Week 7 - Making Progress

On Monday, I had a fortunate and embarrassing realization. Late last week, we seemed to have finally got our method down to a replicable state, but the concentration still seemed to be dropping from the initial spiked amount down to around 3 or 4 μM too quickly. This bothered me, so I rechecked my math, and realized I had completely miscalculated how much aniline I needed to inject into the reaction vial, and was starting the reaction off at 4 μM of aniline rather than 20 μM. This reality meant that our results made much more sense, and that I had an embarrassing talk with Ali. Thankfully, Ali was much less mortified by my mistake than I. We decided that we should adjust the initial concentration to 10 μM to increase our signal to noise ratio, and I performed a few new experiments.

On Tuesday, I performed a few experiments, and had access to the HPLC for part of the day. I tested using a filter to quench the reaction, and using ascorbic acid to quench the reaction. On Wednesday I had the HPLC all day, and so was able to test all of the reactions I had run. We saw that using the filter to quench our reactions produced much noisier results than using ascorbic acid.

On Thursday, I ran an experiment using ascorbic acid to quench the reaction, and took more data points than I have been, and recorded data points further out in time than normal. We want to make sure we can get a very clear reaction coefficient, and want to see further along the extent of reaction to really know what’s happening with our reaction. I also ran a quick and dirty reaction with 2-methoxy-5-nitroaniline instead of 4-chloroaniline. This is the next aniline we are interested in, and I wanted to make sure that it is still possible to get clear results using 2-methoxy-5-nitroaniline with ascorbic acid.

On Friday, I encountered many problems with the HPLC. For some reason we encountered baseline shifting again, and had to spend a bit re-equilibrating the machine. However, I was able to run all of my experiments from Thursday through the HPLC to acquire concentration data. We got reasonable kinetics data for 4-chloroaniline, and discovered that 2-methoxy-5-nitroaniline has considerably slower kinetics than 4-chloroaniline.