Results 261 to 270 of about 133,959 (307)

Steric effects on atropisomerism in tetraarylporphyrins

Journal of the American Chemical Society, 1987
AbstractThe rate of aryl ring rotation in the series of porphyrins (I) is studied by NMR spectroscopy and chromatography.
Leslie D. Field, Margaret M. Harding, Sever Sternhell, Maxwell J. Crossley, Adrienne J. Forster   +4 more
openaire   +3 more sources

Sterically crowded aryloxide compounds of aluminum: electronic and steric effects

Organometallics, 1991
The mononuclear, four-coordinate aluminum compounds AlR 2 (BHT)L and AlR(BHT) 2 L [R=Me, Et; BHT=2,6-di-tert-butyl-4-methylphenoxide; L=2-Mepy, 4-Mepy, 2,6-Me 2 py, CH 3 CN, N(C 2 H 4 ) 3 CH, HNEt 2 , HN i Bu 2 , H 2 N t Bu,H 2 N n Bu, NH 3 , py•O] are obtained when AlR 3 is treated with the correct molar equivalent of BHT-H and the appropriate Lewis ...
Matthew D. Healy, Andrew R. Barron, Joseph W. Ziller   +2 more
openaire   +2 more sources

The question of remote steric effects

Tetrahedron Letters, 1994
Abstract Remote steric effects, thought to arise from long hydrocarbon chains coiling about reactive sites, are absent in three non-aqueous systems designed to maximize the effect.
F.M. Menger, Kingsley H. Nelson
openaire   +2 more sources

Steric effects on geminate recombinations

Journal of the American Chemical Society, 1990
Steric effects on the binding of isonitrile ligands to iron(II) porphyrins were investigated by picosecond flash photolysis. Two different types of steric effects were distinguished and characterized: (1) steric restrictions to porphyrin planarity and (2) blocking of the pathway for ligand approach.
Douglas Magde, Douglas J. Taube, Karen A. Jongeward, Teddy G. Traylor   +3 more
openaire   +2 more sources

Is the Hammett’s Constant Free of Steric Effects?

The Journal of Physical Chemistry A, 2012
In this work, we have explored the validity of the hypotheses on which rest the Hammett's approach to quantify the substituent effect on a reaction center, by applying two DFT energy decomposition schemes. This is performed by studying the change in the total electronic energy, ΔΔE, associated with a proton transfer isodesmic equilibrium.
Luis Rincón, Rafael Almeida
openaire   +3 more sources

Steric effects in hydrosilylation of styrene

Collection of Czechoslovak Chemical Communications, 1980
Hydrosilylation of styrene, 2-phenyl-1-propene, trans-1-phenyl-1-propene by (CH3)R2SiH (R = C2H5, i-C3H7, i-C4H9) and R'3SiH (R' = i-C3H7, t-C4H9) in the presence of [RhCl.{P(C6H5)3}3] (I), [{RhCl(C2H4)2}2] (II) and H2PtCl6 as catalysts has been studied.
Gabriela Kuncová, Václav Chvalovský
openaire   +2 more sources

Substituent effects on steric strain

Chemical Physics Letters, 2003
Accurate quantum chemical calculations were performed on a series of mono-substituted tetrahedranes and [3]-prismanes by the high-level ab initio G3/B3LYP method. The relative stabilities of substituted tetrahedranes vs. their [3]-prismane analogues and the influence of substitution on steric strain are discussed.
openaire   +2 more sources

Steric effects in [2.2]metaparacyclophanes. Steric isotope effect, remote substituent effect on a steric barrier, and other steric phenomena

Journal of the American Chemical Society, 1974
R. A. Barnes, Virgil Boekelheide, S. A. Sherrod, R. Da Costa   +3 more
openaire   +2 more sources

Steric Effect of Methylene Groups. I

Journal of the American Chemical Society, 1945
Richard T. Arnold, Vincent J. Webers, R. M. Dodson   +2 more
openaire   +4 more sources

Steric effects in polybitniophenes

International Conference on Science and Technology of Synthetic Metals, 1994
G. Zotti, Tiziana Benincori, Giuseppe Zerbi, Elisabetta Brenna, T. Pilatic, Franco Sannicolò, Licia Trimarco, Roberto Todeschini, Giorgio Moro   +8 more
openaire   +2 more sources