Concerning the mechanism of the addition of ethanesulfenyl chloride to 3,4-dihydro-2H-pyran

1968 ◽  
Vol 46 (7) ◽  
pp. 1093-1099 ◽  
Author(s):  
M. J. Baldwin ◽  
R. K. Brown
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Sulfur Dioxide ◽  
Resonance Spectrum ◽  
Trans Isomers ◽  
Initial Formation ◽  
Cis And Trans Isomers ◽  
Crude Mixture ◽  
The Stability ◽  
Cis And Trans

The nuclear magnetic resonance spectrum, at −40°, of the crude mixture obtained by the reaction of ethanesulfenyl chloride with 3,4-dihydro-2H-pyran at −40° clearly supports the view that the product is trans-2-chloro-3-ethylthiotetrahydropyran. The possibility that there is initial formation of 3-chloro-2-ethylthiotetrahydropyran followed by its rapid rearrangement to 2-chloro-3-ethylthiotetrahydropyran is ruled out because of the stability of 3-chloro-2-ethylthiotetrahydropyran to distillation under vacuum. The latter compound is obtained as a mixture of cis and trans isomers by the reaction of ethyl mercaptan with 5-chloro-3,4-dihydro-2H-pyran in the presence of sulfur dioxide.

Nuclear magnetic resonance spectroscopic analysis of the selective complexation of the cis and trans isomers of phenylalanylproline by β-cyclodextrin

1995 ◽  
Vol 307 (2-3) ◽  
pp. 449-457 ◽  
Author(s):  
Mengfen Lin ◽  
Dimuthu A. Jayawickrama ◽  
Rachel A. Rose ◽  
John A. DelViscio ◽  
Cynthia K. Larive
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Spectroscopic Analysis ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Magnetic Resonance Spectroscopic Analysis ◽  
Cis And Trans ◽  
Nuclear Magnetic ◽  
Selective Complexation

Identification of cis- and trans-Cinnamoylcocaine in Illicit Cocaine Seizures

1973 ◽  
Vol 56 (5) ◽  
pp. 1199-1205 ◽  
Author(s):  
James M Moore
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Degradation Products ◽  
Mass Spectrometric ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Depth Analysis ◽  
Mass Spectrometric Identification ◽  
Cis And Trans ◽  
Chromatographic Isolation

Abstract During the in-depth analysis of illicit cocaine samples small amounts of other coca alkaloids and cocaine degradation products have been detected. One of these alkaloids, cinnamoylcocaine, has been found in more than half of the samples examined, usually in concentrations of 1% or less of the amount of cocaine present. The presence of cinnamoylcocaine, as its cis and trans isomers, was established by column partition chromatographic isolation of the isomers, followed by ultraviolet, infrared, nuclear magnetic resonance, and mass spectrometric identification.

13C Nuclear Magnetic Resonance Studies. 34. The 13C Spectra of Several Methylcyclopentanones and -cyclohexanones

1974 ◽  
Vol 52 (2) ◽  
pp. 308-314 ◽  
Author(s):  
J. B. Stothers ◽  
C. T. Tan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Model Systems ◽  
Trans Isomers ◽  
Magnetic Resonance Studies ◽  
Cis And Trans Isomers ◽  
13C Nuclear Magnetic Resonance ◽  
The Individual ◽  
Ring Distortion ◽  
Cis And Trans

The 13C spectra of 16 methyl substituted cyclohexanones and 15 methylcyclopentanones have been determined. These series were chosen as model systems for the study of steric and conformation effects on 13C shieldings. Complete assignments of the individual signals were accomplished by intercomparison of the shielding data within each series and the trends observed are readily interpreted in conformational terms. Each of the cyclohexanones exists preferentially in chair conformations although there is evidence of ring distortion in the tetramethyl derivatives. The cyclopentanones apparently strongly favor half-chair forms with maximum puckering at C-3 and C-4. In general, shielding differences between cis and trans isomers are pronounced and the assignment of stereochemistry for some cis–trans dimethyl derivatives is illustrated.Further examples of marked deshielding trends associated with sterically crowded δ nuclei in syn-axial arrangements are described.

Morpholines: stereochemistry and preferred steric course of quaternization

1976 ◽  
Vol 54 (1) ◽  
pp. 126-135 ◽  
Author(s):  
Alan J. Jones ◽  
C. P. Beeman ◽  
M. U. Hasan ◽  
A. F. Casy ◽  
M. M. A. Hassan
Keyword(s):  
Magnetic Resonance ◽  
Chemical Shift ◽  
Nmr Spectra ◽  
Deuterium Nmr ◽  
Free Energies ◽  
Trans Isomers ◽  
Methyl Substitution ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Magnetic Resonance Spectra

The 13C magnetic resonance spectra of a series of methyl and phenyl substituted morpholines, their hydrochlorides, and methiodides have been determined. The effects of methyl substitution adjacent to oxygen and nitrogen are reasonably equivalent and substituent induced chemical shift parameters derived for the series show favorable agreement with those previously observed in both alicyclic and heterocyclic systems. Results for the cis and trans isomers of phendimetrazine (3,4-dimethyl-2-phenylmorpholine), confirm the preferred chair conformations and configurations cis-3-CH3, cis-2-phenyl (cis) and trans-3-CH3, cis-2-phenyl (trans) for these isomers. The preferred course of quaternization of nitrogen in these systems was determined as axial, using deuteriomethyliodide as a label. This 13C–2H technique relies on the observation of the γ-syn-axial effect and is clearly unambiguous and superior to other methods used in evaluating this mechanism. Product ratios and consequently free energies of this reaction were measured from proton and deuterium nmr spectra.

Cis-Trans Isomerization in Natural Polyisoprenes

1960 ◽  
Vol 33 (2) ◽  
pp. 445-456 ◽  
Author(s):  
J. I. Cunneen
Keyword(s):  
Sulfur Dioxide ◽  
Natural Rubber ◽  
Ultraviolet Light ◽  
Low Temperatures ◽  
Structural Changes ◽  
Trans Isomers ◽  
Gutta Percha ◽  
Trans Isomerization ◽  
Cis And Trans Isomers ◽  
Cis And Trans

Abstract The cis and trans isomers of many simple olefins and conjugated polyolefins can be interconverted by the action of heat, light, and various catalysts, and in many such systems the changes in geometric configuration can be readily followed and the isomers separated and identified. Previous attempts to isomerize natural rubber and gutta-percha by treatment with ultraviolet light and various chemicals gave no detectable cis-trans isomerization, and in general configurational changes in unconjugated polyolefins have been unknown until recently when Golub converted the cis-1,4 units in polybutadiene into the corresponding trans units. This isomerization was achieved by irradiation of the cis-polymer with ultraviolet light in the presence of various organic bromides and sulfur compounds, but apparently this method did not isomerize natural rubber. In attempts to retard the rate of crystallization of natural rubber at moderately low temperatures—i.e., −10° to −40° C—by the attachment of side groups which would interfere with the molecular packing, it was observed that very small amounts of thiol acids were remarkably effective. This suggested that structural changes other than simply the attachment of side groups were occurring in the polyisoprene molecule. Recently it was found that thiol acids could interconvert the cis and trans forms of a simple trialkyl ethylene—e.g., 3-methylpent-2-ene—and subsequently, the isomerization of natural rubber and gutta-percha by these reagents was also observed. Following this, natural rubber, gutta-percha, squalene and cis and trans forms of 3-methylpent-2-ene have also been isomerized by treatment with sulfur dioxide and allied compounds; this work, including an investigation of the physical properties of the vulcanizates obtained from some of the isomerized polyisoprenes, is described in the present paper.

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