Electron donor group

Donors a.ndAcceptors. Table 3 Hsts common electron—donor groups, and electron—acceptor groups selected from a large number capable of evoking fluorescence. 

The conjugated chromophore (color-causing) system can be extended by electron-donor groups such as —NH2 and —OH and by electron-acceptor groups such as —NO2 and —COOH, often used at opposite ends of the molecule. An example is the aromatic compound alizarin [72-48-0], also known since antiquity as the ted dye madder. 

The strength of electron-donor groups iacrease ia the order OH < NH < NHR < HNAr. Tetra-substituted anthraquiaones (1,4,5,8-) are more bathochromic than di- (1,4") 01 trisubstituted (1,2,4-) anthraquiaones. Thus, by an appropriate selection of donor groups and substitution patterns, a wide variety of colors can be achieved (see Dyes, anthraquinone). 

Oxadiazoles are difficult to alkylate, unless the ring contains a strong electron donor group such as an amino substituent. 

The LUMO in benzenium ion reveals where electron donor groups are likely to be most effective. 

The inclusion of p-substituted fluorobenzene F-nmr shifts in the basis sets suggests that weakly interacting Y pi electron donor groups are also permitted. 

Y is a strongly pi electron donor group. As previously noted in the results section, examples of Y from Table VI include centers of high pi electron charge density at carbon, sulfur, nitrogen, and oxygen. Also included in Table VI are examples of nucleophilic substitution transition states (cf. reactions 21 and 22) of the type... 

Molecular rotors have in common that fluorescent excitation leads to an ICT, in the case of DMABN from the nitrogen in the dimethylamino electron donor group to the nitrile electron acceptor group (Fig. 1). The ICT leads to a highly polar... 

EDG electron donor group EAG electron acceptor group... 

Fig. 8 Representative structures of DMABN-based rotors with different electron donor groups...

Clusters of H-bond acceptor (electron donor) groups were observed in compounds, which are known to be substrates or modulators of P-gp. Electron donors are electronegative atoms (O, N, S, or X = F, Cl) with an unshared electron pair, or unsat-... 

Fig. 20.4. H-bond acceptor patterns observed two electron donor groups with a spatial in P-gp substrates. Type I units patterns separation of 4.6 + 0.6 A. A denotes a informed by electron donor pairs with a spatial bonding acceptor group (electron donor...

Electron donor groups (EDG) on the aromatic ring favour its displacement to the right while electron withdrawing group (EWG) favours its displacement to the left. Selenobenzophenone monomer in solution is isolated as a dimer in the solid state. Dimerization of the stable 12 to the 1,3-ditelluretane was observed in the solid state, in solution the dimer reforms 12.25 26 Contrary to the reaction in the solid state dimerization does not take place in solution. 

These interactions (dd, di, ii) are a function of dipole moment and polarizability. It has been shown that the dipole moment cannot be replaced entirely by the use of electrical effect substituent constants as parameters52. This is because the dipole moment has no sign. Either an overall electron donor group or an overall electron acceptor group may have the same value of /x. It has also been shown that the bond moment rather than the molecular dipole moment is the parameter of choice. The dipole moments of MeX and PhX were taken as measures of the bond moments of substituents bonded to sp3- and sp2-hybridized carbon atoms, respectively, of a skeletal group. Application to substituents bonded to sp-hybridized carbon atoms should require a set of dipole moments for substituted ethynes. 

A - electron acceptor group D - electron donor group... 

A striking feature of disperse dye development in recent decades has been the steady growth in bathochromic azo blue dyes to replace the tinctorially weaker and more costly anthraquinone blues. One approach is represented by heavily nuclei-substituted derivatives of N,N-disubstituted 4-aminoazobenzenes, in which electron donor groups (e.g. 2-acylamino-5-alkoxy) are introduced into the aniline coupler residue and acceptor groups (acetyl, cyano or nitro) into the 2,4,6-positions of the diazo component. A PPP-MO study of the mobility of substituent configurations in such systems demonstrated that coplanarity of the two aryl rings could only be maintained if at least one of the 2,6-substituents was cyano. Thus much commercial research effort was directed towards these more bathochromic o-cyano-substituted dyes. 

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