So I taught my first organic workshop today…it was a little weird, but things seemed to work out in the end. The first problem set was on Lewis structures, which I’ll always believe are somewhat arbitrary. It’s like, after you figure out the sigma bonds in something like, say, ONNO2, how do you know where to throw the rest of the valence electrons without bringing in MO theory and a bunch of extra crap? How do you make it feel non-arbitrary without drowning the kids in theory? I figured out about halfway through the class to just shut my trap and let them do their own thing on the problem set. Things seemed to end up well.
Anyway, all of that aside, I found an interesting paper today in Chemistry of Materials. Vaidyanathan et al. look at the field-effect mobilities of substituted [5,5′]-bisphenyl-[2,2′]-bithiophenes (PTTPs…phenyl, thiophene, thiophene, phenyl) as a function of their solubility in THF. Interestingly, increased solubility corresponds to decreased mobility, with also correlates with substituent size. The authors speculate (and support, with SAXS data) that the mobility decrease is due to structural disorder caused by steric hindrance. Sayonara, pi-stacking, adios mobility.