摘要:

Sedimentation coefficients (ultracentrifuge), second virial coefficients (light scattering) and intrinsic viscosities have been measured at various concentrations near the θ-point for solutions of polystyrene in cyclohexane and of polyisobutylene in ethyl heptanoate. The results have been analyzed in the light of several current theories, but are correlated satisfactorily only by the theory of Pyun and Fixman.

ISSN:0008-4042    

DOI:10.1139/v72-045

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The dipole moment derivative of the hydrogen bond in ice has been calculated assuming that the molecules can be represented as non-overlapping polarizable charge distributions characterized by dipole and quadrupole moments. The value is 0.1 electron charges which is about one third of the experimental value obtained from the far-infrared spectrum. The model predicts therefore only about one tenth of the experimental integrated intensity from which the effective charge was derived. Most of the intensity must therefore be due to specific hydrogen-bond interactions.

ISSN:0008-4042    

DOI:10.1139/v72-046

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The crystal structure of dinitrato-2,2′-dipyridylsilver(II) has been solved and refined to anR-value of 0.070. Four circle diffractometer measurements were obtained from the twinned triclinic crystals. The unit cell dimensions at 22 °C are:a = 697.5 ± 0.2 pm,b = 999.4 ± 0.2 pm,c = 1032.2 ± 0.2 pm, α = 113.46 ± 0.02°, β = 100.71 ± 0.02°, γ = 95.28 ± 0.02°. The space group is(No. 2) with two molecules per unit cell. The density is 2.06 ± 0.04 g cm−3(measured), 2.02 g cm−3(calculated). The four shortest bond lengths to silver are: Ag—O(1), 214.8 ± 1.5 pm; Ag—O(4), 213.6 ± 1.5 pm; Ag—N(1), 212.4 ± 1.6 pm; Ag—N(2), 220.7 ± 1.6 pm. These four bonds are distorted from square planar geometry with the silver atom lying 19.90 ± 0.17 pm out of the mean plane of the other four atoms. There are also long bonds to the nitrato groups of neighboring molecules: Ag—O(1′), 275.3 ± 1.3 pm; Ag—O(2″), 276.3 ± 1.6 pm. Inclusion of these bonds gives a distorted octahedral silver coordination. Though predominantly unidentate, there is a slight tendency toward bidentate bonding in both nitrato ligands: Ag—O(2), 305.8 ± 1.4 pm; Ag—O(5), 295.0 ± 1.7 pm. O(2) and O(5) approach the convex side of the distorted square planar coordination. The deviation from planarity of the closely bonded square, and angular distortions in the above mentioned octahedral coordination can be rationalized by considering the silver as eight coordinate. The bonds to silver may be grouped 4:2:2 by length or 4:3:1 by angular disposition.

ISSN:0008-4042    

DOI:10.1139/v72-047

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Three dimensional crystal structure analyses have been carried out on two nitrogen isosteres (a)5and (b)6using diffractometer data. The crystal data are: (a) system: monoclinic,P21/c;a = 7.350(3),b = 12.309(5),c = 23.268(8) Å, β = 118.35(8)°; (b) system: monoclinic,P21/c;a = 9.34(1),b = 9.58(1),c = 25.65(3) Å, β = 108.08(8)°.The S … S distances are 2.396(12) and 2.814(8) Å, respectively. This difference is an indication of the cleavage of the S—S "bond" in5when the terminal sulfur atom is methylated. The nature of the bonding of the outer sulfur atom in6is discussed.

ISSN:0008-4042    

DOI:10.1139/v72-048

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The sesquiterpene lactone hydroxyachillin has been isolated fromArtemisiafrigidaWild. The position and stereochemistry of the free hydroxyl group has been established by n.m.r. examination as well as the conformation of the molecule using nuclear Overhauser effects.

ISSN:0008-4042    

DOI:10.1139/v72-049

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A synthesis of (+)-occidentalol (1) has been realized in six steps, starting from the readily available enonealcohol3.

ISSN:0008-4042    

DOI:10.1139/v72-050

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Hydroxy ketone7has been prepared from both (+)-dihydrocarvone (3) and (+)-occidentalol (2), thus establishing the absolute stereostructure of the latter. The three-stage conversion of compound7into (+)-occidentalol constitutes a total synthesis of the sesquiterpene.

ISSN:0008-4042    

DOI:10.1139/v72-051

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A formulation of the diffusion-kinetic model based on the spherical diffusion flame method is presented and discussed. The application of this technique has been made to obtain the relative rates of the reaction of active nitrogen with perfluoroethylene, perfluoropropene, perfluorobutadiene-1,3, and perfluorobutyne-2.

ISSN:0008-4042    

DOI:10.1139/v72-052

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Energy barriers to rotation about Ar—O bonds have been obtained from an analysis of the variable temperature n.m.r. spectra of a number of highly substituted diphenyl ethers. These barriers are explained on the basis of structural and conformational effects and their implication for the resolution of optical isomers is discussed.

ISSN:0008-4042    

DOI:10.1139/v72-053

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The nitroso acetamides, naphthamides, and benzylcarbamates of 3α- and 3β-aminocholestanes were decomposed in various solvents and the nitrous acid deaminations of the free amines in acetic acid and aqueous acetic acid mixtures were studied. In these reactions the intramolecular process leads to products with high degrees of retention of configuration, whereas the intermolecular process leads to products which are predominantly equatorial. Diazoalkanes were shown not to be intermediates in these deaminations.

ISSN:0008-4042    

DOI:10.1139/v72-054

出版商:NRC Research Press    

年代:1972

数据来源: NRC