5J(CH3,SH) as a negative proximate or as a positive σ−π coupling in 2-methylthiophenol derivatives

1985 ◽  
Vol 63 (8) ◽  
pp. 2217-2220 ◽  
Author(s):  
Ted Schaefer ◽  
James Peeling ◽  
Rudy Sebastian ◽  
James D. Baleja
Keyword(s):  
Nmr Spectra ◽  
Sulfhydryl Group ◽  
The Other ◽  
Coupling Mechanism ◽  
Methyl Group ◽  
Tert Butyl ◽  
H Nmr ◽  
Out Of Plane ◽  
Negative Coupling

Analyses of the 1H nmr spectra of 6-chloro-2-methylthiophenol and of 4-tert-butyl-2-methylthiophenol in CCl4 solution, together with double irradiation experiments, show that 5J(CH5,SH) in the former compound is −0.66 Hz and is +0.47 Hz in the latter. In the chloro compound, the sulfhydryl group spends relatively little time in out-of-plane conformations at 300 K. The negative coupling is a consequence of a through-space or proximate coupling mechanism. In the other compound, the sulfhydryl group samples many out-of-plane conformations but relatively few in which the S—H bond lies near the methyl group. Therefore 5J(CH3,SH) is now dominated by a σ−π electron mechanism and is positive. Probably by coincidence, 4J(H,SH) in this compound is equal in magnitude but opposite in sign to 5J(CH3,SH).

Restricted rotation about arene–oxygen bonds in some 1,3-di-tert-butyl-2-methoxyarenedicarbonylphosphorus(III)chromium compounds

1984 ◽  
Vol 62 (11) ◽  
pp. 2566-2569 ◽  
Author(s):  
Eva M. Campi ◽  
Bryan M. K. Gatehouse ◽  
W. Roy Jackson ◽  
Ian D. Rae ◽  
Margaret G. Wong
Keyword(s):  
Crystal Structure ◽  
Low Temperatures ◽  
Nmr Spectra ◽  
Hindered Rotation ◽  
Methyl Group ◽  
Tert Butyl ◽  
H Nmr ◽  
Free Energy Of Activation ◽  
Chromium Compounds ◽  
Related Compounds

The 1H nmr spectra of 1,3-di-tert-butyl-2-methoxybenzenedicarbonyltriphenylphosphinechromium (5) and some related compounds at low temperatures show the presence of two species which interconvert with free energy of activation near 50 kJ mol−1. The species differ in the orientation of the methoxy with respect to the chromium, since the same type of process is observed in a chelate complex in which a phosphinite ligand on chromium is also attached to the arene. Hindered rotation about the arene–chromium axis is not involved. The crystal structure of 5 shows the Ph3P anti to the methoxy and the O-methyl group proximal to chromium.

scholarly journals Crystal structure and solvent-dependent behaviours of 3-amino-1,6-diethyl-2,5,7-trimethyl-4,4-diphenyl-3a,4a-diaza-4-bora-s-indacene

2017 ◽  
Vol 73 (3) ◽  
pp. 378-382
Author(s):  
Lijing Yang ◽  
Brett Drew ◽  
Ravi Shekar Yalagala ◽  
Rameez Chaviwala ◽  
Razvan Simionescu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Fluorescence Spectroscopy ◽  
Title Compound ◽  
Nmr Spectra ◽  
Membered Ring ◽  
The Other ◽  
Time Dependent ◽  
H Nmr ◽  
The Mean ◽  
Over Time

In the title compound (3-amino-4,4-diphenyl-BODIPY), C28H32BN3, the central six-membered ring has a flattened sofa conformation, with one of the N atoms deviating by 0.142 (4) Å from the mean plane of the other five atoms, which have an r.m.s. deviation of 0.015 Å. The dihedral angle between the two essentially planar outer five-membered rings is 8.0 (2)°. In the crystal, molecules are linkedviaweak N—H...π interactions, forming chains along [010]. The compound displays solvent-dependent behaviours in both NMR and fluorescence spectroscopy. In the1H NMR spectra, the aliphatic resonance signals virtually coalesce in solvents such as chloroform, dichloromethane and dibromoethane; however, they are fully resolved in solvents such as dimethyl sulfoxide (DMSO), methanol and toluene. The excitation and fluorescence intensities in chloroform decreased significantly over time, while in DMSO the decrease is not so profound. In toluene, the excitation and fluorescent intensities are not time-dependent. This behaviour is presumably attributed to the assembly of 3-amino-4,4-diphenyl-BODIPY in solution that leads to the formation of noncovalent structures, while in polar or aromatic solvents, the formation of these assemblies is disrupted, leading to resolution of signals in the NMR spectra.

Aliphatic diazo compounds. XIV. The synthesis of 7-substituted 3-diazo-2-norbornanones and the infrared and proton and carbon-13 nuclear magnetic resonance spectra of these diazo ketones and their precursors

1984 ◽  
Vol 62 (9) ◽  
pp. 1751-1766 ◽  
Author(s):  
Peter Yates ◽  
John David Kronis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Diazo Compounds ◽  
Lower Field ◽  
Tert Butyl ◽  
H Nmr ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr ◽  
Shielding Effects

syn- and anti-7-Isopropyl-2-norbornanone (5 and 6) were prepared by catalytic hydrogenation of 7-isopropylidene-2-norbornanone; syn- and anti-7-benzhydryl-2-norbornane (9 and 10) were prepared in analogous fashion. Ketones 5 and 6 and syn- and anti-7-tert-butyl-2-norbornanone (7 and 8) were converted to the corresponding 3-diazo-2-norbornanones 1–4 via the monotosylhydrazones 44–47 of the corresponding α-diketones 40–43. The 1H and 13C nmr spectra of 1–10, 40–47, and their precursors have been analyzed. The 1H nmr spectra of the diazo ketones 1–4 have their C-1 and C-4 bridgehead proton signals shifted to higher and lower field, respectively, relative to the bridgehead signals of the corresponding diketones. The 13C nmr spectra of all pairs of bicyclic epimers shown γ-gauche shielding effects by the 7-substituent at (sp3) C-3 in the syn compounds and at C-5 and C-6 in the anti compounds. A converse effect is found at (sp2) C-2 (and C-3 in the diketones). Comparison of the magnitude of the shielding effects of C-7 methyl, isopropyl, benzhydryl, and tert-butyl substituents gives evidence of δ deshielding effects at C-3 in the syn compounds and at C-5 and C-6 in the anti compounds by methyl substituents on C-8.

Conformations of Chlorophylls a and a′ and their Magnesium-Free Derivatives as Revealed by Circular Dichroism and Proton Magnetic Resonance

1981 ◽  
Vol 36 (8) ◽  
pp. 1000-1009 ◽  
Author(s):  
Paavo H. Hynninen ◽  
Gunnel Sievers
Keyword(s):  
Circular Dichroism ◽  
Magnetic Resonance ◽  
Electronic Absorption ◽  
Proton Magnetic Resonance ◽  
Nmr Spectra ◽  
Cd Spectra ◽  
Steric Strain ◽  
Methyl Group ◽  
H Nmr ◽  
Circular Dichroïsm

Abstract The electronic absorption (UV/VIS), circular dichroism (CD) and proton magnetic resonance (1H NMR) spectra have been recorded for C-10 epimeric chlorophylls a and a′, pheophytins a and a′ as well as pheophorbides a and a′. Although the epimers in each pair showed virtually identical UV/VIS spectra, their CD spectra were profoundly different and exhibited opposite signs at most wavelengths in the UV region. The differences were interpreted as arising, in part, from different C-10 configurations, and, in part, from conformational alterations induced by the steric strain in the crowded periphery of the macrocycle. The conformational alterations were also clearly indicated by the 1H NMR Δδ-values observed for the α,β and δ methine protons, the C-10 protons and most methyl group protons of the epimers in each pair. This was considered to imply changes in the geometry of the whole macrocycle. The Δδ-values were larger for the Mg-free epimers than for the chlorophyll epimers, which shows that the central Mg-atom makes the macrocycle more rigid. Correlations between the signs of the CD bands and configurations are discussed.

Conformational analysis of acyclic compounds with oxygen–sulphur interactions. Part VI. Some 1-thioderivatives of 2-propanol and its acetates

1979 ◽  
Vol 57 (18) ◽  
pp. 2426-2433 ◽  
Author(s):  
Felipe Alcudia ◽  
José L. García Ruano ◽  
Jesús Rodríguez ◽  
Félix Sánchez
Keyword(s):  
Conformational Analysis ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Conformational Study ◽  
Conformational Preference ◽  
Methyl Group ◽  
Opposite Charge ◽  
H Nmr ◽  
Vicinal Coupling Constants

A conformational study of 1-X-2-propanol (X = SH, SMe, SOMe, SO2Me, +SMe2) and their O-acetyl derivatives (X = SMe, SOMe, SO2Me, and +SMe2) is reported. From the relative values of the vicinal coupling constants in 1H nmr spectra it has been possible to establish the conformational preference. When a density of opposite charge is supported by heteratoms, polar factors determined a great predominance of that conformation in which the sulphur function has an anti-relationship with respect to the methyl group. In thiol and thioethers the conformational preference is not so marked.

Cyclopentadienyl–metal bond cleavage and stereospecific bromination. The structure of (η-C5H5)2Ti(OOCPh)2 and its reactions with bromine

1988 ◽  
Vol 66 (3) ◽  
pp. 429-434 ◽  
Author(s):  
C. Robert Lucas ◽  
Eric J. Gabe ◽  
Florence L. Lee
Keyword(s):  
Nmr Spectra ◽  
Bond Cleavage ◽  
The Other ◽  
Ring Cleavage ◽  
Radical Mechanism ◽  
Iodine Monochloride ◽  
Carboxylate Ligands ◽  
X Ray ◽  
H Nmr ◽  
Using Data

The 13C and 1H nmr spectra as well as the X-ray structure determination for (η-C5H5)2Ti(OOCPh)2 are described. The compound crystallizes in space group P21212I with a = 7.5135, b = 12.5166, c = 21.1416 Å, Z = 4, dcalcd = 1.40 g cm−3 (MoKα1, λ = 0.70932 Å). The structure was solved with MULTAN using data collected at 115 K and refined to the final R = 0.059 for 1500 significant reflections. The molecule has two different carboxylate ligands, one of which has a Ti—O—C angle of 135.4(6)° and longer Ti—O (1.976(5) Å) and O—C (1.300(10) Å) bonds while the other has a Ti—O—C angle of 157.0(7)° with shorter Ti—O (1.913(6) Å) and O—C (1.267(10) Å) bonds. With bromine, ring cleavage occurs giving C5H5Br3 or C5H5Br5 in which bromination has occurred stereospecifically. The same reaction occurs with chlorine but not with iodine or iodine monochloride. Related reactions have been observed with (η-C5H5)2MCl2 (M = Ti, Zr, and V). A non-radical mechanism is proposed in which the LUMO and HOMO of Br2 interact simultaneously with one cyclopentadienyl ring and with the metal. This interaction is a consequence of the structure of (η-C5H5)2M(OOCPh)2.

X+ transfer from the halonium ions of adamantylideneadamantane to acceptor olefins. The possibility of chiral induction in the transfer process

1997 ◽  
Vol 75 (12) ◽  
pp. 1844-1850 ◽  
Author(s):  
Alexei A. Neverov ◽  
Theresa L. Muise ◽  
R.S. Brown
Keyword(s):  
Nmr Spectra ◽  
Room Temperature ◽  
Reaction Rate ◽  
Methyl Groups ◽  
Kinetic Behavior ◽  
Methyl Group ◽  
Chiral Induction ◽  
H Nmr ◽  
Group 12 ◽  
Kinetics Of

The bromonium ion of adamantylideneadamantane (Ad=Ad-Br+) has been used to induce the bromocyclization of a 4-pentenyl glycoside (10) and a 5-hexenyl glycoside (11) in dichloroethane. The kinetics of these processes have been studied at 25 °C in the presence of varying [Ad=Ad] and, in the case of the transfer to 10, in the presence of pentanol. The second-order rate constants for bromocyclization of these two alkenes are (1.04 ± 0.06) × 10−1 M−1 s−1 and (5.34 ± 0.2) × 10−1 M−1 s−1, respectively, and in no case does added Ad=Ad or pentanol alter the reaction rate. The kinetic behavior is interpreted in terms of cyclization occurring directly from a 1:1 complex of Ad=Ad-Br+ and 10 or 11. The chiral induction for the bromocyclization of 10 promoted by AdAd-Br+ was measured at 20% e.e., the (−)-(S)-tetrahydrofurfuryl bromide being the dominant stereoisomer. Ad=Ad molecules substituted at one of the homoallylic carbons by an axial methyl group (12), or by two methyl groups (axial and equatorial), were synthesized and the 1H NMR spectra of their bromonium ions is given. These materials are not stable for prolonged times at room temperature. A limited kinetic study of the reaction of 12-Br+ and 4-pentenol indicated that the Br+ transfer is 500 times faster than the comparable transfer from Ad=Ad-Br+ to 4-pentenol. The possibility of using these materials to induce chiral bromocyclization is discussed. Keywords: bromonium ion, halonium, transfer, chiral, adamantylideneadamantane.

1H NMR spectra of some chloro-alkenes

1981 ◽  
Vol 46 (11) ◽  
pp. 2924-2934
Author(s):  
Seán Cawley ◽  
Jan Schraml ◽  
Petr Svoboda ◽  
Robert Ponec ◽  
Václav Chvalovský
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Dipole Moments ◽  
Coupling Constants ◽  
The Other ◽  
Dominant Factor ◽  
Proton Proton ◽  
Electric Field Effects ◽  
H Nmr ◽  
Proton Coupling

1H NMR spectra and electric dipole moments of a series of propene derivatives, (CH3)3-nCln.CCH=CH2 (n = 0-3), were measured and the spectra analyzed. Discrepancies in literature data on compounds with n = 0 and 3 are probably due to systematic spectrometer errors. Vinylic proton chemical shifts are found to vary linearly with n in the direction expected on the electronegativity ground (the variations with n occurs in the order HA > HB ≥ HC). Calculations show that even with the extreme reported values of C-C and C-Cl bond magnetic anisotropies, the shift variations with n cannot be accounted for by magnetic anisotropy effects of a freely rotating (CH3)3-nClnC group. Similar calculations rule out electric field effects as the dominant factor. On the other hand, the electron charge distribution, as obtained from CNDO/2 calculations, including d-orbitals and employing Del Bene-Jaffé parametrization, is linearly related to the vinylic proton shifts. This finding supports the earlier interpretation of NMR spectra of vinylsilanes in terms of back-bonding. The vinyl proton-proton coupling constants decrease with increasing n, the changes being larger in the constants which couple proton A (cis) to the other two.

Schwefeldiimid, S(NH)2, und monosubstituierte Schwefeldiimide, S(NR)(NH), mit R = tert-Butyl und Trimethylsilyl / Sulfur Diimide, S(NH)2, and Monosubstituted Sulfur Diimides, S(NR)(NH), with R = tert-Butyl and Trimethylsilyl

1985 ◽  
Vol 40 (10) ◽  
pp. 1229-1232 ◽  
Author(s):  
Max Herberhold ◽  
Wolfgang Jellen ◽  
Wolfgang Bühlmeyer ◽  
Wolfgang Ehrenreich ◽  
Josef Reiner
Keyword(s):  
Acetic Acid ◽  
Nmr Spectra ◽  
Parent Compound ◽  
Temperature Dependent ◽  
Tert Butyl ◽  
H Nmr

The unstable parent compound of the sulfur diimides, S(NH)2 (1), has been obtained in solution by stoichiometric protonation of the anion SN22- in K2SN2 with acetic acid. An analogous protonation of the salts S(NR)(NK) leads to the m onosubstituted sulfur diimides S(NR)(NH) containing bulky substituents such as R = tert-butyl (2) and R = trimethylsilyl (3); 2 and 3 can be isolated as white solids below -40 °C. The temperature-dependent 1H NMR spectra of 1-3 indicate the presence of two isomers in solution (ratio 4:1) which are reversible interconverted.

Synthesis and nuclear magnetic resonance spectra of platinum compounds with thiourea derivatives

1985 ◽  
Vol 63 (9) ◽  
pp. 2425-2429 ◽  
Author(s):  
F. D. Rochon ◽  
J. Bariyanga ◽  
P. C. Kong
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Sulfur Atom ◽  
Nmr Spectra ◽  
Intramolecular Interaction ◽  
Platinum Compounds ◽  
Thiourea Derivatives ◽  
Methyl Group ◽  
H Nmr ◽  
Nuclear Magnetic Resonance Spectra

Compounds of the type trans-[PtL2T2]Cl2 where L = NH3, methylamine, dimethylamine, pyridine, and 2-aminopyrimidine and T = N-methylthiourea and N,N′-dimethylthiourea and where L = NH3 and T = N,N,N′,N′-tetramethylthiourea have been synthesized. The 1H nmr spectra have shown that the thiourea derivatives are bonded to platinum by the sulfur atom. The methyl protons of N-methylthiourea and one methyl group protons of N,N′-dimethylthiourea in the complexes, where L is aromatic, showed resonance at higher field after coordination to the metal. This was explained by an intramolecular interaction between the methyl group and the aromatic ring. The nmr spectra of the [PtT4]Cl2 compounds were also measured.

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