Results 241 to 250 of about 168,162 (295)

Neo-pentyl Alcohol and Steric Hindrance

Nature, 1947
Whitmore and Rothrock1 showed that the hydroxyl group in neo-pentyl alcohol has remarkable resistance against replacement by a halogen atom through the agency of thionyl chloride and phosphorus tribromide. Dostrovsky, Hughes and Ingold2 attribute this to steric hindrance to end-on approach to the α-carbon atom. Whitmore and Rothrock, however, leave the
W, GERRARD, A, NICHVATAL
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Steric hindrance of acetophosphides

Bulletin of the Academy of Sciences of the USSR Division of Chemical Science, 1968
1. The introduction of a bulky substituent at the carbonyl group in acetophosphides invokes steric hindrance to the existence of the cis isomer. 2. The low-frequency peak νCO in the IR spectra of acetophosphides is due to the trans isomer.
R. G. Kostyanovskii, V. V. Yakshin, S. L. Zimont, I. I. Chervin   +3 more
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Quantum Mechanical Size and Steric Hindrance

The Journal of Physical Chemistry A, 2006
A quantum mechanical definition of molecular size and shape is formulated from the electronic second moment of the Hartree-Fock wave function. The shape tensor is defined to be invariant with respect to the origin. The geometric average of the eigenvalues of the tensor correlates very well with van der Waals and Bragg-Slater radii.
Joshua W, Hollett, Aaron, Kelly, Raymond A, Poirier   +2 more
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STERIC HINDRANCE AND HEATS OF FORMATION

Nature, 1943
IN the low-temperature polymerization of isobutene by boron fluoride, BF3, the heat of polymerization, which has been found to be in the neighbourhood of 10 kcal. per mole, is lower than would be expected on the basis of theoretical calculations1. Both chemical1 and X-ray2 evidence support the head-to-tail chain-structure:
A. G. EVANS, M. POLANYI
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Steric hindrance in acetamidomesitylene

Journal of Applied Chemistry, 1951
AbstractThe acetyl group of acetamidomesitylene is not split off either by acids or by alkalis under analytical conditions. A laboratory preparation of acetamidomesitylene is described.
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Inhibition of Nitrosation by Steric Hindrance

Journal of Agricultural and Food Chemistry, 1997
The nitrosation of piperidine, 2-methylpiperidine, 4-methylpiperidine, 2,6-dimethylpiperidine, and 2-ethylpiperidine in acid medium was studied. Kinetic monitoring of the reactions was accomplished by spectrophotometric analysis of the nitrosamine formed at λ = 249 nm.
Samuel González-Mancebo, Emilio Calle, M. Pilar García-Santos, Julio Casado   +3 more
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Steric Hindrance in Vinyl-Mesitylene

Nature, 1948
A NUMBER of workers have observed various anomalous properties in nuclear-substituted derivatives of mesitylene, such anomalies usually being ascribed to restricted rotation about the bond connecting the substituent to the benzene ring caused by the two ortho-methyl - groups.
F. R. BUCK, G. T. KENNEDY, F. MORTON, E. M. TANNER   +3 more
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The origin of steric hindrance in cyclohexane derivatives

Experientia, 1953
Aus der Veresterungsgeschwindigkeit der stereoisomeren Menthole mitp-Nitrobenzoylchlorid lasst sich schliessen, dass diese Molekule in derjenigen Konstellation reagieren, in welcher die Oxygruppe eine aquatoriale Stellung einnimmt. In starren Molekulen (wie dietrans-Dekalole), bei denen die Verschiebung einer Oxyoder Estergruppe von der polaren in die ...
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Origin of steric hindrance in ethane

International Journal of Quantum Chemistry, 1994
AbstractSteric hindrance has been regarded as a result of nonbonding atomic repulsion and measured in terms of empirically obtained van der Waals radii. The authors sought the cause of steric hindrance using the partial derivatives of the energy‐components with respect to a nuclear coordinate.
Hiroaki Tokiwa, Hiroshi Ichikawa
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Steric hindrance in substituted dibenzofurans

Journal of the Chemical Society, Perkin Transactions 2, 1977
Ten alkyl-substituted dibenzofurans (3) have been synthesized by irridiation of the corresponding diphenyl ethers (4). 13C Chemical shift analysis indicates that some of the highly substituted compounds (3d, g–i) are probably twisted out of the molecular plane due to steric interaction of the substituents in the 1 and 9 positions.
Klaus-Peter Zeller, Stefan Berger
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