Steric Crowding and the Reactivity of Substituted tert-Butyl Perbenzoates

1975 ◽  
Vol 53 (7) ◽  
pp. 979-985 ◽  
Author(s):  
Siddick Icli ◽  
Kandil A. Kandil ◽  
C. Thankachan ◽  
Thomas T. Tidwell
Keyword(s):  
Ground State ◽  
Hydrogen Abstraction ◽  
Activation Parameters ◽  
Carboxyl Group ◽  
Enhancing Effect ◽  
Tert Butyl ◽  
Rate Acceleration ◽  
Steric Crowding ◽  
Polar Factor

The relative rates of decomposition of peroxyesters in cumene at 100° and their activation parameters ΔH≠ (kcal/mol) and ΔS≠ (cal deg−1 mol−1) were tert-butyl perbenzoate (1) 1.0, 34.0, 9.3; tert-butyl pertoluate (7) 1.3, 32.2, 4.8; tert-butyl permesitoate (8) 11, 31.9, 8.4; and tert-butyl 2,4,6-tri-tert-butylperbenzoate (9) 29, 32.9, 13.0. Each peroxyester yielded the corresponding acid as one of the products. The reactions are all interpreted as proceeding through a rate-determining scission of the O—O bond to yield a benzoyloxy radical, which then undergoes competitive decarboxylation and hydrogen abstraction from the solvent. The small rate acceleration due to a para substituent is interpreted as due to a polar factor and the larger rate enhancing effect of the ortho substituents is interpreted as due to destabilization of the ground state due to twisting of the carboxyl group out of conjugation with the ring.

Thermodynamic and Kinetic Investigation of the Solvent Effect on the Oxidation of [Co(en)2SCH2COO]+ with S2O82- In Water-Methanol and Water-tert-Butyl Alcohol Mixtures

1993 ◽  
Vol 58 (5) ◽  
pp. 1001-1006 ◽  
Author(s):  
Oľga Vollárová ◽  
Ján Benko
Keyword(s):  
Transfer Functions ◽  
Activation Parameters ◽  
Butyl Alcohol ◽  
Oxidation Of Co ◽  
Kinetics Of Oxidation ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Alcohol Mixtures ◽  
Kinetics Of

The kinetics of oxidation of [Co(en)2SCH2COO]+ with S2O82- was studied in water-methanol and water-tert-butyl alcohol mixtures. Changes in the reaction activation parameters ∆H≠ and ∆S≠ with varying concentration of the co-solvent depend on the kind of the latter, which points to a significant role of salvation effects. The solvation effect on the reaction is discussed based on a comparison of the transfer functions ∆Ht0, ∆St0 and ∆Gt0 for the initial and transition states with the changes in the activation parameters accompanying changes in the CO-solvent concentration. The transfer enthalpies of the reactant were obtained from calorimetric measurements.

The antioxidant methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate

2014 ◽  
Vol 70 (11) ◽  
pp. 1050-1053 ◽  
Author(s):  
Xiang Li ◽  
Zhi-Gang Wang ◽  
Hou-He Chen ◽  
Sheng-Gao Liu
Keyword(s):  
Hydrogen Bonding ◽  
Dimethyl Sulfoxide ◽  
Methyl Acrylate ◽  
Title Compound ◽  
Intermolecular Hydrogen Bonding ◽  
Tert Butyl ◽  
Ester Carbonyl ◽  
Compound C ◽  
Steric Crowding

The title compound, C18H28O3, was prepared by the reaction of 2,6-di-tert-butylphenol with methyl acrylate under basic conditions using dimethyl sulfoxide as the promoter. The structure of this antioxidant indicates significant strain between theortho tert-butyl substituents and the phenolic OH group. In spite of the steric crowding of the OH group, it participates in intermolecular hydrogen bonding with the ester carbonyl O atom.

Reactions of benzyl methyl substituted-benzyl phosphites with tert-butyl hypochlorite: "balanced TS" validating reactivity/selectivity principle

1998 ◽  
Vol 76 (6) ◽  
pp. 836-842
Author(s):  
Sung Soo Kim ◽  
Yu Zhu ◽  
In Seok Oh ◽  
Chang Gyeong Lim
Keyword(s):  
Benzyl Chloride ◽  
Activation Parameters ◽  
Differential Activation ◽  
Tert Butyl ◽  
Benzyl Chlorides ◽  
Butyl Group ◽  
Tert Butyl Group ◽  
Polar Transition ◽  
Isokinetic Relations ◽  
Selectivity Principle

Reactions of a series of several benzyl methyl substituted-benzyl phosphites with tert-butyl hypochlorite were investigated. The reactions produced phosphates, isobutene, alkyl chlorides, and benzyl chlorides via phosphonium chlorides as intermediates. Furthermore, the phosphates bearing a tert-butyl group underwent fragmentation to yield isobutene and another phosphates. Relative rates of formations of substituted benzyl and benzyl chloride (kY/kH) were measured at the temperatures (-20, 0, 20, 40°C). Logarithms of the rates (log kY/kH) were plotted against sigma + and 1/T, respectively. The former gave Hammett correlations to suggest a polar transition state (TS). The latter yielded differential activation parameters (ΔΔ Hdouble daggerY-H and ΔΔ Sdouble daggerY-H ), which indicate isokinetic relations and enthalpy control of rates. The selectivities (kY/kH) decrease with higher temperatures and thereby follow the reactivity/selectivity principle.Key words: phosphites, tert-butyl hypochlorite, Hammett correlations, differential activation terms, reactivity/selectivity principle.

Activation parameters for tert-butyl rotation in tert-butyldimethylamine

Tetrahedron ◽  
1971 ◽  
Vol 27 (23) ◽  
pp. 5761-5766 ◽  
Author(s):  
C.H. Bushweller ◽  
J.W. O'Neil ◽  
H.S. Bilofsky
Keyword(s):  
Activation Parameters ◽  
Tert Butyl

The reaction between 2,2-di(4-nitrophenyl)1,1,1-trifluoroethane and tert-butoxide ion in tert-butyl alcohol solvent

1980 ◽  
Vol 58 (18) ◽  
pp. 1979-1982 ◽  
Author(s):  
Arnold Jarczewski ◽  
Kenneth T. Leffek
Keyword(s):  
Isotope Effects ◽  
Activation Parameters ◽  
Butyl Alcohol ◽  
Blue Colour ◽  
Butyl Ether ◽  
Tert Butyl ◽  
Kinetic Isotope ◽  
Tert Butyl Alcohol ◽  
Reaction Proceeds ◽  
Alcohol Solvent

The reaction between 2,2-di(4-nitrophenyl) 1,1,1-trifluoroethane and excess sodium tert-butoxide in tert-butyl alcohol takes place rapidly to yield first the olefin, by elimination of HF. This is followed by a slower addition of tert-butoxide to the olefin, which upon reaction with the solvent gives the tert-butyl ether as the final product. The blue anions involved in each of these reactions are observed.Rate constants, the primary deuterium kinetic isotope effects, and the activation parameters have been measured for the appearance of the initial blue colour and also for the formation of the olefin. It is concluded that the reaction proceeds by a reversible ElcB mechanism.

Kinetic studies on the mechanism of the decomposition of a number of β-substituted tert-butyl α, α -dimethylperpropionates

1977 ◽  
Vol 55 (4) ◽  
pp. 612-618 ◽  
Author(s):  
Dennis D. Tanner ◽  
H. Yabuuchi ◽  
H. Lutzer
Keyword(s):  
General Formula ◽  
Activation Parameters ◽  
Kinetic Studies ◽  
Neighboring Group ◽  
Group Participation ◽  
Tert Butyl ◽  
Bond Scission ◽  
Neighboring Group Participation

A series of ter-butyl peresters having a general formula corresponding to I were synthesized.[Formula: see text]The thermally initiated rates of decomposition of these peresters were determined at several temperatures and the activation parameters for these thermolyses were calculated.The rates of decomposition were relatively insensitive to the substituents and followed the order I > C2H5 > C6H5S > H > Br > Cl. The activation parameters and product studies were consistent with a simple two bond scission mechanism and no evidence could be found for neighboring group participation in these homolyses.

Arrhenius Parameters for Reaction of tert-Butylperoxy Radicals with some Hindered Phenols and Aromatic Amines

1973 ◽  
Vol 51 (22) ◽  
pp. 3738-3745 ◽  
Author(s):  
James Anthony Howard ◽  
Edward Furimsky
Keyword(s):  
Hydrogen Atom ◽  
Rate Constants ◽  
Aromatic Amines ◽  
Activation Parameters ◽  
Peroxy Radical ◽  
Hydrogen Atom Transfer ◽  
Tert Butyl ◽  
Radical Decay ◽  
Order Of Magnitude ◽  
Hindered Phenols

The reaction of tert-butylperoxy radicals with some 2,6-di-tert-butyl-4-substituted phenols, α-naphthol, α-naphthylamine, and N-phenyl-α-naphthylamine has been studied by following the change in radical concentration with time using an e.p.r. spectrometer. Rates of radical decay were first-order in both reactants and were not influenced by the presence of tert-butyl hydroperoxideAbsolute values of the second-order rate constants were measured from −35 to −100° and the preexponential factors and activation energies fell in the range 104–105 M−1 s−1 and 0.5–1.0 kcal mol−1. Rate constants for deuterated phenols (OD) and aromatic amines (ND) were an order of magnitude lower than for the corresponding light compoundsThere was no evidence for quantum mechanical tunneling in these hydrogen atom transfer reactions and it would appear that the activation parameters are low because reaction initially involves the formation of a hydrogen bonded peroxy radical – phenol (or aromatic amine) complex, followed by the transfer of a hydrogen atom within the complex

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