Haasnoot equation

Some 14 years after publication of the original Haasnoot equation, it was reparametrized to include a /., group electronegativity scale and specific parameters for substituted ethane derivatives,57 regardless of degree of substitution ... 

C. Altona, R. Francke, R. de Haan, J. H. Ippel, G. J. Daalmans, A. J. A. Westra Hoekzema, and J. van Wijk, Empirical group electronegativities for vicinal NMR proton-proton couplings along a C-C bond Solvent effects and reparameterization of the Haasnoot equation, Magn. Reson. Chem., 32 (1994) 670-678. 

Haasnoot, C. A. G., De Leeuw, F. A. A. M., De Leeuw, H. P. M., Altona, C. Relationship between proton-proton NMR coupling constants and substituent electronegativities. III. Conformational analysis of proline rings in solution using a generalized Karplus equation. Biopolymers 1981, 20,1211-1245. 

For reasons that have been described in detail,33 it was proposed that Eq. (8) be replaced by a new relationship, now known as the Haasnoot or Altona equation ... 

This comprehensive study also tested the relative importance of the various terms in Eq. (18), and its relative performance when compared with modified Karplus equations of the Pachler, Haasnoot, and Colucci el al. types. Based on standard deviations of errors, the ranking of the four most important terms was found to be cos 2ip, cos

important term is the combined electronegativity/electronegativity orientation term, and the fourth most significant one is the bond angle term, the first- and third-ranked terms... 

Secondly, by using the A, B, and C values from Eq. (41), the effect of anomeric configuration was accounted for by fitting the data for the a-furanosides to the full Haasnoot-Altona equation ... 

P. P. Lankhorst, C. A. G. Haasnoot, C. Erkelens, and C. Altona, Carbon-13 NMR in conformational analysis of nucleic acid fragments. 2. A reparametrization of the Karplus equation for vicinal NMR coupling constants in CCOP and HCOP fragments, J. Biomol. Struct. Dyns., 1 (1984) 1387-1405. 

The Vhh couplings have been used by Abraham and Koniotou to determine the conformer populations of cis- and fr ms-cyclopentane-l,3-diol by the use of the Haasnoot, de Leeuw and Altona equation for the C-CH2-CH2-C fragment the following equation has been derived from five- and six-membered cyclic compounds in fixed conformations ... 

A large set of hydroquinone derivatives (Fig. 6a) has been studied by Dobado et al. In order to identify regioisomeric compounds, the authors have performed the calculations of chemical shifts and estimation of J(H,H) using the CAL3JHH program, based on Haasnoot-Leeuw-Altona empirical equation. Calculated V(H,H) averaged according to the Boltzmann distribution were compared with the experimental values. 

Further improvements of the quahty of the fittings can be achieved by using extended Karplus models that can account for substituent effects. The well-known classical Haasnoot-Altona equation [12] for proton-proton vicinal J-couplings... 

C.A.G. Haasnoot, F.A.A.M. de Leeuw, C. Altona, The relationship between proton-proton NMR couphng constants and substituent electronegativities-I. An empirical generalization of the Karplrrs equation. Tetrahedron 36 (1980) 2783. 

Measurement of couplings shows that pyranose rings do not show any large degree of internal flexibility, except for pendant groups such as the hydroxymethyl in hexopyranoses. Interpretation of these uses the Haasnoot parametrization of the Karplus equation for /h-h couplings in HCCH... 

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