摘要:

At temperatures above 100 °C iron(III) oxidizes coordinated EDTA to ethylenediaminetriacetic acid in aqueous solution in the absence of molecular oxygen. The reaction proceeds with an activation energy of 28.6 kcal/mol, and its rate is directly proportional to the concentration of Fe(III) and inversely proportional to pH. At 125 °C, the halflife of Fe(III) in the presence of excess EDTA is about 3 h at pH 9.3, but increases to >70 h at pH 5.4. The reaction is stoichiometric and no other reaction products or by-products were detected by nmr, gc, and gc – mass spectroscopy. In the presence of oxygen iron catalyzes quantitative oxidation of ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) to ethylenediaminetriacetic acid. The copper(II)–EDTA chelate undergoes a similar reaction but higher temperaturesare required. Iron(III) also oxidizes nitrilotriacetic acid (NTA) to iminodiacetic acid (IDA) and glycine. The hydrolyzed species Fe(OH)EDTA is shown to be the reactive intermediate, and the well-known (Fe–EDTA)2O4− μ-oxo dimer is shown not to exist at elevated temperatures (above 100 °C). Probable mechanisms are proposed for these reactions and comparisons are made with earlier work.

ISSN:0008-4042    

DOI:10.1139/v80-318

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Quantum yields of fluorescence as well as of solvated electron and H atom formation have been measured for phenol in several pure solvents and mixtures of varying polarity. The influence of excitation energy has been studied by excitation of phenol in the first and second excited singlet states. The solvent dependences of fluorescence and photoejection parameters are strongly correlated. The results are interpreted in terms of specific solute–solvent interactions, in particular H-bonded structures.

ISSN:0008-4042    

DOI:10.1139/v80-319

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The1H and13C nmr parameters for the recently reported complexes (η5-C5H5)PtR1R2R3where R1, R2, and R3are combinations of CH3, C2H5, and C(O)CH3groups are reported and compared to those for known octahedral di- and trimethylplatinium (IV) complexes. The C5H5group has a relatively weak nmrtrans-influence. A chiral shift reagent study on complex5(R1 = C(O)CH3, R2 = CH3, and R3 = C2H5) resolved the peaks due to the enantiomers, consistent with its structure and establishing its stereochemical stability. The four groups attached to the platinum atom in5differed greatly in their sensitivity to the shift reagent. The methyl groups in complex4(R1 = C(O)CH3, and R2 = R3 = CH3) become diastereotopic in the presence of chiral shift reagent. TheJ(Pt—H) values for5were not affected by the shift reagent.

ISSN:0008-4042    

DOI:10.1139/v80-320

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A general discussion is given of the determination of the proton spin–lattice relaxation rates of natural products, with particular emphasis on use of the null-point method which, for the systems studied here, gives identical results with those obtained via the conventional (and relatively time consuming) computational method.

ISSN:0008-4042    

DOI:10.1139/v80-321

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The conversion of the Diels–Alder adduct of methyl β-nitroacrylate with furan to the title compounds and toD,L-2,5-anhydroglucose derivatives is described.

ISSN:0008-4042    

DOI:10.1139/v80-322

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

During the reaction of the azlactone5with different cinnamaldehyde anils, we obtained α-pyridones with no evidence for the formation of β-lactams. The products have been characterized through elemental and spectral analyses.

ISSN:0008-4042    

DOI:10.1139/v80-323

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Some long-chain spiropyranindolines have been studied at the air–water and the air–solid interfaces. We have measured the surface pressure–area isotherms of these compounds and two of them are characterized by a solid film. We have also investigated the spectroscopic properties (uv–visible) of these spiropyranindolines in monolayer and in solution. The deposition of monolayers on quartz slides allowed the study of the photochromic properties of these compounds at the air–solid interface. The 3′,3′-dimethyl-1′-hexadecyl-6-nitrospiro(2H-1-benzopyran-2,2′-indoline), irradiated at 253.7 nm, showed the appearance of a new absorption band at 570 nm which varied in intensity when the number of monolayers and the time of irradiation were changed.

ISSN:0008-4042    

DOI:10.1139/v80-324

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The condensation of 5,6-dihydro-2-methyl-1,4-oxathiin-3-carbonyl isothiocyanate (1) with ethyl 3-phenylamino-2-butenoate (2) has yielded a mixture of ethyl 1,4-dihydro-2-(5,6-dihydro-2-methyl-1, 4-oxathiin-3-yl)-6-methyl-1-phenyl-4-thioxo-5-pyrimidine carboxylate (3) andN-[(phenylamino)thioxomethyl]-5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxamide (4, R′ = phenyl). It has been discovered that compounds4, in general, rearrange to 1-substituted-2,3-dihydro-5-[(2-hydroxyethyl)thio]-6-methyl-2-thioxo-4(1H)-pyrimidinones (5) at room temperature when stirred with dilute aqueous sodium hydroxide. The products of the reaction of 5,6-dihydro-2-methyl-1,4-oxathiin-3-carbonyl isothiocyanate (1) and phenylhydrazine, when treated with dilute aqueous sodium hydroxide, did not yield the rearrangement product5(R′ = NHC6H5). Instead, a mixture of the two triazole-3-thiones9and10was formed.N,2-Bis(5,6-dihydro-2-methyl-1,4-oxathiin-3-carbonyl)hydrazinecarbothioamide (12) with dilute aqueous sodium hydroxide yielded one rearrangement product (out of a possible four), namely, 5-6-dihydro-2-methyl-N-[1,2,3,4-tetrahydro-5-[(2-hydroxyethyl)thio]-6-methyl-4-oxo-2-thioxo-1-pyrimidinyl]-1,4-oxathiin-3-carboxamide (13).

ISSN:0008-4042    

DOI:10.1139/v80-325

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Ozone cleavage of 12 substituted vinyl chlorides (1) in methanol occurred such that the chlorinated moiety of the double bond afforded the carbonyl fragment (i.e. acyl chloride) and the nonchlorinated moiety afforded the carbonyl oxide fragment. All of these fragments underwent secondary reactions: formyl chloride gave carbon monoxide and hydrogen chloride; all other acyl chlorides yielded the corresponding methyl esters. The carbonyl oxides were converted into the corresponding methoxy hydroperoxides. Under the influence of hydrochloric acid unsubstituted and monosubstituted methoxy hydroperoxides were dehydrated to form the corresponding methyl esters, whereas the disubstituted methoxy hydroperoxide of acetone produced the cyclic trimeric peroxide of acetone.

ISSN:0008-4042    

DOI:10.1139/v80-326

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Recent studies have shown that Ni(II) in human blood serum is bound to albumin and the binding site is located at the NH2-terminus of the protein. In this article, the nature of the Ni(II)-binding site of the NH2-terminal tripeptide segment of human albumin:L-aspartyl-L-alanyl-L-histidine-N-methyl amide (AAHNMA) is reported as deduced by13C- and1H-nmr spectroscopy. The13C spectrum shows that the Ni(II) complex is in slow exchange on the nmr time scale, and resonances for Ni(II)–peptide complex and metal-free peptide are observed clearly in the pH range 6.4 to 9.1. The Asp COO−carbon is most affected by Ni(II) binding. The imidazole ring system also shows large variation. Furthermore, the results implicate the involvement of the NH2group. The introduction of Ni(II) ion into the solution containing peptide causes profound changes in the1H-nmr spectra in the pH range 6.4 to 9.1. Most significantly, there is a complete disappearance of Ala and His N—H protons which confirm the coordination of these two peptide nitrogens. The measurement of the13C spin–lattice relaxation times (T1) for AAHNMA and its 1/1 complex provide confirmatory evidence for the existence of a definite complex. The overall results suggest that Ni(II) forms complex with the NH2-terminal peptide of human albumin involving the α-NH2, N(3) imidazole, two deprotonated peptide nitrogens, and Asp COO−group in a pentacoordinated structure.

ISSN:0008-4042    

DOI:10.1139/v80-327

出版商:NRC Research Press    

年代:1980

数据来源: NRC