scholarly journals Unusual traits of cis and trans-2,3-dibromo-1,1-dimethylindane on the way from 1,1-dimethylindene to 2-bromo-, 3-bromo-, and 2,3-dibromo-1,1-dimethylindene

2016 ◽  
Vol 12 ◽  
pp. 1178-1184 ◽  
Author(s):  
Rudolf Knorr ◽  
David S Stephenson ◽  
Ernst Lattke ◽  
Petra Böhrer ◽  
Jakob Ruhdorfer
Keyword(s):  
Coupling Constants ◽  
Interchange Reaction ◽  
Cis And Trans ◽  
The Way

Do not rely on the widely accepted rule that vicinal, sp3-positioned protons in cyclopentene moieties should always have more positive 3 J NMR coupling constants for the cis than for the trans arrangement: Unrecognized exceptions might misguide one to wrong stereochemical assignments and thence to erroneous mechanistic conclusions. We show here that two structurally innocent-looking 2,3-dibromo-1,1-dimethylindanes violate the rule by means of their values of 3 J(cis) = 6.1 Hz and 3 J(trans) = 8.4 Hz. The stereoselective formation of the trans diastereomer from 1,1-dimethylindene was improved with the tribromide anion (Br3 −) as the brominating agent in place of elemental bromine; the ensuing, regiospecific HBr elimination afforded 3-bromo-1,1-dimethylindene. The addition of elemental bromine to the latter compound, followed by thermal HBr elimination, furnished 2,3-dibromo-1,1-dimethylindene, whose Br/Li interchange reaction, precipitation, and subsequent protolysis yielded only 2-bromo-1,1-dimethylindene.

scholarly journals Symmetry breakdown and coupling constants of leptons

2007 ◽  
Vol 79 (2) ◽  
pp. 195-208 ◽  
Author(s):  
Gil C. Marques ◽  
Dominique Spehler
Keyword(s):  
Coupling Constants ◽  
Electroweak Interactions ◽  
New Approach ◽  
Fundamental Interactions ◽  
Electromagnetic Interactions ◽  
Symmetry Breakdown ◽  
A Value ◽  
Intermediate Bosons ◽  
The One ◽  
The Way

Based on a new approach to symmetries of the fundamental interactions we deal, in this paper, with the electroweak interactions of leptons. We show that the coupling constants, arising in the way leptons are coupled to intermediate bosons, can be understood as parameters associated to the breakdown of SU(2) and parity symmetries. The breakdown of both symmetries is characterized by a new parameter (the asymetry parameter) of the electroweak interactions. This parameter gives a measure of the strength of breakdown of symmetries. We analyse the behaviour of the theory for three values of this parameter. The most relevant value is the one for which only the electromagnetic interactions do not break parity (the maximally allowed left-right asymetric theory). Maximamally allowed parity asymmetry is a requirement that is met for a value of Weinberg's theta-angle that is quite close to the experimental value of this parameter.

In-plane and out-of-plane conformational preferences of the sulfhydryl group in some halothiophenol derivatives

1979 ◽  
Vol 57 (12) ◽  
pp. 1421-1425 ◽  
Author(s):  
Ted Schaefer ◽  
William J. E. Parr
Keyword(s):  
Sulfhydryl Group ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Group ◽  
Recent Analysis ◽  
Phenol Derivatives ◽  
Out Of Plane ◽  
Intramolecular Hydrogen ◽  
Cis And Trans ◽  
Spin Spin Coupling

Long-range spin–spin coupling constants between sulfhydryl protons and ring protons in some halothiophenol derivatives in CCl4 solutions are reported. In contrast to the corresponding phenol derivatives, substantial amounts of out-of-plane conformers are present at 305 K for all but 2,6-dichlorothiophenol. The cis and trans conformers differ by only about 0.2 kcal/mol in free energy for 2,4-dibromothiophenol and 2,4-dichlorothiophenol, in good agreement with a recent analysis of the dipole moment observed for the latter compound. The barrier to internal rotation of the sulfhydryl group is considerably smaller than for a hydroxyl group and rough estimates are given for the barrier in a few compounds. For example, the barrier in 2,3,5,6-tetrafluorothiophenol is lower than in 2,6-dichlorothiophenol. STO-3G MO calculations overestimate the internal barrier to rotation of the sulfhydryl group, but yield charge densities for this group which indicate that a major cause of the relative weakness of its intramolecular hydrogen bonds resides in its lack of polarity.

SOLVENT EFFECTS AS AN AID IN THE ANALYSIS OF THE PROTON MAGNETIC RESONANCE SPECTRUM OF VINYL BROMIDE

1960 ◽  
Vol 38 (11) ◽  
pp. 2066-2073 ◽  
Author(s):  
T. Schaefer ◽  
W. G. Schneider
Keyword(s):  
Chemical Shift ◽  
Solvent Effects ◽  
Resonance Spectrum ◽  
Proton Magnetic Resonance Spectrum ◽  
Coupling Constants ◽  
Vinyl Bromide ◽  
Proton Coupling ◽  
Geminal Proton ◽  
Geminal Coupling ◽  
Cis And Trans

By making use of specific solvent effects it has been possible to vary the relative chemical shift between the geminal protons of vinyl bromide from about +10 cycles/sec to −4 cycles/sec (at 60 Mc/sec) and to study the resultant changes in the proton resonance spectrum in the limiting region of zero chemical shift. Of particular interest is the growth and displacement of the combination lines, which appear in the resonance signals of the proton bonded to the same carbon atom as the bromine. From the variation of the six possible lines in this region it was confirmed that the cis and trans proton coupling constants must have the same sign. The intensity distribution of the lines in the geminal proton region require the geminal coupling constant to be of opposite sign to the other two.

199Hg-1H Spin-spin coupling in vinyl and ethynyl mercurials

1964 ◽  
Vol 17 (11) ◽  
pp. 1204 ◽  
Author(s):  
PR Wells ◽  
W Kitching
Keyword(s):  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Cis And Trans ◽  
Spin Spin Coupling

The proton magnetic spectra of cis and trans-2-chlorovinylmercuric chloride, bis(trans-2-chlorovinyl)mercury, and methylethynylmercury have been determined. Large variations in the 199Hg-1H spin-spin coupling constants are observed for different hybridization states and different geometries.

Synthesis and study of Pt(II)–nitrile complexes. Multinuclear NMR spectra and crystal structures of compounds of the types [Pt(R-CN)Cl3]− and cis and trans-Pt(R-CN)2Cl2

1996 ◽  
Vol 74 (2) ◽  
pp. 144-152 ◽  
Author(s):  
Fernande D. Rochon ◽  
Robert Melanson ◽  
Eryk Thouin ◽  
Corinne Bensimon ◽  
André L. Beauchamp
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Trans Isomer ◽  
Nmr Spectra ◽  
Alkyl Chain ◽  
Coupling Constants ◽  
Trans Isomers ◽  
Multinuclear Nmr ◽  
Cis And Trans ◽  
Bond Trans

Complexes of the type [Pt(R-CN)Cl3]− were synthesized and studied by 1H, 13C, and 195Pt NMR spectroscopies. The 2J(195Pt-13C) coupling constants are about 240 Hz. The signals due to the cyano carbon atoms of the coordinated ligands were observed at higher fields than those of the free ligands. The shielding on the cyano carbon increases as the alkyl chain lengthens and also when the branching increases. The 195Pt signals of all the complexes were observed around −2000 ppm. The crystal structures of (NMe4)[Pt(C3H7-CN)Cl3] (1) and (NMe4)[Pt(p-HO-C6H4-CN)Cl3] (2) were determined. Compound 1 is monoclinic, P21/c, a = 8.384(5), b = 15.336(19), c = 11.759(9) Å, β = 99.52(6)°, Z = 4, R = 0.054, and wR = 0.051. Crystal 2 is tetragonal with a = 16.222(6), c = 12.052(5) Å, Z = 8, R = 0.059, and wR = 0.044. The Pt—CL bond trans to the nitrile ligand is shorter than normal (2.276(3) Å for 1 and 2.264(7) Å for 2) while the two other bonds are normal (2.293(4), 2.287(3) Å for 1 and 2.320(7), 2.275(8) Å for 2). The Pt—N bonds are 1.97(1) Å (1) and 1.92(2) Å (2) and the segments Pt-N≡C-C are linear. Disubstituted compounds were also synthesized and studied by multinuclear NMR. The 195Pt signals of the cis isomers were observed at lower fields than those of the trans isomers (Δ ≈ 65 ppm), while the 13C signals of the cyano carbons of the trans isomers were observed at lower fields than those of the cis compounds (Δ ≈ 0.6 ppm). The cis complexes isomerize to the trans compounds upon heating. The crystal structures of cis-(3) and trans-Pt(C2H5-CN)2Cl2 (4) and also of cis-Pt(p-HO-C6H4-CN)2Cl2 (5) were determined. Crystal 3 is monoclinic, P21/c, a = 7.506(5), b = 9.539(5), c = 14.823(7) Å, β = 92.31(4)°, Z = 4, R = 0.050, and wR = 0.042. The trans isomer 4 is monoclinic with the Pt atom on an inversion centre, P21/c, a = 5.149(4), b = 9.394(8), c = 10.944(10) Å, β = 97.84(7)°, Z = 4, R = 0.017 and wR = 0.020. Finally, compound 5 is triclinic, P-1, a = 7.464(3), b = 10.712(6), c = 12.291(5) Å, α = 75.63(4)°, β = 75.63(4)°, γ = 80.32(4)°, Z = 2, R = 0.045, and wR = 0.056. The Pt—Cl bond distances for the cis isomers are 2.269(5), 2.270(4) Å for 3 and 2.274(2), 2.279(3) Å for 5 while they are 2.289(3) Å for the trans isomer (4). The Pt—N bonds are 1.962(14), 1.988(11) Å (3), 1.972(7), 1.976(7) Å (5) and 1.969(5) Å for 4. Key words: platinum, nitrile, NMR, isomerization, crystal structure.

The High Resolution NMR Spectra of Pesticides. I. Organophosphorus Pesticides

1968 ◽  
Vol 51 (5) ◽  
pp. 1063-1094 ◽  
Author(s):  
Lawrence H Keith ◽  
Arthur W Garrison ◽  
Ann L Alford
Keyword(s):  
Chemical Shifts ◽  
Organophosphorus Pesticides ◽  
Coupling Constants ◽  
Reference Source ◽  
Cis And Trans Isomers ◽  
Nuclear Magnetic Resonance Spectra ◽  
Trifluoracetic Acid ◽  
Methylene Groups ◽  
Dilution Effects ◽  
Cis And Trans

Abstract A description of the 100 MHz nuclear magnetic resonance spectra of forty organophosphorus pesticides is presented as an identification aid and reference source. Chemical shifts and coupling constants are presented in tabular form, along with a discussion and figures of the more complex or unusual spectra. Tables of trends in chemical shifts and coupling constants as related to structure are included. Homonuclear spin decoupling, integration, protonation with trifluoracetic acid, D20 exchange, temperature, solvent and dilution effects, and supplemental 60 MHz spectra all were employed in correlating the spectra with the structures of the corresponding molecules. Interesting phenomena observed include long-range phosphorus to hydrogen coupling through four and five bonds, chemical nonequivalence of methylene groups and methyl groups in (CH3CH20)2P and (CH30)2P moieties, differences in the spectra of the cis and trans isomers of two pesticides due to anisotropic effects of their carbonyl groups, and magnetic nonequivalence of geminal methylene protons adjacent to an asymmetric carbon atom

Cyclic analogues of β-adrenergic blocking agents cis- and trans-3-Amino-6-bromochroman-4-ols

1976 ◽  
Vol 29 (8) ◽  
pp. 1791 ◽  
Author(s):  
BV Lap ◽  
LR Williams
Keyword(s):  
Sodium Borohydride ◽  
Coupling Constants ◽  
Blocking Agents ◽  
Rate Of Hydrolysis ◽  
Cis And Trans ◽  
Adrenergic Blocking ◽  
Hydrolysis Of ◽  
Adrenergic Blocking Agents

N-(6-Bromo-4-oxochroman-3-yl)acetamide (4; R = Ac) can be reduced by sodium borohydride to the cis-N-(6-bromo-4-hydroxychroman-3-yl)acetamide (6) and this can be hydrolysed to give the cis-3-amino-6-bromochroman-4-ol (7) or converted into the corresponding trans-3-amino-6-bromo- chroman-4-ol (12) by chlorination with inversion followed by hydrolysis of the chloride (8) to the alcohol with retention of configuration. The assignment of configuration of the 3,4-substituted chromans is based on the value of the coupling constants between the H3 proton and the methylene protons on C2 and is supported by an observed difference in the rate of hydrolysis of the two N-(6-bromo-4-chlorochroman-3-yl)acetamides.

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