摘要:

The identification of aliphatic hydrocarbons containing multiple asymmetric centers can be difficult because of the complexity of the nmr spectra and because in capillary chromatography the diastereomers may be resolved to varying degrees. We suggest that the most effective method for identifying such hydrocarbons is through the pattern of retention times developed by the mixture of diastereomers on a suitable capillary glc column.This paper presents the results of some studies of a series of alkanes having the general form C2H5—(CH—CH3)n—R, wheren = 1 to 4, and includes the syntheses and13C nmr spectra of the compounds.

ISSN:0008-4042    

DOI:10.1139/v79-061

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

In violation of the 'para' rule, the boron trifluoride catalyzed addition of 4,4-dimethyl-2,5-cyclohexadien-1-one (1) to isoprene gave rise to the unexpected enone3as the only adduct. Under similar conditions, the addition oftrans-piperylene proceeded as predicted by the 'ortho' rule to give the single adduct6. Enone3was converted in three steps to the naturally occurring hydrocarbon ionene (12).

ISSN:0008-4042    

DOI:10.1139/v79-062

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A simple synthesis ofD- andL-apiose using the aldol condensation of furanose with formaldehyde under alkaline conditions as a key reaction is described.

ISSN:0008-4042    

DOI:10.1139/v79-063

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A simple conversion of 2,3-O-isopropylidene-D-hamamelose, prepared by reaction of 2,3-O-isopropylidene-D-ribose with formaldehyde, intoL-dendroketose is described.

ISSN:0008-4042    

DOI:10.1139/v79-064

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Heats of mixing and vapour pressures of chloroform (A)+ methanol (Bn) as a function of concentration have been determined at 303.15 K. The excess Gibbs free energy of mixing,GEvalues, have been obtained from the measured vapour pressure data. The heats of mixing values are negative for solutions rich in methanol but they become positive for solutions rich in chloroform. On the other hand,GEvalues are positive for all the methanol mole fractions andGE > HE. The results have been analysed in terms of Barker and ideal associated model theory of non-electrolyte solutions. The analysis has revealed that only the ideal associated model approach (which here assumes the presence of AmB (m = 1, 2), ABk(k = 2) and Bl(l = 1) molecular species) well describes the general behaviour ofHEwithxAover the entire chloroform concentration range for this mixture. The equilibrium constants for the various association reactions along with the enthalpy of formation of the various molecular species have also been calculated.

ISSN:0008-4042    

DOI:10.1139/v79-065

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Binuclear mixed-metal mixed-ligand monomeric bridged complexes of the type (XCN)2(L)2M(NCX)2Hg(PPh3)2(M = Co(II), Ni(II), Cu(II), Zn(II); L = pyridine, nicotinamide; PPh3 = triphenylphosphine; X = S, Se) have been synthesized and characterized by elemental analysis, molar conductance, magnetic moment, and infrared and electronic spectral studies. In all the complexes, the most likely structure involves pyridine or nicotinamide linked to M and PPh3to Hg. Total softness calculations have also been made to extend support to the structure of the complexes.

ISSN:0008-4042    

DOI:10.1139/v79-066

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The ir spectra of mixtures of methyl propionate/water and methyl propionate/Ba2+in dimethylsulfoxide and in acetonitrile have been recorded in the region of the νCOmode of the ester. Evidence is presented to indicate the presence of different types of complexes; their concentration was determined as a function of the composition of the medium. The spectroscopic results are compared to those from the kinetics of the alkaline hydrolysis in the same conditions. It is demonstrated that the orbital control explains the experimental results better than does the charge density on the carbon of the carbonyl group. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v79-067

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The ν1and ν4bcinfrared absorptions of the NH3D+probe ion dispersed at low concentration in polycrystalline ammonium halides were used to investigate possible correlations between the frequencies of these absorptions and various structural and other parameters of the ammonium compounds. The most important among these parameters are the H … X distance, the acceptor strength of the halogen atom X for hydrogen bonding, and the coordination number C.N. and activation energyEafor reorientation of the ammonium ion. It is found that the ν1and ν4bcfrequencies are affected by the acceptor strength and by the degree of 'compression' of the ammonium ion in the crystal, the volume effect. These two factors affect ν4bcin the same direction but ν1in opposite directions. As a consequence, in a ν4bcvs. ν1plot the halides are separated according to X, C.N., and certain other parameters. The effective radius of the ammonium ion in cubic (NH4)2MX6is shown to increase with the strength of hydrogen bonding.TheEavs ν1plot contains two branches. The low-frequency branch is dominated principally by the strength of the hydrogen bonding and corresponds to C.N. 4 and 8 and tonormalhydrogen bonds. The high-frequency branch is dominated principally by the volume effect and corresponds to C.N. 12 and to hydrogen bonds of highly dynamic character (fluxionalhydrogen bonds). Ammonium ions with C.N. 6 may correspond to either branch, depending on the formal charge on X. Existence of the so-called symmetrically trifurcated hydrogen bond that has been proposed for the ammonium ion in certain coordinations is not supported by the present evidence.The problem of the fundamental vibrational frequencies of the 'free' ammonium ion is discussed and values are proposed for the 'limiting' ν1. and ν4bcfrequencies in ammonium halides. Criteria of hydrogen bonding in ammonium halides are reviewed and comment is offered on symmetry aspects of crystallographic transformations in cubic hexahalometallates(IV), A2MX6.

ISSN:0008-4042    

DOI:10.1139/v79-068

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Perturbation molecular orbital analysis has been used for a computation of the through-bond and through-space orbital interactions of oxygen lone pairs in dimethoxymethane (DMM). The analysis predicts the symmetrical combination ofp-type lone pairs as a highest occupied orbital in an antiperiplanar conformation. The conformational dependence of through-bond orbital interactions has the character of theV2term in the Fourier expansion of the rotation potential function about the C—O bond. Contrary to the recent theoretical interpretation that the anomeric effect (preference ofgaucheconformation) is caused by superjacent orbital control, the orbital interactions in DMM are not dominant terms with respect to the anomeric or exoanomeric effect. The dipole–dipole interactions of the C—O bonds stabilizing thegaucheconformation should thus be considered as the primary cause of the anomeric effect in DMM. The frontier orbital energies and geometric parameters in DMM are strongly influenced by a variation of orbital interaction with rotation. Results obtained for DMM are used to explain the conformational behaviour of other molecules containing the acetal moiety, such as pyrane heterocycles, sugars, and polyoxymethylene.

ISSN:0008-4042    

DOI:10.1139/v79-069

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The products of the incubation of androst-5-ene-3,17-dione (2a), 3β-hydroxyandrost-5-ene-17-one (2b), and androsta-3,5-diene-17-one (3) withRhizopus arrhizusATCC 11145 under a variety of conditions have been identified and the mechanisms of their formation discussed. In addition, several C-(4,5)- and C-(5,6)-epoxyandrostanes have been incubated withR.arrhizus, the products identified and possible pathways for their formation presented.

ISSN:0008-4042    

DOI:10.1139/v79-070

出版商:NRC Research Press    

年代:1979

数据来源: NRC