Monday, February 25, 2008
I recently posted sample exams for CHEM 233. While I think studying from samples can be dangerous since this sometimes encourages students to memorize material rather than learn it, the samples communicate clearly the type, formate and difficulty level of content to be tested. My aim was also to eliminate any disparity between students without samples and those who acquired old exams from classmates who had previously taken 233. My recommendation is to use the sample exams as an evaluation tool after you have studied the material. Review homework questions, assigned reading, course manual readings and prelab lecture notes first, then attempt one of the samples to gauge how well you understand the laboratory concepts and techniques.
Friday, February 15, 2008
The latest spectra are now posted online. The lidocaine specs look pretty good!! The final product, lidocaine bisulfate, is not very soluble in CDCl3, which is why some of you may have observed cloudy NMR sample solutions. The book uses dimethyl sulfoxide (DMSO) for the NMR sample, which is much more polar and better able to dissolve your final product. We don't have any DMSO currently, so CDCl3 will have to do; Navid's spectra turned out great in CDCl3 anyway. Just be aware that the chemical shift values (ppm) for each proton signal will be slightly different than those reported in your textbook since chemical shift is solvent dependent.
The slides for Friday's (Feb. 15) lecture are now posted. Also, I updated the slides with each student's synthetic target assignments for Project Two. Plan your syntheses so that you will obtain approximately 200 mg of product. Because deciding on a recrystallization solvent system can be time consuming, I will tell you what system works best for the final product: water/ethanol.
Wednesday, February 6, 2008
For those students interested in subscribing to this blog as an RSS feed, click on the link entitled "Blog RSS Feed" at the bottom of the sidebar to the left of this page. There is another link above entitled, "RSS." This will simply open the RSS feed for comments only. To be honest, I'm not sure why that's there or how to remove it.
As many of you have already realized, there is a mistake in the textbook excercise # 5. You should use equation 8.4 (Hooke's Law), not equation 8.5. This question is very similar to 3 & 4. Also, while I'm on the topic of Hooke's law, let me point out that the masses in the equation refer to the mass of a single atom. The most common error is to use molecular weights, rather than atomic masses. You can find atomic mass by dividing the molar mass by Avogadro's number.