ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The determination of the dimerisation constant (KD) for the weak self-association of a compound C in dilute solution according to the equilibrium, 2C⇌C2 is described. The method uses chemical shifts measured on a series of solutions of C at different concentrations: the optimum KD is defined by a linear regression best-fit procedure, which simultaneously determines optimum values for δo and also for δ∞, the intrinsic chemical shifts for nuclei in the monomer and dimer species. The dimerisation of caffeine in D2O is used as a model to demonstrate the working of the method and the quality of results obtained. The most probable value of KD for caffeine at 30.5° is found in the range 5.5-6.0 kg solution · mol-1, and the enthalpy and entropy of dimerisation are found to be ΔH⊖ = -15.1 kJ · mol-1 and ΔS⊖ = -35.3 J · °C-1 · mol-1, respectively. The influence of small errors in δo on the confidence limits of KD is discussed.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19840670316
Permalink