Resonance capabilities

Scheme 2.8 Resonance capabilities of carboxylic acids compared to alcohols.

Equation (2) for a reaction giving a set of apparent substituent constants o can be rewritten in the form, (o- t/ ) = r a - cr ), where r is constant for the reaction regardless of substituents. As the increment of any o-from (f should be a reasonable measure of the resonance capability of the respective substituents, this proportionality represents a linear resonance energy relationship. The original form (Yukawa and Tsuno, 1959, 1965) using cr instead of (f in (2) has the same significance since the proportionality relation holds for the resonance increment (a - t/ ) or (a - cr). The definition of resonance substituent constants Ao by any set of (o— o") is arbitrary, and the definition of the r scale is also arbitrary. While the definition of the r = 0 scale by [Pg.269]

The term resonance has also been applied in valency. The general idea of resonance in this sense is that if the valency electrons in a molecule are capable of several alternative arrangements which differ by only a small amount in energy and have no geometrical differences, then the actual arrangement will be a hybrid of these various alternatives. See mesomerism. The stabilization of such a system over the non-resonating forms is the resonance energy. 

Unlike the typical laser source, the zero-point blackbody field is spectrally white , providing all colours, CO2, that seek out all co - CO2 = coj resonances available in a given sample. Thus all possible Raman lines can be seen with a single incident source at tOp Such multiplex capability is now found in the Class II spectroscopies where broadband excitation is obtained either by using modeless lasers, or a femtosecond pulse, which on first principles must be spectrally broad [32]. Another distinction between a coherent laser source and the blackbody radiation is that the zero-point field is spatially isotropic. By perfonuing the simple wavevector algebra for SR, we find that the scattered radiation is isotropic as well. This concept of spatial incoherence will be used to explain a certain stimulated Raman scattering event in a subsequent section. 

It IS important to recognize that an enol is a real substance capable of mdepen dent existence An enol is not a resonance form of a carbonyl compound the two are constitutional isomers of each other... 

Ion trap analyzer. A mass-resonance analyzer that produces a three-dimensional rotationally symmetric quadrupole field capable of storing ions at selected mass-to-charge (m/z) ratios. 

The formation of copolymers involves the reaction of (at least) two kinds of monomers. This means that each must be capable of undergoing the same propagation reaction, but is is apparent that quite a range of reactivities is compatible with this broad requirement. We shall examine such things as the polarity of monomers, the degree of resonance stabilization they possess and the steric... 

A modified definition of resonance energy has been introduced by Dewar (66T(S8)75, 69JA6321) in which the reference point is the corresponding open-chain polyene. In principle this overcomes the difficulties inherent in comparing observed stability with that of an idealized molecule with pure single and double bonds, as thermochemical data for the reference acyclic polyenes are capable of direct experimental determination. In practice, as the required data were not available, recourse was made to theoretical calculations using a semiempirical SCF-MO method. The pertinent Dewar Resonance Energies are listed in Table 30. 

A comparison of the various post-ionization techniques electron-gas bombardment, resonant and nonresonant laser ionization, etc. While some of the numbers are outdated, the relative capabilities of these methods have remained the same. This is a well-written review article that reiterates the specific areas where post-ionization has advantages over SIMS. 

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