Carbanions ionization potentials

Platinum-cobalt alloy, enthalpy of formation, 144 Polarizability, of carbon, 75 of hydrogen molecule, 65, 75 and ionization potential data, 70 Polyamide, 181 Poly butadiene, 170, 181 Polydispersed systems, 183 Polyfunctional polymer, 178 Polymerization, of butadiene, 163 of solid acetaldehyde, 163 of vinyl monomers, 154 Polymers, star-shaped, 183 Polymethyl methacrylate, 180 Polystyrene, 172 Polystyril carbanions, 154 Potential barriers of internal rotation, 368, 374... 

Ionic dissociation of carbon-carbon a-bonds in hydrocarbons and the formation of authentic hydrocarbon salts, 30, 173 Ionization potentials, 4, 31 Ion-pairing effects in carbanion reactions, 15, 153 Ions, organic, charge density-NMR chemical shift correlations, 11,125 Isomerization, permutational, of pentavalent phosphorus compounds, 9, 25 Isotope effects, hydrogen, in aromatic substitution reactions, 2,163... 

Figure 3.9a may also represent the interaction of a nonbonded ( lone-pair ) orbital with an adjacent polar n or a bond [67]. If a polar n bond, one can explain stabilization of a carbanionic center by an electron-withdrawing substituent (C=0), or the special properties of the amide group. If a polar a bond, we have the origin of the anomeric effect. The interaction is accompanied by charge transfer from to A, an increase in the ionization potential, and a decreased Lewis basicity and acidity. These consequences of the two-electron, two-orbital interaction are discussed in greater detail in subsequent chapters. 

Ostoja Starzewski and Bock83 reported the photoelectron spectra of an extensive series of phosphonium ylides, focusing on the substituent effects. Their lowest ionization potential (IP) is associated with the carbanion orbital. Their main results are given in Table 9. A number of important trends can be identified and interpreted. Replacement of the methyl groups on P with phenyl groups reduces the IP of the carbanion. The phenyl group is able to stabilize the P+ charge, which reduces the ability of the phosphonium to stabilize the... 

Basis sets used for carbanions have to include diffuse functions because anions generally have low ionization potentials, i.e. there is a pair of (or a single) electrons in the form of a diffuse charge cloud that extends relatively far from the nuclei and therefore is easily lost. Without diffuse functions, even larger basis sets such as DZ + P are not entirely successful either in the calculation of absolute acidities or in the ordering of acidities. 

The most utilized Umpolung strategy is based on formyl and acyl anion equivalents derived from 2-lithio-l,3-dithiane species. These are readily generated from 1,3-dithianes (thioacetals) because the hydrogens at C(2) are relatively acidic (p f 31). In this connection it should be noted that thiols (EtSH, pi 11) are stronger acids compared to alcohols (EtOH, 16). Also, the lower ionization potential and the greater polarizability of the valence electrons of sulfur compared to oxygen make the divalent sulfur compounds more nucleophilic in Sj,2 reactions. The polarizability factor may also be responsible for the stabilization of carbanions a to sulfur. ... 

Thus the introduction of a heteroatom at an active position tends to favor the formation of a carbanion and to disfavor production of a cation. For example, such substitution in an odd AH radical increases both its electron affinity and its ionization potential. 

The perturbation of the yr-systems of radical anions of R3M substituted naphthalenes, formed by polarographic reduction, is discussed in terms of their ionization potentials, charge transfer excitations, reduction potential, and e.s.r. spin distribution. Base cleavage of arylsilanes is consistent with the formation of the carbanion XCeH4 as the rate determining step. The nature of the Ar—M... 

Ionic dissociation of carbon-carbon CT-bonds in hydrocarbons and the formation of authentic hydrocarbon salts, 30, 173 Ionization potentials, 4, 31 Ion-pairing effects in carbanion reactions, 15, 153... 

In the Sjyjl- like process the R-X bond ionizes in the strong potential field gradient (107V /cm) 296 at the electrode/electrolyte interface and the carbonium ion is subsequently reduced to the carbanion (Eq. (225) ). It has been suggested 1... 

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