摘要:

A recently developed empirical method for measuring beats of vaporization (ΔHv25) by a combination of gas chromatography and calorimetric heats of solution in the stationary phase has been applied to a series of 9 monoalkylcyclohexanes having C1–C12side chains. The uncertainties in the measurements (0.07 – 0.23 kcal/mol) are critically evaluated. Comparison with literature ΔHvmeasurements indicates good agreement for low boiling compounds, and for high boiling compounds, values substantially more reliable than were previously obtained from vapor pressure measurements.

ISSN:0008-4042    

DOI:10.1139/v78-408

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The transient free radicals formed when furil was photoreduced have been characterized by esr and CIDEP. Two furil derived radicals were observed: one was the protonated form of the semidione radical (FH•) while the other was an allyl radical formed by radical addition to the furil ring. Initial polarization was observed for FH•which was consistent with the triplet mechanism and these CIDEP results indicate that phenol is a better chemical quencher of the furil triplet than pentachlorophenol which is in turn more efficient than 2-propanol. A method to estimate relativeT1of radicals is also described.

ISSN:0008-4042    

DOI:10.1139/v78-409

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The exchange reaction between M+PQ−•ion-pairs and MeHgCl leads to the formation of MeHgPQ•adduct with a characteristic lowg-factor of 2.00052 and a small methyl proton splittings of 0.16 G. The dynamic and equilibrium aspects of the exchange depend upon the alkali cation, the concentration of MeHgCl, and for M+PQ−•also on temperature. The MeHgPQ•is found to be relatively stable at room temperature and in the presence of water. These results may be of potential value to toxicology studies of methylmercury.

ISSN:0008-4042    

DOI:10.1139/v78-410

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Syntheses of 4-epi-aubergenone, a sesquiterpenoid related to eudesmane, are described. One synthesis afforded this sesquiterpenoid as a racemate (12) whereas another, utilizing (+)-carissone as starting material, afforded an enantiomer (12a). The fact that naturally occurring aubergenone is the C(4) epimer of the thermodynamically more stable synthetic12was revealed by the discovery that it was completely converted into the latter by treatment with base. This epimeric relationship is substantiated by comparison of the nmr spectra of the two isomers. Evidence requiring the reformulation of the structure of aubergenone as13is adduced.

ISSN:0008-4042    

DOI:10.1139/v78-411

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Pyrazolato bridged binuclear complexes of palladium and of platinum, (C8H12X)2M2(μ-Pz2) (X = OCH3or pyrazolato), are obtained by reaction of (1,5-cyclooctadiene)dichloro-palladium(II) or -platinum(II) with a 1 unsubstituted pyrazole and sodium hydroxide in methanol.

ISSN:0008-4042    

DOI:10.1139/v78-412

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Treatment of PtCl(CNR)(acac) (R = p-tolyl; acac = acetylacetonate) withp-toluidine gives the carbene compound PtCl{C(NHR)2}(acac). Reaction of this complex with a silver salt, followed by treatment with a neutral ligand L, gaveortho-metallated species [Pt{C(NHC6H4CH3)(NHC6H3CH3)}L2]+which have been isolated as crystalline salts. The molecular structure of the ClO4−salt with L2 = bisdiphenylphosphinoethane has been determined by X-ray diffraction. Crystals are monoclinic, space groupP21/n, with four formula units in a cell of dimensionsa = 20.370(3),b = 18.116(3),c = 10.770(2) Ǻ, and β = 99.47(6)°. Full matrix least-squares refinement onFusing 3252 observations gave a conventional agreement factorR. = 0.047. While the formation of theseortho-metallated carbene complexes restricts the further extension of this chemistry, the ready reversal by acid treatment is unusual

ISSN:0008-4042    

DOI:10.1139/v78-413

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Dibromobis(thiosemicarbazide)mercury(II), HgBr2(tsc)2, is isostructural with dichlorobis-(thiosemicarbazide)mercury(II). The crystal is orthorhombic witha = 8.825(9),b = 8.587(11),c = 15.939(22) Å,Z = 4, space groupPbcn. Some bond lengths and angles are: Hg—Br = 2.860(4) Å, Hg—S = 2.45(1) Å, C—S = 1.76(4) Å and. In both HgCl2(tsc)2and HgBr2(tsc)2, the configuration of the coordinated thiosemicarbazide (tsc) is the same as that of the free molecule. The ir and Raman (R) spectra for the complexes and tsc in the region 300–1600 cm−1are very similar. The strong band at 800 (807 R) cm−1in the tsc due to v(C—S) is shifted to 773 (796 R), 777 (796 R), and 660 (680 R) cm−1for HgCl2−(tsc)2, HgBr2(tsc)2, and HgCl2(tsc) correspondingly. A strong band at 368 (R) cm−1present uniquely for HgCl2(tsc) can be assigned to v(Hg—N), The halides in HgX2(tsc)2are bonded to one mercury(II) ion and weakly bridged to a neighboring molecule with Hg … Cl = 3.250(3) Å and Hg…Br = 3.436(4) Å. As a result, two Raman bands due to Hg—X are expected. For HgCl2(tsc)2, the two Raman bands occur at 236 and 166 cm−1, whereas for HgBr2(tsc)2, one was observed at 190 cm−1but the other was masked by lattice modes. In HgCl2(tsc), the two Hg—Cl bonds are different and bands at 220 and 190 cm−1are assigned to v(Hg—Cl)t.

ISSN:0008-4042    

DOI:10.1139/v78-414

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The catalytic decomposition of 2-propanol has been studied in a flow System from 200 to 280 °C on vanadium pentoxide and modified vanadium pentoxide catalysts. Results were obtained with separate melts of the oxide containing 9.09 mol% of each of the alkali metal sulfates and with individual preparations of the pentoxide containing 1.01, 2.00, and 4.98 mol% potassium sulfate, respectively. In addition to expected dehydration and dehydrogenation reactions, propane was formed over the entire temperature range and became a dominant product at higher temperatures.Kinetic experiments showed that the dehydration and dehydrogenation reactions were zero order with respect to ail components while the propane-forming reaction gave a rate order of 0.3 with respect to 2-propanol concentration. Elimination-type mechanisms have been proposed to explain the results and some evidence of a relationship between catalyst activities and surface acidity is presented. The observed kinetic compensation effect bas been shown to compare well with previous work on 2-propanol decomposition on metal oxides.

ISSN:0008-4042    

DOI:10.1139/v78-415

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The vapour pressures for the decomposition of the solid and liquid compounds AMCl6where A = Na, K, Rb, or Cs, and M = Nb or Ta, were measured by a fused quartz Bourdon spiral pressure gauge. The hexachlorotantalates were found to be more stable thermally than the hexachloroniobates. Enthalpies of decomposition were calculated. The dissociation temperatures of each sequence of compounds increase with increasing size of the radius of the alkali-metal cation. Partial pressures of NbCl5or TaCl5vapour in equilibrium with solutions representing the binary Systems KCl–KNbCl6and KCl–KTaCl6, respectively, are also reported.

ISSN:0008-4042    

DOI:10.1139/v78-416

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Powder samples of cesium oxypentafluorouranate(VI) were studied by both neutron diffraction and19F broad Une nuclear magnetic resonance.CsUOF5crystallises with thespace group, with the parametersa = 5.41 ± 0.01 Ǻ; α = 95°34′ ± 5′. The structure, which was found to be unchanged at temperatures as low as 4.2 K, was interpreted by a statistical occupation of six-fold equivalents sites, the occupation rate being 1/6 and 5/6 for oxygen and fluorine, respectively. The nmr study showed that the disorder corresponding to this structure was of dynamic type, and that the UOF5−ions were in isotropical rotation. The motion is observable at temperatures as low as 223 K with a characteristic time τ equal to3 × 10-5s at 266 K. On the other hand, it was also shown through this nmr study that the point symmetry of the UOF5−ion corresponds to theC4vgroup, with the axial fluorine being more covalent than the equatorial ones. Consistency of the diffraction and nmr results is discussed

ISSN:0008-4042    

DOI:10.1139/v78-417

出版商:NRC Research Press    

年代:1978

数据来源: NRC