摘要:

Nitrogen-containing heterocyclic hydrazones have been used as analytical reagents, mainly to metallic ion spectrophotometric determinations in natural water samples. Using the reagent di-2-pyridil ketone benzoilhydrazone (DPKBH) we have developed a spectrophotometric method for the determination of Ni(II) in samples of several sources. DPKBH was used in excess in order to coordinate Ni(II) and the highest sensitivity was obtained in 50% v/v ethanol solutions when ammonium acetate buffer was added to maintain pH≅6.

ISSN:0038-7010    

DOI:10.1080/00387019708006687

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Virgatic acid triterpene, extracted fromsalviaplants, is found to be quenched by singlet oxygen at chemical and photosensitized oxygenations. A charge-transfer energy transfer is attributed to the quenching of singlet oxygen, which may be accounted as a protective mechanism ofsalviaplants to photooxygenations.

ISSN:0038-7010    

DOI:10.1080/00387019708006688

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The preparative thin layer chromatography using silica gel and solvent systems n. butanol : acetic acid: water (4:1:1 V/V) and 96% ethanol : water (70 : 30 v/v) were used to separate the amino acids mixture into groups that can be eluted and one or two of amino acids can be determined by derivative spectroscopy. This was done for determining histidine in presence of cystine, arginine in presence of lysine and ornithine, tryptophan in presence of tyrosine and phenylalanin, and methionine in presence of aspartic acid. The proposed method is applied for determination of these amino acids in baby food, Neslac, Dialac and Nestogen. The statistical analysis of the results were found to be good and in agreement with the ion exchange chromatographic method.

ISSN:0038-7010    

DOI:10.1080/00387019708006689

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

1H and13C NMR data, AMI calculations and X-ray diffraction in 3,3a,4,5,6,7-hexahydro-3-trichloromethyl[2,1]benzo isoxazole (1), obtained from the cyclization of trichloroacetyl cyclohexanone with hydroxylamine, are reported.1H and13C NMR data shown that only one pair of the diastereoisomers was obtained and the AMI calculations indicated that1a(3S3aS/3R3aR) is 2.63 kc:al.mol−1more stable than1b(3S3aR/3R3aS). The X-Ray diffraction data confirmed that only the structure1awas obtained.

ISSN:0038-7010    

DOI:10.1080/00387019708006690

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A considerable increase of optogalvanic signal amplitude for N2and hollow cathode plasma stabilization were obtained by using appropriate (N2+He) mixtures. A qualitative interpretation of this positive effect of He addition was made.

ISSN:0038-7010    

DOI:10.1080/00387019708006691

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

IR spectra were measured for an antitubercular agent,D-cycloserine (CS), and the hydrolyzate, β-aminooxy-D-alanine (AOA) and the dimer, cis-3, 6-bis(aminooxymethyl)-2, 5-piperadinedione (CS-dimer) at various pHs in aqueous solutions. Molecular species existing in the ionic equilibria were characterized by the pH dependence of the spectra. Band assignments were carried out by reference to the spectra of D20 solutions and those of related compounds. Spontaneous transformation of CS to CS-dimer was observed by the IR spectra for the neutral aqueous solution. The spectral evidence suggested that the non-ionic form of CS plays a key role in the dimerization process.

ISSN:0038-7010    

DOI:10.1080/00387019708006692

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Hollow cathode discharges in argon at various pressures and currents have been studied by optical emission spectroscopy. The cathodes were made of copper, bronze and brass. The discharges were supplied by direct, 100 kHz and 13.5 MHz currents. Atomic and ionic spectra of plasma gas and elements of cathode materials and molecular bands of ZnH and PN formed due chemical reactions between plasma components have been excited and measured. Relations between emission intensities, excitation temperatures and discharge conditions have been analysed and discussed.

ISSN:0038-7010    

DOI:10.1080/00387019708006693

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The reaction of trichloroacetanilide in alkaline medium was followed by means of infrared spectroscopy. Several intermediates and reaction products have been proved: the N-anion of the started trichloroacetanilide, the decarboxylation products of pnenylcarbamic acid - carbon dioxide and aniline, the end-product N,N-diphenylurea. The data obtained support the presupposed reaction mechanism involvingin situgeneration of phenylisocyanate.

ISSN:0038-7010    

DOI:10.1080/00387019708006694

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Analysis of NMR spectra of selectedmodel compoundscan be of great value in understanding aspects of hindered rotation and magnetic anisotropy in drugs and other compounds of much intrinsic importance. One- and two- dimensional1H NMR (300 MHz) and13C NMR (75 MHz) studies have been performed at ambient temperatures on the Diels-Alder adduct of N-carbamoylmaleimide with phencyclone,1.The data for the adduct,2, are interpreted as being consistent with: a) essentially slow exchange limit (SEL) spectra with respect to rotation about the C(sp2)-C(sp3) bonds to the unsubstituted bridgehead phenyls, b) slow rotation on the NMR timescale for the amide NH2group, and c) fast rotation about the amide N-CONH2bond to the ring nitrogen. The assignedendostereochemistry for adduct2and the conclusions regarding bond rotation rates are based on numbers of observed NMR signals and magnetic anisotropic effects. Full1H NMR spectral assignments and preliminary13C assignments are presented.

ISSN:0038-7010    

DOI:10.1080/00387019708006695

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

FTIR, Raman and SERS spectra of spermine phosphate hexahydrate have been recorded and analysed. Vibrational spectra show the protonation of amino and imino groups indicated by the presence of HPO42-ion. The molecule is found to be adsorbed to the metal surface through nitrogen and oxygen atoms of the molecules. Distortion of the HPO42-ion, change of symmetry of the molecule due to chemisorption and the enhancement in intensity of the amino group vibrations are discussed.

ISSN:0038-7010    

DOI:10.1080/00387019708006696

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor