Resonant charge exchange reactions

The second step in this reaction chain is resonant (comparable to resonant charge exchange between H-atoms and protons), if the molecules are vibrationally excited in the v = 4 level. 

Cosmic ray ionization of H leads to the formation of HD through a sequence of reactions. The resonant charge-exchange reaction, whose rate constant has been given (Watson et al. 1978)... 

The resonance study (6 ) of B10H12I2 establishes that the I atoms are substituted on the two B s giving B peaks at highest field. It is important that in this and the following B resonance studies of substituted boron hydrides, the positions of boron resonances are but little shifted from their relative positions in the pure hydrides. This discovery has made the field of substituted boron hydrides easily studied by NMR techniques, and should lead to the identification of presently unassigned resonance peaks in the pure hydrides themselves and provide a basis for studies of internal exchange reactions. Thus, we can expect more detailed analyses of the charge distributions in both the hydrides and their substitution products to appear in the near future. 

An indication of the importance of the steric inhibition of resonance in aromatic substitution reactions has been gained by a study of the exchange reaction of dialkylanilines with deuterium oxide.21 With di-methylaniline, for example, the ortho and para hydrogen atoms equilibrate readily with deuterium oxide. This reaction, like most aromatic substitution reactions (see Chapter 13), is believed to proceed by the attack of a positively charged fragment (in this case a hydrogen or deuterium ion) at a point of high electron density. Consequently, the ease with which equilibration occurs can be taken as an approximate measure of the contribution of forms such as XLV or XLVI to the structure of the... 

Accidental resonant charge transfer is an electron exchange between unlike species also represented by reaction (47), but the energy defect AE is exactly or very close to zero. 

Explanations are the same as for curve 2 except the energy acquired by 4" at resonance is less. Possible reasons are (1) lower double-resonance strength (2) higher source drift velocity (3) higher pressure. Charge-exchange reactions often show this behavior since they seldom exhibit maximum rate constant at thermal kinetic energy. 

The most simple ion-molecule reaction, the resonant charge exchange, occurs by electron tunnelling. This theoretically explains the absence of activation energy. 

The decomposition of dioxetanone may involve the chemically initiated electron-exchange luminescence (CIEEL) mechanism (McCapra, 1977 Koo et al., 1978). In the CIEEL mechanism, the singlet excited state amide anion is formed upon charge annihilation of the two radical species that are produced by the decomposition of dioxetanone. According to McCapra (1997), however, the mechanism has various shortfalls if it is applied to bioluminescence reactions. It should also be pointed out that the amide anion of coelenteramide can take various resonance structures involving the N-C-N-C-O linkage, even if it is not specifically mentioned. 

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