Electronegativities, group, estimated

The equilibrium situation for simple substituted 2-ulkenyl alkali metal derivatives can be estimated by a rule of thumb electron-accepting and electropositive substituents ( ) prefer the exo position, but electron-donating and electronegative substituents ( ), including alkyl groups, tend to occupy the endo position. With increasing steric demand of the substituent, the exoisomer becomes more favored. 

Mullay JJ (1987) Estimation of Atomic and Group Electronegativities. 66 1-25 Muller A, Baran E), Carter RO (1976) Vibrational Spectra of Oxo-, Thio-, and Selenometallates of Transition Elements in the Solid State. 26 81-139 Muller A, Diemann E, Jorgensen CK (1973) Electronic Spectra of Tetrahedral Oxo, Thio and Seleno Complexes. Formed by Elements of the Beginning of the Transition Groups. 14 23-47... 

The pentafluorophenyl-group has an electronegativity value which has been estimated as being between that of chlorine and bromine so- 2). As would be expected, 3-pentafluorophenyltrifluorobenzyne (9) reacts with benzene to form the 1,4-cycloadduct in good yield 63>. 

Owing to their dative character, the 0 XH3 bonds of group 15 oxides differ rather remarkably from ordinary covalent bonds involving the same elements. For example, a normal ono bond (e.g., in hydroxylamine, HONH2) would be estimated from Eq. (3.76) to have /no = —0.17, polarized toward the more electronegative O. However, the dative ctn o NBO of 0 NH3... 

Table 5.7 Estimate of the electronegativities of some common groups...

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