摘要:

The synthesis, physical properties, and crystal structure of the dirhodium species [MeGa(N2C3H3)3]2Rh2(μ-CO)3containing three carbonyl bridges are reported. Crystals of tri(μ-carbonyl)bis[methyltris(1-pyrazolyl)gallato]dirhodium – benzene (1:1) are monoclinic,a = 11.660(4),b = 15.2917(7),c = 11.750(4) Å, β = 119.09(1)°,Z = 2, space groupP21. The structure was solved by conventional heavy-atom techniques and was refined by full-matrix least-squares procedures toR = 0.030 andRw = 0.033 for 2604 reflections withI ≥ 3σ(I). The molecule contains a Rh—Rh single bond of 2.5818(8) Å bridged by three CO ligands, the overall molecular symmetry being close toD3h. Other important mean structural parameters are: Rh—C = 2.007(10), Rh—N = 2.181(14) Å, Rh—C—Rh = 80.1(5)°, and Rh—C—O = 140.0(7)°.

ISSN:0008-4042    

DOI:10.1139/v84-107

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Synthesis of βDGalNAc(1→4)βDGal(1→4)βDGlc—O(CH2)8COOCH3(21) and βDGal(1→3)βDGalNAc(1→4)βDGal(1→4)βDGlc—O(CH2)8COOCH3(33) are presented starting from βDGal(1→4)βDGlc—O(CH2)8COOCH3(1) andD-galactose. Improvements in the preparations ofD-galactal triacetate (7) and tri-O-acetyl-2-azido-2-deoxy-α-D-galactopyranosyl bromide (11) are reported. The syntheses proceeded by way of the tri-O-acetyl-2-deoxy-2-phthalimido-β-D-galacto-pyranosyl and 4,6-di-O-acetyl-3-O-(tetra-O-acetyl-β-D-galactopyranosyl)-2-deoxy-2-phthalimido-β-D-galactopyranosyl bromides (18and30), which, in turn, were prepared from the corresponding allyl glycosides (15and23). The13C chemical shifts for the tri- and tetrasaccharide portions of21and33are assigned from the chemical shifts that were observed for the carbon atoms in the disaccharides which make up these structures. The trisaccharide (21) only very weakly inhibited the agglutination of human A red cells by the lectin ofDolichosbiflorus. The tetrasaccharide (33) was inactive.

ISSN:0008-4042    

DOI:10.1139/v84-108

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The fragmentation under electron impact of various methyl-2-pyrimidones is investigated. The fragmentation is markedly influenced by the methyl substituent in the 4- or 5-position and the main fragmentation pathways of the molecular ion involve the loss of carbon monoxide or methyl radical. The latter fragmentation process shows that the methyl groups are more labile in the 4- and(or) 6-position than in the 5-position. This is corroborated by the study of trideuteriomethylated analogues. One can thus distinguish by mass spectrometry the different isomers of position, 4-methyl and 5-methyl or 4,5-dimethyl and 4,6-dimethyl-2-pyrimidones.

ISSN:0008-4042    

DOI:10.1139/v84-109

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The crystal structure ofsyn-9-phenyl-2,11-dithia[3,3]metacyclophane,6, has been determined by single crystal X-ray diffraction and refined to anRvalue of 0.0723. The crystal structure is triclinic witha = 9.573(2),b = 12.010(4),c = 8.433(2) Å, α = 108.02(2)°, β = 95.95(2)°, γ = 102.25(3)°, and the space group iswith two molecules per cell, D(meas) = 1.313 g cm−3, D(calc) = 1.306 g cm−3. The bridging S atoms differ in their conformations so that the S … S distance is 6.391 Å. The metacyclophane rings have a distance of 3.57 Å between their centres and form a dihedral angle of 20.5°. The phenyl substituent forms an angle of 78.6° with the adjacent ring and has anorthoH-atom very close to the internal H-atom of the opposite ring. The phenyl substituted aromatic ring is non-planar and in a shallow boat form, the ring atoms C(11) (internal) and C(14) being 0.038(4) and 0.037(5) Å out-of-plane on the outside, the methylene C substituents are 0.212(5) and 0.199(5) Å out-of-plane on the inside. The first atom of the phenyl group is in the bowsprit position and is 0.274(4) Å above the mean plane on the outer side of the molecule. The opposite metacyclophane ring is less strained but in a similar boat form with the methylene C-atoms 0.092(4) and 0.067(6) Å to the inside. The mean bond angle at S is 103.5(2)°, the angles at C (methylene) range from 113.3(3)° to 118.0(3)°.The variable temperature1Hmr spectra results are consistent with thesynconformer6being dominant in solution and frozen at temperatures <60 °C as conformerA, with only relatively restricted further twisting of the biphenyl being found at ambient temperature.

ISSN:0008-4042    

DOI:10.1139/v84-110

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Active nitrogen produced at atmospheric pressure by a microwave discharge is found to require less energy consumption for the decomposition of nitrogen oxides. Important parameters improving the energy cost are described: NOxmust be introduced in a visually well-limited zone where the nitrogen atom concentration is maximum, the energy cost is then nearly equal to the theoretical cost.

ISSN:0008-4042    

DOI:10.1139/v84-111

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

L-Glucose has been synthesized fromD-glucose by a convenient method involving methyl 2,3-O-isopropylidene-β-D-gulo-furanosiduronic acid (6) as a key intermediate. Compound6was converted intoL-glucono-1,5-lactone (8), which, by a selective reduction, affordedL-glucose (9).

ISSN:0008-4042    

DOI:10.1139/v84-112

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A new method for production of chloride ion adducts, MCl−, via a sequence of bimolecular ion molecule reactions involving chloroformate esters is described. These reactions have been used in trapped-ion ion cyclotron resonance thermal equilibrium studies to determine the relative chloride ion affinities of twenty compounds with Cl−binding energies in the range 10–25 kcal mol−1. The present results are found to be in good agreement with chloride affinities obtained by other methods. The resulting chloride affinity scale establishes a convenient framework for the systematic investigation of effects of molecular structure and chemical properties on the binding energy of Cl−to both Lewis and Brønsted acids.

ISSN:0008-4042    

DOI:10.1139/v84-113

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Protonations of isaxonine phosphate are studied by performing CNDO/2 and CNDO/S molecular orbital calculations. Results are compared with previously published data. Wiberg's bond indices andScharacter percentages calculated using electronic populations are shown to correctly predict variations of bond lengths and bond angles as well ascoupling constants. A good prediction of proton chemical shift variations using a calculation of the screening constant was obtained.

ISSN:0008-4042    

DOI:10.1139/v84-114

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A theoretical study of fourteenN,N-linked biazoles has been carried out using the MNDO method with full optimization of the geometries. The variation of energy as a function of the conformation around the centralN—Nbond shows in all cases the higher stability of the orthogonal or near-orthogonal form. The contribution of the three main types of "ortho" interactionsand the effect of quaternization have been evaluated. Of the electronic properties calculated, one must emphasize the excellent agreement of dipole moments with experimental values.

ISSN:0008-4042    

DOI:10.1139/v84-115

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

An X-ray diffraction study of [Pt3S2(PMe2Ph)6][BEt4]2shows that it crystallises in the monoclinic space group,C2/c, witha = 15.447(2),b = 18.033(3),c = 26.505(5) Å, β = 96.73(2)°. The cation consists of three, distorted, square-planarcis-PtS2(PMe2Ph)2moieties combined by sharing of the two sulphur atoms to produce a central Pt3S2unit withC2symmetry and Pt—Pt distances of 3.182(1) Å (one edge) and 3.108(1) Å (two edges). Complete analysis and computer simulation of31P{1H} and195Pt{1H} nuclear magnetic resonance spectra give values for1J(Pt—P), 3202 Hz;3J(Pt—P), −25 Hz; and2J(Pt—Pt), 476 Hz. The structure is compared with previous results for analogous Ni and Pd complexes and the structural and nmr parameters are discussed with reference to the possibility of metal–metal interactions.

ISSN:0008-4042    

DOI:10.1139/v84-116

出版商:NRC Research Press    

年代:1984

数据来源: NRC