Barfield effect

Schaefer et al studied departures from the Karplus-type relationship ( Barfield effect ) to determine the ring pucker in 2-phenyl-1,3-dithiane. The dependence of the 7(H,H) Karplus equation on the internal C—C—H angles was given in mathematical form by Barfield et al., who also recalculated the... 

Fogle, A. W, B. J. Barfield, and V. P. Evangelou. 1991. Solution sodium/caicium ratio effects on bentonite floe density. J. Env. Sci. Health. A266 1003-1012. 

The non-bonded, through-space transmission of spin information, known as the Barfield transmission effect, has been investigated theoretically for five-membered rings by the FPT-INDO-SCF-MO method.50 An early observation of this effect was the non-equivalence of /endo-endo and exo-exo in norbomanes,51,52 which was also... 

M. Barfield, S. A. Conn, J. L. Marshall, and D. E. Miiller, Experimental and theoretical studies of the conformational and substituent dependencies of vicinal 13C-13C coupling constants. Impinging multiple rear-lobe effects,./. Am. Chem. Soc., 98 (1976) 6253-6260. 

Substituent effects on 37(C-C) values in a series of 1-substituted butyl compounds and in a series of 11-substituted 1-methyladamantane compounds have recently been reported by Barfield et al. (84) The experimental results are shown in Table VI. In the adamantane derivatives V(C-C) values are 1-2 Hz to 1-4 Hz less than the vicinal... 

Chemical shift maps for 1-substituted pentanes were worked out by Barfield," who could analyse various substitution effects in dependence on the molecular conformation. Of special interest was the origin of the - and -elfect. 

Important solvent effects on /(C,H) couplings within the side-chain in phenylallene were reported by Schaefer et a/. They found trends opposite to those expected from the current literature and discussed earlier by Barfield and Johnston and Ando and Webb. ... 

A useful conformational probe is the effect of a carbonyl group on the geminal coupling constant of the vicinal protons. This effect was used in an analysis of the H n.m.r. spectrum at — 160°C of [2,2,7,7- H J cyclo-octanone which adopts a boat-chair conformation. The Barfield-Grant relationship was shown to be wrong in the region of 0 = 120°. ... 

Conquest, L., Spyridakis, J., Haselkom, M., and Barfield, W. 1993. The effect of motorist information on commuter behavior Classification of drivers into commuter groups. Transportation Research, Part C, 1(2), 183-201. 

Various more serious attempts have been made to explain the y gauche effect by MO computations. The most recent are those of Barfield and Yamamura [4], using an ab initio method with a double-C basis set. Although this level of computation is a little less than that required to give the best available absolute shieldings, it reproduces very adequately a wide range of steric shifts in hydrocarbons (i.e. those dependent solely upon variations in stereochemistry) and also... 

That particle shape has a basic effect upon instrument calibration was proposed in 1957 and has continued in later theories. It is however a constant effect and, as indicated by Barfield et al.,26-28 dependent on... 

There is a gas-to-liquid shift in the BF coupling constant in BF3. The density dependence of this coupling in the gas phase and the temperature dependence in the pure liquid (liquid density varies with temperature) are both measures of the effects of van der Waals interactions on the BF coupling constant. The effects of solvent on coupling constants have been reviewed by Barfield and Johnston. ... 

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