Chemical exploration

For small molecules, the accuracy of solutions to the Schrodinger equation competes with the accuracy of experimental results. However, these accurate ab initio calculations require enormous computation and are only suitable for the molecular systems with small or medium size. Ab initio calculations for very large molecules are beyond the realm of current computers, so HyperChem also supports semi-empirical quantum mechanics methods. Semi-empirical approximate solutions are appropriate and allow extensive chemical exploration. The inaccuracy of the approximations made in semi-empirical methods is offset to a degree by recourse to experimental data in defining the parameters of the method. Indeed, semi-empirical methods can sometimes be more accurate than some poorer ab initio methods, which require much longer computation times. 

A notable utilization of the Hinsberg procedure was executed in the synthesis of a thiophene analogue of porphyrin. A previous synthesis of the tetrathioporphyrin dication of 7 found this material to be unsuitable for chemical exploration as a result of its limited accessibility and solubility. Efforts by Vogel et al. were then directed toward... 

The Chemical Principles Web site is at www.whfreeman.com/chemicalprinciples4e The Web-based media support for Chemical Principles offers students a range of tools for problem solving and chemical exploration, including ... 

The discovery of the binary (Yb,Ca)-Cd i-QCs [19] was a remarkable milestone in the history of QCs. The reasons are apparent they offered unique opportunities for structural analyses as they exhibited negligible chemical disorder, probably because of the large differences in the chemical crystallography of the components, in contrast to more common problems with ternary intermetallics. In addition, they also represented new (Tsai) types of AC cores and of i-QCs with a structural motif different from those of the Mackay and Bergman types (above) that were better known at the time. Without doubt, such a breakthrough discovery must lead to an era of related chemical explorations or tunings. Actually, almost all of the i-QC systems developed since 2000 are Tsai types [28,29], including our own additions (below). 

Few known and thermodynamically feasible molecular structures are presently seen as impossible goals for synthesis. New transformations and effective strategies permit chemists to synthesize highly complex molecules, such as new natural compounds discovered in the continued chemical exploration of the natural world. Again, the point of such work is to develop new chemistry that permits an approach to structures of the type found in nature. This expands the power of chemistry and allows medicinal chemists to synthesize complex structures. 

The first organic free radical to be discovered was triphenylmethyl, the result of the effort of Gomberg to prepare hexaphenylethane.6 In geographical exploration, isolated white spaces on the map rarely contain anything strikingly different from the neighboring explored regions chemical exploration leads to all sorts of surprises. 

A high-level quantum chemical exploration of the Horner-Wandsworth-Emmons reaction has indicated that ring closure of the P—O bond (which favors formation of -product) is rate determining in the gas phase and that the C—C bond-forming addition step is rate determining in most solvated systems several effects that could account for the E/Z selectivities observed have been identified. 

Sorensen, B. (2004e). Quantum chemical exploration of PEM fuel cell processes. In "Proc. 15 World Hydrogen Energy Conf., Yokohama". 28K-02, CD Rom, Hydrogen Energy Soc. Japan. 

The Ecstatic Adventure Reports of Chemical Explorations of the Inner World... 

Sanderson, R.T., 1940. Some neglected aspects of chemical exploration. Geophysics, 5 284-294. 

Brandt, P., Norrby, P.-O., Martin, I., Rein, T. A Quantum Chemical Exploration of the Horner-Wadsworth-Emmons Reaction. J. Org. Chem. 1998, 63, 1280-1289. 

H. Mcllwain, The Chemical Exploration of the Brain, Elsevier, Amsterdam, 1963. 

East of these regions lie the halogens fluorine in the north to iodine in the south, and immediately below iodine the little-known astatine, on the southern shore. The halogens, apart from astatine, are enormously useful to nature and to industry, and these regions have been extensively exploited by both. Fluorine was largely a laboratory curiosity during the first incursions of chemical explorers into the region in the late nineteenth century it is a particularly chemically virulent gas, and, indeed, is difficult to store, because of the ease with which it launches attacks on containers and transforms them into sieves. However, in the mid-twentieth century it became necessary to separate the isotopes of uranium for use in... 

The chemical exploration of perchloro-organic chemistry was initiated early last century by the almost simultaneous discovery of three chlorocar-bons perchloroethane, perchloroethylene and perchlorobenzene (Faraday, 1820 Julin, 1821 Muller, 1862, 1864 Phillips and Faraday, 1821a,b). In spite of its early, rather sudden, start, this chemistry remained almost dormant until the second third of the current century. 

A group of questionably qualified chemical explorers have decided that the best way to correlate reaction equihbrium is directly through the change in mols via... 

The class of oxide materials has greatly benefited from the chemical exploration of multinary systems, virtually right from the beginning. Thus, besides a number of binary compounds, mainly in use as structural ceramics, there is an impressive pleAora of multinary oxide materials being applied as functional, as well as structural ceramics. In some instances these are even... 

There is a surprisingly large number of inconspicuous chemical explorers out there all over the world, doing their synthetic thing in their private laboratories. They are truly the astronauts of inner space. 

Cui Sanyuan. 2005. Predicting Method Study on Water Disaster of Coal Mine by Mach Information Resources. Journal of Physical and Chemical Exploring, 557-560,29(6). 

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