Stereochemical Implications from the Conformational Analysis of the Seven-membered Ring in 5-Oxabenzocycloheptene

1974 ◽  
Vol 52 (21) ◽  
pp. 3581-3588 ◽  
Author(s):  
Louis Canuel ◽  
Maurice St-Jacques
Keyword(s):  
Conformational Analysis ◽  
Isotope Effect ◽  
Computer Analysis ◽  
Line Shape ◽  
Activation Parameters ◽  
Membered Ring ◽  
Coupling Constants ◽  
Deuterium Isotope Effect ◽  
Long Distance ◽  
Deuterated Derivative

The computer analysis (LAOCN-3 program) of the p.m.r. spectrum of 5-oxabenzocycloheptene (3) at −105° has provided values for all coupling constants about the C3—C4 bond, while the complete line-shape simulation (DNMR program) has provided the following activation parameters: ΔG≠ = 9.5 kcal/mol (at −57°), ΔH≠ = 9.9 kcal/mol, and ΔS≠ = 1.5 e.u. A novel long distance (transannular) deuterium isotope effect has been discovered during the analysis of the spectrum of a partially deuterated derivative of 3. A comparison of the p.m.r. parameters for 5-oxabenzocycloheptene and benzocycloheptene provides the basic data from which stereochemical and conformational inferences can be made for more complex derivatives in this series.

Kinetics of the hydrolysis of thiochloroformate esters in pure water

1970 ◽  
Vol 48 (4) ◽  
pp. 522-527 ◽  
Author(s):  
A. Queen ◽  
T. A. Nour ◽  
M. N. Paddon-Row ◽  
K. Preston
Keyword(s):  
Isotope Effect ◽  
Structural Changes ◽  
Pure Water ◽  
Activation Parameters ◽  
Deuterium Isotope Effect ◽  
Hydro Carbon ◽  
Electron Donation ◽  
Kinetics Of ◽  
Hydrolysis Of

The effects of structural changes on the rates of hydrolysis of a series of thiochloroformate esters in water have been investigated. The reactivity is enhanced by increased electron donation by the hydro carbon group. These results, the activation parameters for the hydrolysis of methyl thiochloroformate and the solvent deuterium isotope effect, are shown to be consistent with the operation of the SN1 mechanism.

Studies on the decomposition of tetra-alkylammonium salts in solution. Part I. Phenylbenzylmethylallylammonium iodide

1968 ◽  
Vol 46 (8) ◽  
pp. 1215-1220 ◽  
Author(s):  
K. T. Leffek ◽  
F. H.-C. Tsao
Keyword(s):  
Reaction Kinetics ◽  
Isotope Effect ◽  
Optical Activity ◽  
Chloroform Solution ◽  
Activation Parameters ◽  
Deuterium Isotope Effect ◽  
Alkylammonium Salts ◽  
Triple Ion

The loss of optical activity from phenylbenzylmethylallylammonium iodide in chloroform solution has been found to be entirely due to decomposition; racemization as such does not take place. The products are benzyl iodide and allylmethylaniline. A mechanism involving decomposition via a triple ion is deduced from the reaction kinetics. The activation parameters (ΔH≠ and ΔS≠) and a secondary deuterium isotope effect are reported.

Kinetics of Proton Transfer Reactions of Carbon Acids. IV. Primary Deuterium Isotope Effect in the Reaction of Di-(4-nitrophenyl)methane-d2 with t-Butoxide

1974 ◽  
Vol 52 (4) ◽  
pp. 592-596 ◽  
Author(s):  
Jae-Hang Kim ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Activation Parameters ◽  
Proton Transfer Reaction ◽  
Transfer Reactions ◽  
Deuterium Isotope Effect ◽  
Enthalpy Of Activation ◽  
Proton Transfer Reactions ◽  
Carbon Acids ◽  
Kinetics Of

The primary deuterium isotope effect has been measured for the proton transfer reaction from di-(4-nitrophenyl)methane to t-butoxide ion in a solvent consisting of 10% v/v toluene in t-butanol at a series of temperatures between 20 and 45 °C. The isotopic rate ratio, kH/kD, is 7.3 at 25 °C. The activation parameters showed an enthalpy of activation difference (ΔHD≠ − ΔHH≠) of only ca. [Formula: see text] kcal mol−1 and an entropy isotope effect (ΔSD≠ − ΔSH≠) of −2.4 cal mol−1 deg−1. The latter indicates, according to the theory of Bell, that tunnelling of the proton through the energy barrier is unimportant in this reaction. This result is compared to other reactions in the literature, in which tunnelling has been postulated to occur.

scholarly journals The influence of crown ethers on the kinetics of E1cB and E2 β-elimination reactions of di(4-nitrophenyl)fluoroethanes with sodium methoxide in methanol

1982 ◽  
Vol 60 (24) ◽  
pp. 3077-3080
Author(s):  
Kenneth T. Leffek ◽  
Grzegorz Schroeder
Keyword(s):  
Isotope Effect ◽  
Crown Ethers ◽  
Rate Constant ◽  
Rate Constants ◽  
Sodium Methoxide ◽  
Activation Parameters ◽  
Deuterium Isotope Effect ◽  
Kinetic Order ◽  
Elimination Reactions ◽  
Kinetics Of

The addition of crown ethers 1,4,7,10,13-pentaoxacyclopentadecane (15C5) and 1,4,7,10,13,16-hexaoxacyclooctadecane (18C6) in quantities equimolar to the base, to β-elimination reactions of 1,1,1-trifluoro-2,2-di(4-nitrophenyl)ethane and 1-fluoro-2,2-di(4-nitrophenyl)ethane promoted by sodium methoxide in methanol, has been investigated. In the E2 reaction of the monofluoro compound, the crown ethers caused no change in the kinetic order and only small changes in the second-order rate constants and activation parameters. The primary deuterium isotope effect was also unaltered by the presence of crown ethers.For the (E1cB)R reaction of the trifluoro compound, no change in kinetic order was found, but slightly larger rate constant changes and an increase in the isotope effect from kH/kD = 1.0 to 1.25 at 25 °C was observed. This is interpreted as an alteration in mechanism from (E1cB)R towards (E1cB)I.

Deuterium Isotope Effect in Proton—13C Coupling Constants

1965 ◽  
Vol 42 (10) ◽  
pp. 3724-3725 ◽  
Author(s):  
Gideon Fraenkel ◽  
William Burlant
Keyword(s):  
Isotope Effect ◽  
Coupling Constants ◽  
Deuterium Isotope Effect

Biotelemetry and Computer Analysis of Electrocardiograms

1969 ◽  
Vol 08 (03) ◽  
pp. 120-127 ◽  
Author(s):  
P. R. Amlinger
Keyword(s):  
Computer Analysis ◽  
Rural Areas ◽  
Applied Research ◽  
Research Effort ◽  
Pilot Project ◽  
Modern Medicine ◽  
Modern Technology ◽  
Long Distance ◽  
Regional Medical ◽  
Medical Program

Routine transmission of electrocardiograms and their computer interpretation via long-distance telephone lines has been proven feasible in the Automated Electrocardiogram Project of the Missouri Regional Medical Program. Though this Pilot Project — the first on a state-wide basis — is still viewed as an applied research effort rather than a service, such biotelemetry is rapidly gaining acceptance as a medium to bring modern medicine, through modern technology, to urban and remote rural areas as well, where it is most needed.The computer executes all the wave measuraments and calculations with incredible speed. It takes over a most boring, repetitive part of the physician’s work. However, it can only follow the instructions of the diagnostic program, compiled by expert cardiologists. Thus, it is an ever-ready, never-tiring servant for the physician and his patients.

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