Elimination reactions of 3-pentyl halides. Relative deuterium isotope effects for cis- and trans-pent-2-ene formation

1968 ◽  
pp. 438
Author(s):  
Dean L. Griffith ◽  
Burton Singerman
Keyword(s):  
Isotope Effects ◽  
Deuterium Isotope Effects ◽  
Elimination Reactions ◽  
Cis And Trans

scholarly journals Deuterium Isotope Effects in the Oxidation of 2,3-Dimethyl-2-butene via the Bromohydroperoxide, by Singlet Oxygen and by Triphenyl Phosphite Ozonide

1972 ◽  
Vol 50 (24) ◽  
pp. 4034-4049 ◽  
Author(s):  
Karl R. Kopecky ◽  
Johan H. van de Sande
Keyword(s):  
Singlet Oxygen ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Bond Breaking ◽  
Triphenyl Phosphite ◽  
Deuterium Isotope Effect ◽  
Major Isomer ◽  
Deuterium Isotope Effects ◽  
Oxygen Oxidation ◽  
Cis And Trans

The partially deuterated alkenes (CH3)2C = C(CD3)2 (1b) and CH3CD3C = CCH3CD3 (1c) were prepared and converted to the corresponding allylic hydroperoxides by the routes shown in the title. Two bromohydroperoxides were formed from 1b in a 1.6:1 ratio with the major isomer having the OOH group on the carbon bearing the CH3's. On treatment with base at 0° this mixture formed two allylic hydroperoxides in a 2.2:1 ratio with the major isomer having the OOH group on the carbon bearing the CD3's, showing migration of the OOH group. This isomer predominated in a 1.4:1 ratio when 1b was oxidized with singlet oxygen at 15 or −52° and in a 1.6:1 ratio when 1b was oxidized with triphenyl phosphite ozonide at −70°. Under the same conditions C—H bond breaking also predominated in the oxidation of 1c, by 2.1:1 via the bromohydroperoxide, by 1.4:1 with singlet oxygen, and by 1.3:1 with triphenyl phosphite ozonide. Migration of the OOH group in the reaction of the bromohydroperoxide of 1b does not occur by way of a 1,2-dioxetane. A perepoxide may be the intermediate. Neither perepoxides nor 1,2-dioxetanes are involved in the singlet oxygen oxidation of 1b and c. At −70° the triphenyl phosphite ozonide oxidations do not proceed by way of these intermediates, either, or by way of singlet oxygen. The intermolecular deuterium isotope effect in the singlet oxygen oxidation of both cis- and trans-2,3-diphenyl-2-butene was found to be 1.1.

Kinetics and isotope effects of the β-elimination reactions of some 2,2-di(4-nitrophenyl)chloroethanes promoted by tetramethylguanidine in aprotic solvents

1985 ◽  
Vol 63 (6) ◽  
pp. 1194-1197 ◽  
Author(s):  
Arnold Jarczewski ◽  
Malgorzata Waligorska ◽  
Kenneth T. Leffek
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Activation Parameters ◽  
Aprotic Solvents ◽  
Polar Solvents ◽  
Deuterium Isotope Effects ◽  
Elimination Reactions

Rate constants for the β-elimination of HCl from 2,2-di(4-nitrophenyl)-1,1-dichloroethane (I) and 2,2-di(4-nitrophenyl)-1,1,1-trichloroéthane (II) promoted by tetramethylguanidine in the aprotic solvents acetonitrile, tetrahydrofuran, and n-hexane have been measured. The activation parameters are characterized by small enthalpies of activation (4.1 to 7.3 kcal mol−1) and large negative entropies of activation (−35 to −50 cal mol−1 deg−1). The primary deuterium isotope effects at 20° C range from kH/kD = 4.8 to 10.3. The results are interpreted to indicate an (EcB)1 mechanism for both substrates I and II in acetonitrile solvent and an E2H or mixed (ElcB)1–E2H mechanism in the less polar solvents, tetrahydrofuran and n-hexane.

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