Study of conformation of dienophile in transition state of diene condensation reactions of trans-piperylene with alkyl acrylates by the method of change in volume involving steric effects

1982 ◽  
Vol 31 (5) ◽  
pp. 1067-1067
Author(s):  
S. K. Shakhova ◽  
B. S. �l'yanov
Keyword(s):  
Transition State ◽  
Steric Effects ◽  
Diene Condensation ◽  
Alkyl Acrylates ◽  
Condensation Reactions

Hydroboration of acyclic allenes with disiamylborane

1969 ◽  
Vol 47 (6) ◽  
pp. 1083-1086 ◽  
Author(s):  
D. S. Sethi ◽  
G. C. Joshi ◽  
D. Devaprabhakara
Keyword(s):  
Carbon Atom ◽  
Transition State ◽  
Steric Effects ◽  
Electrophilic Attack ◽  
Terminal Carbon Atom ◽  
Central Carbon Atom ◽  
Central Carbon

The present investigation demonstrates the hydroboration of 1,2-nonadiene, phenylpropadiene, 3-phenyl-1,2-butadiene, 4,5-nonadiene, and tetramethylallene with disiamylborane. All the allenes except tetramethylallene underwent 100% conversion. Examination of the products indicated preferential electrophilic attack of boron on the least substituted terminal carbon atom in the case of 1,2-nonadiene, phenylpropadiene, 3-phenyl-1,2-butadiene, and on the central carbon atom in 4,5-nonadiene. In tetramethylallene boron, attack was exclusively on the central carbon atom. These results have been explained in terms of steric effects on a four-centered transition state.

scholarly journals Separating Electronic from Steric Effects in Ethene/α-Olefin Copolymerization: A Case Study on Octahedral [ONNO] Zr-Catalysts

Processes ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 384 ◽  
Author(s):  
Francesco Zaccaria ◽  
Roberta Cipullo ◽  
Andrea Correa ◽  
Peter H. M. Budzelaar ◽  
Vincenzo Busico ◽  
...  
Keyword(s):  
Transition State ◽  
Electronic Properties ◽  
Polymerization Kinetics ◽  
Relative Reactivity ◽  
Steric Effects ◽  
Reactivity Ratios ◽  
Ancillary Ligand ◽  
Electronic Effects ◽  
Dft Modeling

Four Cl/Me substituted [ONNO] Zr-catalysts have been tested in ethene/α-olefin polymerization. Replacing electron-donating methyl with isosteric but electron-withdrawing chlorine substituents results in a significant increase of comonomer incorporation. Exploration of steric and electronic properties of the ancillary ligand by DFT confirm that relative reactivity ratios are mainly determined by the electrophilicity of the metal center. Furthermore, quantitative DFT modeling of propagation barriers that determine polymerization kinetics reveals that electronic effects observed in these catalysts affect relative barriers for insertion and a capture-like transition state (TS).

ChemInform Abstract: Polyfluoroalkyl Vinyl Ethers in Diene Condensation Reactions. The First Examples of 2-Polyfluoroalkoxy-3,4-dihydro-2H-pyrans.

ChemInform ◽  
2010 ◽  
Vol 28 (19) ◽  
pp. no-no
Author(s):  
L. L. DMITRIEVA ◽  
V. P. ZINOV'EVA ◽  
G. I. SARAPULOVA ◽  
O. B. BANNIKOVA ◽  
N. A. NEDOLYA
Keyword(s):  
Diene Condensation ◽  
Vinyl Ethers ◽  
Condensation Reactions

scholarly journals Ligand-Controlled Regiodivergence in Nickel-Catalyzed Hydroarylation and Hydroalkenylation of Alkenyl Carboxylic Acids

2020 ◽  
Author(s):  
Zi-Qi Li ◽  
Yue Fu ◽  
Ruohan Deng ◽  
Van Tran ◽  
Yang Gao ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Transition State ◽  
Carboxylic Acids ◽  
Alkyl Group ◽  
Steric Effects ◽  
High Yield ◽  
Mechanistic Studies ◽  
Ligand Environment ◽  
Ligand Free ◽  
Electronic And Steric Effects

<div>A nickel-catalyzed regiodivergent hydroarylation and hydroalkenylation of unactivated alkenyl carboxylic acids is reported, whereby the ligand environment around the metal center dictates the regiochemical outcome. Markovnikov hydrofunctionalization products are obtained under mild ligand-free conditions, with up to 99% yield and >20:1 selectivity. Alternatively, anti-Markovnikov products can be accessed with a novel 4,4-disubstituted Pyrox ligand in excellent yield and >20:1 selectivity. Both electronic and steric effects on the ligand contribute to the high yield and selectivity. Mechanistic studies suggest a change in the turnover-limiting and selectivity-determining step induced by the optimal ligand. DFT calculations reveal that in the anti-Markovnikov pathway, repulsion between the ligand and the alkyl group is minimized (by virtue of it being 1° versus 2°) in the rate- and regioselectivity-determining transmetalation transition state. <br></div>

Kinetics of reactions of para-substituted phenyl isocyanates with amines and alcohols

1991 ◽  
Vol 56 (8) ◽  
pp. 1662-1670 ◽  
Author(s):  
Ivan Danihel ◽  
Falk Barnikol ◽  
Pavol Kristian
Keyword(s):  
Transition State ◽  
Solvent Effects ◽  
Rate Constants ◽  
Substituent Effects ◽  
Steric Effects ◽  
Stopped Flow ◽  
Partial Charges ◽  
Hammett Correlation ◽  
One Step ◽  
Kinetics Of

The reaction of para-substituted phenyl isocyanates with amines and alcohols was studied by stopped-flow method. The Hammett correlation obtained showed that the sensitivity of the above mentioned reactions toward substituent effects is the same as that of analogous reactions of phenyl isothiocyanates (ρ ~ 2). The rate constants of these reactions were found to be affected more by steric effects than by solvent effects. An one step multicentre mechanism with partial charges in transition state has been proposed for the title reactions.

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