Nuclear magnetic resonance conformation analysis of cis and trans isomers of 1,2-dichloro-2,3,3-trifluorocyclobutane and related molecules

Tetrahedron ◽  
1974 ◽  
Vol 30 (18) ◽  
pp. 3253-3256 ◽  
Author(s):  
R.A. Newmark ◽  
R.E. Watson ◽  
T.S. Croft
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Conformation Analysis ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Nuclear Magnetic

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.

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.

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