摘要:

The 60 MHz1H NMR spectra of clenbuterol,1, have been studied in CDCl3solution with the achiral shift reagent, tris (6,6,7,7,8,8,8-hepta-fluoro-2,2-dimethyl-3,5-octanedionato)europium (III),2, and the chiral reagent tris[3-(heptafluoropropylhydroxyn1ethyl-ene)-(+)-canphorato]europiunr(III),3. Use of3resulted in observable enantiomeric shift differences, ΔΔσ, for thet-butyl, NH2benzylic CH and the aryl proton signals. Values of ΔΔσ as high as 135.1 Hz (2.25 ppm) and 86.5 Hz (1.44 ppn) were seen for the methine and aryl protons, respectively, with a solution 0.1035 molal in1and a1:3molar ratio of 0.551. The aryl resonance is especially well suited for direct optical purity determinations of1.

ISSN:0038-7010    

DOI:10.1080/00387018908053901

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In earlier studies the methods for determination of chlorine by aluminium monochloride molecular absorption spectrometry have been based on the use of the continuous light sources.

ISSN:0038-7010    

DOI:10.1080/00387018908053902

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Integration of the31P spectrum of phosphite formed after reaction of phosphorus tricholoride with partially deuterated water is found to yield an accurate measurement of the percent of deuteration (or protonation) after correction for the kinetic isotope effect. A kinetic isotope effect favoring proton reaction by a factor of 3.2 ± .25 is found. The method is tested over the range of 10% to 90% deuterium. The results are found to be accurate to ± 6% relative, which is probably limited by experimental error in the determination of the integral. Measurements outside the 10 to 90% range are possible, but require longer acquisition times because of the low signal-to-noise ratio of the small peaks.

ISSN:0038-7010    

DOI:10.1080/00387018908053903

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The carbon-13 chemical shifts of seven N-(4-substituted phenyl) piperidine; the corresponding N-oxides, and their thermal rearrangement products were analyzed and assigned. The N-oxidation effect on the carbon-13 chemical shift is discussed, a correlation of N-oxidation effect with substituent constant (σp, σm, σIand σR) has been studied; dual substituent-parameter equation produce better correlation.

ISSN:0038-7010    

DOI:10.1080/00387018908053904

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A method is proposed for the calculation of heteronuclear dipolar coupling between two 1/2 nuclei, X and Y, by measuring the spin-lattice relaxation rates of the abundant Y nucleus and of the satellite peaks (1H,31P,19F) due to the scalar coupling of Y with the less abundant X nucleus. The1H-13C dipolar interaction has been evaluated from the proton spin-lattice relaxation rates of tyrosine in water solution and the effective correlation times of the aromatic moiety have been calculated.

ISSN:0038-7010    

DOI:10.1080/00387018908053905

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The diffusion coefficient of butylated hydroxy toluol (BHT) in solvent casted PVC films from tetrahydrofurane (THF) was studied by UV spectroscopy. Diffusion coefficient of BHT in PVC at 140, 160 and 180°C were determined as 1.0 × 10−123.0 × 10−12and 6.0 × 10−12m2/s. The activation energy of diffusion (Ea) was 66 kj/mol.

ISSN:0038-7010    

DOI:10.1080/00387018908053906

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

During the investigation of the glycosidic constitutents of Calendula arvensis L. we isolated the previously reported Arvensoside A, Arvensoside B, Calenduloside C and Calenduloside D. The complete assignment1H NMR spectra of these compounds was achieved through the concerted application of 2D-homonuclear chemical shift correlations. Calenduloside C and Calenduloside D were isolated for the first time from the fresh aerial parts ofCalendula arvensis L.

ISSN:0038-7010    

DOI:10.1080/00387018908053907

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Molecular mechanics calculations were made for 2-chloro-2,3-dimethylbutane, 2-chloro-2,4-dimethylpentane, and 2-chloro-2,5-dimethylhexane in order to compare the results with conclusions obtained from vibrational spectra concerning the conformational behavior of these compounds. The structures, relative energies, and heats of formation were also calculated.

ISSN:0038-7010    

DOI:10.1080/00387018908053908

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Normal coordinate calculations were made for 1-butyne, propionitrile, and the two conformers each of 1-pentyne and butyronitrile, using a thirty-one parameter modified valence force field. Only the triple bond stretching force constant was assumed to be different in the two families of compounds. Twenty force constants were refined to fit 117 frequencies of the six molecules, with the average error being 5.1 cm−1, or 0.65%.

ISSN:0038-7010    

DOI:10.1080/00387018908053909

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A simple spring model for molecular vibrations is described in which Cartesian co-ordinates are used for both longitudinal and transverse displacements. The transverse restoring forces are shown to be electrostatic in origin and much weaker than the elastic longitudinal forces. The technique is applied to diatomic and centrosymmetric triatomic molecules. In the latter case, an analytical expression for the bending mode frequency is obtained which is equivalent to that derived by conventional methods using bending constants and internal co-ordinates. The model offers certain advantages when applied to the dynamics of crystals, for which Cartesian co-ordinates, aligned with the unit cell axes, are the natural choice. Reference is made to recent work on molecular and ionic crystals using extensions of this model.

ISSN:0038-7010    

DOI:10.1080/00387018908053910

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor