摘要:

The acetylene complex Pt(P(cyclo-C6H11)3)2(F3CC≡CCF3) crystallizes in the monoclinic space groupP21/cwith four formula units in a cell of dimensionsa = 10.902(2),b = 21.766(3),c = 19.808(3) Å, and β = 116.52(1)°. Three-dimensional X-ray data were collected on a four circle automatic diffractometer using Cu radiation. The structure was solved by the heavy atom method, and refined by full-matrix least-squares methods on F. A conventional agreement factor of 0.062 was achieved, employing 6678 observations for whichI > 0. The coordination geometry at the platinum atom is essentially planar, for the acetylene triple bond makes an angle of 6.5(5)° with the plane formed by the Pt and the two P atoms. The triple bond length is 1.260(10) Å. The acetylene adopts acis-bent geometry, with a mean bend-back angle of 45.5(8)°. The ligand is considerably perturbed upon coordination to the Pt atom, as is evident from the Δv(C≡C) value of 578 cm−1.

ISSN:0008-4042    

DOI:10.1139/v77-446

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

It has been shown previously that halofluorocarbons having anesthetic potency hinder the formation of hydrogen bonds (HB) of thetypes and it has been suggested that this is linked to a competitive mechanism involving another type of association. Since some of the most potent and widely used fluorocarbon anesthetics contain a mobile hydrogen atom the question arises if in such molecules the competitive mechanism involves the formation of HB's with the anesthetic as the proton donor instead of, or in addition to, association due to the electron acceptor properties of the higher halogens as seems to be the case for those fluorocarbon anesthetics which contain no hydrogen. Chloroform, halothane, methoxyflurane, enflurane, and 4,5-dichloro-2,2-difluoro-l,3-dioxolane have been studied from this point of view with the result that both mechanisms appear to operate.

ISSN:0008-4042    

DOI:10.1139/v77-447

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Raman and infrared spectra have been recorded for polycrystalline samples of TIClO3, TIBrO3, and T1IO3at room temperature. The vibrational spectra of these rhombohedral (R3m, C3v5) crystals are closely related to each other, and to single crystal Raman spectra of isomorphous RbClO3and KBrO3reported by others. Spectral assignments are made. The uni-molecular unit cell yields no correlation field splitting, but lack of a center of inversion leads to TO/LO splitting of each active mode in these uniaxial piezoelectric crystals. Relationships between the thallium(I) halates and the NaN3and MXY3perovskite structures are considered.

ISSN:0008-4042    

DOI:10.1139/v77-448

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Detailed investigations involving the electrophilic attack of various reagents on the 3,4-double bond of catharanthine derivatives (e.g.3, R = O) furnished a series of novel derivatives of potential use in the syntheses of naturally occurring bisindole alkaloids. These studies include such reagents as peracid, osmium tetroxide, and positive iodine.

ISSN:0008-4042    

DOI:10.1139/v77-449

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A detailed study involving the Polonovski-type coupling of vindoline (2) with several novel catharanthine derivatives is described. Coupling of vindoline (2) with theN-oxide intermediate of 3β,4β-epoxydihydrocatharanthine (1) provides a laboratory synthesis of the bisindole alkaloid leurosine (3, R=CO2CH3) and an unambiguous proof of the stereochemistry of the epoxide function in that alkaloid. The coupling of2with theN-oxides of 3α,4α-epoxydihydrocatharanthine (4) and 4α-hydroxydihydrocatharanthinic acid lactone (6) provide the rearranged bisindole products5,7, and8.

ISSN:0008-4042    

DOI:10.1139/v77-450

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Analysis of the proton magnetic resonance spectrum of phenyltrifluorosilane yields the spin–spin coupling constants between the fluorine nuclei and the protons. These are compared with the analogous long-range coupling constants in benzotrifluoride, toluene, and phenylsilane and are rationalized in terms of coupling mechanisms. The coupling over six bonds is assessed as a base point for the estimation of hindered rotation about the carbon–silicon bond.

ISSN:0008-4042    

DOI:10.1139/v77-451

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The extent and mechanism of cupric ion binding by humic acid (HA) at lowpH'swhere the material was insoluble in aqueous media was investigated. It was shown that significant amounts of Cu(II) were bound by HA even at pH'sas low as 1.35. Two major types of HA—Cu2+binding were observed. Binding which was accompanied by exchange of H+was more prevalent at high pH'sand [Cu2+]. Nonexchange bonding occurred at all pH's, but assumed greater importance at low pH's. Since the pattern of Cu(II) uptake could not be interpreted in terms of basic ion exchange or surface adsorption theory, a new model was proposed which qualitatively explained the dependence of Cu(II) on pHand [Cu2+]. The model assumed that the intermolecular bonding in flocculated HA was determined by the relative amounts of H+and Cu2+available for forming bridging bonds between the HA molecules. The model suggested that at high concentrations of Cu(II) and/or high pH's, the floc structure was such that the formation of copper bridge bonds was maximized.

ISSN:0008-4042    

DOI:10.1139/v77-452

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The aqueous solution chemistry of the trimethyllead(IV) species and the trimethyllead(IV) complexes of six carboxylic acids of pKavalues ranging from 2.75 to 4.95 has been investigated by proton magnetic resonance spectroscopy. Equilibrium constants for the reaction of (CH3)3Pb+with hydroxide ion to form (CH3)3PbOH and ((CH3)3Pb)2OH+, and the formation constants of the carboxylic acid complexes were determined from the pHdependence of the chemical shift of the methyl protons of trimethyllead. The formation constants of the complexes increase as the pKaof the ligand increases. The lead-207-proton coupling constant was found to be insensitive to complexation.

ISSN:0008-4042    

DOI:10.1139/v77-453

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Natural abundance13C Ft nmr spectra of four different series of title compounds have been examined. Unambiguous chemical shift assignments could be made for all the carbons of the 11-memberedcis-3,3-dimethyl-5-keto-6-alkyl-8-decenolides. In the rest of the 9- to 16-membered ketolactones, unique as well as logical assignments have been made using the standard13C chemical shift rules. In the case of two benzo- and naphthoketolactone series examined, the available shielding parameters for the substituted benzenes were employed with success to the naphthalene series for the assignment of aromatic carbons.

ISSN:0008-4042    

DOI:10.1139/v77-454

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

A short, general synthetic sequence has been developed, involving cycloaddition and a new decarboxylation/aromatization step, to prepare isomerically puremeta-bis-annelated benzenes. Some new bis annelated benzoic acids were isolated as by-products. Examples of a new decar–boxylation of (annelated) benzoic acids catalyzed by Pd/C are reported.

ISSN:0008-4042    

DOI:10.1139/v77-455

出版商:NRC Research Press    

年代:1977

数据来源: NRC