretching of the aromatic carbon-carbon bonds. Since all of the derivatives contain a ring that has carbon nitrogen double bonds, all of the spectra showed peaks at about 1610 cm-1 – 1680 cm-1.

Although there were many similar peaks that are shown in the spectra of all ten derivatives, there are also some unique characteristics shown. For example, all of the structures that contain methyl groups on the substituent, such as sulfamethazine, sulfamerazine, sulfamethoxazole, sulfamethizole, and sulfasoxazole, all show peaks in the wave region of about 1380 cm-1 where the methyl group undergoes bending. Sulfamethazine has the peak at the wavenumber of 1347 cm-1, sulfamerazine has the peak at 1335 cm-1, sulfamethizole has the peak at 1310 cm-1, sulfisoxazole has the peak at 1391 cm-1, and sulfamethoxazole at 1310 cm-1.

Sulfadimethoxine and sulfameter both contain ethers on the pyrimidine structure. Sulfadimethoxine’s had a peak at 1282 cm-1 and sulfameter had a peak at 1280 cm-1 and 1319 cm-1. These peaks are in the region of 1150 cm-1 – 1300 cm-1 that can be attributed to the ether. The only derivative that contains a thiazole shows distinguishing vibrations. There is out of plane bending of the carbon hydrogen bonds on the thiazole ring that can be seen at the wavenumbers 637 cm-1 and 726 cm-1. The thiazole ring also undergoes vibrations. The regions are from 930 cm-1 – 1160 cm-1, 1175 cm-1 – 1340 cm-1, and 1480 cm-1 – 1690 cm-1. In the spectrum it can be seen that sulfathiazole has peaks at 930 cm-1, 1159 cm-1, 1350 cm-1, and 1502 cm-1 that can all be attributed to this ring stretching.

Sulfadiazine contains only the pyrimidine and didn’t have any distinguishing peaks. As for sulfachloropyridazine, the data obtained was did not provide much information as the spectrum did not exhibit many peaks. This was concluded to be due to the color of the solid form being yellow when it was tested.

When trying to determine which spectrum belongs to which derivative, it will be necessary to look at the differing substituents. However, for the derivatives like sulfadiazine, which have only a pyrimidine ring, or such as sulfamerzine and sulfamethazine, whose only differences are the number of methyl groups attached, determining which spectrum belongs to which derivative will be much more challenging.

There is a slight shift observed in the Raman peaks when the ten sulfonamide antibiotics were mixed in their solid form together. It was observed that there is a very distinct peak seen at a wavenumber of 1593 cm-1, which is likely due to the aromatic ring structure that all ten derivatives have. It can also be seen that they have a very intense peak at 1148 cm-1 that is probably due to the sulfonamide functional group stretching.

Overall I learned a lot during this study. I learned how to properly assign vibrational bond modes using the computer program Gaussian and how to analyze Raman spectra. Not only did I learn how to trouble shoot issues that came up as the experiment went on but I have gained valuable lab experience that will help me in my future career. I had the amazing opportunity to present my research at the American Chemical Society’s National convention in San Francisco. Being at a national convention, presenting, and making connections with all of the other scientists was an experience like no other. Doing research as an undergraduate has really made my time here at Pace University so much more valuable. I would not have been able to do any of this without the help and guidance of my wonderful mentor Elmer-Rico E. Mojica. I have learned so much during my time in his research group and I hope in the future I have the opportunity to impact young minds in the same way he has impacted me.












Computational Studies and Vibrational Analysis of Sulfa Drug Blog

My research on the Density Functional Theory and Raman spectroscopy of ten different sulfonamide antibiotic derivatives has really been coming along. I have now completed the assigning of the different vibrational modes for all of the bonds in all ten of the antibiotics. This part of the experiment has taken me the longest to complete. As I was creating the graphs of the Raman spectra data, I noticed that my signal to noise ratio was a little low. This means that the peaks weren’t intense enough compared to the background interferences. To improve the signal to noise ratio, I ran my samples three more times each under the same conditions. Then I used to average of all three runs to plot new graphs with more intense data.

Being a part of this project has taught me a lot so far. Not only have I become quite comfortable using the portable Raman spectrometer that we have here at Pace and using the computer program Gaussian to analyze the theoretical data but I have learned that running an experiment requires a lot of patience. A lot of my time is spent waiting for the samples to finish a run and then I am able to analyze it. It also requires a lot of thinking on your feet because not everything goes as planned and you have to be ready for that.

I have finally been able to create a poster to show the results that I have obtained so far. The next step is to assign the functional groups in charge for the molecular vibrations at the particular peaks.

Blog 2

My research on the computational studies and Raman spectra of ten different sulfa antibiotics has been going well. I have assigned functional groups to most of the peaks that are in the spectra. I have identified peaks that are common throughout the different antibiotics and I have also identified a few distinguishing peaks between them. I have begun to assign bond movements to each of the peaks as well. This process includes inputting the entire structure of the antibiotic into the computer program Gaussian and looking at the theoretical peaks that can be generated after performing an optimization and frequency test. Then I observe and record what movement I see when looking at each peak that is present in the spectra. By the end of the study I will have done this for all 10 of the antibiotics. It is a very time consuming process but in the end it can tell us a lot about the molecule.

This past week I worked in the lab here at Pace and ran the samples of 7 out of the 10 antibiotics again using the mini Raman Spectrometer. I had to determine what settings for the time average and multiplier, which are settings on the program that determine how long the sample is run for, would give me the most intense peaks. I did this by running a sample of Tylenol as a control first, since we know what the Raman spectra of Tylenol should look like. Once I found the best setting I ran the sulfa antibiotics under the same conditions. I am going to compare the new spectra that I obtained with the older data that I have from before. I will be looking for any abnormalities in the data, if there is anything new, and if the data is just better overall.



Computational Studies and Vibrational Analysis of Sulfa Drug

For this study I am continuing to do research with Dr. Mojica in the Mojica research group on the vibrational spectroscopy of antibiotics, focusing on the computational studies and Raman spectra of ten sulfa drugs. Sulfa antibiotics are most commonly used in the treatment of respiratory and urinary tract infections in humans and in aquaculture as herbicides. The goal of this study is to identify the chemical bonds that are unique to sulfa drugs, which will not only provide a way to quantitate amounts of the drug in a sample but it will also help in the understanding of the chemical properties of the drugs. To do this study I must use Raman spectroscopy, which is a way to obtain information about the molecular vibrations of a compound. The particular sulfa drugs that I have tested and will continue to test are sulfamethazine, sulfamethoxazole, sulfachloropyridazine, sulfadimethoxine, sulfathiazole, sulfamerazine, sulfisoxazole, sulfamethizole, sulfameter, and sulfadiazine.

As of now I have obtained the complete first round of Raman spectra and I am processing the data by assigning the functional groups on the peaks that I have observed. I have also obtained the theoretical Raman spectra for each of the drugs using the computer program Gaussian and am currently assigning the bond movements that are observed at the different wavelengths of the spectra. I plan on doing another round of testing using the portable Raman as well.