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The effect of the tert-butyl group on the progress of a chemical reaction is called the Thorpe–Ingold effect illustrated in the Diels-Alder reaction below. Compared to a hydrogen substituent, the tert-butyl substituent accelerates the reaction rate by a factor of 240. [2] tert-Butyl effect. The tert-butyl effect is an example of steric hindrance.
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. Various arrangements of atoms in a molecule that differ by rotation about single bonds can also be referred to as different conformations ...
A Newman projection is a drawing that helps visualize the 3-dimensional structure of a molecule. [1] This projection most commonly sights down a carbon-carbon bond, making it a very useful way to visualize the stereochemistry of alkanes.
In a Newman projection, the molecule will be in a staggered arrangement with the anti-periplanar functional groups pointing up and down, 180° away from each other (see Figure 4). Figure 5 shows 2-chloro-2,3-dimethylbutane in a sawhorse projection with chlorine and a hydrogen anti-periplanar to each other.
The Cram's rule of asymmetric induction named after Donald J. Cram states In certain non-catalytic reactions that diastereomer will predominate, which could be formed by the approach of the entering group from the least hindered side when the rotational conformation of the C-C bond is such that the double bond is flanked by the two least bulky groups attached to the adjacent asymmetric center. [3]
The iodine group is homolytically removed to form an aryl radical by a tributyltin hydride/triethylboron/oxygen mixture as in the Barton–McCombie reaction. Although the hindered rotation is now removed in the aryl radical, the intramolecular reaction with the alkene is so much faster than is rotation of the carbon–nitrogen bond that the ...
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]
In alkanes, optimum overlap of atomic orbitals is achieved at 109.5°. The most common cyclic compounds have five or six carbons in their ring. [6] Adolf von Baeyer received a Nobel Prize in 1905 for the discovery of the Baeyer strain theory, which was an explanation of the relative stabilities of cyclic molecules in 1885.