Electronic effects infrared absorption shift

The UV-spectra of azolides have already been discussed in the context of hydrolysis kinetics in Chapter 1. Specific infrared absorptions of azolides were mentioned there as well increased reactivity of azolides in nucleophilic reactions involving the carbonyl group is paralleled by a marked shift in the infrared absorption of the corresponding carbonyl bond toward shorter wavelength. For example, for the highly reactive N-acetyl-tetrazole this absorption is found in a frequency range (1780 cm-1) that is very unusual for amides obviously the effect is due to electron attraction by the heterocyclic sys-tem.[40] As mentioned previously in the context of hydrolysis kinetics of both imidazo-... 

The electron effective mass in GaN is now reasonably well established by cyclotron resonance measurements [14-16] asm, = (0.22 0.0 l)m, and the low frequency dielectric constant (appropriately averaged spatially) e(0) = 9.5 0.2, from infrared refractive index and optic phonon energy measurements [17]. We can therefore derive a reliable value for the hydrogenic donor ionisation energy of EDH = (33.0 1.5) meV which compares well with IR absorption measurements, giving Ed = (35 1) meV [18] (see below). The discrepancy is readily explained in terms of a small chemical shift. 

The solvated electron in ammonia has a strong absorption band in the infrared region, and /Imax shifts from 1850 nm at 23 °C to 1410 nm at —75°C this is attributed to the effect of temperatiu-e on the orientation of the ammonia molecules in the first solvation shell [37], On the other hand, G(e am) = 0-32 pmol J remains constant over the same temperature range [37]. It is relatively straightforward, therefore, to study one-electron redox reactions in liquid ammonia by pulse radiolysis, but relatively few investigations have been made. 

The numerous reactions and physical properties that can be correlated with electronic substituent constants suggest that they reflect a basic mechanism for the effect of the substituent on the reaction or the property. Many reactions were correlated by the Hammett equation, such as electrophilic (4, 31, 32, 33), nucleophilic (4, 34) and radical (35, 36, 37). Spectroscopic properties, such as infrared and ultraviolet absorption frequencies and intensities (38). nuclear magnetic resonance shifts of various nuclei, e.g., -H, F, (39), and mass spectroscopic ionization... 

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