摘要:

The deuteron–proton liquid phase isotopic disproportionation constant in hydrogen sulphide,K1, defined for the equilibriumhas been measured at 25.7 °C. The value ofK1was 3.99 ± 0.11, based upon direct measurements of the concentrations of the three molecular species H2S, HDS, and D2S by1H and2H nuclear magnetic resonance spectroscopy (nmr) of carefully purified samples. This compares with the theoretical vapour phase isotopic distribution constantKv = 3.92, calculated from ideal gas vapour phase isotopic partition function ratios (1, 2).

ISSN:0008-4042    

DOI:10.1139/v85-471

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Excess volumes for the binary liquid mixtures of methylisobutylketone with benzene, toluene, chlorobenzene, bromobenzene, and nitrobenzene have been measured at 303.15 and 313.15 K. Excess volumes were negative for all the systems over the entire range of composition and at both the temperatures. The behaviour ofVEas a function of composition and temperature was studied. Viscosity data have also been determined for the five systems at 303.15 K. The excess viscosity, Δ ln η, has been calculated and its behaviour as a function of composition was investigated. The results ofVEand Δ ln η have been discussed in terms of dipole – induced dipole and dipole–dipole interactions between the components.VEand Δ ln η were analysed in the light of Prigogine–Patterson–Flory equation of state theory and Bloomfield and Dewan's viscosity relations.

ISSN:0008-4042    

DOI:10.1139/v85-472

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

From Hg(SbF6)2and an appropriate amount of the ligands Ph2PCHRPPh2(R = H or Me), 2:2, 1:2, and 1:3 M:L complexes have been prepared in MeNO2solution and characterized by1H,31P, and199Hg nmr spectroscopy. The 2:2 complexes are ligand-bridged, as are [Hg(Ph2PCH2PPh2)(Ph2PCHMePPh2)Hg]4+and [Hg(Ph2PCH2PPh2)2Ag]3+(prepared from Hg(SbF6)2, Ag(AsF6), or Ag(SbF6) and the ligand), examined by nmr for comparison. The complex [Hg(μ-Ph2PCHMePPh2)2Hg]4+exists as two isomers, which interconvert slowly on the preparative timescale. The 1:2 complexes, and the analogous mixed ligand complex are shown by their nmr spectral properties to be examples of tetrahedral bis(chelate) complexes, which are very unusual for the Ph2PCHRPPh2ligands. In the 1:3 complexes, and the one of the two possible mixed complexes identified, both η1-and η2-ligands appear to be present and these undergo rapid intramolecular η1-to-η2exchange. The η1-bonding mode of Ph2PCH2PPh2also occurs in [(η-Ph2P(CH2)2PPh2)Hg(η1-Ph2PCH2PPh2)2]2+and [Hg(η1-Ph2PCH2PPh2)4]2+as evidenced by their reduced temperature31P nmr spectra in Me2CO—MeNO2.The complex [Hg(η2-Ph2PCH2PPh2)2]2+has31P and199Hg nmr spectral properties significantly different from those of its acyclic analog [Hg(PMePh2)4]2+. To place this anomaly in perspective, the31P and199Hg nmr spectra of a much wider series of new bis(chelate) complexes [Hg(LL)(L′L′)]2+have been obtained, with the ligand combinations LL = L′L′ = Ph2PNPhPPh2; LL = dppm, L′L′ = Ph2PNPhPPh2; LL = L′L′ = Ph2P(CH2)nPPh2(n = 2–4); LL = Ph2P(CH2)mPPh2, L′L′ = Ph2P(CH2)nPPh2(m ≠ n;m = 1–3,n = 1–5). From the data for the last two series, it is found that only the bis(chelate) complex of Ph2PCH2PPh2shows a large anomaly in its199Hg chemical shift (anomalously high shielding), and that in [Hg(LL)(L′L′)]2+values of2J(PP),1J(HgP), and31P chemical shifts vary systematically with the ligand combination; of particular note,1J(HgP) to LL decreases as the chelate ring size of L′L′ increases. These observations are discussed in terms of the variation in the intra-and inter-chelate PHgP angles expected in the complexes.

ISSN:0008-4042    

DOI:10.1139/v85-473

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Six new metabolites (2,5–9) were isolated from the extracts ofRyaniaSpeciosaVahl. These compounds are closely related to ryanodine, the known insecticidal toxic alkaloid from this plant.

ISSN:0008-4042    

DOI:10.1139/v85-474

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The key chiral synthons, (R)-3-isopropenyl-6-heptenoic acid and (R)-3-isopropenyl-6-heptenal, needed for the synthesis of (3Z,6R)-3-methyl-6-isopropenyl-3,9-decadien-1-yl acetate, a component of the sex pheromone of the California red scale,Aonidiellaaurantii, have been prepared by asymmetric synthesis. The chiral acid was synthesized in 86% ee by an asymmetric 1,4-addition of isopropenylmagnesium bromide to thel-ephedrine amide derived from (E)-2,6-heptadienoic acid, followed by base hydrolysis. Acid hydrolysis gave the chiral 3-(3-buten-1-yl)-4,4-dimethylbutyrolactone. The chiral aldehyde was prepared in greater than 99% ee by an asymmetric 1,4-addition of isopropenylmagnesium bromide to the imine derived from (S)-(+)-tert-butyl 2-amino-3,3-dimethylbutyrate and (E)-2,6-heptadienal. The 1,4-addition reactions ofn-butyllithium or isopropenyllithium to (4S,5S)-(+)-2-[1-(E-1,5-hexadienyl)]-4-methoxymethyl-5-phenyl-2-oxazoline gave the addition products, and sequential mild hydrolysis and reduction of these adducts yielded chiral 3-n-butyl-6-hepten-1-ol for the former adduct but a mixture of products was obtained from the latter adduct.

ISSN:0008-4042    

DOI:10.1139/v85-475

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The synthetic route to 6-chloromercuricholest-5-en-3β-ol has been studied and the yield improved from 2% to 20%. The reaction of 6-chloromercuricholest-5-en-β-ol with fluorine, chlorine, bromine, and iodine has been examined. 6-Bromocholest-5-en-3β-ol and 6-chlorocholest-5-en-3β-ol have been directly prepared from 6-iodocholest-5-en-3β-ol using cuprous halides. A new intermediate, 6-tosyloxycholest-5-en-3β-ol, has also been synthesized by the action of silver tosylate on 6-iodocholest-5-en-3β-ol. The structures of the compounds were proven by a combination of high-resolution1Hmr and13Cmr. A new crystal modification of 6-chloromercuricholest-5-en-3β-ol has been found.

ISSN:0008-4042    

DOI:10.1139/v85-476

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

We describe the preparation of the six configurationally distinct cyclobutane-type photodimers generated by the acetone-sensitized uv irradiation of thymidine in aqueous solution. Also prepared as minor photoproducts are the 5Rand 5Sdi-astereoisomers of 5,6-dihydrothymidine, and two novel molecules, the 5Rand 5Sdiastereoisomers of 5-acetonyl-5,6-dihydrothymidine. The purification of the ten molecules by chromatographic techniques (hplc, tlc) is described, along with their extensive characterization by uv, ir, cd, FAB-ms and1H nmr. The proton chemical shifts and coupling constants are discussed in terms of the geometry of the pyrimidine, cyclobutane, and sugar rings.

ISSN:0008-4042    

DOI:10.1139/v85-477

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

On the basis of previously reported, as well as new, experimental results, a review is presented of the kinetic and chemical influences of alkenes on the pyrolysis of alkanes. The results confirm that theadditionof free H• atoms to the double bonds of alkenes is not sufficient to explain their inhibiting influence on the pyrolysis of alkanes. On the contrary, our results show that the processes of addition can account for thechemicaleffects of added alkenes on the pyrolysis of alkanes, namely, the modifications brought to the nature and the ratio of the products formed during the reaction. The results presented here confirm that the addition of alkyl free radicals to the double bond of alkenes does not lead to important chemical effects. The previously reported experimental results (pyrolysis of ethane in the presence of ethylene or propene, the pyrolysis of 2,2-dimethylbutane in the presence of propene, isobutene, or two isopentenes), completed by our new results (pyrolysis of ethane in the presence of isobutene, pyrolysis of isobutane in the presence of ethylene, of propene, oftrans-2-butene, or of 2-methyl-2-butene), can lead to very simple general rules, on the basis of which it is possible to explain the results and to predict the modifications (relating to the nature of the products and to their ratios) that will result from the addition of an alkene during the pyrolysis of an alkane at a temperature of 500 °C (773 K). Aside from their fundamental aspects, these observations and their mechanistic consequences could be useful for the preparation of models for these thermal reactions, especially for the simplification of complex models. These observations also explain certain facts observed in industry and can help in solving some of the problems associated with the thermal cracking of heavy oils.

ISSN:0008-4042    

DOI:10.1139/v85-478

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

For the purpose of preparing the ring-expanded analogue of anthracene, 1,2,4,5-tetrakis[(1E,3Z)-4-methylhexa-1,3-dien-5-ynyl]benzene,8, and 1,2,4,5-tetrakis[(Z)-2(2-ethnylphenyl)ethenyl]benzene,16, were oxidatively coupled; however, both of them affordedm-bridged derivatives, i.e., 1,3:4,6-bis[(1E,3Z,9Z,11E)-4,9-dimethyldodeca-1,3,9,11-tetraene-5,7-diyne-1,12-diyl]benzene,3, and 1,3:4,6-bis[(1E,11E)-3,4:9,10-dibenzdodeca-1,11-diene-5,7-diyne-1,12-diyl]benzene,5. To ascertain the structures of3and5, the related model compounds were also prepared.

ISSN:0008-4042    

DOI:10.1139/v85-479

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The basic dehydrohalogenation reactions of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD) have been studied in cationic micelles of hexadecyltrimethylammonium bromide (CTAB) and hexadecyltrimethylammonium hydroxide (CTAOH). Different theoretical approaches are discussed, considering the fraction of micellar head group neutralized, β, as a constant, or supposing different kinds of variation in its value. The following two empirical expressions for β have been found: β = 0.8 + 0.5 ([NaOH] + [KBr]) for DDT, and β = 0.8 + 1 ([NaOH] + [KBr]) for DDD, and this is the best way to explain the experimental results.

ISSN:0008-4042    

DOI:10.1139/v85-480

出版商:NRC Research Press    

年代:1985

数据来源: NRC