Results 241 to 250 of about 290,507 (301)

Attractive steric effects

Journal of Chemical Education, 1973
Attractive steric effects cause some organic structures to be more stable when bulky side-groups are closer together.
A. Liberles, A. Greenberg, J. E. Eilers
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Steric effect on fluorescence quenching

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2005
In this communication we have reported the steric effect on the fluorescence quenching rate constants of the electron transfer (ET) process. We have done a comparative study using donor (D)-acceptor (A) systems with different exergonicity (-deltaG(f)). Different carbazole derivatives (CZ): 1,4-dicyanobenzene (DCB) systems (-deltaG(f) = 0.7-0.8 eV) were
Suchandra, Chatterjee, Samita, Basu, Nandita, Ghosh, Manas, Chakrabarty   +3 more
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Steric effects in heteroboranes

Journal of Organometallic Chemistry, 1994
Abstract In (Ph 3 PCu) 2 Ph 2 C 2 B 9 H 9 ( Ia ) and {( o -tol) 3 PCu} 2 Ph 2 C 2 B 9 H 9 ( Ic ) one copper atom occupies a polyhedral vertex position but is slipped away from the cage carbon atoms (the latter the more so) to relieve phosphine ṫ C cage -phenyl crowding. The second copper atom is exo -facially bonded to the B(8)B(9)B(12) triangular
Kerry J. Adams, Jill Cowie, Steven G.D. Henderson, Gillian J. McCormick, Alan J. Welch   +4 more
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Steric effects in dispersion forces interactions

Physical Review E, 2008
Classically, there have been two different ways to obtain mean-field theories for liquid crystals. One is based on short-range repulsive steric forces and the other on long-range attractive dispersion forces. In the former approach, it is the anisotropic shape of the molecules that leads to the anisotropic interaction, and in the latter it is the ...
SONNET A. M, VIRGA, EPIFANIO GUIDO GIOVANNI   +1 more
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On the origin of the steric effect

Physical Chemistry Chemical Physics, 2012
A quantitative analysis of the steric effect of aliphatic groups was carried out from first principles. An intuitive framework is proposed that allows the separation and straightforward interpretation of two contributors to the steric effect: steric strain and steric shielding (hindrance). When a sterically demanding group is introduced near a reactive
Pintér, Balasz, Fievez, Tim, Bickelhaupt, F.m., Geerlings, Paul, De Proft, Frank   +4 more
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Steric Effects and Solvent Effects in Ionic Reactions

Science, 2002
Rates of S N 2 reactions of chloride ion with methyl- and tert -butyl–substituted chloroacetonitrile were measured by using Fourier transform–ion cyclotron resonance spectrometry to follow the isotopic exchange reaction.
Colleen K, Regan, Stephen L, Craig, John I, Brauman   +2 more
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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, Joseph W. Ziller, Andrew R. Barron   +2 more
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Remote Control by Steric Effects

Science, 2014
A rhodium-catalyzed reaction places a silicon substituent on the site farthest away from the largest group present on an aromatic ring. [Also see Research Article by Cheng and Hartwig ]
Mamoru Tobisu, Naoto Chatani
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σ‐Correlations and steric effects

Organic Magnetic Resonance, 1982
AbstractCarbon‐1 shifts in 1‐dimethylimino‐3‐dimethylamino‐1‐(4‐substituted)phenylprop‐2‐ene perchlorates show high correlation and negative dependence v. a σ set having high f character, similar to α and carbonyl carbon shifts in 4‐substituted styrenes and N,N‐dimethylbezamides, respectively.
S. N. Balasubrahmanyam, I. M. Mallick
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Steric effects in carbene cycloadditions

Tetrahedron Letters, 1983
Abstract Steric effects in cycloadditions with alkenes prevent the occurrence of a general linear free energy relationship between the reactivities of carbenes. Nevertheless, the isoselective temperature remains constant.
Bernd Giese, Woo Bung Lee, Carola Stiehl
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