Donor—acceptor series

The effect of polarity on vinyl monomer copolymerization has long been recognized and is a major factor in the Q, e scheme and copolymerization theory. Mayo, Lewis, and Walling tabulated a number of vinyl monomers into an average activity series and an electron donor-acceptor series (62). The activity series showed the effect of substituents on the ease with which an ethylene derivative reacted with an average radical and on stabilizing the radical which was formed thereby. The electron donor-acceptor series indicated the ability of the substituents to serve as donors or acceptors in radical-monomer interactions. It is significant that in both series the dominant factor is the radical-monomer interaction. 

It was further indicated that copolymerization of two monomers which were close together in the donor-acceptor series gave a random copolymer, while monomers which were well separated in the series had a marked tendency to give an alternating copolymer. 

Some of the possible molecular groups have been ranked in a donor-acceptor series [7, p. 141] ... 

Hence, to eliminate the EDL, either acidic or basic properties must be imparted to the surface by surface modification. Thus the application of any of the following donor-acceptor series containing various functional groups can change the surface charge density. 

Hence, in order to eliminate the electrical component, we must give the surface donor or acceptor properties [141] this may be done by modification of the surface, namely, replacing certain surface molecular groups by others. Possible molecular groups may be placed [142] in a donor—acceptor series ... 

Figure C3.2.7. A series of electron transfer model compounds with the donor and acceptor moieties linked by (from top to bottom) (a) a hydrogen bond bridge (b) all sigma-bond bridge (c) partially unsaturated bridge. Studies with these compounds showed that hydrogen bonds can provide efficient donor-acceptor interactions. From Piotrowiak P 1999 Photoinduced electron transfer in molecular systems recent developments Chem. Soc. Rev. 28 143-50.

The series of neutral B-containing carbocycles as complex ligands within the theme of metal-boron donor-acceptor relationships concludes with the 4,5-dihydro-borepines. l-Phenyl-4,5-dihydroborepine is able to substitute pyridine, acetonitrile or CO... 

The investigations included donor adducts with PO [93], 34,PS [+) [94], 35, and P(NMes ) +) [95], 36. While 34 was only formulated as an intermediate species, the other donor-acceptor complexes, 35 and 36, were characterized by X-ray investigations. To complete this series it may also be compared with bis(ylide)-substituted phosphonium halides [96], 37. For these cases the donors refer to... 

The above relationships between the thiiranes (20) and their dioxides (17) are reminiscent of those between cyclopropane and cyclopropanone. The entire phenomena of the C—C bond lengthening and the concomitant C—S bond shortening in the three-membered ring sulfones and sulfoxides can be accounted for in terms of the sulfur 3d-orbital participation and the variation in the donor-acceptor capacities of the S, SO and S02 . The variations of the calculated valence-state orbital energies, together with the corresponding variations of the C—C overlap populations, can be used to understand the discontinuous variations of the C—C and the C—S bond lengths in the series thiiranes -... 

Messina MT, Metrangolo P, Resnati G (2000) Resolution of racemic perfluorocar-bons through self-assembly driven by donor-acceptor intermolecular recognition. In Ramachandran PV (ed) Asymmetric fluoro-organic chemistry synthesis, applications, and future directions. ACS symposium series 746. American Chemical Society, Washington DC, p 239... 

The valence-bond approach may be used to provide a qualitative account of the /lmax values, and hence the hues, of many dyes, particularly those of the donor acceptor chromogen type. The use of this approach to rationalise differences in colour is illustrated in this section with reference to a series of dyes which may be envisaged as being derived from azobenzene, although in principle the method may be used to account for the colours of a much wider range of chemical classes of dye, including anthraquinones (see Chapter 4), polymethines and nitro dyes. 

Table 2.3 Xmax values for a series of donor-acceptor substituted azobenzenes (16a-f)...

Polyene and polymethine dyes are two structurally related groups of dyes which contain as their essential structural feature one or more methine (-CH=) groups. Polyene dyes contain a series of conjugated double bonds, usually terminating in aliphatic or alicyclic groups. They owe their colour therefore simply to the presence of the conjugated system. In polymethine dyes, electron-donor and electron-acceptor groups terminate either end of the polymethine chain, so that they may be considered as typical donor-acceptor dyes. 

The quantitative treatment of the electron-transfer paradigm in Scheme l by FERET (equation (104)) is restricted to the comparative study of a series of structurally related donors (or acceptors). Under these conditions, the reactivity differences due to electronic properties inherent to the donor (or acceptor) are the dominant factors in the charge-transfer assessment, and any differences due to steric effects are considered minor. Such a situation is sufficient to demonstrate the viability of the electron-transfer paradigm to a specific type of donor acceptor behavior (e.g. aromatic substitution, olefin addition, etc.). However, a more general consideration requires that any steric effect be directly addressed. 

In LiF (,1 1) ion-dipole complexes, donor-acceptor charge leakage from F to Li+ is apparent in each member of the series, but the incremental CT, expressed as a percentage of a full electronic charge, is progressively weakened with each added F ion,... 

Linear triatomic anions The pioneering crystallographic studies of Odd Hassel140 on trihalides and related donor-acceptor species led to a far-reaching analysis of such Hassel compounds by Henry Bent.141 The triiodide ion (I3-, stable in aqueous solution) and other known linear trihalide XYZ- species also served as the prototype for Pimentel s incisive three-center MO analysis of hypervalency. We shall therefore begin with NBO/NRT investigation of a series of hypervalent and non-hypervalent triatomic anions in order to make contact with these classic studies. While ab initio studies add many quantitative details to the understanding of these species, the basic picture sketched by Bent and Pimentel is found to be essentially preserved. 

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