Showing papers in "Australian Journal of Chemistry in 1968"

Atomic interactions in argon

Abstract: The potential energy function for interaction of two argon atoms is determined as closely as possible by fitting a multiparameter potential function to experimental data on molecular beam scattering and second virial coefficients, and to the known long-range interaction coefficients. These data are consistent with a range of potential functions between which gas transport properties do not enable a clear choice to be made. In particular, gas viscosities calculated with any of the potential functions show deviations from experiment which are tentatively ascribed to unexpectedly large slip in the viscosity measurements. Third virial coefficients calculated with allowance for the triple-dipole dispersion three-body interaction are close to experimental values whichever function is used, suggesting that other non-additive interactions must be small. Assuming this, the properties of crystalline argon at 0oK are used to specify a single potential function.

Conformational analysis in carbohydrate chemistry. I. Conformational free energies. The conformations and α : β ratios of aldopyranoses in aqueous solution

Abstract: The relative free energies of the aldopyranoses in aqueous solution have been calculated, taking non-bonded interaction energies and the anomeric effect into account. It is shown that the calculated free-energy values correctly predict the predominant conformation of the α- and β-pyranose forms of each aldose. The α- to β-pyranose ratios of the aldoses in aqueous solution, calculated from these values, are in reasonable agreement with those determined experimentally.

Corrigenda - Flavan derivatives. XXI. Nuclear magnetic resonance spectra, configuration, and conformation of flavan derivatives

Abstract: Nuclear magnetic resonance spectra of 80 compounds belonging to several classes of flavan derivative have been analysed, and chemical shifts and coupling constants of heterocyclic ring protons and aromatic protons are tabulated and discussed. Compounds examined include flav-2-enes, flav-3-enes, 3-substituted flavanones and flavans, 2- and 4-substituted isoflavans, 3,4-disubstituted flavans, and flavan-4-ols. The geometrical configurations of substituents in the heterocyclic ring follow unequivocally from the magnitudes of the vicinal coupling constants.

Conformational analysis in carbohydrate chemistry. II. Equilibria between reducing sugars and their glycosidic anhydrides

Abstract: The position of the equilibria between aldohexoses and 3-deoxyaldohexoses and their 1,6-anhydrides, and between heptuloses and their 2,7-anhydrides, has been determined by gas chromatography. The results are in good agreement with data calculated from conformational interaction energies. D-Talose gives equal amounts of the 1,6-anhydropyranose and the 1,6-anhydrofuranose. D-glycero-D-gulo-Heptose gives 66% of the 1,7- and only 9% of the 1,6-anhydride.

A multilayer model of a solid-regular solution interface

Abstract: A multilayer model of the interface between a solid and a regular solution has been developed by treating the solution phase in the grand canonical ensemble. The partition functions necessary for the evaluation of the grand partition function are obtained using either the quasi-chemical or Bragg-Williams approximations. The equilibrium concentration profile normal to the interface is then found from the maximum term in the multiple sum for the grand partition function. The adsorption, surface tension, and heat of wetting for the multilayer model are derived, and methods of obtaining the model parameters from experimental data are suggested. A comparison has been made between the quasi-chemical and Bragg-TVilliams approximations for the multilayer model. The monolayer model is also discussed, and compared with the multilayer for both the solid-regular solution and the low-density vapour-regular solution interfaces. It is shown that the monolayer model can often be fitted to the multilayer model by a suitable choice of parameters. It is concluded that in the absence of absolute methods of obtaining the area of the solid-solution interface, the experimental data may not provide outright support for the multi- layer model, but internal inconsistencies discourage the use of the monolayer model. There is an increasing interest in the properties of the interface between a solid and a non-electrolyte solution.1 The majority of experimental studies of this type of interface have been restricted to the measurement of adsorption, but in some instances the heat of wetting as a function of bulk phase composition has also been determined. In most cases, the complexity of the liquid phase and the surface region has allowed only a qualitative interpretation of the experimental results. Neverthe- less, there have been a few investigations in which solutions of comparatively simple molecules have been used and the experimental results have been treated in a quantitative manner.2-5 Some simple monolayer models of the solid-solution inter- face have been proposed for which the structure of the solid phase has been ignored, Division of Applied Chemistry, CSIRO Chemical Research Laboratories, Melbourne, Vic. 3001. Kipling, J. J., "Adsorption from Solutions of Non-Electrolytes." (Academic Press: London 1965.) Billet, D. F., Everett, D. H., and Wright, E. H. &I., Proc. chem. Soc. 1964, 216. 3 Blackburn, A., and Kipling, J. J., J. chem. Soc., 1954, 3819. 4 Blackburn, A., Kipling, J. J., and Tester, D. A., J. chem. Soc. 1957, 2373. 5 Wright, E. H. &I., Trans. Paraday Soc., 1966, 62, 1275. Aust. J. Chem., 1968, 21, 827-51

Energetic considerations in the assignment of some fragment ion structures

Abstract: Based on energetic considerations, new structures are presented for fragment ions from phenol, aniline, the naphthols, and coumarin. Previously proposed structures are shown to be inconsistent with the energetics of formation of the ions. Some deficiencies in the methods of assigning structures to fragment ions both by comparison with the mass spectra of related compounds and by consideration of the reactions of metastable ions of the same composition are discussed.

Carbonyl halides of the Group VI transition metals. V. Carbon monoxide carriers and some sulphur and nitrogen derivatives of molybdenum halocarbonyls

Abstract: The blue compounds MX2(CO)2(Ph3P)2 (M = Mo and W, X = Cl and Br) have been shown to absorb carbon monoxide very readily indeed to form the corresponding tricarbonyls, and as reported earlier, the tricarbonyls may be easily converted into the dicarbonyls. The dicarbonyl is therefore a carbon monoxide carrier. The compounds Mo(CO)3 dtc2 and Mo(CO)2 dtc2 (dtc = diethyldithiocarbamate) also represent a carbon monoxide carrying system, but in this case both compounds are rather unstable. The compounds MoX2(CO)2 btp2 (btp = N-n-butylthiopicolinamide; X = Cl, Br) have been prepared by direct interaction of the ligand and the appropriate halocarbonyl. Although these compounds are believed to be monomeric they do not absorb carbon monoxide.

Electronic absorption spectra of KMnF3, RbMnF3, and MnF2

Abstract: The absorption spectra of KMnF3 and RbMnF3 in the region 17000-47000 cm-l are reported in detail for room temperature and 20oK. Excellent agreement between experiment and a ligand field calculation using the free atom representation is obtained for the bands with energy less than 35000 cm-l. The analysis of the bands with energy greater than this requires an explanation involving the simultaneous excitation of pairs of manganese ions, and consistent assignments of these bands for the spectra of KMnF3, RbMnF3, and MnF2 are given. The relative order of the 4A1g and 4Ega states is established, and a theoretical argument to support this uses differences in inter-electronic repulsion energies for the 4Ega; and 4Egb states. The theoretical line shapes for the magnon-exciton bands of MnF2 at 25000 cm-1 are compared with the observed shapes.

Phosphato complexes of cobalt(III). I. General structural and hydrolytic properties

Abstract: Phosphorus-32 tracer experiments have demonstrated that the phosphato ligand in [Co en2PO4]0 [Co(NH3)4PO4]O, [CO(NH3)4OH2HPO4]+, and [Co en2OH2.HPO4]+ undergoes slow substitution in acid and alkaline media at 40-60o and that a reversible hydrolysis equilibrium is established from pH 3 to 11. Outside this pH range, acid and base hydrolysis of all these phosphato complexes to diaquo or dihydroxo complexes is complete. The infrared spectra of [Co en2PO4]0 and [Co(NH3)4PO4]0 are consistent with a bidentate phosphato structure and with a monodentate phosphato ligand in CO(NH3)5PO4 and probably [Co(NH3)4OH2HPO4]+I-. The bidentate and monodentate complexes may be rapidly and reversibly interconverted but significant concentrations of the bidentate complexes only persist in the range pH 5.5-7.5. P.m.r, studies have established the predominantly cis configuration of the aquophosphato complexes. These complexes exhibit four acidity constants, one due to the aquo ligand, and three due to the monodentate phosphato ligand. The bidentate [Co en2PO4]0 exhibits a single acidity constant above pH 2. The aquophosphato complexes undergo both acid and base hydrolysis entirely by Co-O bond rupture. Acid hydrolysis of [Co en2PO4]0 also proceeds entirely by Co-O bond rupture but at pH 6.8 and in 0.25M NaOH hydrolysis proceeds by 60-65% Co-O bond rupture and by 30-35% P-O bond rupture.

Terpenoid chemistry. XV. 1,5-Dimethylcyclodeca-1,5,7-triene, the precursor of geijerene in Geijera parviflora (Lindley)

Abstract: Geijera parviflora leaves which yield geijerene when worked up under the usual conditions of steam-distillation and fractional distillation have been found to contain a new hydrocarbon, Cl2H18 (pregeijerene), and only a trace of geijerene. The structure of pregeijerene has been shown by degradative and spectral examination to be 1,5-dimethylcyclodeca-1,5,7-triene, the disubstituted double bond having a cis configuration. The hydrocarbon forms a crystalline adduct with silver nitrate and rearranges thermally to yield geijerene.

Carbonyl halides of the Group VI transition metals. XII. Isolation of halocarbonyls and halocarbonyl anions of molybdenum and tungsten

Abstract: Dibromotetracarbonylmolybdenum, Mo(CO)4Br2, and the dihalotetracarbonyltungsten compounds, W(CO)4X2 (where X = Cl, Br), have been isolated and characterized. These highly reactive compounds are all diamagnetic. The trihalotetracarbonyl anions [M(CO)4X3]- (M = Mo, W) have been isolated as their tetraethylammonium salts from the parent halocarbonyls. These yellow diamagnetic compounds are the first tetracarbonyl derivatives to be prepared from the parent halocarbonyls.

The magnetic properties of the Tris(2-methyl-1,10-phenanthroline)iron(II) ion

Abstract: The magnetism of the salts [Fe mephen3]X2 (X = I-, ClO4-, BF4-, PF6-; mephen = 2-methyl- 1,l0-phenanthroline) has been investigated over the temperature range c. 100-300oK. The compounds exhibit anomalous behaviour, and this has been qualitatively interpreted as being the result of the presence of nearly equi-energetic ground terms 1A1 and 5T2 of the complexed iron(11) ion, a thermal equilibrium between these terms causing the magnetic moments to be markedly temperature dependent. This behaviour is apparently the result of the sterie hindrance to the coordination of an iron(11) ion induced by the presence of the methyl group in the ligand and the consequent lowering of the effective strength of the ligand field. The colour of the salts varies with temperature, and this has been discussed in terms of π-bonding between the iron(11) ion and the ligand.

Complexes of Di-2-pyridyl ketone. I. Complexes of first-row transition elements in normal oxidation states

Abstract: All the complexes of di-2-pyridyl ketone (DPK) described appear to involve N,N-chelation of the ligand. In CU(DPK)2SO4,2H2O the water molecules are added across the ketone groups yielding gem-dihydroxy functions. Several previously reported solvated DPK-cupric complexes which were assigned N,O-chelated structures probably have analogous N,N-chelated structures with solvent molecules (H2O or alcohols) added across the ketone group. The compounds M(DPK)2Cl2 (M = MnII, FeII, CoII, NiII) are tentatively assigned cis-octahedral structures, and a number of mono- and bis-DPK-cupric complexes appear to have the common tetragonal or square-planar geometries. The compounds of stoicheiometry Co(DPK)2(OH)2Cl,½H2O and CO(DPK)2(OH)2NO3, prepared from the corresponding cobalt(11) salts, are cobalt(111) derivatives in which one or both of the DPK units is reduced and probably acts as a tridentate ligand.

Derivatives of orthoacids. IV. Acid-catalysed thermal eliminations and baseinduced eliminations of some 2-Ethoxy-1,3-dioxolans

Abstract: A series of phenyl substituted 2-ethoxy-1,3-dioxolans (orthoformates) has been prepared and their stereochemistry assigned. When heated in the presence of a carboxylic acid they underwent a stereospecific cis elimination to form the corresponding olefins, carbon dioxide, and ethanol. Provided that one 4 or 5 position in these dioxolans was unsubstituted, they reacted with butyllithium through elimination of the elements of ethyl formate and the formation of a carbonyl compound. The eliminated portion was always converted by the butyllithium into nonan-5-ol. A simple preparative method for cis-stilbene is described.

Constituents of some Curvularia species

Abstract: Thirteen Gurvularia and related species were examined and the following metabolites obtained: brefeldin A, curvularin, curvulin, curvulinic acid derivatives, D-mannitol, 1,4,5,8-tetrahydroxy-2,6-dimethylanthraquinone, saturated and unsaturated fatty acids, and fatty acid esters.

Copper(II) complexes of o-hydroxyarylcarbonyl compounds

Abstract: A series of copper(11) complexes has been prepared of the type CuL2Bn, where L is an o-hydroxy-aryl-, or naphthyl-, aldehyde, ketone, or ester, B is water or 4-methylpyridine, and n = 0, 1, or 2. All these complexes have a strong infrared band in the region 1600-1660 cm-l, showing that the oxygen atoms in the chelate ring are non-equivalent ; their magnetic moments fall in the range usual for copper(11) compounds. Equilibrium constants determined for the addition of one molecule of 4-methylpyridine to the anhydrous compounds in chloroform solutions fall in the range 0.5 < k < 40 and are comparable to the constant for the addition of 4-methylpyridine to bis(acetylacetonato)copper(11) (b 2.7). Increased stability of the adducts can be associated with the inductive effects of ligand substituents. Ligand field spectra in the solid state and in solution closely resemble those of corresponding bis(acetylaoetonato)copper(11) complexes and provide evidence for square-planar structures of the anhydrous complexes and square-pyramidal structures of the 1 : 1 adducts with 4-methylpyridine or water. No evidence is available for the structures of 1 : 2 adduots which may be formed in solutions in 4-methylpyridine; these solutions are unstable, but the nature of the slow reactions which occur in these solutions is not known.

Mass spectrometric studies. III. Bis(diphenylamino)methane, Bis(diphenylphosphino)methane, Bis(diphenylarsino)methane, and related compounds

Abstract: The compounds listed in the title, together with the analogous 1,2-bis(diphenyl-phosphino)- and 1,2-bis(diphenylarsino)-ethanes, as well as triphenylarsine have been subjected to electron bombardment at 70 eV. The nitrogen compound undergoes simple fragmentation whereas the diphosphines and the diarsines undergo fragmentations which clearly demonstrate migration of phenyl groups to give, inter alia, triphenylphosphine and triphenylarsine cations. These subsequently fragment in the same way as intact triphenylphosphine and triphenylarsine molecules.

Organoaluminium compounds. XIV. Evidence for association through unlike bridging groups

Abstract: Proton magnetic resonance spectroscopy has revealed the formation of Me2AlXYAlMe2 from Me2AIX2Me2 and Me2AlY2AlMe2, where X and Y are bridging groups. In the cases studied, X = Cl, Y = Me, Br, or PhCC; X = Br, Y = Ph, PhCC, or OPr1; and X = PhCC, Y = Opr1. The position of equilibrium varies widely from one case to another. Formation of Me2AlXYAlMe2 is rapid except when dimethylaluminium isopropoxide is one of the reactants. The variation with temperature of the spectra of methylaluminium sesquibromide, methylaluminium sesquichloride, and mixtures of the latter with dimethylaluminium chloride has been examined and interpreted in terms of facile dissociation of the double halogeno bridge with a low probability of reassociation by way of methyl bridges.

The ionization energies of some phenothiazine tranquillizers and molecules of similar structure

Abstract: Charge-transfer spectroscopy was used to determine the ionization energies of ten phenothiazine tranquillizers and similar molecules which are stimulants, in order to throw light on the proposed relation between physiological action and electron-donating power, and to compare the ionization energies of the phenothiazines with molecular orbital calculations. All the ionization energies obtained lie in the range 7.0-8.4 eV. The phenothiazines are thus strong electron donors, in agreement with calculations. There is little difference in ionization energies and equilibrium constants of complex formation between tranquillizers and either non-tranquillizers or timulants. The difference in physiological action of the drugs therefore cannot be dependent on electron-donating power alone.

N-Substituted salicylaldimine complexes of iron(III). I. Synthesis, infrared and mass spectra

Abstract: Complexes of iron(111) and N-substituted salicylaldimines have been prepared of general formulae Fe(sal-NR)3,? Fe(sal-NR)2 sal, FeCl3(salH-NR)2, Fe(sal-NR)2X (X = Cl, Br), and [Fe(sal-NR)2]2O. The complexes all show spin-free magnetic behaviour with moments at room temperature of the order of 5.9 B.M. except for the oxygen-bridged complexes which have low moments (c.2 B.M.) believed due to a spin-exchange process. The infrared spectra and mass spectra of the complexes are discussed.

The stereochemistry of oxindole alkaloids: uncarines A, B (formosanine), C (pteropodine), D (speciophylline), E (isopteropodine), and F

Abstract: A study of the N.M.R. spectra, circular dichroism, and equilibration reactions of the four stereoisomeric oxindole alkaloids, uncarines C (pteropodine), D (speciophylline), E (isopteropodine), and F, isolated from Ulzcaria berlzaysii F. Muell, and Uncaria ferrea D.C., has allowed assignment of the configuration at all five asymmetric centres. Partial synthesis of uncarines C, D, E, and F from tetrahydroalstonine has provided proof for the assigned stereochemistry of the rings D and E. Comparison of the spectra of uncarines C, D, E, and F, mitraphylline, and isomitraphylline with those of formosanine (uncarine B) has shown that in formosanine and uncarine A the D/E ring junction is trans, and not cis, as previously reported. Formosanine and uncarine A are therefore the C19 epimers of mitraphylline and isomitraphylline respectively.

Organoaluminium compounds. XIII. Association through aryl and phenylethynyl bridges

Abstract: Proton magnetic resonance spectrometry has been used to show that dimethylphenylaluminium and dimethyl-p-tolylaluminium dimers are held together by aryl bridges. Phenylethynyl groups serve as bridges in the dimer of dimethyl-(phenylethynyl)aluminium. Mixed aryl-methyl, phenylethynyl-methyl, and phenyl-phenylethynyl bridges have also been shown to exist.

Catalytic deuterium exchange reactions with organics. XL. Pyridine, the quinolines, azines, and aniline on unsupported Group VIII transition metals

Abstract: Pyridine, the quinolines, pyridazine, pyrimidine, pyrazine, s-triazine, and aniline have been exchanged with heavy water on the following Group VIII transition metals: Fe, Co, Ni, 0s. Ru, Rh, Pd, Ir, and Pt. Three types of catalyst activation have been used, including self-activation, hydrogen and sodium borohydride reduction of the inorganlo salts. Platinum is the most useful catalyst for general exchange whereas cobalt possesses valuable specificity for selective a exchange in a large number of the heterocyclic compounds. A kinetic study of the deuteration of pyridine on platinum has been performed. The exchange results have been rationalized in terms of charge-transfer adsorbed intermediates. E.s.r. has been used to support this conclusion for the interaction between pyridine and potassium chloropalladite. π-Complex mechanisms have been proposed to explain the observed deuteration behaviour.

Spectrum of azulene. IV. Rotational analysis of the 0-0 band of the 3500 Ǻ transition

Abstract: The bands of the 3500 Ǻ transition of azulene-do and azulene-ds show two unequal peaks 2.3 cm-l apart, followed by closely spaced fine structure. These bands have been analysed as type A bands of a planar, prolate asymmetric top. Rotational constants for both molecules in the excited state have been determined. The fine structure is due to multiple line coincidences in the high-J, low-K region of the qP branch. To each multiple line can be attributed a running number n = J+m, where m = J-K-1. Given sufficient resolving power, such "lines" should be rather commonly observed in type A and type B bands of large, planar, prolate molecules.

VESCF-MO studies of molecules containing atoms from the second row of the Periodic Table. II. Properties of the fluorides of silicon, phosphorus, sulphur, and chlorine for a minimal basis set excluding 3d-orbitals

Abstract: A study has been made of the electronic structures of the fluorides of silicon, phosphorus, sulphur, and chlorine by the VESCF molecular-orbital method with a minimal basis set, not including 3d-orbitals on the central atom. It proves possible to understand variations in bond lengths and charges on fluorine ligands, dipole moments, force constants, and some n.q.r. data. The calculations are found to be sensitive to assumptions about scaling factors for monocentric coulomb repulsion integrals and penetration integrals. We have not discovered any justification for including 3d-orbitals in the description of the electronic structure of these molecules.