摘要:

At any pressure the heat of vaporization can be expressed as a quadratic function of the boiling point at that pressure. A seven parameter equation expressing the simultaneous dependence on boiling point and pressure can be fitted to the data; six pressures from 1 to 760 Torr (1 Torr = 133.3 Pa) were used. ΔHvap = b11 + b12In (p) + b13p + (b21 + b22In (p))tbp + (b31 + b32In (p))tbp2. This relationship served as a guide for developing a relationship between vapour pressure at 25 °C and the calorimetric heat of vaporization, and also a relationship between vapor pressure at 25 °C and the boiling point at some other pressure. Parameters for both these relationships could be derived from the parameters obtained for ΔHvapas a function of temperature and pressure. A third method was developed starting from an equation for vapor pressure and fitting to the heat of vaporization, the heat capacity of vaporization, and at least onet,ppoint. These methods allow the estimation of the vapor pressure at room temperature from very meager data. The problems of errors in estimated values are discussed.

ISSN:0008-4042    

DOI:10.1139/v86-103

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Reactions of hydrocarbon and carbon/nitrogen ions with diacetylene and of the diacetylene radical cation with various molecules have been examined with a view to molecular growth by ion–molecule reaction. Measurements were performed with a Selected-Ion Flow Tube (SIFT) apparatus at 296 ± 2 K of the rate constants and product distributions for the reactions of C+, CH3+, C2H2+, C3H+, CN+, C2N+, and C2N2+with C4H2and of C4H2+with H2, CO, C2H2, C2N2, and C4H2. Condensation and association reactions which build up the carbon content of the ion were observed to compete with charge transfer. For the reactions of CN+and C2N2+with C4H2this growth involved the addition of cyanide to the carbon chain. The kinetics of protonation of diacetylene were also investigated. It was possible to bracket the proton affinity of diacetylene between the known proton affinities of HCN and CH3OH with a value for PA(C4H2) = 177 ± 5 kcal mol−1, which results in a heat of formation for C4H3+of 305 ± 5 kcal mol−1. Numerous secondary association reactions were observed to form adduct ions in helium buffer gas at total pressures of a few tenths of a Torr with rates near the collision rate. This was the case for C6H4+(C4H2+•C2H2), C7H5+(C3H3+•C4H2), C8H4+(C4H2+•C4H2), C8H5+(C4H3+•C4H2), C9H3+(C5H+•C4H2), C9H4+(C5H2+•C4H2), C9H5(C5H3+•C4H2), C10H4+(C6H2+•C4H2), C10H5+(C6H3+•C4H2), C11H7+(C3H3+•(C4H2)2), C12H6+(C4H2+•(C4H2)2), C9H3N+(HC5N+•C4H2), and C10H4N+(C2N+•(C4H2)2) where the reactants are indicated in parentheses. The observed high rates of association imply the formation of chemical bonds in the adduct ions but the structures of these ions were not resolved experimentally. In most instances there seems little basis for preferring acyclic over cyclic adduct ions.

ISSN:0008-4042    

DOI:10.1139/v86-104

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A facile method for the introduction of a highly functionalized isopropyl unit, in the form of β-hydroxyproprionitrile or acrylonitrile, to the β carbon of an α,β-unsaturated ketone has been developed usingS-tert-butyl cyanothiolacetate as a β-hydroxyproprionitrile equivalent in Michael reactions.

ISSN:0008-4042    

DOI:10.1139/v86-105

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The first total synthesis of α-costal (1) in racemic form has been achieved in an unequivocal manner whereby the structure previously assigned to the natural aldehyde is confirmed. A salient feature of the synthesis is the use ofS-tert-butyl cyanothiolacetate to facilitate the introduction of the labile acrolein unit.

ISSN:0008-4042    

DOI:10.1139/v86-106

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A1H nmr study of Fe(C5H4CHMeNMe2-η)(C5H4PPh2-η),2, using the nOe difference experiment, shows a spatial correlation between the —NMe2group and the site of stereoselective lithiation.

ISSN:0008-4042    

DOI:10.1139/v86-107

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The synthesis of 5,5,7,7-tetramethyl-1-oxa-6-azaspiro[2.5]octane and modified synthesis of 5,5,7,7-tetramethyl-1-oxa-6-azaspiro[2.5]oct-6-yloxy are described. Reaction of these spiro-oxiranes with phenols gave corresponding 4-aryloxymethyl 4-piperidinols and their 1-piperidinyloxy derivatives. The same products have also been obtained by reaction with ethanol. The crystal structures of two derivatives: 4-phenoxymethyl-2,2,6,6-tetramethyl-4-piperidinol (3a, 2880 reflections,R = 0.054) and 4-phenoxymethyl-4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (6a, 4395 reflections,R = 0.084) have been determined. Piperidine rings are in a chair conformation in both compounds with the phenoxymethyl substituent in an equatorial position. Thegroup is not planar, with the N—O bond inclined by 18.4° to the CNC plane. Although the space groups are different for these two compounds the molecules are packed in the crystal lattice in a topologically equivalent way.

ISSN:0008-4042    

DOI:10.1139/v86-108

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Molar excess thermodynamic quantitieshE,, andvEhave been measured at 25 °C over the whole composition range for mixtures of four globular Sn(CnH2n+1)4(SnR4) (n = 1–4) witht-decalin, and 2,2,4,4,6,8,8-heptamethylnonane (br-C16) as well ashEfor the same SnR4compounds with 2,2,4-trimethylpentane (br-C8). The excess viscosities are measured at −20, 25, and 40 °C for thet-decalin + SnR4systems. By introducinggEin the solution activation energy, the free energy of mixing can be related to and calculated from the excess viscosities. The steric hindrance contribution, corresponding to an increase of order or diminution of mobility in solution, known to occur either with compounds having highly substituted atoms or with flat-shaped molecules, was investigated. The free volume contribution to the different thermodynamic properties is calculated from the Prigogine–Patterson–Flory theory. The difference between the experimental and calculated excess data is associated with the steric hindrance contribution. Values ofhE,,vE, andsEconfirm the existence of a large steric hindrance contribution (hE < −200 J mol−1andTsE < −400 J mol−1for two systems). Another contribution, found to occur for the two smaller globular SnR4, may originate in the liberation of movement induced in solution by the second component.

ISSN:0008-4042    

DOI:10.1139/v86-109

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A premixed, fuel-rich, methane–oxygen flame at atmospheric pressure was doped separately with 0.2 mol% of H2S, OCS, and SO2to probe the behaviour of fuel sulphur during combustion. These three additives represent compounds occurring early, intermediate, and late in the oxidation sequence of fuel sulphur. They are chemically ionized in the reaction zone of a hydrocarbon flame to give large signals of sulphurous negative ions. Those detected include S−, SH−, SO−(uncertain), SO2−(S2−), SO3−, HSO3−, CH3O−•SO2, SO4−(S2O2−, S3−), and HSO4−. Ion concentration profiles of these ions were measured along the conical flame axis by sampling the flame into a mass spectrometer. The shapes of the profiles are insensitive to the nature of the additive, but their relative magnitudes are indicative of the additive's position in the sulphur oxidation sequence. For each additive, the very large HSO4−signal has analytical implications as an indicator for total fuel sulphur. The sulphurous anion chemistry is discussed for each additive in terms of roughly twenty ion (electron)-molecule reactions of six basic types, whose rate constants were known previously, or were measured at room temperature using the York flowing afterglow apparatus.

ISSN:0008-4042    

DOI:10.1139/v86-110

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A photoconductivity study was made on γ-irradiated low and high density polyethylene using 3-methylpentane, methylene chloride, and hexafluorobenzene as dopants. Electron spin resonance (esr) and optical absorption measurements were made together with photoconductivity. A study was also made for poly(4-methylpentene-1). The process of photocurrent generation is not ascribed totally to photodetrapping of trapped electrons in polyethylene; the process by photodetrapping of trapped electrons dominantly contributes to photocurrent generation in the ir region and may partly contribute in the visible region but not in the uv region. Another process for photocurrent generation other than photodetrapping of trapped electrons exists in the uv and perhaps partly in the visible region. We have tentatively ascribed this process to photodetachent of electrons from carbanions whch are formed by the reaction between radicals and electrons.

ISSN:0008-4042    

DOI:10.1139/v86-111

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Electrochemical behaviour of salicylidene-2-aminopyridine has been investigated in 0.1 Mtetraethylammonium perchlorate–dimethylformamide solutions by cyclic voltammetric and convolution potential sweep voltammetric methods. It was found that the depolarizer exhibits two well-defined diffusion-controlled irreversible one-electron waves. The cyclic voltammetric characteristics and the convolution, deconvolution, and logarithmic convolution analyses reveal that salicylidene-2-aminopyridine in such conditions follows a set of two one-electron transfer reactions each followed by an irreversible chemical reaction. The values of the first-order rate constant of the irreversible chemical reaction andE1/2were computed.

ISSN:0008-4042    

DOI:10.1139/v86-112

出版商:NRC Research Press    

年代:1986

数据来源: NRC