Showing papers in "Australian Journal of Chemistry in 1982"
TL;DR: In this paper, the self-exchange rate for the one-electron oxidation of ascorbate dianion (A2-) by bis(terpyridine)cobalt(III)ion (8.5 × 106 dm3 mol-1 s-1) and pentaammine(pyrinyridine)ruthenium(III), and of the monoanion (HA-) by tetraammine (bipyridine), rutheniammion (III) ion (2.1 × 105
Abstract: Rate constants for the one-electron oxidation of ascorbate dianion (A2-) by bis(terpyridine)cobalt(III)ion (8.5 × 106 dm3 mol-1 s-1) and pentaammine(pyridine)ruthenium(III) ion (6.0 × 109 dm3 mol-1 s-1), and of the monoanion (HA-) by tetraammine (bipyridine)ruthenium(III)ion (2.1 × 105 dm3 mol-1s-1) have been determined in aqueous solution at 25oC and ionic strength 0.1 (NaNO3 or NaClO4). It is shown that these rate constants, and other published rate constants for oxidation of HA- and A2-, are consistent with the Marcus cross relation, on the assumption that the self-exchange rate constants for both the HA-/HA and A2-/A-couples are 106 dm3 mol-1 s-1. One electron redox potentials for the ascorbate/dehydroascorbate system have been derived from scattered literature data.
192 citations
TL;DR: In this paper, the reactions between iron(III) and the phenols gallic acid, catechol, protocatechuic acid and pyrogallol have been studied in aqueous solution at 25oC (I 0.10 M KCl).
Abstract: The reactions between iron(III) and the phenols gallic acid, catechol, protocatechuic acid and pyrogallol have been studied in aqueous solution at 25oC (I 0.10 M KCl). From spectrophotometric and pH titration data it was established that (i) complexes with 1 : 1, 1 : 2 and 1 : 3 (M : L) stoichiometry are formed in oxygenated solution, (ii) the redox reaction given at low pH by these ligands Fe3+ + ½phenol → Fe2+ + ½quinone + H+ is not reversed by complexing of Fe3+ at higher pH, and (iii) the percentage composition of iron(II) and iron(III) in solutions of these ligands is a function of ER (ligand), the pH and age of solutions and the partial pressure of dissolved oxygen.
141 citations
TL;DR: In this article, a range of synthetic carbonated apatites and human dental enamel have been studied at low temperatures (50 K) by laser Raman spectroscopy, showing that carbonate exists in two crystallographically distinct sites of different symmetry within the apatite structure.
Abstract: A range of synthetic carbonated apatites and human dental enamel have been studied at low temperatures (50 K) by laser Raman spectroscopy. The widths of the Raman spectral bands of hydroxyapatite were significantly reduced at low temperatures with the appearance of several peaks unobserved at room temperatures. The number of observed phosphate and hydroxyl ion Raman peaks was consistent with the space group P63. Spectra of carbonated apatites were not further resolved at low temperatures and Raman peak broadening due to loss of long-range translational order in the apatite structure was linearly correlated with the carbonate content of the sample. The same Raman peak broadening occurred in the spectrum of dental enamel. The number of carbonate bands in the Raman spectrum of carbonated apatites indicated that carbonate exists in two crystallographically distinct sites of different symmetry within the apatite structure.
135 citations
TL;DR: In this article, an analysis of the Raman band due to C-C stretching in acetone yields solvation numbers for the Li+ ion of the order of 3, and the dependence on salt concentration of all four species has been determined.
Abstract: Vibrational spectra and 7Li, 13C and 35C1 n.m.r. spectra have been obtained for solutions of LiC104 in acetone for salt concentrations from 0 05 to 6 m. Infrared spectra give qualitative indications of ion association. Analysis of the Raman band due to C-C stretching in acetone yields solvation numbers for the Li+ ion of the order of 3. Component band analysis of the CIO4- symmetric stretching vibrational band and the various n.m.r. spectra lead to the identification of solvent- separated ion pairs, contact ion pairs and ion aggregates, in addition to free solvated ions. The dependence on salt concentration of all four species has been determined. The association quotient for the association equilibrium.
76 citations
TL;DR: In this paper, the structure of boesenbergin A has been established and its acid-catalysed cyclization has been studied using X-ray crystallographic analysis and spectroscopic studies.
Abstract: Partly racemized pinostrobin and pinocembrin, together with 2',6'-dihydroxy-4'-methoxychalcone, cardamonin and a new chalcone (±) boesenbergin A, have been isolated from Boesenbergia pandurata Schl. (syn. Kaempferia pandurata Roxb., Zingiberaceae). Spectroscopic studies and X-ray crystallographic analysis have established the structure (±)-(E)-1-[7'-hydroxy-5'-methoxy-2'-methyl- 2'-(4''-methylpent-3''-enyl)-2'H-chromen-8'-yl]-3-phenylprop-2-enone for boesenbergin A. A simple synthesis of boesenbergin A has been achieved and its acid-catalysed cyclization has been studied.
69 citations
TL;DR: In this article, it was shown that the carbon-centred radicals formed by interaction of cumyloxyl with the respective monomers were trapped as stable adducts of 1,1,3,3-tetramethyl-isoindolin-2-yloxymethyloxyl.
Abstract: Cumyloxy (1-methyl-1-phenylethoxy) radicals have been generated by thermolysis (60o) of dicumyl hyponitrite in methyl methacrylate and styrene. The carbon-centred radicals formed by interaction of cumyloxyl with the respective monomers were trapped as stable adducts of 1,1,3,3-tetramethyl-isoindolin-2-yloxyl. Extensive hydrogen atom abstraction and methyl radical generation as well as double-bond addition were observed in methyl methacrylate. Styrene underwent only double-bond addition by both cumyloxy and methyl radicals. Some possible implications of these results for polymer structure are discussed. A kinetic study of the decomposition of dicumyl hyponitrite in cyclohexane at various temperatures gave k=7.7 × 1014exp(-13600/T) s-1 for the rate constant. Rate constants for the addition of cumyloxyl to methyl methacrylate (k ≈ 2 × 104 dm3 mol-1 s-1) and styrene (k≈2 × 105 dm3 mol-1 s-1) at 60ohave been estimated.
63 citations
TL;DR: The complexes RU(CO)2Cl2L [L = 1,l0-phenanthroline (phen) or 2,2'-bipyridyl (bpy)] react with silver carboxylates to yield Ru(CO 2(OCOR)2L derivatives (R = Me or CF3).
Abstract: The complexes RU(CO)2Cl2L [L = 1,l0-phenanthroline (phen) or 2,2'-bipyridyl (bpy)] react with silver carboxylates to yield Ru(CO)2(OCOR)2L derivatives (R = Me or CF3). Reactions of Ru(CO)2(OAc)2L and Ru(CO)2(OAc)2(phen) with trifluoroacetic and trifluoromethanesulfonic acid give Ru(CO)2(OCOCF3)2L and Ru(CO)2(OSO2CF3)2(phen) respectively. In acetonitrile, Ru(CO)2(OAC)2L complexes react with trifluoromethanesulfonic acid to give [Ru(CO)2(MeCN)2L] (O3SCF3)2. The complexes [RU(CO)2L2]2+, [Ru(CO)2(phen)(bpy)]2+, and [Ru(C02(phen)(tmp)]2+ (tmp = 3,4,7,8-tetramethyl-1,l0-phenanthroline) have been prepared by reaction of [Ru(CO)2- (MeCN)2L]2+ and/or Ru(CO)2(OSO2CF3)2 phen with an excess of the appropriate bidentate ligand. A similar series of reactions has yielded Ru(C0)2(OAc)2(py)2, [Ru(CO)2(MeCN)2(py)2] (O3SCF3)2, and [RU(CO)2(py)2L]2+ from Ru(CO)2Cl2(py)2. Stereochemical assignments have been made for all complexes.
56 citations
TL;DR: In this paper, the antimicrobial properties of the carbamates and benzoxinones were evaluated, and it was shown that they are readily cyclable to the corresponding 3-aryl-4-nitromethyl-3,4-dihydro-2H-1,3-benzoxazin-2-ones.
Abstract: The hitherto unknown 2-(2-nitroethenyl)aryl and 1-(2-nitroethenyl)naphthalen-2-yl N-arylcarbamates (2) and (5) are readily obtained through the uncatalysed interaction of aryl isocyanates with the corresponding 2-nitroethenyl phenols (1) and (4). The carbamates (2) and (5) cyclize readily at ambient temperature under base catalysis to the corresponding 3-aryl-4-nitromethyl-3,4-dihydro-2H-1,3-benzoxazin-2-ones (3) and 2-aryl-1-nitromethyl-2,3-dihydro-1H-naphth[l,2-e][1,3]oxazin-3-ones (6). The oxazinones (3) are cleaved by hot pyridine affording the corresponding 2-(2-nitroethenyl)phenols and N,N'-diarylurea, whereas, with butylamine, the corresponding aryl(butyl)urea and salicylaldehyde are obtained. The antimicrobial properties of the carbamates and benzoxazinones are evaluated.
56 citations
TL;DR: Excess and interaction second virial coefficients have been measured in the temperature range 290-320 K for 20 binary gaseous systems as discussed by the authors, and the present values are in excellent agreement with his results.
Abstract: Excess and interaction second virial coefficients have been measured in the temperature range 290-320 K for 20 binary gaseous systems. Several of these systems have previously been studied by Brewer. The present values are in excellent agreement with his results. The excess virial coefficients have been used to calculate excess molar enthalpies of mixing at 300 K.
55 citations
TL;DR: In this paper, a combination of one-and two-dimensional n.m.r. techniques has been used to construct the structure of the title compound (6a) on the basis of chemical and spectroscopic data.
Abstract: The structure (6a) is proposed for the title compound, on the basis of chemical and spectroscopic data. In particular, a combination of one- and two-dimensional n.m.r. techniques has led to this assignment. Compound (6a) is relatively unstable and its isolation requires a careful extraction process.
55 citations
TL;DR: In this article, the isolation of five known cembranoid diterpenes, (1), (2), (3), (4) and ( 5 ), is reported from the soft coral Nephthea brassica.
Abstract: The isolation of five known cembranoid diterpenes, (1), (2), (3), (4) and ( 5 ) , is reported from the soft coral Nephthea brassica. These diterpenes co-occur with several new but related diterpenes: (13S)-cembra-1,3,7,11-tetraen-13-ol (6) and its corresponding 13-acetate (7), 15-acetoxycembra-3,7,11-triene (8), (10S)-10,15-diacetoxy-7,8-epoxycembra-3,11-diene (9) and its corresponding 10-monoacetoxy derivative (10). Two related cembranoid diterpenes, (14S)-acetoxycembra-1,3,7,11-tetraene (15) and (14S)-cembra-1,3,7,11-tetraen-14-01 (16), are reported from a soft coral of the genus Sarcophyton.
TL;DR: In this article, the catalysts for the asymmetric addition of hydrogen cyanide to alkenes were described and the corresponding complex of platinum with diop has also been found to be less useful as a catalyst as were the complexes of these three metals with other chelating diphosphines.
Abstract: [(+)-(diop)]2Pd and [(+)-(diop)]2Ni have been prepared and used as catalysts for the asymmetric addition of hydrogen cyanide to alkenes. The corresponding complex of platinum with diop has also been prepared and found to be less useful as a catalyst as were the complexes of these three metals with other chelating diphosphines.
TL;DR: The dichloromethane extract of the brown alga Dilophus marginatus has yielded 17 new diterpenes which were found to possess a new bicyclic diterpene skeleton which was named secospatane as mentioned in this paper.
Abstract: The dichloromethane extract of the brown alga Dilophus marginatus has yielded 17 new diterpenes. Nine of these metabolites were found to possess a new bicyclic diterpene skeleton which we have named secospatane, five had the recently reported spatane skeleton whilst three compounds had a new tricyclic diterpene skeleton.
TL;DR: In this article, synthetic routes to resolved unsymmetrical (u) isomers of [Co(dats)Cl] (ClO4)2 [datn = 1,4-bis(2-aminoethyl)-1-thia-4,7-diazacyclononane (tasn) was reported.
Abstract: Synthetic routes to the resolved unsymmetrical (u) isomers of [Co(dats)Cl] (ClO4)2 [dats = 4,7-bis-(2-aminoethyl)-1-thia-4,7-diazacyclononane] and [Co(datn)Cl] (ClO4)2 [datn = 1,4-bis(2-aminoethyl)-1,4,7-triazacyclononane] are reported. The new macrocyclic ligand 1-thia-4,7-diazacyclononane (tasn) was synthesized during the former preparation, and the cis-[Co(tasn)2] (ClO4)3 complex prepared. Base hydrolysis of each chlorocobalt(III) complex proceeds with two consecutive steps. The first reaction in each case is chloride hydrolysis, with kOH(dats) 3.6 × 104 dm3 mol-1 s-1 and kOH(datn) 2.85 × 103 dm3 mol-1 s-1 at 25oC and 10.1 M. The second reaction for the dats complex is a base-catalysed dissociation of the thioether to the cis-[Co(dats)(OH)2]+ complex, characterized by 13C n.m.r. experiments, and occurring approximately 20 times slower than chloride hydrolysis. However, the datn complex undergoes a base-catalysed terminal ring opening to the cis-[Co(datn)- (OH)2]+ complex at a rate approximately 30 times slower than chloride hydrolysis.
TL;DR: In this article, ten new terpenoid compounds have been isolated from the brown alga Cystophora moniliformis and their isolation and structural elucidation, mainly on spectral evidence, was discussed, together with data on four previously reported compounds.
Abstract: Ten new terpenoid compounds have been isolated from the brown alga Cystophora moniliformis. Their isolation and structural elucidation, mainly on spectral evidence, is discussed, together with data on four previously reported compounds.
TL;DR: In this paper, it was shown that a CO2 molecule in a double substitutional site gives a higher v3 and lower v2 frequency than a single substitution site, where the CO2 molecules occupied the place of two adjacent argon atoms and a single argon atom.
Abstract: Evidence is presented that the cause of the doubling of the infrared bands of CO2 in an argon lattice is the presence of two types of acceptable sites for the CO2 molecule. The nature of these sites is discussed; it is concluded that the sites are double substitutional sites, in which a CO2 molecule occupies the place of two adjacent argon atoms, and single substitution sites, in which the CO2 molecule occupies the place of a single argon atom. A CO2 molecule in a double substitutional site is a more stable situation than a CO2 molecule in a single substitutional site: the former gives a higher v3 and lower v2 frequency than the latter.
TL;DR: A fluorochrome has been isolated in analytically pure form from a commercial sample of the triaryl-methane dye aniline blue by spectroscopic means and confirmed by synthesis as discussed by the authors.
Abstract: A fluorochrome has been isolated in analytically pure form from a commercial sample of the triaryl-methane dye aniline blue. Its structure has been shown to be sodium 4,4'-[carbonylbis(benzene-4,1-diyl)bis(imino)]bisbenzenesulfonate by spectroscopic means and confirmed by synthesis. Its fluorescence emission, which is markedly solvent-dependent, is 150 times greater in butan-1-ol than in water (however, the wavelength of the emission maximum is not altered significantly). In the presence of a cationic surfactant, hexadecyltrimethylammonium bromide, the fluorescence intensity reaches a maximum at approximately the critical micelle concentration of the surfactant.
TL;DR: In this paper, a series of 17 compounds which ignite and explode upon heating have been synthesized and the ability of these compounds to sensitize the primary explosive lead azide to stab initiation has been determined on 1 : 10 admixtures.
Abstract: A series of 17 compounds which ignite and explode upon heating have been synthesized. Ignition temperatures range from 122" to 261'. The ability of these compounds to sensitize the primary explosive lead azide to stab initiation has been determined on 1 : 10 admixtures. The general trend observed was that stab initiation energies increase with sensitizer ignition temperature but the overall correlation is poor. An assessment of the dependence of the ratio of sensitizer to lead azide on stab initiation energies is also included for two of the compounds. The results are interpreted in terms of possible mechanisms for the initiation process and support the hypothesis that frictional processes are of primary importance.
TL;DR: In this article, eight new sesquiterpenes, (ll, (12), (14)-(16), (18), (20) and (21), have been isolated from four separate small collections of the sponge Dysidea herbacea.
Abstract: Eight new sesquiterpenes, (ll), (12), (14)-(16), (18), (20) and (21), have been isolated from four separate small collections of the sponge Dysidea herbacea. The structures of these compounds, all of which contain a furan group, were derived by comparison of their spectral properties with those of known sesquiterpenes.
TL;DR: Isomeric dibenzoporphyrins having the fused rings attached to either adjacent or opposite pyrrolic rings have been prepared and their properties compared as mentioned in this paper, and the chemistry of some of the intermediates encountered during the synthesis of a benzoporphrin has been examined.
Abstract: Isomeric dibenzoporphyrins having the fused rings attached to either adjacent or opposite pyrrolic rings have been prepared and their properties compared. The chemistry of some of the intermediates encountered during the synthesis of a benzoporphyrin has been examined.
TL;DR: In this paper, six branched-chain lipids containing a γ-lactone ring have been isolated from the Gorgonian Plexaura flava and two new terpenoids of mixed biosynthesis.
Abstract: Six novel branched-chain lipids containing a γ-lactone ring have been isolated from the Gorgonian Plexaura flava. These compounds were accompanied by two new terpenoids of mixed biosynthesis.
TL;DR: In this article, scalarane sesterterpenes have been isolated from a Western Australian sponge (Lendenfeldia sp.) and several of these metabolites are extremely potent inhibitors of platelet aggregation.
Abstract: Five new scalarane sesterterpenes have been isolated from a Western Australian sponge (Lendenfeldia sp.). As with earlier reported examples of these compounds, several of these metabolites of this sponge are extremely potent inhibitors of platelet aggregation.
TL;DR: Nuclear Overhauser difference spectra showed that a reverse turn similar to that previously suggested for an encephalitogenic nonapeptide isolated from the protein (guinea pig determinant) occurs also in the protein itself, thus supporting the concept of special low-energy conformations responsible for biological activity.
Abstract: Myelin basic proteins from human, cow, pig, rabbit and chicken central nervous systems were studied in aqueous solution by proton n.m.r. at 400 MHz. Species comparisons and other techniques led to the assignment of resonances of 23 specific amino acid residues in the primary structure. Resonances from side chains of polar amino acids adjacent to aspartic residues could be assigned by anomalous effects of pH on the chemical shifts. The pK values of histidine side chains all fall in the range 6.0-6.9, and four specific histidine residues were assigned. The conformation of the protein in aqueous solution is that of an extended non-random polypeptide chain with regions of localized structure. Nuclear Overhauser difference spectra showed that a reverse turn similar to that previously suggested for an encephalitogenic nonapeptide isolated from the protein (guinea pig determinant) occurs also in the protein itself, thus supporting the concept of special low-energy conformations responsible for biological activity. Upfield chemical shifts of some side chain methyl groups from the central region of the primary structure suggest ring-current shifts due to higher-order structuring.
TL;DR: In this paper, the enantiomer composition of the 2-propylthietan isolated from the anal gland secretion of the stoat (Mustela erminea) was determined.
Abstract: (2S)-2-Propylthietan (10) has been synthesized to determine the enantiomer composition of the 2-propylthietan isolated from the anal gland secretion of the stoat (Mustela erminea).
TL;DR: A variety of 2-substituted benzimidazoles have been irradiated with ultraviolet light to determine the effects of substituents on the photochemical behavior of the benzinidazole ring system.
Abstract: A variety of 2-substituted benzimidazoles have been irradiated with ultraviolet light to determine the effects of substituents on the photochemical behaviour of the benzimidazole ring system. Benzimidazol-2-amine gave [2,5'-bibenzimidazol]-2'-amine and [2,4'-bibenzimidazol]-2'-amine, showing that this derivative behaves in the same way as benzimidazole. 2-Chlorobenzimidazole loses chlorine forming a dimeric species and benzimidazol-2(3H)-one, which is itself inert to photolysis. 2-Trichloromethylbenzimidazole also loses chlorine to form a variety of products depending on the solvent. 2-Trifluoromethylbenzimidazole does not lose fluorine but forms a dimer and also undergoes imidazole ring cleavage. Benzimidazole-2-thiol also undergoes imidazole ring cleavage with loss of sulfur. The 2-phenyl group stabilizes the benzimidazole ring system to photolysis as does the 2-thiazolyl group; however, the latter suffers thiazole ring cleavage.
TL;DR: In this paper, 1,4-Epoxy-1, 4-dihydroarenes are converted in high yields into the corresponding arenes with enneacarbonyldiiron in refluxing benzene solution.
Abstract: 1,4-Epoxy-1,4-dihydroarenes are converted in high yields into the corresponding arenes with enneacarbonyldiiron in refluxing benzene solution.
TL;DR: Tributyldiiodophosphorane and diiodotriphenylphosphoranes, prepared in situ from the corresponding phosphine and iodine, are generally able to convert primary and secondary alcohols into iodides at room temperature in diethyl ether or benzene containing two equivalents of hexamethylphosphoric triamide as discussed by the authors.
Abstract: Tributyldiiodophosphorane and diiodotriphenylphosphorane, prepared in situ from the corresponding phosphine and iodine, are generally able to convert primary and secondary alcohols into iodides at room temperature in diethyl ether or benzene containing two equivalents of hexamethylphosphoric triamide. Tertiary alcohols, as gauged by the lack of reactivity of t-butyl alcohol, are, however, inert to these iodinating agents. 6-Hydroxyhexanoic acid yields a mixture of 6-iodohexanoic acid and 7-heptanolide. The first reagent also promotes facile condensation of secondary and tertiary alcohols with carboxylic acids to form hindered esters in good yields. The phosphorane derived from tris-(dimethy1amino)phosphine and iodine, while less effective as an iodinating agent, rapidly converts 6-hydroxyhexanoic acid into 6-iodo-N,N-dimethylhexanamide, and hexanoic and benzoic acids into the corresponding N,N-dimethylamides in excellent yields at room temperature. Treatment of 3β- tosyloxycholest-5-ene with lithium iodide yields 3β-iodocholest-5-ene, and not 3α-iodocholest-5-ene, as previously reported.
TL;DR: Two volatile compounds isolated from seven species of prawns and one species of sand-lobster have been shown by g.l.m.c., micro-reaction and synthesis to be oct-1-en-3-ol (2) and (5Z)-octa-1,5-dien-3ol (3) as mentioned in this paper.
Abstract: Two volatile compounds isolated from seven species of prawns and one species of sand-lobster have been shown by g.l.c., micro-reaction g.l.c., n.m.r., mass spectrometry and synthesis to be oct-1-en-3-ol (2) and (5Z)-octa-1,5-dien-3-ol (3). These alcohols, which have respectively a mushroom-metallic and a metallic flavour in dilute aqueous solutions, impart a metallic flavour when added to the flesh of crustaceans.
TL;DR: The chemical defensive system of the ladybird Cryptolaemus montrouzieri consists mainly of three related alkaloids, one of which is very unstable and readily isomerizes to (3).
Abstract: The chemical defensive system of the ladybird Cryptolaemus montrouzieri consists mainly of three related alkaloids. Two of these have been identified as cis-1-(6-methyl-2-piperidyl)propan-2-one (3) and 1-methyl-9-azabicyclo[3,3,1]nonan-3-one (2); the third is very unstable and readily isomerizes to (3).
TL;DR: Carbon-13 nuclear magnetic resonance studies have been carried out on a number of molybdenum(II) carbonyl halide species and it has been found that for these seven-coordinate capped octahedral complexes there is a very large shift to high frequency for a carbonyls group in the capping position.
Abstract: Carbon-13 nuclear magnetic resonance studies have been carried out on a number of molybdenum(II) carbonyl halide species. It has been found that for these seven-coordinate capped octahedral complexes there is a very large shift to high frequency for a carbonyl group in the capping position. Thus carbon-13 n.m.r. provides a useful tool to distinguish between possible isomers. Trends in stability and isomer formation previously suspected from circumstantial evidence can now be rationalized.