In this problem you will use the molecular electronic structure methods described in

Chapter 15, Problem 15.14

(choose chapter or problem)

In this problem you will use the molecular electronic structure methods described in Chapter 11 to investigate the hypothesis that the magnitude of the 13C chemical shift correlates with the net charge on a 13C atom. (a) Using molecular modelling software3 and the computational method of your choice, calculate the net charge at the C atom para to the substituents in this series of molecules: benzene, phenol, toluene, trifluorotoluene, benzonitrile, and nitrobenzene. (b) The 13C chemical shifts of the para C atoms in each of the molecules that you examined in part (a) are given below: Substituent OH CH3 H CF3 CN NO2 130.1 128.4 128.5 128.9 129.1 129.4 Is there a linear correlation between net charge and 13C chemical shift of the para C atom in this series of molecules? (c) If you did find a correlation in part (b), use the concepts developed in this chapter to explain the physical origins of the correlation.