Colton effects

Noteworthily. the sign of the 220-200 CD band of enones is not sensitive to conformational changes. Examples of the Colton effects of two configurational types of bicyclic enones are shown below51. 

Sometimes the value of C -c, IS given aafre. Iffre is positive i i > ,). a b called a positive Colton effect, etc. 

Fig. 12.25 The Cbllon effect (a) positive Colton effect (b) negative Colton effect. The absorption band is not Shown it would be a positive Gaussian curve centered on A,, but off scale. The dashed line represents the ORD curve (and relates to the refractive index scale on left). The solid line represents the CD curve (e( - e scale on right). The maximum absorption, zero values of ORD. and maxima and minima of CD values occur at A . The two figures, (a) and (b), represent two enantiomers. These are ideal curves Tor an absorption peak well separated from other absorptions. [Modified from Gillard. R. D. Prog, fnorg. Chem. 1966. 7. 215-276. Reproduced with permission.]...

The behaviours of CD and ORD curves in the vicinity of an absorption band are collectively known as the Cotton effect after the French physicist A. Colton who discovered them in 189S. Their importance in the present context is that molecules with the same absolute conhguration will exhibit the same Cotton effect for the same d-d absorption and, if the configuration of one compound is known, that of closeiy similar ones can be established by comparison. 

Steric effects in substituted halocarbonyls of molybdenum and tungsten. R. Colton, Coord. Chem. Rev., 1971, 6,269-284 (29). 

R. Colton Coord. Chem. Rev. 6, Steric effects in substituted halo- 16 Complexes with chelating bis-... 

The reported (14) mechanisms of action of allelochemlcals Include effects on root ultrastructure and subsequent Inhibition of Ion absorption and water uptake, effects on hormone-induced growth, alteration of membrane permeability, changes In lipid and organic acid metabolism, inhibition of protein synthesis and alteration of enzyme activity, and effects on stomatal opening and on photosynthesis. Reduced leaf water potential Is one result of treatment with ferulic and p-coumaric acids (15). Colton and Einhellig (16) found that aqueous extracts of velvetleaf (Abutllon theophrastl Medic.) Increased diffusive resistance In soybean fGlycine max. (L.) Merr.] leaves, probably as a result of stomatal closure. In addition, there was evidence of water stress and reduced quantities of chlorophyll In Inhibited plants. 

This article is concerned with six- and seven-coordinate halocarbonyl complexes of molybdenum(II) and tungsten(II) (Section II), of which earlier reviews by Colton et al.2 on substituted halocarbonyls of group 6 transition metals and on steric effects in substituted halocarbonyls of molybdenum and tungsten3 have been published. Also, reviews on the structures of seven-coordinate compounds by Drew in 19774 and by Melnik and Sharrock in 1985s contain relevant material. 

In 1844, a young American medical student named Gardner Quincy Colton decided to lecture on nitrous oxide and exhibit the effects of the gas after a fellow medical student suggested the idea to him. Colton s first demonstration thrilled him, leaving... 

Colton, R.H., Pahl, I., Ottaviano, L., Bodeutsch, T., and Meyeroltmanns, F., Study of protein adsorption effects on crossflow filtration using BSA and milk protein, J. Pharm. Sci. Technol., 56, 20, 2002. 

In the longer term, picoindentation instruments are likely to be widely used to extend the technique to a still smaller scale, with the help of techniques developed for atomic force microscopy. Already, plastic deformation at depths of a few atomic layers, as well as the effect of surface forces, have been quantified by means of depth-load measurements, using a point force microscope, i.e. an AFM operated in static (non-scanning) mode (Burnham Colton, 1989). 

Although IR frequencies provide a useful measure of the extent of tt bonding in carbonyl complexes, a better quantitative picture can be obtained from C—O force constants. These values are commonly derived from IR data by means of the Colton-Kraihanzel force-field technique. This procedure makes certain simplifying assumptions in order to provide a practical solution to a problem that would be extremely difficult to solve rigorously. Among the important assumptions are that the C—0 vibrations are not coupled to any other vibrational modes of the molecule and that the observed frequencies can be used without correction for anharmonic effects. The results of force constant calculations of this type provide a means of setting up a tr-acceptor series ... 

Meldon, J.H., Smith K.A., and Colton C.K. The effect of weak acids upon the transport of carbon dioxide in alkaline solutions. Chemical Engineering Science, 1977, 32, 939. 

Vilker, V.L., Colton, C.K., and Smith, K.A. The osmotic-pressure of concentrated protein solutions - effect of concentration and ph in sahne solutions of bovine serum-albumin. Journal of Colloid and Interface Science, 1981, 79, No. 2, p. 548-566. 

Zukowska-Grojec, Z., Pruszczyk, P., Colton, C., Yao,J., Shen, G.H., Mayers, A.K. etal. (1993b) Mitogenic effect of neuropeptide Y in rat vascular smooth muscle cells. Peptides 14,263-268. 

Table 1, compiled from data given in Colton and Wilkinson (7) and from Eigen and Wilkens (2, 3), illustrates the differences in inner sphere water lability, as measured by H2O substitution rates, for the aquo ions. Note that within a series (Ni—Cu and Zn—Hg) there is an approximate correlation between ionic radius and the lability of bound water. Eigen and Wilkens (2) have suggested that the deviation from this trend shown by Cu(II) is the result of a Jahn-Teller effect which results in the distortion of the octahedral complex and the labilization of the apical ligands. 

Harrison JA, Colton RJ, White CT, Brenner DW (1993) Effect of atomic-scale siuface roughness on friction a molecular dynamics study of diamond siufaces. Wear 168 127-133... 

Meldon, J.H., Smith, K.A. and C.K. Colton. "An analysis of electrical effects induced by CO2 transport in alkaline solutions." Recent Developments in Separation Science 3 (1979) 1-10. 

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