摘要:

The analytic solution of vibrational relaxation in a low-pressure gas is applied to the thermal dissociation of O3in helium and of SO2in argon. Use is made of experimental relaxation times to obtain average energy lost per collision. Calculated weak-collision rate constants are in very good agreement with experiment in the case of SO2, but only in fair agreement in the case of ozone. Several curious aspects of the ozone system, both experimental and theoretical, are discussed.

ISSN:0008-4042    

DOI:10.1139/v81-369

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

We examine the conjecture that the principal difference between weak-collision and strong-collision behaviour in thermal unimolecular reaction systems arises from a difference in internal energy randomisation rates. To do this, we solve analytically the strong-collision master equation for a thermal unimolecular reaction including explicit allowance for the randomisation processes, and we show that all weak-collision effects so far observed in thermal systems can be accommodated within this framework.In an appendix, we give the extension of this analytic solution for reactions yielding two (or more) distinct sets of products.

ISSN:0008-4042    

DOI:10.1139/v81-370

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

From the effect of added methanol on the decomposition temperatures of the clathrate hydrates of ethylene oxide and tetrahydrofuran, it was recently reported that methanol can be readily enclathrated in hydrates of both structure I and II. Dielectric and nmr studies of these two hydrates prepared in the presence of methanol do not support this conclusion. It is shown thermodynamically that the original measurements may be interpreted without the need for incorporation of methanol in the hydrates formed.

ISSN:0008-4042    

DOI:10.1139/v81-371

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Principal factor analysis has been applied to Raman spectra of 26 sulfuric acid/water mixtures covering the 0–100% H2SO4concentration range. The analysis greatly facilitates the identification of peaks due to different species. The results show that SO42−ions and "free" HSO4−ions do not co-exist with undissociated H2SO4molecules in solution and that two water molecules rather than one are required for the first ionization of H2SO4. A species with the composition H2SO4•2H2O, assigned a hydrated ion pair structure, reaches maximum concentration at the same medium composition at which SO42−, free HSO4−, and H2SO4are at concentration minima, about 75% w/w. The only species apparent in the more concentrated solutions are the ion pair and undissociated H2SO4, which could be taken to mean that H2SO4is a weaker acid than H3O+, but a stronger one than H3O+•H2O (or H5O2+, if this entity has a real existence). Separate peaks due to the postulated H3O+•H2SO4(or H5SO5+) were not observed.

ISSN:0008-4042    

DOI:10.1139/v81-372

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The densities and heat capacities per unit volume of 1,3-dioxane and trioxane were measured in water at 25 °C in the concentration range 0.1 to 1 mol kg−1. Apparent molal volumesandheat capacities were derived. The infinite dilutionshows excellent group additivity with other cyclic ethers in water but the additivity is less satisfactory for. No simple correlation can be made for the concentration dependence of these functions.

ISSN:0008-4042    

DOI:10.1139/v81-373

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Enzymatic deamination of adenosine 1-N-oxide gave 1-hydroxyinosine (2a) which was acetylated and then chlorinated to give 2,6-dichloro-9-(2,3,5-tri-O-acetyl-(β-D-ribofuranosyl)purine (3). Ammonia in dry 1,2-dimethoxyethane converted3into 2-chloro-adenosine triacetate (4a). Treatment of4awith trimethylamine at elevated temperatures in acetonitrile resulted in formation of 2-N,N-dimethylaminoadenosine triacetate (4b). Guanosine (5) was acetylated smoothly by an improved procedure. The resulting triacetate (6) was chlorinated in ∼85% yield to give 2-amino-6-chloro-9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)purine (7). Treatment of7with trimethylamine at ambient temperature for 28 hours gave the 6-N,N-dimethylamino compound (8d). However, potassium fluoride or sodium azide with catalytic quantities of trimethylamine in DMF or acetonitrile gave the 2-amino-6-fluoro (8a) or 2-amino-6-azido (8b) products in yields of greater than 90%.

ISSN:0008-4042    

DOI:10.1139/v81-374

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Treatment of 2,6-diamino-9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)purine (1c) withtert-butyl nitrite (TBN) in 60% anhydrous hydrogen fluoride/pyridine at −20 °C gave 2-fluoroadenosine triacetate (2) in 48% yield. Analogous treatment of the acetylated 2-amino-6-fluoropurine nucleoside (1a) gave the 2,6-difluoro compound (3a) in 63% yield. Anhydrous ammonia in 1,2-dimethoxy-ethane converted3a → 2without ammonolysis of the acetate groups. The overall conversion of1a → 3a → 2without isolation of3aproceeded in 80% yield. Similar diazotization of the 2-amino-6-chloro nucleoside (1b) in HF/pyridine gave the 2-fluoro-6-chloro analogue (3b) in 89% yield. Treatment of1bwith TBN and pyridine hydrochloride in dichloromethane (77%) or TBN and antimony trichloride in 1,2-dichloroethane (84%) gave the 2,6-dichloropurine nucleoside (4b). The latter conditions converted1ato the 2-chloro-6-fluoro product (4a) in 77% yield. Conversions of1aand1bto the 2-bromo-6-fluoro (5a, 67%) and 2-bromo-6-chloro (5b, 78%) analogues were effected using TBN and antimony tribromide in dibromomethane.

ISSN:0008-4042    

DOI:10.1139/v81-375

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The irradiation of the pyranthione1has been reinvestigated. The reaction proceeds through the (n,π*) triplet and can be quenched with ferrocene. The reaction can be sensitized with Michler's ketone or triphenylene. The elimination of sulfur from two molecules of1to give the dipyranylidene2requires, surprisingly, a hydrogen donor solvent, and the quantum yield of product has been found to increase with greater dilution, presumably because of the well-known quenching of triplet thiones by the ground state thione. A mechanism for the formation of2is suggested.

ISSN:0008-4042    

DOI:10.1139/v81-376

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The preparation of fatty acid methyl esters for glc analyses and of various aryl esters for hplc analyses has traditionally been carried out in totally unrelated operations. This paper draws attention to the use of fatty acid – trifluoroacetic acid mixed anhydrides which may be directly and efficiently converted into either type of ester. The utility of the method was demonstrated by the preparation of a series of methyl, 2-naphthyl, and vanillin fatty acid esters. The spectral characterization of some aryl fatty acid esters is recorded.

ISSN:0008-4042    

DOI:10.1139/v81-377

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The products from the reaction of 2-butene with BF3.CH3OH are olefins in the range C8to above C20; about 60% of the product is the normal dimer–trimer–tetramer material but the remaining 40% is rearranged product. We have identified most of the skeletal structures up to C13and suggest that the rearrangements are most easily interpreted by postulating that akyl transfers can occur in the same way as proton transfers.

ISSN:0008-4042    

DOI:10.1139/v81-378

出版商:NRC Research Press    

年代:1981

数据来源: NRC