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The gauche conformation on the right is a conformer, while the eclipsed conformation on the left is a transition state between conformers. Above: Newman projection; below: depiction of spatial orientation. In chemistry, rotamers are chemical species that differ from one another primarily due to rotations about one or more single bonds.
The gauche effect is very sensitive to solvent effects, due to the large difference in polarity between the two conformers.For example, 2,3-dinitro-2,3-dimethylbutane, which in the solid state exists only in the gauche conformation, prefers the gauche conformer in benzene solution by a ratio of 79:21, but in carbon tetrachloride, it prefers the anti conformer by a ratio of 58:42. [9]
The molecular configuration of a molecule is the permanent geometry that results from the spatial arrangement of its bonds. [1] The ability of the same set of atoms to form two or more molecules with different configurations is stereoisomerism.
More complex molecules, such as butane, have more than one possible staggered conformation. The anti conformation of butane is approximately 0.9 kcal mol −1 (3.8 kJ mol −1) more stable than the gauche conformation. [1] Both of these staggered conformations are much more stable than the eclipsed conformations.
When two fluorine atoms are in vicinal (i.e., adjacent) carbons, as in 1,2-difluoroethane (H 2 FCCFH 2), the gauche conformer is more stable than the anti conformer—this is the opposite of what would normally be expected and to what is observed for most 1,2-disubstituted ethanes; this phenomenon is known as the gauche effect. [9]
In everyday language, and often in materials science, a chemical substance is said to be "stable" if it is not particularly reactive in the environment or during normal use, and retains its useful properties on the timescale of its expected usefulness. In particular, the usefulness is retained in the presence of air, moisture or heat, and under ...
Cyclohexane is the most stable of the cycloalkanes, due to the stability of adapting to its chair conformer. [4] This conformer stability allows cyclohexane to be used as a standard in lab analyses. More specifically, cyclohexane is used as a standard for pharmaceutical reference in solvent analysis of pharmaceutical compounds and raw materials.
Below the boiling point, the liquid is the more stable state of the two, whereas above the boiling point the gaseous form is the more stable. Common transitions between the solid, liquid, and gaseous phases of a single component, due to the effects of temperature and/or pressure are identified in the following table: