PCh10 15 lec 1

(5/1/20, bes)

Greetings...so the calcs worked for some and not for others. One of the reasons i wanted to do this phenolphthalein comp chem lab was to show you that comp chem jobs aren't always as easy as they have been. One of the first rules of comp chem is "crap in --> crap out." It is critical that when you create a structure that it represents all of your past knowledge of chemistry...bonding, sp3, sp2, sp / geometry. It may be a bit confusing, but the molecular structure is really very simple to determine...HF/STO-3G will do this for most molecules...and as you are learning, HF theory does not even acknowledge any electron correlation! Adding electron correlation, ie Moller-Plesset (MP#), takes a lot more time to arrange the electrons based on the location of all of the other electrons...THIS IS NO SIMPLE TASK!

I sent an email that said that if you cannot get you MP/6-31G(d) job to run, then switch over to HF/6-31G(d)...if this job finishes, then you could consider using the HF results to then run the MP job. I saw one of my friends shifted to the most simple basis set...MP2/STO-3G...and it worked; i don't recommend this, but It will be interesting to compare the results.

As noted by Bob Gotwals in his version of this comp chem lab activity, the absolute UV-Vis spectra are not great (using HF), but relatively the pink-form will show the expected red shift...i was hoping the the MP calcs would be closer to experimental data...???

Keep working on this project and hopefully i will be able to pull together class results and share on Monday. By the way, the reporting for this lab just needs to be done by next weds.

End of lecture.