bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal and molecular structure of the salicylaldehydatogallium dimethyl dimer
Authors: Rettig Steven J. , Storr Alan , Trotter James
Published: May 2006

Crystals of the salicylaldehydatogallium dimethyl dimer, [C7H5O2•GaMe2]2, are triclinic, a = 9.845(1), b = 8.6892(8), c = 7.4153(6) Å, α = 118.236(5), β = 92.46(1), γ = 115.81(1)°, Z = 1, space group [Formula: see text] The structure was solved by Patterson and Fourier syntheses and was refined by full-matrix least-squares procedures to a final R of 0.050 and Rw of 0.064 for 1644 reflections with I ≥ 3σ(I). The structure features a five-coordinate gallium atom having distorted trigonal bipyramidal geometry. Monomer units link via the formation of a four-membered Ga2O2 ring to form the centrosymmetric dimers. Bond lengths in the molecule are: Ga—O(eq), 1.933(3), Ga—O(ax), 2.127(3) and 2.469(3), Ga—C, 1.944(6) and 1.946(5), C—O, 1.333(4) and 1.231(6), C(ar)—C(sp2), 1.432(7), mean C—C(ar), 1.395(8), mean C(sp3)—H, 0.92(4), and mean C(sp2)—H, 0.93(2) Å. Bonds not involving hydrogen have been corrected for thermal motion.
Structure of 2′,3′-dimethyl-3,5-diiodo-D,L-thyronine, a fixed-conformation analogue of the thyroid hormone 3,5,3′-triiodo-L -thyronine
Authors: Fawcett J. Keith , Camerman Norman , Camerman Arthur
Published: May 2006

The three-dimensional molecular structure of 2′,3′-dimethyl-3,5-diiodo-D,L-thyronine (2′,3′-DMT2) has been determined by X-ray diffraction in order to establish the conformational characteristics responsible for biological activity in thyroid hormone analogues. Crystals of 2′,3′-DMT2 hydrochoride hydrate are monoclinic with cell dimensions a = 29.76, b = 6.84, c = 24.09 Å, β = 91.4°, space group C2/c with Z = 8 molecules per cell. The structure was solved by Patterson and Fourier techniques and refined by least squares. The atoms comprising the alanine portion of the molecule are disordered but the conformation of the diphenyl ether rings is clear: the β-ring 2′-methyl and 3′-methyl groups are situated distal to the α-ring. Thus the conformation postulated for this compound in biological tests of fixed-conformation thyromimetics is now structurally supported.
Macroscopic viscosity and the dielectric relaxation of some substituted benzenes
Authors: Srivastava S. C. , Crossley J.
Published: May 2006

Microwave dielectric constants and losses, and viscosities (η) have been obtained for acetophenone, anisole, bromobenzene, and p-dimethoxybenzene in n-heptane, n-hexadecane, paraffin oil, and three n-heptane + paraffin oil mixtures between 15 and 60 °C. The dielectric results have been analyzed for mean relaxation times (τ0). Plots of ln τ0T against ln η for bromobenzene are compared with those for the other solutes in an attempt to determine the effect of contributions from intramolecular relaxation processes. The results suggest that measurements employing several solvents at one temperature provide a better insight into mechanisms of dipole reorientation than those with one solvent at several temperatures.
The conversion of phthalideisoquinolines into spirobenzylisoquinolines and rhoeadine precursors
Authors: Holland Herbert L. , Curcumelli-Rodostamo Michael , MacLean David B.
Published: May 2006

Treatment of hydrastine with p-nitrophenylchloroformate in the presence of diethylisopropylamine resulted in opening of the isoquinoline ring with the formation of an ene-lactone carbamate. The latter compound rearranged upon treatment with methanolic sodium methoxide to an indan-1,3-dione carbamate which gave, on basic hydrolysis, the corresponding amine. This was ring closed to a spirobenzylisoquinoline. In addition, acid-catalysed dehydration of the amino indandione led to the formation of two isomeric benzazepines, synthetic precursors of the rhoeadine alkaloids. The predominately formed isomer has a substitution pattern identical with that of the rhoeadines.
Influence of remote substituents on ionization potential. Part II. Enamines
Authors: Brown R. S.
Published: May 2006

Electronic interactions in vinylamines can be divided into nN − π conjugation, and effects arising as a consequence of the electron-withdrawing abilities (−I) of both the nitrogen and π-system. Dehydroquinuclidine represents an ideal model which minimizes nN − π conjugation, and exhibits a pe spectrum which indicates that both the nN and π-orbitals are stabilized by about 0.4 eV relative to quinuclidine and bicyclooctene respectively. This stabilization is proposed to be a consequence of −I effects of each group and/or rehybridization of the nitrogen. Similar inductive effects are assumed to operate in enamines which do not prohibit nN − π interaction. In these cases, strong conjugative effects are operative in addition to the −I effects.
The reaction of catechol and derivatives with potassium superoxide
Authors: Lee-Ruff E. , Lever A. B. P. , Rigaudy J.
Published: May 2006

Semiquinones are produced in the oxidation of o- and p-dihydroxyarenes with potassium superoxide. These radical anions in the case of o-dihydroxyarenes are further oxidized to dicarboxylic acids. The semiquinones were also obtained by reduction of the corresponding quinones with potassium superoxide.
Electronic absorption spectra and dipole moments of diazafluoren-9-ones studied by the MIM, PPP, and CNDO/2 methods
Authors: Gandolfo Concetta , Buemi Giuseppe , Grasso Domenico , Fasone Salvatore
Published: May 2006

The electronic spectra of three diazafluoren-9-one isomers have been measured in cyclohexane solution and the results compared with those of 'molecules in molecules'(MIM) and PPP calculations. A satisfactory agreement between experimental and theoretical data has been found, and five π → π* transitions can be assigned to their uv spectra. For two compounds dipole moments in benzene solution have been measured and results are compared with theoretical values obtained by MIM and CNDO/2 calculations.
A total synthesis of (±)-cedrol and (±)-cedrene via an intramolecular Diels–Alder reaction
Authors: Breitholle Edward G. , Fallis Alex G.
Published: May 2006

A total synthesis of racemic cedrol and cedrene is described in which a key step is the intramolecular Diels–Alder reaction of alkyl cyclopentadiene 3 to give the tricyclic olefin 4. Oxidation of this material followed by ring expansion gives cedrone (6) which is converted to the sesquiterpenes. Modification of the functionality of the starting materials will permit the application of this general route to diverse tricyclic systems.
On the entropy production in chemically reacting Systems
Authors: Lissi Eduardo
Published: May 2006

The concept of monotonicity of entropy production is discussed regarding its application to chemically reacting systems. It is concluded that the concept cannot be generally applied even to elementary reactions in ideal homogeneous systems.
Alkaline methanolysis of 1,1,1-trichloro-2-hydroxy-4-alkanones
Authors: Kiehlmann Eberhard , Wells J. I. , Reeve Wilkins
Published: May 2006

Derivatives of the carboxylic acids RCOCH2CH(OCH3)COOH and RCOCH=CHCOOH (R = Me, i-Bu, or tert-Bu) have been identified among the major methanolysis products of three 1,1,1-trichloro-2-hydroxy-4-alkanones, RCOCH2CH(OH)CCl3. In addition, β-methoxy esters RCOCH(OCH3)CH2COOCH3 are obtained if hydrogen atoms are present at the alkyl carbon directly attached to the carbonyl group (R = Me or i-Bu). 1,1,1-Trichloro-2-hydroxy-4-pentanone (1) yields the known methyl 5-chloro-2,4-pentadienoate (9) as a minor by-product. An α,α-dichloro epoxide (15) is postulated as the key intermediate in the methanolysis mechanism leading to the β-methoxy esters.
The metal-ligand oxidations of dibenzobicyclo[2.2.2]octatriene by lead tetraacetate – hydrogen fluoride, lead tetraacetate, thallium(III) acetate, and mercuric acetate
Authors: Tanner Dennis D. , Van Bostelen Peter B. , Lai Mathew
Published: May 2006

The isoelectronic series lead tetraacetate–hydrogen fluoride, lead tetraacetate, thallium(III) acetate, and mercuric acetate were used to oxidize the bicyclic olefin dibenzobicyclo[2.2.2]octatriene. The stereochemistry of the products formed from these reactions substantiates the proposal that the first formed intermediate in these oxidations is the cis-molecular addition product of the metal and its ligand to the bicyclic olefin. Subsequent stereospecific rearrangement of the adducts in the case of the lead and thallium reagents verified the absence of the involvement of homolytic processes in the formation or decomposition of the adducts.
A study of non-bonded interactions of nitro and nitronate substituents in inositols
Authors: Baer Hans H. , Kovář Jan
Published: May 2006

In the family of mutually interconvertible δ-O-methyl-deoxynitroinositols having the myo-5 (1), neo-2 (2), allo-5 (3), epi-1 (4), epi-6 (5), and cis(6)configurations the relative thermodynamic stabilities of the individual members and of the three corresponding sodium nitronates 1′, 3′, and 5′ were assessed by determining equilibria of epimerization at pH 8.2 and pH > 12. The orders of stability are [Formula: see text] and 1′ > 3′ > 5′. The equilibrium data, together with those previously obtained for the stereoisomeric series comprising the corresponding scyllo (7), myo-1 (8), epi-3 (9), and muco-3 (10) epimers and their nitronates 7′, 8′, and 9′, were compared with theoretical values that were obtained from calculated conformational energies. The non-bonded interactions of the nitro and the nitronate group were evaluated and variable energy parameters were devised on the basis of differing gauche arrangements.
Charge distributions and chemical effects. X. Enthalpies of formation of alkanes, a calculation from 13C nuclear magnetic resonance shifts
Authors: Henry Hervé , Fliszár Sándor , Julg André
Published: May 2006

An analysis of the molecular energy in terms of bond contributions indicates that the latter (εij) can be approximated by a linear combination of the changes in net charges qi and qj. From the equation ΔH(atomization) = ∑εij, and the relationship between 13C chemical nmr shifts and C net charges, it is then possible to derive a two-parameter equation, ΔHf0 = ΔHf0(C2H6) + ν(N–2) + λ∑(Ncc + 1)δeth, which enables the calculation of enthalpies of formation of alkanes CNH2N+2 from 13C nmr shifts (δeth = shift relative to ethane, Ncc = number of CC bonds formed by the C atom whose shift is δeth).
Comportement photochimique de cétones α,β-insaturées sous excitation directe
Authors: Deflandre André , Lheureux André , Rioual Armel , Lemaire Jacques
Published: May 2006

The initial quantum yields of the primary photochemical processes which occur with five α,β-unsaturated ketones were measured under conditions of monochromatic excitation. The quantum yields of EZ isomerization and possibly of transposition (deconjugation) lead to a quantitative interpretation of the nonradiative deactivation of the S1 (nπ) and S2(ππ) excited states of these ketones. These substances show a remarkable photostability even in the presence of dissolved oxygen. [Journal translation]
The synthesis, Mössbauer and vibrational spectra of some triorganotin derivatives of phosphorus oxyacids
Authors: Chivers T. , Roode J. H. G. Van , Ruddick J. N. , Sams J. R.
Published: May 2006

Trimethyltin hypophosphite, Me3SnPO2H2, bis(trimethyltin) phosphite dihydrate, (Me3Sn)2PO3H.2H2O, and bis(triphenyltin) phosphite, (Ph3Sn)2PO3H, have been obtained from the organotin chloride and aqueous solutions of the sodium salt of the corresponding phosphorus oxy-acid. (Me3Sn)2PO3H.2H2O can be dehydrated under vacuum at 25 °C, but disproportionation occurs on heating. Tris(trimethyltin) orthophosphate, (Me3Sn)3PO4, was prepared from trimethyltin chloride and silver phosphate in methanol and gave an adduct formulated as [Formula: see text] after recrystallization from 1,4-dioxane. Vibrational spectra and Mössbauer data for Me3SnPO2H2 are consistent with a trigonal bipyramidal structure in which planar Me3Sn groups are bridged symmetrically by PO2H2 groups. The Mössbauer spectra of (Me3Sn)2PO3H, (Ph3Sn)2PO3H, and (Me3Sn)2PO3H.2H2O suggest that the two tin atoms are in similar (probably pentacoordinate) environments, implying at least one three coordinate oxygen per formula unit. For (Me3Sn)3PO4, the vibrational spectra, Mössbauer data, and physical properties are consistent with a weakly associated structure in which all three tin atoms are in similar environments. It is suggested that association is achieved via the phosphoryl (P=O) oxygen atom, which is weakly coordinated to three tin atoms leading to a distortion of the tetrahedral arrangement around tin towards trigonal bipyramidal.
13C magnetic resonance spectra of some isoquinoline alkaloids and related model compounds
Authors: Hughes Donald W. , Holland Herbert L. , MacLean David B.
Published: May 2006

The natural abundance 13C nuclear magnetic resonance spectra of a number of isoquinoline alkaloids and related model compounds have been recorded. In almost all cases comparison of the spectra of the alkaloids with those of the model compounds has permitted unambiguous assignment of the alkaloid carbon resonances. The ability of 13C nmr spectroscopy to distinguish between diastereomeric pairs of both protoberberine and phthalideisoquinoline alkaloids has been demonstrated.
The effect of steric crowding on an E2 transition state
Authors: Dyson George Stanley , Smith Peter James
Published: May 2006

The mechanism of the reaction of 9-(4-substituted benzyl)fluorene-9-trimethylammonium ions with ethoxide is a normal E2 process. The magnitude of the primary hydrogen–deuterium isotope effect at 60 °C increased with increasing electron-donating ability of the 4-substituent, i.e., 4.15, 5.10, 5.34, 5.65, 5.75, and 5.91 for the 4-CF3, 4-Br, 4-Cl, 4-H, 4-CH3, and 4-OCH3 substituents, respectively. The magnitude of the nitrogen isotope effect at 70 °C decreased with increased electron-donating power of the 4-substituent, i.e., [(k14/k15)–1]100 = 1.24, 0.95, 0.92, 0.91, and 0.80 for the 4-CF3, 4-F, 4-H, 4-CH3, and 4-OCH3 substituents, respectively. A small Hammett ρ value of +1.33 was observed for the reaction. It is concluded that the reaction proceeds via a transition state where the proton is more than one-half transferred to base. It is further concluded that for a reaction in which the 4-substituents decrease the rate, both carbon–hydrogen and carbon–nitrogen bond rupture is more advanced in the transition state. This variance with Hammond's postulate is discussed in the light of steric crowding at the transition state.
Synthèse de nouveaux phospholènes et phospholes avec substituants fonctionnels sur le phosphore
Authors: Mathey François , Lampin Jean-Pierre , Thavard Daniel
Published: May 2006

1-Bromo-3,4-dimethyl-3-phospholene quaternizes readily with functional organic halides Z—(CH2)n—X with Z = OR, SR, C(O)R, CH(OR)2, COOR, CONR2, CN, n = 1 or 2, and X = Cl or Br. The adducts thus obtained are formally related to the diene-dihalophosphine McCormack cycloadducts. When reacting with H2O or H2S they yield the corresponding P-functional phospholene oxides or sulfides. Phospholes are also obtained by reaction with DBU when n = 1 and Z = OR, SR, or when n = 2 and Z = CN. Some chemical properties of these new compounds are described and pmr data are given.
The interaction of α-diazoketones with hydroxylic solvents
Authors: Cataliotti Rosario , Sorriso Salvatore , Paliani Giulio
Published: May 2006

The diazo and carbonyl stretching bands of four diazoketones were studied inCCl4/MeOH mixtures as solvent, where the amount of hydroxylic solvent was linearly varied. The analogous behaviour afforded by the C—O band, either where cis/trans conformers are present (diazoacetone) or when conformational equilibria are hindered by chemical and/or steric reasons (the other three molecules), clearly indicates that local vibrator–solvent interactions are operative, probably via hydrogen bonding. Some minor effects due to the bulk dielectric constant of the medium were also observed.
The crystal structure of the complex salt: benzimidazole benzimidazolium fluoroborate
Authors: Quick Andrew , Williams David J.
Published: May 2006

The crystal structure of benzimidazole benzimidazolium fluoroborate has been determined at room temperature from three-dimensional diffractometer data, and refined by block-diagonal least-squares to a final R = 0.050. The planar benzimidazole rings are inclined at 7.6° to each other and linked by a hydrogen bond of 2.787(3) Å with the proton in an asymmetric single minimum. The asymmetric siting of the hydrogen atom has produced characterising effects on the bond lengths and angles of the ring to which it is attached.
L'étude de l'adsorption des halogenures d'ammonium quaternaire à l'interface mercure–solution
Authors: Ménard Hugues , Kimmerle Frank M.
Published: May 2006

We examined the adsorption of 16 tetraalkylammonium halides, R4NX (where R = CH3, C2H5, n-C3H7 and n-C4H9 and X = F−, Cl−, Br− I−), at the mercury – aqueous electrolyte interface. From electrocapillary data we defined ΓΔ, the structural surface excess, which was interpreted in terms of the same ion–ion and ion–solvent interactions proposed for homogeneous solutions. If we treat mercury at the Epcn as a hydrophobic surface having infinite curvature, this parallelism extends even to the numerical calculation of the free energy of adsorption.
The reactivity of cyclic germoxycarbene complexes of manganese and rhenium towards nucleophiles
Authors: Webb M. J. , Graham W. A. G.
Published: May 2006

Several acylate salts and noncyclic carbene complexes of manganese and rhenium, containing organogermanium ligands, have been prepared via the reactions of the cyclic germoxycarbene complexes of empirical formula Ph2GeM(CO)4COMe (M = Mn, Re) with the nucleophiles methyllithium or methoxide ion. In each case the observed product could be rationalized in terms of nucleophilic attack at germanium. Treatment of Ph2GeRe(CO)4COMe with methyllithium, followed by ethylation with aqueous Et3OBF4, afforded cis-Ph2MeGeRe(CO)4C(OEt)Me. The manganese analog of this product could be obtained if excess methyllithium were used in the first step. The use of a deficit of methyllithium, however, followed by ethylation, yielded cis-Ph2FGeMn(CO)4C(OEt)Me. Solution infrared spectra have indicated that lithium methoxide and lithium bromide impurities in the methyllithium are involved in this reaction. The reaction of Ph2GeMn(CO)4COMe with sodium methoxide is presumed to involve nucleophilic attack at germanium to give a methoxygermanium species. Subsequent treatment with aqueous tetraethylammonium bromide gave the hydroxygermanium complex, [cis-Ph2(HO)GeMn(CO)4C(O)Me][Et4N]. Ethylation of the same species with aqueous Et3OBF4 afforded cis-Ph2FGeMn(CO)4C(OEt)Me.
Carbon kinetic isotope effects in the oxidation of oxalate by permanganate in aqueous solutions of sulfuric acid
Authors: Betts Robert H. , Buchannon Wayne D.
Published: May 2006

Fractionation of the carbon isotopes occurs during the oxidation of oxalate by permanganate in aqueous sulfuric acid. The isotope effect, expressed as k12/k13, rises from near unity in the very early stages of the reaction, to reach a value of 1.037 ± 0.001 after completion of the induction period. Addition of fluoride prolongs the induction period, and reduces the isotope effect to values near 1.000. These observations are consistent with there being two essentially independent paths for formation of carbon dioxide. The first, operative in the early stages, involves rate-controlling electron transfers from Mn(VI) or Mn(IV) to the oxalate ion, while the second involves oxidative decomposition of an oxalate complex of Mn(III), for which the rate-controlling step is C—C bond rupture.
Metal complexes of sulfur–nitrogen chelating agents. V. 2-N-Ethylaminocyclopentene-1-dithiocarboxylic acid complexes of Ni(II), Pd(II), Pt(II), Co(II), Co(III), and Cu(I)
Authors: Nag K. , Joardar D. S.
Published: May 2006

2-N-Ethylaminocyclopentene-1-dithiocarboxylic acid (EACDA) acts as an ambidentate ligand toward several metal ions. Bis-chelates have been obtained with Ni(II), Pd(II), Pt(II), and Co(II), and tris-chelate with Co(III). Cu(I) forms a 1:1 complex. The bonding sites involved in the metal chelates and their stereochemistry have been ascertained from electronic, infrared and nmr spectra, magnetic moment, and thermal analysis. In the Co(II) and Co(III) chelates bonding takes place from (S,S−) donor sites, whereas in the Ni(II), Pd(II), and Pt(II) chelates (N,S−) type bonding occurs. The Cu(I) complex appears to be polymeric in nature.
13C and 33,34S isotope effects on the vapour pressure of liquid carbon disulfide
Authors: Betts Robert H. , Buchannon Wayne D.
Published: May 2006

Precision isotope ratio mass spectrometry has been used to determine the relative vapour pressures of the four principal isotopic species of liquid carbon disulfide. Relative to the principal species 12C32S32S = 1.000000, the vapour pressures of the other species are: 12C32S34S = 0.999855, and 13C32S32S = 1.00162. A value of 0.999927 for 12C32S33S is deduced by application of the rule of the geometric mean. The results are invariant with temperature between −20 and +56 °C. Qualitatively similar effects have been reported earlier for 13C and 18O substitution in 12C16O2, a chemical analogue of CS2.
Excess volume and viscosity of binary liquid acid–base mixtures
Authors: Sólimo Horacio N. , Riggio Roque , Espíndola José A. , Alonso Silvia del V. , Katz Miguel
Published: May 2006

Densities, viscosities, and refractive indices at 25 °C were determined for the systems: o chlorophenol + N,N-dimethylaniline, o-chlorophenol + aniline, o-chlorophenol + m-toluidine, and o-chlorophenol + pyridine. From the experimental results the excess volume, excess viscosity, excess molar free energy of activation of flow, and the excess partial molar volume were calculated. There is evidence of complex formation between o-chlorophenol and the four bases.
Convergence properties of the ω-β-variable method
Authors: Castro Eduardo Alberto
Published: May 2006

The convergence properties of the ω-β-variable method are studied in order to extend some previous theoretical results about deviations of the electronic populations from the self-consistent final values. A linear correction for the whole effective Hückel Hamiltonian is employed and the inclusion of overlap integrals is discussed.
Catalysed Diels–Alder reactions. The realization of orientation control with a bifunctional aliphatic dienophile
Authors: Kakushima Masatoshi , Espinosa Jesús , Valenta Zdenek
Published: May 2006

The Lewis acid catalysed addition of methyl trans-4-oxobutenoate (7) to trans-piperylene (8) gives selectively product 9. SnCl4 is a particularly efficient catalyst. A postulate of the preferential formation of a complex with the formyl group is used to explain the regio- and stereo-specificity of the reaction. Synthetic implications of this finding are discussed.
Synthesis of 5,10,11,12,17,22,23,24-octahydrotetrabenzo[a,d,i,l]cyclohexadecene derivatives
Authors: Renaud Roger N. , Bovenkamp John W.
Published: May 2006

The reaction between 2,2′-bis(bromomethyl)diphenylmethane and diethyl sodiomalonate gives mainly 11,11,23,23-tetracarboethoxy-5,10,11,12,17,22,23,24-octahydrotetrabenzo[a,d,i,l]-cyclohexadecene together with some polymeric compounds. No eight-membered ring products were detected. Starting from the tetracarboethoxy compound described above, the syntheses of a series of di- and tetrasubstituted tetrabenzo[a,d,i,l]cyclohexadecenes are described.
A Mössbauer study of organotellurium compounds. Part II. Halides, acetates, and benzoates
Authors: Berry Frank J. , Jones Colin H. W.
Published: May 2006

125Te Mössbauer data, measured at 4.2 K, are reported for a number of organotellurium(IV) compounds, including Ar2TeF2, ArTeF3, Ar2Te(OCOCH3)2, Ar2Te(OCOC6H5)2, where Ar = Ph, p-EtOC6H4, p-MeOC6H4, p-C7H7, and the compounds Ph2(CH3)TeI and Ph(CH3)2TeI. Evidence is presented that while the difluorides appear to be similar in structure to the other dihalides(X = Cl, Br, I), in the trifluorides the co-ordination about the tellurium is significantly different to that found in the other trihalides (X = Cl, Br, I). The iodides studied have parameters consistent with their formulation as Ph2(CH3)Te+I− and Ph(CH3)2Te+I−. The dicarboxylates have parameters similar to those of the dihalides, although the diphenyl tellurium diacetate and dibenzoate have relatively small Δ's in comparison with those of the other derivatives studied and it would appear that subtle changes in the co-ordination about tellurium occur with changes in the aryl ligand.
13C nuclear magnetic resonance spectra of steroids: the assignments of chemical shifts for C-15 and C-16 in 17β-acetyl steroids
Authors: Kim Dong Je , Colebrook Lawrence D. , Adley T. J.
Published: May 2006

Previously reported 13C chemical shift assignments for C-15 and C-16 of a number of 17β-acetyl steroids related to progesterone have been shown to be reversed. Based on the revised assignment the effect of bromo- and hydroxy-substitution at C-17 on C-12, C-14, C-15, and C-16 is assessed.
Interionic potentials for the alkali metal chlorides
Authors: Corish J. , Parker Brenda M. C. , Jacobs P. W. M.
Published: May 2006

Various models for the interionic potential in the alkali metal chlorides have been examined. The parameters in these potentials have been determined by fitting the equilibrium, elastic and dielectric properties of each substance. The potentials are compared graphically with each other, with the theoretically derived potentials of Kim and Gordon (1,2) and with a potential derived earlier by Catlow, Diller, and Norgett (3) by fitting the properties of sixteen alkali halides simultaneously. Intrinsic defect properties of the four chlorides have been calculated from these potentials. The results show that while it is possible to derive adequate two-body potentials for these salts from fitting their bulk properties, it is concluded, as found earlier by Catlow, Diller, and Norgett (3), that such potentials need to have the anion–cation interaction hardened by neglecting completely the Van der Waals interaction between nearest neighbours. Inclusion of non-central forces does not improve the potential, as judged by the criterion of the results of defect calculations.
Gas phase ion equilibria studies of the proton in hydrogen sulfide and hydrogen sulfide – water mixtures. Stabilities of the hydrogen bonded complexes: H+(H2S)x(H2O)y
Authors: Hiraoka Kenzo , Kebarle Paul
Published: May 2006

The temperature dependence of the equilibria [Formula: see text] was measured for n = 1 to 5 in a pulsed electron beam mass spectrometer with a high pressure ion source. The ΔHn+1,n values obtained were (2,1) 15.4, (3,2) 9.1, (4,3) 8.4, (5,4) 6.7 kcal/mol. Possible structures of the clustered ions are proposed.Addition of water vapor leads to mixed cluster ions such as H+(H2S)x(H2O)y, with x + y from 1 to 6, observed as the ion source temperature was decreased to −100 °C. The temperature dependence of the equilibria for the exchange reactions [Formula: see text]and the association reaction [Formula: see text]were also measured. For all ions measured, the hydration process is energetically more favorable than the solvation by H2S.
Kinetic studies of Dakin oxidation of o- and p-hydroxyacetophenones
Authors: Hocking M. B. , Ong J. H.
Published: May 2006

Rates of oxidation of aqueous o-, and p-hydroxyacetophenone with alkaline hydrogen peroxide to yield catechol and hydroquinone, respectively, have been followed spectrophotometri-cally. Both ketones showed smooth pseudo first-order behaviour, the ortho isomer yielding rate constants in the range 2.6 to 6.6 × 10−2 min−1 at 0 °C, and the para isomer of 0.73 to 7.10 × 10−2 min−1 at 35 °C for the concentrations of hydrogen peroxide and base used. The order in hydrogen peroxide was, unexpectedly, found to be 1.4. A simple test established that this fractional order was probably not the result of hydrogen peroxide involvement in simultaneous first- and second-order processes of differing rates. Other plausible pathways to explain this are proposed.
Gas phase competitive anionic cleavage of esters
Authors: Comisarow M.
Published: May 2006

The gas phase reaction of deuteriomethoxide with methyl benzoate and with methyl tri-fluoroacetate yields the corresponding carboxylate anions and not protiomethoxide ion. These results are opposite to what would be expected based upon the known reactions in solution of anions with esters. The reasons for the different behavior between the gas phase and the solution phase are discussed.
Diamagnetic susceptibilities and susceptibility exaltations of some 7-substituted cycloheptatrienes
Authors: Childs Ronald F. , Pikulik Ivan
Published: May 2006

The diamagnetic susceptibilities of several 7-substituted cycloheptatrienes have been measured and used in conjunction with estimated values of their susceptibilities (Haberditzl increment system) to obtain the susceptibility exaltations of these compounds. These exaltations were found to be very large and to vary as a function of the size of the C7 substituent. There was no apparent correlation of the exaltation of a compound with the electronic properties of its substituent. The effect of a substituent on the susceptibility exaltation is interpreted in terms of conformational changes in the seven-membered ring. The magnitude of the susceptibility exaltations of these cycloheptatrienes, for example 7-tert-butylcycloheptatriene (Λ = 14.8), in comparison to that of benzene (Λ = 13.7) would suggest that the presence of an induced diamagnetic ring current is not a good criterion of its aromaticity.
Reactions of ozonides. XII. Ozonolysis of methylenecyclohexane
Authors: Kerur Dundappa R. , Diaper Dennis G. M.
Published: May 2006

Ozonization of methylenecyclohexane in various solvents gives several peroxides and the ozonide in competing reactions. All products can be adequately explained by adaptation of the Criegee theory, without invoking a Baeyer–Villiger reaction of carbonyl solvents. Solvent effect on product proportions is not linked with dielectric constant or enol content, but appears to be a zwitterion solvation effect.
The chromous chloride promoted addition of N-haloamides to olefins. III. Scope and limitations for the synthesis of N-(2-haloalkyl)amides
Authors: Driguez Hughes , Paton John M. , Lessard Jean
Published: May 2006

A study of the chromous chloride promoted addition of various N-chloro- and N-bromoamides (ZCONHX) to a variety of olefins shows that two types of addition products can be obtained, namely N-(2-haloalkyl)amides (1,2-adducts) which generally predominate and N-alkylamides (1,H-adducts). The total yield of addition products, the relative proportion of N-(2-haloalkyl)amide(s) and N-alkylamide, and the stereochemistry of 1,2-addition to cyclic olefins vary with the N-haloamide, that is with both Z and X, and also with the olefin. The best yields of 1,2-adducts were obtained with N-chlorocarbamates (Z = O-alkyl) and the proper choice of Z (e.g., 2,2,2-trichloroethoxy, benzyloxy) shows the potential of this method for the synthesis of N-protected β-chloro primary amines where the amino group is attached to the less substituted carbon atom. The use of an excess of N-haloamide results in high yields (>90%) of 1,2-addition based on the olefin, the excess of N-haloamide being simply reduced to the corresponding amide. N-Chloro-N-alkylamides (ZCONRCl) do not add to cyclohexene and are simply reduced to the corresponding amides.
The balance between electronic and nuclear energy in conformational change
Authors: Csizmadia Imre G. , Theodorakopoulos Giannoula , Schlegel H. Bernhard , Whangbo Myung-Hwan , Wolfe Saul
Published: May 2006

The relative contributions of nuclear repulsion and electronic attraction to conformational rotational potentials have been analysed for several types of systems. It is shown that decomposition of a computed total energy into these two components provides a diagnostic tool for the evaluation of the reliability of such computations. It is also pointed out that Hartree–Fock theory is sufficient to reproduce experimental stereochemical observations, provided that one is aware of the accuracy needed to compute the molecular electronic wave function. This accuracy is predetermined by the nuclear or electronic dominance of the process.
The preparation of some potential intermediates for syntheses of aminopolydeoxy sugars related to antibiotics
Authors: Baer Hans H. , Georges Fawzy F. Z.
Published: May 2006

Starting from methyl 3,6-dideoxy-3-nitro-α-D-glucopyranoside (1) and proceeding through its 4-mesylate (2) and 2,4-dimesylate (3), respectively, methyl 3,4,6-trideoxy-3-nitro-α-D-xylo-hexopyranoside (4) and methyl 2-O-acetyl-3,4,6-trideoxy-3-nitro-α-D-threo-hex-3-enopyrano-side (5) were prepared. The 4,6-O-benzylidene derivatives (6, 8, and 10) of methyl 2-O-acetyl-3-deoxy-3-nitro-β-D-glucopyranoside, methyl 3-deoxy-3-nitro-α-D-glucopyranoside, and methyl 2,3-dideoxy-3-nitro-α-D-arabino-hexopyranoside were found to undergo without difficulty the Hanessian–Hullar reaction with N-bromosuccinimide, to give good yields of the corresponding 6-bromo-4-benzoates (7, 9, and 11). Partial anomerization giving the β-anomer 12 of 11 was observed under certain circumstances.
A laser interferometric study of the diffusion of O2, N2, H2, and Ar into water
Authors: O'Brien Robert Neville , Hyslop William Frank
Published: May 2006

The diffusion constants of O2, N2, H2, and Ar at 24 °C in H2O are calculated from interferometric data. The question of surface resistance to diffusion of O2 into water is discussed. There appears to be no such resistance.
Thermodynamics of basic ionization of some aminoethers in water
Authors: Lobo Sheila Teresa , Robertson Ross Elmore
Published: May 2006

not available
Flow nuclear magnetic resonance detection and characterization of an intermediate on the reaction pathway in a nucleophilic aromatic substitution reaction
Authors: Fyfe C. A. , Koll A. , Damji S. W. H. , Malkiewich C. D. , Forte P. A.
Published: May 2006

The use of high resolution flow nmr has made possible the detection and characterization by nmr of the transient intermediate σ-complex on the actual substitution pathway in the nucleophilic aromatic substitution reaction of 1-ethoxy-2,4-dinitronaphthalene (3) with n-butylamine, and the assignment of its uv-visible spectrum. The intermediate is unambiguously identified as the σ-complex (4) and the reaction is one where the two-step mechanism is clearly applicable.
Analysis of a proposal for nitric-oxide abatement in jet-aircraft engines
Authors: Craig Roger A. , Pritchard Huw O.
Published: May 2006

Modifications are reported to a conventional gas-kinetics computer program which allow for the continuous addition of chemical species to the flowing gas. This is necessary in modelling the gas flows in a jet engine where air is continuously entrained with the burnt or burning gases, and it also facilitates the investigation of introducing chemical additives into a flowing reaction mixture.The program is used to compare, under the same one-dimensional modelling approximations, the nitric-oxide emissions from a conventional jet engine and from a proposed lean-burning modification, and it is concluded that the lean-burning model has potential for reducing nitric-oxide emission by more than two orders of magnitude.
Etude de l'équilibre dans les oxazolo[2,3-e], thiazolo[2,3-e] et isoxazolo[2,3-d]tétrazoles. II. Etude de l'effet de la température par dipolemetrie et résonance magnétique nucléaire
Authors: Faure Robert , Galy Jean-Pierre , Vincent Emile-Jean , Fayet Jean-Pierre , Mauret Pierre , Vertut Marie-Claire , Elguero José
Published: May 2006

The equilibrium constant in dioxane between azido and tétrazole isomers has been obtained for five heterocyclic azides (2-azido thiazoles, benzothiazole, benzoxazole, and 3-azido isoxazole) by proton nmr and dipole moment- studies. The last method involves a comparison between experimental and calculated (INDO, CNDO/2, CNDO/S) dipole moments. The CNDO/S method gives the best equilibrium constants and entropy factor (ΔS ∼ 50 J K−1 mol−1). A value of 114° for the C—N—N angle is found to account satisfactorily for certain properties (energy, dipole moment, photoelectron spectra) of aromatic azides. The heterocyclic azidoimines prefer the Z conformation.
The role of electronic processes in the electrical breakdown of insulating liquids (Extended Abstract)
Authors: Devins John C. , Rzad Stefan J. , Schwabe Robert J.
Published: May 2006

not available
Localized electronic states in amorphous semiconductors
Authors: Adler David , Yoffa Ellen J.
Published: May 2006

The experimental results pertaining to the electronic structure of covalent amorphous semiconductors are briefly reviewed. It is found that three classes of materials exist, depending on the lowest-energy coordination of the predominant chemical component. In each case, the transport properties are ordinarily controlled by the localized states in the gap resulting from the minimum-energy defect sites, in which the local coordination is not optimal for certain atoms. These localized states are treated in terms of a Hubbard model, in which the effective repulsion between two electrons simultaneously present on the same center is taken as positive for tetrahedrally bonded solids and negative for chalcogenide and pnictide glasses. The electronic structure is discussed in detail. It is shown that even such a simple model can account for almost all of the experimental properties of the major classes of amorphous semiconductors.
Bond equilibrium theory for Te-rich liquid Tl–Te alloys
Authors: Cutler Melvin
Published: May 2006

Recent work has provided independent information about the behavior of the hole concentration c in TlxTe1−x as a function of temperature T and composition x in the range 0.2 ≤ x ≤ 0.6. This makes possible a critical reexamination of a molecular bond model for the structure of the alloy, in which holes are generated by broken Te—Te bonds. The earlier theory is revised to formulate an unrestricted independent bond model (ibm), for which the equations are simple and have obvious physical interpretations. This provides a good description of c(T) but only a qualitatively correct c(x). Using a Thomas–Fermi model for the screening interaction between holes and the acceptor ions, it is shown that the equilibrium constant can be expected to increase rapidly with c at large enough values. A modification in which the free energy of a dangling bond is decreased by proximity to a Tl—Te bond is found to significantly improve the result for c(x). The thermochemical behavior is derived. The entropy of mixing is in fair agreement with experiment, but the enthalpy of mixing is grossly wrong. This reflects the neglect of intermolecular interactions in the theory, which, it seems, can easily account for the remaining discrepancies in the predicted behavior of c.
Field-dependent electron mobility in methane–ethane liquid mixtures
Authors: Rao Bappanadu N. , Bush Robert L. , Funabashi K.
Published: May 2006

Some aspects of the mobility of excess electrons in liquid hydrocarbons are discussed. Certain salient features of the experimental data on high-field mobility in ethane–methane mixtures are explained in terms of a hopping model, in which disorder plays an important role. The disorder is compositional, like that in a binary alloy, and enters the model in the form of two distinct jump distances for hopping motion. It is shown that decreasing the coherence length for a quasi-free electron increases the binding energy of a localized electron and hence affects the activation energy and rate of hopping. The effects of temperature and impurity concentration for high-mobility liquids are shown to be consistent with a scattering model.
Electrical properties of some molten ternary semiconductors
Authors: Nakamura Yoshio , Naoi Masamitsu , Shimoji Mitsuo
Published: May 2006

The electrical conductivity and thermoelectric power of molten AgTlSe2, AgTlSe, and Tl2Se3 have been measured as a function of temperature. The effect of doping with Ag, Tl, and Se on the electrical properties of molten AgTlSe has also been studied. The results are discussed in terms of the pseudogap model.
High field transport of excess electrons and holes in amorphous SiO2 (Extended Abstract)
Authors: Hughes R. C.
Published: May 2006

not available
Organic sulfur mechanisms. 20. Sulfenes from 1-haloalkanesulfinic acids: the 'abnormal route'
Authors: King James Frederick , Beatson Rodger Peter , Buchshriber Joseph Max
Published: May 2006

1-Haloalkanesulfinic acids react with water, p-toluidine, or an enamine in the presence of added base to give products expected from an intermediate sulfene. It is concluded that sulfenes are formed, and hence may be presumed to react, via the 'abnormal route', i.e., loss of a nucleophile from the carbon (rather than the sulfur) of the incipient sulfene, or, for the reverse process, addition of a nucleophile to the carbon (rather than the sulfur) of the sulfene. Since addition at the sulfur is well precedented, these conclusions indicate that sulfene is an 'ambifunctional' electrophile of a previously unknown kind. The mechanism of the sulfene formation is discussed in the light of deuterium labelling and kinetic experiments.
Some reactions of ethyl azidoformate with quinones
Authors: Chauhan Mohinder S. , McKinnon David M. , Cooke Raymond G.
Published: May 2006

Ethyl azidoformate has been allowed to react with 1,4-naphthoquinone, 1,2-naphthoquinone, and 2-methoxy-1,4-naphthoquinone under different thermolytic conditions. A variety of products involving addition, substitution, insertion, and molecular rearrangement have been observed. The nature and yields of these products under different conditions are discussed inrelation to the mechanisms proposed for these reactions.
Synthesis and photochemistry of 4,4-diphenyl- γ-pyran. Di-π-methane rearrangement in a new chromophore
Authors: Gravel Denis , Leboeuf Christian , Caron Serge
Published: May 2006

A synthesis of 4,4-diphenyl-γ-pyran (1) was elaborated from diphenylmethane. Prolonged irradiation of pyran 1 in tert-butyl alcohol led to: trans-endo-5,6-diphenyl-2-oxabicyclo[3.1.0]-hexene (18), isomeric 3,5-diphenylpenta-2,4-dienals (6), trans-tert-butyl 3,5-diphenylpent-2-enoate (7), cis-tert-butyl 3,5-diphenylpent-2-enoate (8), and isomeric 3,5-diphenylpent-2-enoic acids (9). It was established that the photolysis of γ-pyran 1 yields only one primary photoproduct: the oxabicyclo[3.1.0]hexene derivative 18 via a di-π-methane rearrangement. The other compounds isolated result from further irradiation of the primary product. The results observed are discussed in the light of the di-π-methane rearrangement mechanism.
Studies of the behavior in magnetic fields of some lyomesophase systems with respect to electrolyte additions
Authors: Chen Douglas M. , Fujiwara Fred Y. , Reeves Leonard W.
Published: May 2006

A systematic investigation has been made of some lyotropic mesophases (lyomesophases) which macroscopically orient in magnetic fields. These mesophases have been classified into type I which have a positive diamagnetic anisotropy (Δχ > 0) and type II with Δχ < 0. The mesophase behavior has been observed as a function mainly of electrolyte additions to binary and ternary systems. The electrolyte has a profound effect on the mesophase behavior at extremely low concentrations. It has the effect in the ternary system, sodium decylsulphate/decanol/water, of converting a type I to a type II mesophase with less than 1 wt.% electrolyte. The addition of electrolytes to binary surfactant/water systems had the effect of increasing the mesomorphic region to higher water concentrations. In the case of sodium and cesium decylsulphate, and potassium laurate, these ternary mesophases were of type I and for decylammonium chloride of type II. The method used to distinguish mesophases and determine the degrees of order of water and some hydrocarbon chain segments has been deuterium magnetic resonance.
Motion of the SO3−NH radical trapped in potassium sulfamate. Electron spin resonance dipolar coupling tensors for the motionless radical
Authors: Bonazzola L. , Michaut J. P. , Roncin J.
Published: May 2006

The temperature dependence of the esr couplings in SO3−NH radical trapped in potassium sulfamate single crystals allows the study of the motion of this radical in the matrix and the determination of N and H dipolar tensors corresponding to the motionless radical. These values are compared with different theoretical calculations.
Synthesis and characterization of Cu(I) complex compoundswith methyl isonicotinate
Authors: Goher Mohamed A. S.
Published: May 2006

not available
Aromatic substitutions with carbanion nucleophiles. III. The kinetics of the reaction of picryl chloride with diethylmalonate anion
Authors: Leffek Kenneth T. , Matinopoulos-Scordou Anna E.
Published: May 2006

The reaction between 1-chloro-2,4,6-trinitrobenzene (picryl chloride) and diethylmalonate anion in benzene–DMSO 7:1 v/v solvent has been investigated by means of stopped-flow and uv–visible spectrophotometers. The results support a simple bimolecular aromatic substitution with a fast formation of a Meisenheimer-like coloured intermediate, followed by a slower decomposition to the picryl ester. The latter is rapidly deprotonated by the excess base. The steps of the reaction were followed separately and the rate constants and activation parameters have been measured.
Aromatic substitutions with carbanion nucleophiles. IV. The kinetics and mechanism of the reaction of picryl bromide with diethylmalonate anion
Authors: Leffek Kenneth T. , Matinopoulos-Scordou Anna E.
Published: May 2006

The reaction of picryl bromide with sodium diethylmalonate has been studied in benzene–DMSO 7:1 v/v by means of stopped-flow and uv–visible spectrophotometers. A Meisenheimer-like intermediate was detected, decomposing to yield the stable violet anion of the substitution product. The rate constants of the individual steps have been measured and the activation parameters calculated. Comparison with those obtained for picryl chloride support a bimolecular substitution via the 1,1-complex. The reaction with 1,3,5-trinitrobenzene is too fast to be measured in the same solvent system. The equilibrium constant is estimated to be of the order of 104–105.
On the blue complexes of ruthenium. Part II. The structure of fac-trichlorotriammineruthenium(III)
Authors: Bottomley Frank
Published: May 2006

The structure of [RuCl3(NH3)3] prepared from the blue chloro-ammine complex of ruthenium is described. The crystals are orthorhombic, a = 9.933(3), b = 6.522(2), c = 5.475(2) Å, Z = 2, space group Pmn21. The structure analysis used 283 observed reflections, whose intensity was measured on a Picker FACS-1 diffractometer. The structure was refined (full-matrix) to R = 0.029. The crystal is composed of chains of fac-[RuCl3(NH3)3], and is disordered, approximately 10% of the chains being reversed in direction and displaced one-half in z. The Ru–ligand distances and angles are normal.
C-Nucleosides and related compounds. XIII. Synthesis of D,L-2′-deoxyshowdomycin (1d)
Authors: Just George , Lim Mu-Ill
Published: May 2006

Starting from the Diels–Alder adduct of furan and methyl β-nitroacrylate, the synthesis of the title compound is described.
C-Nucleosides and related compounds. XIV. The synthesis of a nitrogen analogue of showdomycin
Authors: Just George , Donnini G. Paul
Published: May 2006

Starting from teloidinone 5a, 2-(2′α,3′α-dihydroxy-4′β-hydroxymethyl-N-carbomethoxypyrrolidin-1β-yl)maleimide 1b, a showdomycin analogue in which the ribofuranosyl ring oxygen is replaced by an N-carbomethoxy group, has been synthesized in 7% overall yield.
125Te Mössbauer spectra of the polyatomic cations of tellurium
Authors: Jones C. H. W.
Published: May 2006

125Te Mössbauer data for frozen solutions of tellurium in HSO3F and in oleum are reported together with data for solid samples which may have contained the Te42+, Tenn+, and Te62+ cations. The data demonstrate that the quadrupole splitting reflects the sequential oxidation of the tellurium through the steps Te → Te42+ → Tenn+ → Te(II) → Te(IV) → TeO2. The quadrupole splittings for samples identified as containing Te42+ are consistent with a unit quadrupole splitting of 12 mm s−1 for 125Te.