Electron-accepting group

As with pyridine acids, the presence of a positive center or an electron accepting group facilitates decarboxylation that must proceed by way of the anion. 

The alkene substituted with the electron accepting group has the LUMO (it ) lowered by the interaction with the vacant orbital of the substituent. The high-lying SOMO interacts with the LUMO of the alkene more effectively than with the HOMO. The interaction is the symmetry-allowed it - n interaction (Scheme 30a). The configuration of the alkene is retained. 

The frontier orbital theory was developed for electrophilic aromatic substitution (Chapter Elements of a Chemical Orbital Theory by Inagaki in this volume). Application is successful to the ortho-para orientation (Scheme 23a) for the benzenes substituted with electron donating groups. The ortho and para positions have larger HOMO amplitudes. The meta orientation (Scheme 23b) for the electron accepting groups is under control of both HOMO and the next HOMO [25]. 

Orbital Mixing in Benzenes Substituted with an Electron Accepting Group... 

When the substituent is an electron-accepting group, the substituent LUMO is important. The iTj orbital has the substituent orbital mix in phase and is stabilized. The energy remains unchanged with the substimtion. The HOMO is which has the... 

Scheme 26 Next HOMO (NHOMO) polarization of benzenes with an electron accepting group...

Additions of an electrophile (E) to the n bond (If) substituted by an electron-donating group (EDG) and an electron-accepting group (EAG) occur at the P and a positions, respectively. Transition states are considered as non-cyclic E-Il-EDG(EAG) systems (Scheme 16). 

From the r, and r2 values it may be inferred that trialkylstannyl electron-accepting groups suppress almost completely the addition of TASM to its own radical. 

By comparing the constants of the copolymerization of MA with organotin methacrylates with the known values for the copolymerization of the MA — MMA system = 0.03 and r2 = 3.5)89) where almost no complexation takes place, the following conclusion on the effect of the electron-accepting groups SnR3 on free-radical copolymerization and be reached. 

In cases where both types of compounds are present in significant amount, the use of a mixture of solvents, nucleophilic and electrophilic, was suggested. In such cases, an amphiprotic solvent could also be suitable (an amphiprotic solvent contains simultaneously an electron donating and electron accepting groups in a single molecule), for instance ethanolamine. 

The rate of eh reaction with ethylene is low, 106 M-1s-1. An electron-donating group adjacent to NH2 or OH makes the rate very low. Similarly, an electron-accepting group enhances the rate as in the case of pyrrole, vinyl alcohol, or ethylene derivatives, where some reactions proceed at diffusion-controlled rates. 

The reactivity of haloaliphatic compounds decreases in ascending order. This seems to be related to polarizability. RX ion has been postulated as an intermediate, but it has not been experimentally observed. Again, the reactivity is increased by adjacent electron-accepting groups. 

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