

Hallo Andreas,

The conzepts of group elektronegativities are relative old. There are some scales. 
- S.G. Bratsch, J. Chem. Educ. {\bf 62} (1985), 101
- N. Inamoto, S. Masuda, Chem. Lett. (1982), 1003
- R.T. Sanderson, ``Polar Covalence'', Academic Press, New York, (1983), 41
- J.E. Huheey, J. Phys. Chem. {\bf 70} (1966), 2086

You have to be careful if the groups are at aromatic or aliphatic compounds.

Viele Gruesse, Stephan

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