Solvents Coupling Constants

Specinfo, from Chemical Concepts, is a factual database information system for spectroscopic data with more than 660000 digital spectra of 150000 associated structures [24], The database covers nuclear magnetic resonance spectra ( H-, C-, N-, O-, F-, P-NMR), infrared spectra (IR), and mass spectra (MS). In addition, experimental conditions (instrument, solvent, temperature), coupling constants, relaxation time, and bibliographic data are included. The data is cross-linked to CAS Registry, Beilstein, and NUMERIGUIDE. 

Polar solvents shift the keto enol equilibrium toward the enol form (174b). Thus the NMR spectrum in DMSO of 2-phenyl-A-2-thiazoline-4-one is composed of three main signals +10.7 ppm (enolic proton). 7.7 ppm (aromatic protons), and 6.2 ppm (olefinic proton) associated with the enol form and a small signal associated with less than 10% of the keto form. In acetone, equal amounts of keto and enol forms were found (104). In general, a-methylene protons of keto forms appear at approximately 3.5 to 4.3 ppm as an AB spectra or a singlet (386, 419). A coupling constant, Jab - 15.5 Hz, has been reported for 2-[(S-carboxymethyl)thioimidyl]-A-2-thiazoline-4-one 175 (Scheme 92) (419). This high J b value could be of some help in the discussion on the structure of 178 (p. 423). 

Coupling(azo) Coupling constant Coupling solvents Couplingsugar CoveUite... 

The direct coupling constants (A/) of pyridine, obtained from a spectrum of the molecule in a nematic liquid crystal solvent, are listed in Batterham s monograph (B-73NMR, p. lo). These data provide information about the geometry of the molecule, as the couplings are proportional to the inverse cube of the distance (r,/) between the nuclei. 

The H NMR spectrum of pyridazine shows two symmetrical quartets of an A2X2 or A2B2 type dependent on the solvent and concentration. The satellites have been used to obtain all coupling constants. Spectra of C-substituted pyridazines, methylthio- and methylsulfonyl-pyridazines, both as neutral molecules and as cations, N-1 and N-2 quater-nized species, pyridazinones, hydroxypyridazinones, A-oxides and 1,2-dioxides have been reviewed (b-73NMR88> and are summarized in Tables 6, 7 and 8. 

Compound Solvent H-1 H-2 Chemical shift (S-values) H-3 H-4 H-5 H-6 H-7 H-8 Coupling constants (Hz) Ref... 

A number of studies on the NMR spectra of isoxazole has been compiled and this list includes the coupling constants in various solvents as well as the neat liquid. The N signal for isoxazole appears at 339.6 p.p.m. relative to TTAI and is at much lower field than in other azoles. Reports of spectra of substituted isoxazoles also abound (79AhC(25)147, p. 201). 

Give a clear indicaUon of solvent, concentration, and temperature. These parameters have a much greater effect on chemical shifts and coupling constants for fluorine than for protons. 

The H and 13CNMR spectra of various cyclopentazepines have been recorded (Tables 1 and 2), as has the HNMR spectrum of 7V,7V-dimethylcyclopent[e]azepin-l-amine.68 A detailed analysis of geminal and long-range 13C-H coupling constants for cyclopent[c]azepine is also available.87 The HNMR spectra of 9//-pyrrolo[l,2-a]azepin-9-one (8b) and its fully delocalized cation have been recorded in various solvents.7... 

The proton magnetic resonance spectrum of the product in trifluoroacetic acid shows that the isomeric purity is greater than 90%. The proton magnetic resonance spectral properties for the isomeric amino ketones in both trifluoroacetic acid and chloroform-d are as follows (solvent) 8 (multiplicity, number of protons, assignment, coupling constant J in Hz.) 1-... 

Solvent effects on the magnitude of spin-spin coupling constants in phosphoryl compounds have been reported, as have the solvent effects on the relative strengths of phosphoric acid and some of its partially esterified derivatives.The variation of i.r. frequencies of (122) and (123)... 

A fluxional amido-salt (24), in which the y-nitrogen atom acts as an internal nucleophile, has been identified by variable-temperature n.m.r. spectroscopy. At — 63 °C two methyl signals are observed, one a singlet, one a doublet (J = 11 Hz) whereas at + 60 °C there is only one signal, a doublet with J = 5.5 Hz (the average of the low-temperature coupling constants). The solvent extraction of organophosphorus compounds has also been studied by and H n.m.r, ... 

Instrumentation. H and NMR spectra were recorded on a Bruker AV 400 spectrometer (400.2 MHz for proton and 100.6 MHz for carbon) at 310 K. Chemical shifts (< are expressed in ppm coupling constants (J) in Hz. Deuterated DMSO and/or water were used as solvent chemical shift values are reported relative to residual signals (DMSO 5 = 2.50 for H and 5 = 39.5 for C). ESl-MS data were obtained on a VG Trio-2000 Fisons Instruments Mass Spectrometer with VG MassLynx software. Vers. 2.00 in CH3CN/H2O at 60°C. Isothermal titration calorimetry (ITC) experiments were conducted on a VP isothermal titration calorimeter from Microcal at 30°C. 

The H Sn- C coupling constants observed in spectra in various solvents are given in Table I. A representative spectrum... 

Table I. Observed Sn- C Coupling Constants in Poly(Tri-n-butyltin Methacrylate/Methyl Methacrylate)in Various Solvents a...

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