Solvolysis of 2-substituted-9-(otrho-substituted phenylmethyl)fluoren-9-yltrimethylammonium ions in various solvents. The effect of steric crowding on alkene formation

1986 ◽  
Vol 64 (6) ◽  
pp. 1060-1071 ◽  
Author(s):  
Peter James Smith ◽  
Jyotsna Pradhan
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Butyl Alcohol ◽  
Reaction Proceeding ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Leaving Group ◽  
Steric Crowding ◽  
Hydrogen Deuterium ◽  
Deuterium Isotope Effects

The solvolytic reaction of several 9-(ortho-substituted phenylmethyl)fluoren-9-yltrimethylammonium salts has been investigated in several different solvents. Substitution and elimination products were found for the reactions in all the solvents studied, with the exceptions that reaction in both tert-butyl alcohol and chloroform led exclusively to the alkene product. The observed rate constants for alkene formation and the percent alkene were measured and it was found that the di-ortho compounds reacted at a faster rate but produced less alkene than the reaction of the corresponding mono-ortho salts. Hydrogen–deuterium isotope effects were also determined for the various reactions. The results are discussed in terms of the reaction proceeding by way of the E1 mechanism, where steric acceleration promotes the loss of the bulky ammonium leaving group to give the carbocation intermediate.

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.

The reactivity of allyl and propargyl alcohols with solvated electrons: temperature and solvent effects

1979 ◽  
Vol 57 (8) ◽  
pp. 839-845 ◽  
Author(s):  
Alexei M. Afanassiev ◽  
Kiyoshi Okazaki ◽  
Gordon R. Freeman
Keyword(s):  
Activation Energy ◽  
Ethylene Glycol ◽  
Rate Constants ◽  
Allyl Alcohol ◽  
Trap Depth ◽  
Activation Energies ◽  
Butyl Alcohol ◽  
Solvated Electrons ◽  
Tert Butyl ◽  
Tert Butyl Alcohol

The rate constants k1 for the reaction of solvated electrons with allyl alcohol in a number of hydroxylic solvents differ by up to two orders of magnitude and decrease in the order tert-butyl alcohol > 2-propanol > 1-propanol ≈ ethanol > methanol ≈ ethylene glycol > water. In methanol and ethylene glycol the rate constants (7 × 107 M−1 s−1 at 298 K) and activation energies (16 kJ/mol) are equal, in spite of a 32-fold difference in solvent viscosity (0.54 and 17.3 cP, respectively) and 3-fold difference in its activation energy (11 and 32 kJ/mol, respectively). The reaction in tert-butyl alcohol is nearly diffusion controlled and has a high activation energy that is characteristic of transport in that liquid (E1 = 31 kJ/mol, Eη = 39 kJ/mol). The activation energies in the other alcohols are all 16 kJ/mol, and it is 14 kJ/mol in water. They do not correlate with transport properties. The solvent effect is connected primarily with the entropy of activation. The rate constants correlate with the solvated electron trap depth. When the electron affinity of the scavenger is small, a favorable configuration of solvent molecules about the electron/scavenger encounter pair is required for the electron jump to take place. The behavior of the rate parameters for propargyl alcohol is similar to that for allyl alcohol, but k1, A1, and E1 are larger for the former. The ratio k(propargyl)/k(allyl) at 298 K equals 10.5 in water and decreases through the series, reaching 1.3 in tert-butyl alcohol. Rate parameters for several other scavengers are also reported.

Secondary α-deuterium kinetic isotope effects for the E2 reaction of the 2-phenylethyl halides with tert-butoxide ion in tert-butyl alcohol

1985 ◽  
Vol 63 (1) ◽  
pp. 100-102 ◽  
Author(s):  
Peter James Smith ◽  
Kanchugarakoppal S. Rangappa ◽  
Kenneth Charles Westaway
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Order Rate Constant ◽  
Butyl Alcohol ◽  
Tert Butyl ◽  
Kinetic Isotope ◽  
Tert Butyl Alcohol ◽  
Elimination Reactions ◽  
Leaving Groups ◽  
High Base

Secondary α-deuterium kinetic isotope effects have been determined for the elimination reactions of 2-phenylethyl halides with tert-butoxide in tert-butyl alcohol at 40 °C in the presence and absence of the crown ether 18C6. The second-order rate constant k2 and the normal (kH/kD)α effect remained constant when the tert-butoxide concentration was varied for reaction of the iodo and bromo compounds. However, both the magnitude of k2 and the secondary α-deuterium isotope effect were significantly dependent on [t-BuO−] when chlorine and fluorine are the leaving groups. It is noteworthy that (kH/kD)α is inverse for the reaction of both the chloro and fluoro compounds at "low" base concentrations and normal at "high" base concentrations. These results are discussed in terms of both syn- and anti-elimination pathways promoted by various associated and dissociated base species. It is suggested that the (kH/kD)α effect may be useful as a criterion for determining the stereochemistry of E2 elimination reactions.

An-Additions to 2,5-dimethoxy-2,5-dihydrofurans, containing electron-accepting substituents in position 3

1982 ◽  
Vol 47 (11) ◽  
pp. 3055-3061 ◽  
Author(s):  
Ivan Stibor ◽  
Jan Šrogl ◽  
Miroslav Janda ◽  
Naděžda Piričová ◽  
Karel Vlažný
Keyword(s):  
Sodium Salt ◽  
Diethyl Malonate ◽  
Addition Product ◽  
Butyl Alcohol ◽  
Reaction Proceeding ◽  
Tert Butyl ◽  
Tert Butyl Alcohol

3-Acetyl-2,5-dimethoxy-2,5-dihydrofuran (V) was alkylated in position 4 with lithium dimethylcuprate and lithium dibutylcuprate. The reaction, proceeding with loss of methanol, afforded 4-acetyl-3-methyl-2-methoxy-2,3-dihydrofuran (X) and 4-acetyl-3-n-butyl-2-methoxy-2,3-dihydrofuran (XI), respectively. Addition of sodium salt of diethyl malonate gave 3-acetyl-4-bis(ethoxycarbonyl)methyl-2,5-dimethoxytetrahydrofuran (XVII) in 69% yield. Addition of methanol, n-butanol and tert-butyl alcohol to methyl 2,5-dimethoxy-2,5-dihydro-3-furoate (VI) in the presence of the corresponding alkoxides afforded the 4-alkoxy derivatives in 95%, 62% and 56% yield, respectively. Reaction of the compound VI with ethyl lithioacetate led to 3-ethoxycarbonylmethyl-4-methoxycarbonyl-2-methoxy-2,3-dihydrofuran (XVI) arising from the addition product by loss of methanol.

Using secondary alpha deuterium kinetic isotope effects to determine the stereochemistry of an E2 reaction; the stereochemistry of the E2 reaction of 1-chloro-2-phenylethane with potassium tert-butoxide in tert-butyl alcohol

2001 ◽  
Vol 79 (7) ◽  
pp. 1145-1152 ◽  
Author(s):  
Peter James Smith ◽  
David AJ Crowe ◽  
Kenneth Charles Westaway
Keyword(s):  
Transition State ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Butyl Alcohol ◽  
State Structure ◽  
Transition State Structure ◽  
Isotopic Labelling ◽  
Tert Butyl ◽  
Kinetic Isotope ◽  
Tert Butyl Alcohol

Isotopic labelling studies have shown that the E2 reaction of 1-chloro-2-phenylethane with potassium tert-butoxide in tert-butyl alcohol occurs via an anti-periplanar stereochemistry. This demonstrates that the different secondary alpha deuterium kinetic isotope effects found for the high and low base concentrations and in the presence of 18-crown-6 ether are because of changes in transition state structure that occur when the form of the reacting base changes rather than to a change in the stereochemistry of the reaction.Key words: E2 reaction, stereochemistry, secondary alpha deuterium kinetic isotope effects, transition state.

Photobehavior of aqueous uranyl ion and photo-oxygenation of isobutane using light from the visible region

2003 ◽  
Vol 81 (3) ◽  
pp. 219-229 ◽  
Author(s):  
Trevor M Bergfeldt ◽  
William L Waltz ◽  
Xiangrong Xu ◽  
Petr Sedlák ◽  
Uwe Dreyer ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Perchloric Acid ◽  
Rate Constants ◽  
Butyl Alcohol ◽  
Uranyl Ion ◽  
Quantum Yields ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Butyl Radical ◽  
Electronically Excited

The photochemical and photophysical behavior of the aqueous uranyl ion [UO2(H2O)5]2+ has been studied under the influence of visible light and with added perchloric acid over the range of 0.01–4 M. In the presence of 2-methylpropane (isobutane), photo-oxygenation of isobutane occurs to yield, as the major product, 2-methyl-2-propanol (tert-butyl alcohol) along with lesser amounts of 2-methyl-2-propene (isobutene) and other C1–C8 products. The quantum yield for formation of tert-butyl alcohol is independent of light intensity at the irradiation wavelength of 415 nm and of uranyl concentration, but it increases from 0.016 ± 0.001 at 0.01 M HClO4 (pH 2) to 0.13 ± 0.01 at 4 M HClO4. The emission spectrum from the electronically excited uranyl ion and the associated quantum yields have been measured in the presence and absence of isobutane, as a function of added perchloric acid. While in both cases the shape of the spectrum remains invariant, the quantum yields increase with increasing perchloric acid concentration. The strong dependence on added perchloric acid is interpreted within the context of the presence and interconversion of two electronically excited species, an acid form, *[UO2(H2O)5]2+, and a base form, *[UO2(H2O)n(OH)]+. It is proposed that both forms react with isobutane to give a tert-butyl radical, and that oxidation of coordinated aqua ligands occur, the latter generating a hydroxyl radical whose reaction with isobutane rapidly leads also to a tert-butyl radical. The reaction of this alkyl radical with ground-state [UO2(H2O)5]2+ then gives rise to the stable tert-butyl alcohol product and reduced forms of uranyl ion. Based upon the values of the quantum yields and of excited-state lifetime measurements reported in the literature, a comprehensive mechanism has been developed in a quantitative manner to provide calculated values of the rate constants for the individual mechanistic steps. The calculated rate constants provide a basis to calculate the values of quantum yields for emission and chemical reaction, as well as for lifetimes, that agree very satisfactorily with the experimental values over a 400-fold concentration change in added perchloric acid.Key words: photo-oxidation, photo-oxygenation, uranyl ion, isobutane, tert-butyl alcohol, lifetime, quantum yield, acid–base dissociation.

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.

scholarly journals Impacts of Sn(II) doping on the Keggin heteropolyacid-catalyzed etherification of glycerol with tert-butyl alcohol

2021 ◽  
pp. 116913
Author(s):  
Márcio José da Silva ◽  
Diego Morais Chaves ◽  
Sukarno Olavo ferreira ◽  
Rene Chagas da Silva ◽  
Jose Balena Gabriel Filho ◽  
...  
Keyword(s):  
Butyl Alcohol ◽  
Tert Butyl ◽  
Tert Butyl Alcohol
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