Spin density distributions in some fluorinated radical cations

A theoretical study of π-electron spin density distributions has been made for a series of fluoro-substituted hydrocarbon radical cations using unrestricted Hartree-Fock theory. Although some of the predicted proton splittings are not in very good agreement with experiment, the overall agreement with experiment can be passed as fairly satisfactory considering the approximate nature of the theory used. The experimental fluorine splittings can be well predicted by using a one-parameter relationship between the isotropic fluorine splitting (a_F) and the π-electron spin density (ρ_CC) on the attached carbon. It has been further shown that both ρ_CC and the proportionality constant (Q_eff) in the linear relation, are fairly insensitive to the parameter choice.     

Adsoprtion and adsorptive separations: A bibliographical update (1992–1993)

This article provides a bibliographic listing of published journal papers concerned with adsorptive separations during 1992–1993. The references are taken from the 40 most important chemical engineering journals. This paper provides an update to the literature as provided in previous bibliographic papers [1, 2]. These previous papers also included membrane-type separations, however due to the number of papers and the diversity of membrane and associated processes, this material is to be published separately [3].Other bibliographic papers covering the more traditional unit operations, e.g. distillation [4], and equilibrium-staged separations in general [5, 6] have been published. Liquid-liquid extraction [7] is the subject of a separate bibliography (for 1992–1993), due to the number of publications on this topic. A bibliography detailing supercritical extraction from 1980–1993 is also to be published separately due to the current interest in this relatively new technology [8]. A complete bibliography of the chemical engineering journal literature from 1967–1993 has been published by the author [9–12]. An earlier bibliography [13] provides access to the literature prior to 1967.     

Oxygen atom transfer reactivity from a dioxo-Mo(VI) complex to tertiary phosphines: synthesis, characterization, and structure of phosphoryl intermediate complexes

The oxygen atom transfer (OAT) reactivity of TpMoO2Cl with PMe3, PEt3, and PPhMe2 (where Tp = hydrotris(3,5-dimethylpyrazol-1-yl)borate) has been investigated. The OAT reactions proceed through a diamagnetic Mo(IV) phosphoryl intermediate complex of general formula TpMoOCl(OPR3) (OPR3 = OPMe3, OPEt3, OPPhMe2), which have been isolated and characterized by 1H and 31P NMR, UV-visible, and infrared spectroscopies and electrospray ionization mass spectrometry. Solid-state crystal structures of TpMoOCl(OPMe3) and TpMoOCl(OPPhMe2) are also reported, the oxygen-to-phosphorus distances agree with a double-bond formulation and a single bond between the metal and the phosphoryl oxygen atom. The stability of the phosphoryl intermediate complexes depends on the steric properties of the coordinated phosphine-oxides. These intermediate complexes have been converted to solvent-coordinated species, TpMoOCl(solv) (solv = acetonitrile or dmf), and the coordinated solvents exchange with the bulk solvent.     

Three-component coupling of alkynes, Baylis-Hillman adducts and sodium azide: a new synthesis of substituted triazoles

A three-component coupling was used to prepare a series of 1,4-disubstituted-1,2,3-triazoles from the corresponding acetylated Baylis-Hillman adducts, sodium azide and terminal alkynes. This one-pot reaction further increases the efficacy of ‘Click’ synthesis and diversifies the preparation of multi-functional 1,4-disubstituted-1,2,3-triazoles.