Correlations with structures

The X-ray photoelectron spectroscopy of metal halides and their complexes halogen binding energies and their correlation with structure. R. A. Walton, Coord. Chem. Rev., 1976,21, 63-91 (112). 

XIII. Biological Activity Correlation with Structure. 127... 

Even though qualitative bonding descriptions of metal atom clusters up to six or seven atoms can be derived and in some cases correlated with structural detail, it is clear that most structures observed for higher clusters cannot be treated thus. Nor do the structures observed correlate with those observed for borane derivatives with the same number of vertices. Much of borane chemistry is dominated by the tendency to form structures derived from the icosahedron found in elemental boron. However, elemental transition metals possess either a close-packed or body-centered cubic arrangement. In this connection, one can find the vast majority of metal polyhedra in carbonyl cluster compounds within close-packed geometries, particularly hexagonal close-packing. 

Fig. 11.3. Electron ionization and methane Cl mass spectra of toluene. The key features of the respective mass spectra are labeled. Spectral interpretation is based on recognition and understanding of these key features and how they correlate with structural elements of the analyte molecule of interest. The signal representing the most abundant ion in a mass spectrum is referred to as the base peak, and may or may not be the molecular ion peak (which carries the molecular mass information). Cl spectra provide confirmation of molecular mass in situations where the El signal for the molecular ion (M+ ) is weak or absent. The Cl mass spectrum provides reliable molecular mass information, but relatively little structural information (low abundance of the fragment ions). Compare with Fig. 11.4.

The spectra presented in this chapter correlate with structure. They appear to be of suitable resolution to encourage more widespread application of this branch of spectroscopy and to justify comparisons with theory. 

The material presented in Section II warrants, apparently, the conclusion that the main test of aromaticity and antiaromaticity is represented by the energetic criterion realizable within the framework of various schemes for calculating resonance energies. In most cases it correlates with structural and magnetic criteria moreover, it often accords well with a manifestation of numerous properties of compounds, which, being regarded as attributes of aromaticity, make its very concept substantially broader. Indeed, the concept of aromaticity claims an increasing number of types of compounds and requires a more and more sophisticated classification. 

The discussion of a series displacement index for classifying mass spectra and for correlation with structural stability includes some monoterpenoids e.g. myrcene limonene, santene). ... 

D. Padro, A. P. Howes, M. E. Smith and R. Dupree, Determination of titanium NMR parameters of ATiOa compounds correlations with structural distortion. Solid State Nud. Magn. Reson., 2000,15, 231-236. 

We take up now the detailed question of how the chemical shifts correlate with structure, then consider relatively recent work on nuclear spin-spin coupling in pyridine and derivatives, and finally illustrate how external influences, solvent, complexation and so on, affect NMR patterns in this area. 

All compounds analyzed have higher 5D values than terrestrial samples, confirming the enrichments seen in bulk measurements. Some individual compounds have very high 5D values, in one case as high as 3600 permil (4.6 times the solar system ratio). The high 5D values seem to correlate with structures that include branching methyl groups. 

Ignition temperature was used with partial success (52, 57, 74, 135,189). Results depended critically on the method used—e.g., adiabatic compression, ignition limits in tubes, or crucible method. Jackson (70, 86, 87) determined ignition temperatures for a large number of hydrocarbons by the crucible method and developed correlations with structure. 

Raman spectroscopy was used by Sane et al. [1.165] to quantitate structural changes in proteins freeze- or spray-dried. Monoclonal antibodies(e.g. RhuMAbVEGF) underwent secondary structural changes in the absence of a lyoprotectant. Increasing molar ratios of cryoprotectant could lead to complete structural preservation. The long-term stability of the dried proteins correlates with structural changes observed by Raman spectroscopy. 

Abstract The fracture properties and microdeformation behaviour and their correlation with structure in commercial bulk polyolefins are reviewed. Emphasis is on crack-tip deformation mechanisms and on regimes of direct practical interest, namely slow crack growth in polyethylene and high-speed ductile-brittle transitions in isotactic polypropylene. Recent fracture studies of reaction-bonded interfaces are also briefly considered, these representing promising model systems for the investigation of the relationship between the fundamental mechanisms of crack-tip deformation and fracture and molecular structure. 

While physicochemical and spectroscopic techniques elucidate valuable physical and structural information, thermal analysis techniques offer an additional approach to characterize NOM with respect to thermal stability, thermal transitions, and even interactions with solvents. Information such as thermal degradation temperature (or peak temperature), glass transition temperature, heat capacity, thermal expansion coefficient, and enthalpy can be readily obtained from thermal analysis these properties, when correlated with structural information, may serve to provide additional insights into NOM s environmental reactivity. 

A knowledge of the kinetics of the reaction at the active sites is of primary importance in determining the nature of catalytic action in heterogeneous catalysis. Information about the nature of the catalyst-substrate interaction can be obtained from the way in which the rate constants in the kinetics change on variation of such parameters as temperature, catalyst treatment, and catalyst composition. In addition, these constants are the quantities which should correlate with structural information such as that obtained by the methods of solid state physics. However, the true kinetics at the active sites is not always obtained unless certain precautions are taken, as has been pointed out in a recent volume of Advances in Catalysis (1). 

Beltrame, P, Beltrame, P.L., Cartini, P, Guardione, D., Lanzetta, C. (1988) Inhibiting action of chlorophenols on biodegradation of phenol and its correlation with structured structural properties of inhibitors. Biotechn. Bioeng. 31, 821-828. 

The end products of the analysis (measurement and interpretation of mineral absorption spectra by crystal field theory) are some parameters that can be correlated with structural properties. 

Based on the earlier work of Meyer and Overton, who showed that the narcotic effect of anesthetics was related to their oil/water partition coefficients, Hansch and his co-workers have demonstrated unequivocally the importance of hydrophobic parameters such as log P (where P is, usually, the octanol/water partition coefficient) in QSAR analysis.28 The so-called classical QSAR approach, pioneered by Hansch, involves stepwise multiple regression analysis (MRA) in the generation of activity correlations with structural descriptors, such as physicochemical parameters (log P, molar refractivity, etc.) or substituent constants such as ir, a, and Es (where these represent hydrophobic, electronic, and steric effects, respectively). The Hansch approach has been very successful in accurately predicting effects in many biological systems, some of which have been subsequently rationalized by inspection of the three-dimensional structures of receptor proteins.28 The use of log P (and its associated substituent parameter, tr) is very important in toxicity,29-32 as well as in other forms of bioactivity, because of the role of hydrophobicity in molecular transport across cell membranes and other biological barriers. 

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