摘要:

Excess molar volumes υEat 298.15 and 308.15 K and normal atmospheric pressure for the binary mixtures 2-pentanone + 1-chloroalkane (from 1-chlorobutane to 1-chlorooctane) were obtained from measurements of the density with an Anton Paar densimeter. The υEvalues for all mixtures were positive, and increase as the 1-chloroalkane length increases. Excess molar volumes depend slightly on the temperature. The same characteristics were found previously for the excess molar enthalpies of the same mixtures. Experimental υEvalues are compared with theoretical results using the Prigogine–Flory–Patterson model.Keywords: thermodynamics, liquid mixtures, excess volumes, ketones, chloroalkan

ISSN:0008-4042    

DOI:10.1139/v95-021

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

A CW CO2laser is used as a directed heat source to carry out the vacuum pyrolysis of 1,2,3-benzo-triazine (1a) and 4-methyl-1,2,3-benzotriazine (1b). We report the first HeI photoelectron (pe) spectrum of benzazete (2a), which correlates with ionization energies calculated with HAM/3 using an equilibrium geometry obtained at the ab initio HF/6-31G** level of the theory. The pe spectrum ofo-benzyne (3) obtained in this study correlates with the spectrum published by Zhang and Chen, but not with the spectra reported in two earlier publications.Keywords: 1,2,3-benzotriazines, vacuum pyrolysis, HeI ultraviolet photoelectron spectra, benzazete, benzyne.

ISSN:0008-4042    

DOI:10.1139/v95-022

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The title compound is a 3-dimensional polymer with a completely ordered triclinic structurea = 12.380(2) Å,b = 14.434(2) Å,c = 9.683(3) Å, α = 90.36(2)°, β = 105.44(2)°, γ = 90.75(2)°, Z = 2). Every B atom is tetrahedrally coordinated by N(1) atoms of the imidazole rings, every Li(1) atom is tetrahedrally coordinated by N(3) atoms, and every Li(2) atom is coordinated by two N(3) and two oxygen atoms, one from the H2O molecule and one from a MeOH molecule. The imidazole rings connected by the B—N(1) and Li—N(3) bonds thus generate a 3-dimensional covalent polymeric network. The MeOH molecules of coordination are hydrogen-bonded to unengaged N(3) atoms, thereby supplementing the covalent bonding system. The H2O molecules are hydrogen-bonded to the MeOH molecules of solvation to form centrosymmetric [Ow … OMeOH]2rings, which in turn are connected to the covalent network by OMeOH—H … N(3) bonds to the remaining unengaged N(3) atoms. Every atom in the structure except the H(C) hydrogens is thus involved in the 3-dimensional bond system. The excellent consistency of the bond lengths and endocyclic bond anglesin the eight imidazole rings of the title compound has provided an opportunity for investigating the effect of substitution on the geometry of the imidazole ring in a sample of 17 substituted imidazoles. While the bond lengths have been found at most weakly correlated, the multilinear correlations of thein this sample are highly significant. Among the substituents the NO2, group is the mostipso--expanding and the anionic B (in the title compound) the mostipso--contracting. Protonation or deprotonation at the N atoms affect theipsoC—N—C angles considerably. Limited comparisons are drawn with the results of the classical investigations by Domenicano et al. on the effect of substitution on the geometry of the benzene ring.Keywords: hydrogen bond, imidazole, lithium compounds, polymers, tetrahedral boron ions.

ISSN:0008-4042    

DOI:10.1139/v95-023

出版商:NRC Research Press    

年代:1995

数据来源: NRC