摘要:

Vibrational spectra of 4-methyl-1,2,4-triazole, its hydrochloride salt, and some of their deuterated homologs have been studied from 4000 to 200 cm−1. An attribution of most of the fundamental modes is proposed, and the effect of protonation on fundamental frequency values is explained.

ISSN:0008-4042    

DOI:10.1139/v87-418

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The orientational order parameters of monochlorobenzene have been determined, as functions of temperature and concentration, in two nematic solvents, EBBA and ZLI-1132. There are significant differences in the orientation of the solute molecule in the two solvents as reflected in the values of corresponding potential energy parameters as well as in the concentration dependence of the order parameters. These differences are caused mainly by a stronger interaction between the aromatic ring and the solvent ZLI-1132, since the change in the potential function terms for chlorobenzene parallel those for unsubstituted benzene. Attempts to correlate the orientation potential with molecular polarizability and molecular shape lead to the conclusion that neither of these properties plays a dominant role in determining the potential.

ISSN:0008-4042    

DOI:10.1139/v87-419

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

It is shown that1H–13C shift-correlated two-dimensional spectra obtained for polarization transfer via two-bond and three-bond13C–1H coupling can, in conjunction with related experiments, be used to assign unambiguously the molecular skeletons of two of the less common triterpenes, moretenone and 3-acetylaleuritolic acid. It is concluded that this is a technique of considerable generality for assigning structures of triterpenes and is more reliable than alternative approaches such as mass spectral fragmentation patterns. It has the additional benefit of simultaneously providing reliable13C and1H spectral assignments for these compounds.

ISSN:0008-4042    

DOI:10.1139/v87-420

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The title dications are prepared in a single step by the reaction ofN,N,N′,N′-tetramethyl-1,2-diaminoethane (tmen) with the halogenoalkanes CH2X2(X = Cl, Br, or I)orCH2XCH2X (X = Cl or Br), respectively. These bulky dications are useful for the precipitation of complex ions from solution, and show selectivity for doubly-charged anions. Tmen also reacts with CBr4to yield a dibromo-imidazolidinium heterocyclic dication, whereas reaction with CHBr2CHBr2produces the dihydrobromide of tmen. Vibrational and nmr spectra are reported, and the protons of the CH2group between the two quaternary nitrogen atoms of the tetramethylimidazolidinium dication are shown from the nmr data to possess acidic character.

ISSN:0008-4042    

DOI:10.1139/v87-421

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Diffusion studies show that benzophenone (BP), linoleic acid, and methyl linoleate partition completely into the micelles of phosphate buffer/0.10 MSDS. Water-soluble compounds 4-sulphomethylbenzophenone, sodium salt (BP−), azobis(2-amidinopropane•HCl) (ABAP) and 2,5,7,8-tetramethyl-6-hydroxychroman-2-carboxylate (Trolox) show partial partitioning into the micelles. BP- and BP−-photosensitized oxidation of linoleic acid in 0.50 MSDS exhibited characteristics of free radical chain reactions including: (1) inhibition by phenolic antioxidants, (2) no retardation by singlet oxygen quenchers, and (3) the formation of conjugated hydroperoxides withcis,transtotrans,transratios of geometrical isomers typical of autoxidation. Quantitative kinetic studies of the order in substrate, RH, and the rate of chain initiation,Ri, show that the classical rate law, −d[O2]/dt = kp/2kt1/2[RH]Ri1/2applies to BP-photoinitiated autoxidation of linoleic acid in SDS and the oxidizability (kp/2kt1/2 = 4.42 × 10−2 M−1/2 s−1/2) is the same as that found with a thermal initiator. The rotating sector method gave absolute rate constants for linoleic acid autoxidation in 0.50 MSDS for propagation (kp = 36.2 M−1 s−1) and termination (2kt = 3.52 × 105 M−1 s−1), significantly lower than values in polar organic solvents; attributed to solvation of polar peroxyls in aqueous SDS. Depressed inhibition rate constants (kinh) for α-tocopherol, Trolox, and pentamefhylhydroxychroman (PMHC) in 0.50 MSDS compared tokinhintert-butyl alcohol are attributed to hydrogen bonding effects on the peroxyl radicals and on the inhibitors.

ISSN:0008-4042    

DOI:10.1139/v87-422

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Kinetics of autoxidation of bilayer mixtures of oxidizable dilinoleoylphosphatidylcholine (DLPC) with saturated phospholipids as solvents (dimyristoyl-, DMPC, and dipalmitoyl-phosphatidylcholine, DPPC) follow the classical rate law of autoxidation: −d[O2]/dt = kp/2kt1/2[RH]Ri1/2. The kinetic order in substrate [RH] was found to be unity for peroxidation initiated by a lipid-soluble initiator, azobis-2,4-dimethylvaleronitrile (ADVN), and by the water-soluble azobis(2-amidinopropane•HCl) (ABAP). The kinetic order in rate of chain initiation,Ri, was found to be one-half for both initiation by ADVN, photochemically decomposed, and by ABAP. The oxidizability of unilamellar DLPC liposomes (kp/2kt1/2 = 0.232 M−1/2 s−2) is twice that of multilamellar DLPC (kp/2kt1/2 = 0.116 M−2 s−2). Analysis of the hydroperoxides formed during ABAP-initiated autoxidations of mixed DLPC + DPPC liposomes showed a linear trend between the ratio ofcis,transtotrans,trans geometrical isomeric hydroperoxides and [DLPC], consistent with the peroxidation mechanism proposed for homogeneous systems.31P nmr spectra of mixed bilayers were used to distinguish between heterogeneous and homogeneous mixtures of DLPC + DPPC. Such spectra taken at various stages of oxidation indicate that the bilayer structure of DLPC is preserved at least to the 10% extent of oxidation used in kinetic studies. At much higher oxidative conversion, the spectra indicate changes in lamellar structures.

ISSN:0008-4042    

DOI:10.1139/v87-423

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Sodium and potassium phenoxide, in the presence of one equivalent of dicyclohexano-18-crown-6 (cis–anti–cisisomer) and dibenzo-18-crown-6, form complexes that have a ratio of 1:1:1 (crown:salt:phenol) in ethereal solvents containing excess phenol. On the other hand, complexes having 1:1:2 ratios (crown:salt:phenol) are obtained under the same conditions when the macrocycle is 18-crown-6 or dicyclohexano-18-crown-6 (cis–syn–cisisomer). When only one equivalent of phenol is present, then 1:1:1 complexes are obtained with 18-crown-6 and dicyclohexano- 18-crown-6 (cis–syn–cisisomer). No complexes containing only the metal salts were isolated from these solutions. The infrared spectral data obtained from the complexes show that the phenol hydroxyl hydrogens in the complexes form either strong or very strong hydrogen bonds. The nuclear magnetic resonance chemical shifts of the phenol protons in the complexes have been obtained from deuterated dimethoxyethane solutions. Comparisons are made with the chemical shifts of the phenol hydroxyl protons obtained from the corresponding solutions containing only the equivalent salt/phenol solutions.

ISSN:0008-4042    

DOI:10.1139/v87-424

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The crystal structures of the 1:1:1 complexes of dicyclohexano-18-crown-6 (isomer B) with potassium phenoxide and phenol, and of dicyclohexano-18-crown-6 (isomer A) with sodium phenoxide and phenol have been determined. The potassium phenoxide complex crystallizes in space groupPncawitha = 14.150(3),b = 23.794(6),c = 9.491(1) Å, andZ = 4. Thesodium phenoxide complex crystallizes in space groupPbcawitha = 21.201(4),b = 24.406(6),c = 12.492(3) Å, andZ = 8. Both structures were solved by direct methods and refined by full matrix least-squares calculations to residuals,R, of 0.059 for the potassium phenoxide complex, and 0.069 for the sodium phenoxide complex. In the potassium phenoxide complex, the cation sits on a centre of symmetry, in the centre of the cavity formed by the crown ether in its regular conformation. The potassium is coordinated to all six crown oxygens as well as to two phenol/phenoxides, one on each side of the crown. Groups of phenol/phenoxide–potassium–phenol/phenoxide are linked by the hydrogen atoms to form a chain: K+… O … H … O … K+. The distance between the oxygens of the phenol/phenoxides is short, 2.48(1) Å. The hydrogen was initially located halfway between the two oxygens, on a 2-fold axis special position. Inspection of the difference Fourier map and refinement on the hydrogen position revealed, however, the presence of statistical or dynamical disordering. In the sodium phenoxide complex, the hexaether adopts an irregular conformation. The distances between the sodium and the crown oxygens range from 2.45 to 2.89 Å, while a distance of 2.363 Å is found with the phenoxide oxygen. Strong hydrogen bonding is found between the oxygens of the phenol and phenoxide. The O ….O distance is 2.471(4) Å.

ISSN:0008-4042    

DOI:10.1139/v87-425

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

High resolution13C CPMAS spectra for three configurationally isomeric dicyclohexyl-18-crown-6 ethers and three complexes derived therefrom are presented. Spectra are consistent with conformationally locked crown ether structures at 298 K. Data are discussed in terms of the symmetry properties of the macrocycles and stereochemical effects on13C chemical shifts in the solid phase. For the complex of 18-crown-6 with NaSCN and H2O, a single line is observed at 298 K. Temperature reduction removes the chemical shift averaging as the different torsional angles of the solid crown ether undergo distortions that become slow on the nuclear magnetic resonance timescale.

ISSN:0008-4042    

DOI:10.1139/v87-426

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Phenylindanes were obtained from the reaction ofN-acyl-1-arylalkylamines with polyphosphoric ester (PPE).cis-1-Methyl-3-(3,4-dimethoxyphenyl)-5,6-dimethoxyindane was synthesized to determine which stereoisomer was produced byN-formyl andN-acetyl-1-(3,4-dimethoxyphenyl)ethylamine with PPE. Nuclear magnetic resonance specra (1H and13C) of several mono-, 1,3-di-, and 1,2,3-tri-substituted indanes were fully analyzed to provide information on steric interactions and conformation of the cyclopentene ring. Possible cyclodimerization pathways are proposed.

ISSN:0008-4042    

DOI:10.1139/v87-427

出版商:NRC Research Press    

年代:1987

数据来源: NRC