ISSN:
1572-8927
Keywords:
C-acid-base reaction
;
thermodynamic parameters
;
solvent effects
;
solvatochromism
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Equilibrium constants K for reaction of the C-acid, 4-nitro/phenylnitromethane with 1,8-diazabicyclo [5.4.0] undec-7-ene have been determined in aprotic solvents over a range of temperature. Corresponding measurements have been made for the deuterated acid 4-NPNM-d2. Thermodynamic parameters K, ΔHo and ΔSo, for proton and for deuteron transfers are not very differet in a given solvent, but show a considerable solvent dependence. There is an increase in magnitude of K with increase in solvent dielectric constant, a finding which is consistent with formation of an ion-pair. The range of extent of exothermicity of the reaction is quite small, −40 to-65 kJ-mol−1, and the values of ΔSo (large, negative) indicate, in general, increasing solvent restriction by the product with increasing solvent polarity. A modest bathochromic solvatochromism of the product is observed as the dielectric constant increases.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00647205
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