Unexpected Steric Effects of “Remote” Alkyl Groups on the Rate of Conjugate Additions to Alkyl α,β-Ethylenic Sulfones, Sulfoxides, and Esters

2007 ◽  
Vol 72 (7) ◽  
pp. 2329-2334 ◽  
Author(s):  
Aimee R. Usera ◽  
Gary H. Posner
Keyword(s):  
Steric Effects ◽  
Conjugate Additions ◽  
Alkyl Groups

The Sulfinyl Group as a Remote Chiral Auxiliary in Stereoselective Conjugate Additions of Alkyl Groups to α-Methylidene Carbonyl Compounds Initiated by Et3B/O2

2013 ◽  
Vol 2013 (9) ◽  
pp. 1796-1804 ◽  
Author(s):  
José Antonio Fernández-Salas ◽  
M. Carmen Maestro ◽  
M. Mercedes Rodríguez-Fernández ◽  
José L. García Ruano
Keyword(s):  
Carbonyl Compounds ◽  
Chiral Auxiliary ◽  
Conjugate Additions ◽  
Alkyl Groups ◽  
Sulfinyl Group

THE KINETICS OF THE INHIBITED AUTOXIDATION OF TETRALIN. II

1965 ◽  
Vol 43 (10) ◽  
pp. 2724-2728 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Transfer Reaction ◽  
Chain Transfer ◽  
Steric Effects ◽  
Alkyl Groups ◽  
Chain Transfer Reaction ◽  
Phenoxy Radicals ◽  
Kinetics Of

The kinetics of the oxidation of tetralin inhibited by a number of phenols have been examined. The chain transfer reaction between phenoxy radicals and hydroperoxides is subject to both polar and steric effects. The rate of this reaction is increased by electron-attracting substituents on the phenol and is decreased both by ortho-alkyl groups on the phenol and by an increase in the size of the substituents on the hydroperoxides.

Effect of Alkyl Group Structure on Cure Characteristics of N,N-Dialkylthio-Carbamyl-N′,N′-Dialkylsulfenamide Vulcanization Accelerators

1974 ◽  
Vol 47 (4) ◽  
pp. 906-910 ◽  
Author(s):  
R. D. Taylor
Keyword(s):  
Carbon Atom ◽  
Steric Hindrance ◽  
Alkyl Group ◽  
Group Structure ◽  
Substituent Effects ◽  
Steric Effects ◽  
Alkyl Groups ◽  
Inductive Effects ◽  
Cure Rates ◽  
Alpha Carbon

Abstract Wide variations in scorch times and cure rates can be attained with tetraalkylthiocabamylsulfenamides through variation in alkyl groups. Substituent effects are substantial on either the carbamate nitrogen or on the sulfenamide nitrogen. Both inductive effects and steric effects influence the scorch times and cure rates. Positive inductive effects shorten scorch times and increase cure rates. Steric hindrance at the sulfenamide nitrogen increases the scorch time. Branching at the carbon atom beta to the nitrogen has a larger effect on scorch time than branching at the alpha carbon. Thiocarbamylsulfenamides can give appreciably higher cure rates and cure efficiencies than their benzothiazole sulfenamide analogs.

Generalization of an empirical model for bond dissociation energies

1993 ◽  
Vol 71 (4) ◽  
pp. 572-577 ◽  
Author(s):  
Yu-Ran Luo ◽  
Philip D. Pacey
Keyword(s):  
Experimental Data ◽  
Steric Effects ◽  
Bond Dissociation Energies ◽  
Average Deviation ◽  
Ring Strain ◽  
Methyl Substitution ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Alkyl Groups ◽  
Leaving Groups

A relationship between homolytic bond dissociation energies (BDEs) of C—X bonds and the electronegativity of X and the degree of methyl substitution of C has been extended. The range of leaving groups, X, now includes SiH3, GeH3, and PH2 and a variety of C-, N-, and O-centred radicals. Alkyl groups with ethyl and propyl chains attached to the radical centre have been incorporated. Steric effects, including those in bulky silanes, have been treated. The method is believed to be generally applicable where resonance and ring strain are not significant. BDEs for 73 bonds have been calculated; in the 42 cases where experimental data are available, the average deviation is 0.7 kcal/mol.

ChemInform Abstract: The Sulfinyl Group as a Remote Chiral Auxiliary in Stereoselective Conjugate Additions of Alkyl Groups to α-Methylidene Carbonyl Compounds Initiated by Et3B/O2.

ChemInform ◽  
2013 ◽  
Vol 44 (32) ◽  
pp. no-no
Author(s):  
Jose Antonio Fernandez-Salas ◽  
M. Carmen Maestro ◽  
M. Mercedes Rodriguez-Fernandez ◽  
Jose L. Garcia Ruano
Keyword(s):  
Carbonyl Compounds ◽  
Chiral Auxiliary ◽  
Conjugate Additions ◽  
Alkyl Groups ◽  
Sulfinyl Group

STERIC EFFECTS IN THE SYNERGIC EXTRACTION OF THE LANTHANIDES, YTTRIUM, AND SCANDIUM

1963 ◽  
Vol 41 (3) ◽  
pp. 658-666 ◽  
Author(s):  
P. G. Manning
Keyword(s):  
Rare Earth ◽  
Metal Ion ◽  
Equilibrium Constants ◽  
Rare Earth Metals ◽  
Steric Effects ◽  
Organic Species ◽  
Alkyl Groups ◽  
Synergic Extraction ◽  
Carrier Free ◽  
Organic Solutions

From a study of the partitioning of the carrier-free radioisotopes Tm170, Ce144, Eu152/154, Tb160, Lu177, and Y91 between nitric acid and organic solutions containing various proportions of thenoyltrifluoroacetone (HTTA) and dialkyl alkyl phosphonates (S) in odorless kerosene, concentration equilibrium constants (k2) have been computed for the reaction[Formula: see text]where M represents a metal ion, and "w" and "o" are aqueous and organic species respectively.When used in conjunction with the data of Bronaugh and Suttle, the equilibrium constants determined in this study yielded comparative equilibrium constants (k3) for the solvation process [Formula: see text]for the rare-earth metals listed.In the extraction of Sc46, however, the species extracted is dependent on the alkyl groups of the phosphonates, the butyl and 2-ethylhexyl derivatives giving mono- and di-solvates respectively.It is concluded that steric effects are dominant in these synergic systems.

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