Calculation of Dipole Moment
2011.6.28
Lecture note of Dr. Hiroshi Yamamoto
Dipole moment is not so important for chemical engineering area. When you want to synthesis something with Micro Wave, dipole moment may become important. Or if you want to know the Hansen Solubility parameter polarity term, dipole moment value is needed.
The experimental value of dipole moment is not listed in database so much. And not increasing. And these day, they use the dipole moment calculated by molecular orbital or charge equilibration. But experimental dipole moment and calculated dipole moment is very different for some case. You need to know which compounds lead large error.
I validated the 1852 compounds that have experimental dipole moment with MOPAC result. I plotted result below. The correlation is so small.
Let’s examine which is good, which is bad. When I calculate MOPAC, it produce the type of Point Group of molecule. I validated the result according to the point groups.
C1 group compounds
These compounds are out of line.
C2 group compounds
The compounds that have polar functional group both the side, such symmetry compounds are out of line. With calculation, Dipole moment will be negated for MO calculation but not so in real solvent.
C2v, C3v compounds are much better with MO calculation.
These compounds are out of line.
Cs group compounds
These compounds are out of line.
Ci, D*h, D2, D2d, D2h, D3, D3d, D3h, D4h, D6h, Oh, Td,C3, C2h, C3h, C*v you would better not use calculated value.
So, the compounds that have more than 2 same polar functional group and symmetry compounds, you would better not use calculated value. And some large compounds that have polar unit you would better not use calculated value.
