Steric Effects in Displacement Reactions. VI. The Heats of Formation of the Addition Compounds of Boron Trifluoride with the Monoalkylpyridines. A Linear Relationship Involving Sterically Hindered Reactants1

1955 ◽  
Vol 77 (7) ◽  
pp. 1733-1737 ◽  
Author(s):  
Herbert C. Brown ◽  
Raymond H. Horowitz
Keyword(s):  
Linear Relationship ◽  
Boron Trifluoride ◽  
Heats Of Formation ◽  
Steric Effects ◽  
Displacement Reactions ◽  
Sterically Hindered

Sterically Hindered Aromatic Compounds. VI. A Remote ε-Deuterium Kinetic Isotope Effect in the Solvolysis of Perdeutero-2,4,6-tri-tert-butylbenzyl Chloride

1975 ◽  
Vol 53 (21) ◽  
pp. 3171-3174 ◽  
Author(s):  
L. Ross C. Barclay ◽  
John R. Mercer ◽  
Peter J. MacAulay
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Aromatic Compounds ◽  
Kinetic Isotope Effect ◽  
Inductive Effect ◽  
Steric Effects ◽  
Deuterium Isotope Effect ◽  
Tert Butyl ◽  
Kinetic Isotope ◽  
Sterically Hindered

2,4,6-Tri-tert-butylbenzyl chloride deuterated at the three tert-butyl groups was synthesized. Conductimetric solvolysis studies of the normal and perdeutero-2,4,6-tri-tert-butylbenzyl chloride at 30.06 °C in 80% ethanol–water provides evidence for an inverse remote ε-deuterium isotope effect, kH/kD = 0.873−0.874. Under the same conditions the α-deuterium isotope effect was kH/kαD = 1.166 per deuterium, indicative of limiting solvolytic behavior. The remote ε-deuterium isotope effect for the perdeutero compound is discussed in terms of the inductive effect of deuterium and steric effects on the transition state conformation.

scholarly journals THE RELATIVE ACCEPTOR POWER OF BORON TRIHALIDES AND BORANE TOWARD TRIMETHYLAMINE BY PROTON N.M.R. MEASUREMENTS

1964 ◽  
Vol 42 (7) ◽  
pp. 1518-1523 ◽  
Author(s):  
J. M. Miller ◽  
M. Onyszchuk
Keyword(s):  
Linear Relationship ◽  
Chemical Shifts ◽  
Dipole Moments ◽  
Chloroform Solution ◽  
Heats Of Formation ◽  
Methyl Proton ◽  
Acceptor Activity ◽  
Proton Resonances ◽  
Proton Chemical Shifts

Proton n.m.r. spectra of trimethylamine adducts of the boron trihalides and borane have been measured in chloroform solution. Chemical shifts of methyl protons relative to tetramethylsilane decrease in the order: BBr3 > BCl3 > BH3 > BF3, suggesting that this is the order of acceptor activity toward trimethylamine. This is supported by the existence of a linear relationship between methyl proton chemical shifts and the heats of formation, dipole moments, or infrared vibrational shifts of boron trihalide and borane adducts. Splitting of methyl proton resonances into quartets have been observed for (CH3)3N•BCl3 and (CH3)3N•BBr3 but not for (CH3)3N•BF3 and (CH3)3N•BH3.

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