bluuebunny/crossref_metadata_2025 huggingface dataset:
Methyl–Methyl Proton Spin–Spin Coupling Constants in Some Six-membered Ring Compounds. A Test for Delocalization in Borazine
Authors: Rowbotham J. Brian , Schaefer T.
Published: May 2006

Spin–spin coupling constants over five, six, and seven bonds between protons in different methyl groups are reported for the xylenes, derivatives of benzene, pyridine, pyrimidine, pyridinium salts, p-benzoquinone, and borazine. The coupling magnitudes are characteristic of the substitution pattern in the delocalized systems. Calculations at the INDO-MO-FPT level of methyl proton couplings in N- and B-methylborazines are in agreement with the available experimental evidence in indicating a relatively weak transmission of spin density information via the presumed π electron system of borazine.
Metals Intercalated in Graphite. II. The Friedel–Crafts Reactions with AlCl3–Graphite
Authors: Lalancette Jean-Marc , Fournier-Breault Marie-Josée , Thiffault Raymond
Published: May 2006

Aluminum trichloride can be intercalated in the lattice of graphite. This intercalate is a milder catalyst than AlCl3 for the alkylation reactions and gives less polysubstituted reaction products.
THE ALKALINE HYDROLYSIS OF N-ACYLTHIOUREAS
Authors: Congdon Wayne I. , Edward John T.
Published: May 2006

N-Benzoylthiourea (pKHA 10.9) and other N-acylthioureas ionize in alkaline solution, and then are rapidly hydrolyzed to thiourea and a carboxylic acid. The rates become independent of hydroxide ion concentration when this exceeds about 0.1 M and point to a mechanism in which hydrolysis takes place by attack of an hydroxide ion on the un-ionized molecule of N-acylthiourea. This mechanism accords with the Arrhenius parameters for the hydrolysis of N-benzoylthiourea in 0.2 N sodium hydroxide, and with the Hammett ρ value of 0.10 for the hydrolysis of m- and p-substituted N-benzoylthioureas in 1.0 N potassium hydroxide.
Crystal and Molecular Structure of 2-Deacylusnic Acid
Authors: Macdonald Alistair L. , Rettig Steven J. , Trotter James
Published: May 2006

Crystals of the title compound are monoclinic a = 9.801(2) b = 9.120(1) c = 8.026(2) Å, β = 107.45(1)°, Z = 2, space group P21. The structure was determined by direct methods, and refined by electron-density and full-matrix least-squares procedures to R = 0.0325 for 1363 observed reflections. An attempt to determine the absolute configuration by use of the anomalous scattering of oxygen and carbon atoms has been made. The most important structural feature is delocalization in the cyclohexadiene ring. There are two intramolecular O—H … O hydrogen bonds, O … O distances 2.532(3) and 2.712(2) Å. The crystal structure consists of molecules linked by intermolecular O—H … O hydrogen bonds, O … O = 2.625(2)Å, to form continuous spirals about the 21 axes.
Synthesis of 2,6-Naphthyridine, 4-Methyl-2,6-naphthyridine, and their Derivatives
Authors: Taurins Alfred , Li Rosita Tan
Published: May 2006

A detailed outline of the experimental procedures for the synthesis of 2,6-naphthyridine and 4-methyl-2,6-naphthyridine is given. Cyclization of 2-(4-cyano-3-pyridyl)propionitrile with anhydrous hydrogen bromide lead to 3-amino-4-methyl-2,6-naphthyridine which was transformed into 4-methyl-2,6-naphthyridine in a series of reactions. The u.v. spectra of 2,6- and 4-methyl-2,6-naphthyridine and their amino and halogen derivatives were recorded.
The EPR Spectra of Hydrazyl and Some 1-Substituted Hydrazyl Radicals in Solution
Authors: Malatesta V. , Lindsay D. , Horswill E. C. , Ingold K. U.
Published: May 2006

Hydrogen atom abstraction by tert-butoxy radicals from hydrazine, methyl-, benzyl-and carboethoxy-hydrazine yields the hydrazyl radical and the appropriate 1-substituted hydrazyls, [Formula: see text] The radical structures are assigned on the basis of their e.p.r. spectral parameters. It has been shown by 15N labelling that in 1-alkylhydrazyls the larger nitrogen splitting is produced by the divalent nitrogen that formally bears the unpaired electron. This result contrasts with the behavior of 2,2-dialkylhydrazyls (1).
The Radiochemistry of Organoiron Compounds. IV. FeCp(CO)2
Authors: Kanellakopulos-Drossopulos W. , Wiles D. R.
Published: May 2006

The radiochemical yields of [Cp50Fe(CO2]• in neutron-irradiated [CpFe(CO)2]2 and [CpFe(CO)2]I are 6.9 and 14.8%, respectively. Other prominent products are [CpFe(CO)2]2-59Fe, 59Fe(CO)5, and 59FeCp2, in both target compounds.Thermal treatment at 75 °C increases the yields of 59Fe(CO)5, and of the radioactive target compound in both cases, and does not affect the yields of the other two products. The radioactive radical [Cp59Fe(CO)2]• is stable to 75° in the solid [CpFe(CO)2]2, and on dissolution is rapidly scavenged by iodine transfer from carrier [CpFe(CO)2]I.It is suggested that complex molecular products are not reformed following the nuclear activation, but are rather preserved during and despite the nuclear reaction. An effective "hot zone" need not contain more than two or three molecules.Production of [Cp59Fe(CO)2]• and [Cp59Fe(CO)2]2 is observed in neutron irradiated solutions of Fe(CO)5 and benzene with either FeCp2 or C5H6.
A Stereospecific Synthesis of the Denudatine Skeleton: Stereospecificity of the C/D Ring Construction by Diene Addition
Authors: Wiesner Karel , Ho Pak-Tsun , Oida Sadao
Published: May 2006

The diene 20 synthesized by the aziridine rearrangement method was shown to add maleic anhydride with complete stereospecificity to yield the adduct 21. The causes of this stereospecificity and its implications for the synthesis of denudatine type compounds are discussed.
Kinetics of the Nitrosation of Pyrrolidine and Proline
Authors: Okany A. , Massiah T. F. , Rubin L. J. , Yates K.
Published: May 2006

The kinetics of the nitrosation of pyrrolidine and proline have been investigated in buffer solutions of mildly acidic pH's in the temperature range 40–100 °C. The rate constants were determined and the enthalpy and the entropy of activation were calculated for both reactions. Examples are presented in which are estimated the maximum amounts of nitroso compounds formed under conditions relevant to meat processing.
Crystal Structure of Synthetic Mg-Whitlockite, Ca18Mg2H2(PO4)14
Authors: Gopal Ramanathan , Calvo Crispin , Ito Jun , Sabine W. K.
Published: May 2006

Crystals of synthetic Mg-whitlockite, Ca18Mg2H2(PO4)14, have been grown by hydrothermal techniques and their structure refined by full-matrix least-squares methods, using 1626 unique reflections measured with a Syntex [Formula: see text] automatic diffractometer, to a final R value of 0.046. The crystals have space group R3c with ZR = 1, a = 13.765(8) Å and α = 44.25(5)° with the equivalent hexagonal parameters a = 10.350(5), c = 37.085(12) Å and ZH = 3. The structure, although similar to that of βCa3(PO4)2, differs significantly. The structure contains interconnected infinite chains of polyhedra paralleling the hexagonal c axis with links in the chains consisting of three CaO8 polyhedra separated by two PO4 tetrahedra. Six of these chains surround a chain of MgO6 octahedra and PO4H groups which lie on the three-fold axes. These chains however contain only half the formula unit density of the calcium containing ones and a proton, presumably disordered, is attached to the oxygen atom on the triad axes.
Formation of Adducts in the Nitration of 2,3- and 3,4-Dimethylbenzonitriles, and their Rearomatization. A 1,3-Nitro Shift
Authors: Fischer Alfred , Greig Colin Campbell
Published: May 2006

Nitration of 2,3-dimethylbenzonitrile in acetic anhydride gives the adduct 2-cyano-3,4-dimethyl-4-nitro-1,4-dihydrophenyl acetate as well as the expected nitro substitution products. Similarly 3,4-dimethylbenzonitrile affords 2-cyano-4,5-dimethyl-4-nitro-1,4-dihydrophenyl acetate as well as the 3,4-dimethylnitrobenzonitriles. Thermolysis or decomposition in acetic acid of the adducts gives the original dimethylbenzonitrile and its 5-nitro derivative as the major products, the latter apparently being formed by an intramolecular 1,3-shift of the nitro group. Decomposition of the adducts under more strongly acidic conditions results in the elimination of nitrous acid and the formation of 2-cyano-3,4-dimethylphenyl acetate and 2-cyano-4,5-dimethylphenyl acetate, respectively. In acidified methanol the adducts undergo transesterification at the acetate function and 2-cyano-3,4-dimethyl-4-nitro-1,4-dihydrophenol and 2-cyano-4,5-dimethyl-4-nitro-1,4-dihydrophenol are obtained.
Intramolecular Bromoamination. Part I
Authors: Horning Donald E. , Muchowski Joseph M.
Published: May 2006

The addition of bromine to 2,2-diphenyl-4-pentenylamine (8a) resulted in the formation of 2-bromomethyl-4,4-diphenylpyrrolidine hydrobromide (10a), the structure of which was established by its mass spectrum and other properties. Analogous products were obtained from the corresponding methyl secondary amine and two methyl-substituted primary amines.The bromomethylpyrrolidines 10a and 10c gave the aziridines 11a and 11b on treatment with sodium hydride in DMF. Dry hydrogen bromide converted the unsubstituted aziridine 11a to 3,3-diphenyl-5-bromopiperidine hydrobromide (12a). Liberation of the methyl substituted bromomethylpyrrolidine 10b from the hydrobromide salt resulted in the spontaneous transformation to a single 2-methyl-3-bromopiperidine (12b) of unestablished stereochemistry.
Solar Ultraviolet Flux below 50 Kilometers
Authors: Ackerman M.
Published: May 2006

The available values of the solar flux from 1700 Å to 4000 Å are presented. The penetration of this radiation in the stratosphere is discussed and the role of scattering on direct and global radiation in the troposphere is emphasized.
The Reaction of 2,4,6-Trinitrotoluene and 2,4,6-Trinitrotoluene-d3 with Sodium Isopropoxide in Isopropyl Alcohol
Authors: Buncel E. , Norris A. R. , Russell K. E. , Sheridan P. , Wilson H.
Published: May 2006

The reaction of sodium isopropoxide with 2,4,6-trinitrotoluene (TNT) and TNT-d3 (deuterated methyl group) in isopropanol has been investigated using stopped-flow techniques. Two absorbing species, identified as a σ-complex and the TNT anion (TNT−) are formed in this reaction. The formation of TNT− involves a rate determining proton transfer as shown by the observation of an isotope effect[Formula: see text] A spectrum of the σ-complex was calculated from initial rate data and was observed experimentally at low temperatures (λmax = 435, 495 nm). The effects of added salts on rates and equilibria of σ-complex and TNT− formation have been determined.In this study the possible involvement of free alkoxide ions and ion-pairs in the reactions has been evaluated. The free alkoxide ion is the more reactive species in deuteron transfer whilst in σ-complex formation the free ions and ion-pairs have comparable reactivity. A rationale of this behavior is presented.The kinetic parameters are, for deuteron transfer: kiD = 850 ± 100 M−1s−1 at 30 °C, ΔH≠ = 14.9 ± 1.1 kcal mol−1, ΔS≠ = 5.1 ± 2.9 cal deg−1 mol−1; for σ-complex formation: k′ = 1870 ± 150 M−1 s−1 at 30 °C, ΔHσ≠ = 10.2 ± 0.3 kcal mol−1, ΔSσ≠ = −9.8 ± 1.1 cal deg−1 mol−1.
The Relationship Between Ormocastrine and Podopetaline
Authors: McLean Stewart , Misra Renuka
Published: May 2006

The difficulties that arose when an X-ray crystal structure analysis showed that podopetaline has the structure and stereochemistry previously assigned to ormocastrine have been resolved by showing that ormocastrine is in fact podopetaline hydrochloride. It has also been demonstrated that, of the other three constituents that had been isolated from O. semicastrata, 18-epiormosanine was obtained as its hydrochloride but ormosanine and piptanthine were free bases. The pKa values of the alkaloids have been determined.
Group V Chalcogenide Complexes of Boron Trihalides
Authors: Boorman P. M. , Potts D.
Published: May 2006

The preparation of the complexes BX3•R3PY (X=Cl, Br, I; R=Me, Ph, cyclohexyl; Y=S, Se) is reported. The corresponding BF3 adducts could not be isolated. The infrared spectra for all complexes are presented as well as the n.m.r. spectra for the methyl adducts. The shifts in ν(P—Y) upon co-ordination are amongst the largest ever reported for these ligands when they function as non-bridging species, and are in fact comparable to shifts observed in bridging situations. The spectral data are consistent with an increase in the B—Y bond strength as the atomic weight of X increases.
Composés d'addition de SbF5 avec H2O et HF. Formation d'ions hydronium
Authors: Bonnet B. , Roziere J. , Fourcade R. , Mascherpa G.
Published: May 2006

A differential thermal analysis study of solutions of SbF5 in H2O and HF has enabled us to determine the thermal treatments required to obtain the stable crystalline phases: SbF5•2H2O, 4SbF5•5H2O, SbF5•H2O, 3SbF5•2H2O, and SbF5•HF•2H2O.The SbF5 adducts were characterized by X-ray powder diagrams.The vibrational spectra of SbF5•2H2O and SbF5•HF•2H2O are consistent with the ionic structures H3O+SbF5OH− and H5O2+SbF6−.The other hydrates are simple donor-acceptor complexes with the structure H2O → SbF5, in which one water molecule is coordinated to the SbF5 and the others are bound by hydrogen bonds to the coordinated water molecule.
The High Temperature and Dilute Acid (HTDA) Procedure as a General Method of Replacing Aromatic Hydrogen by Deuterium. II
Authors: Werstiuk Nick H. , Kadai Tony
Published: May 2006

The preparation of aniline-d5, phenol-d5, and benzoic acid-d5 utilizing the conditions of high temperature and dilute acid (HTDA) is described.
Kinetic and Equilibrium Studies of the Reactions of 2,4,6-Trinitrotoluene and 2,4,6-Trinitrotoluene-d3 with Sodium and Potassium t-Butoxide in t-Butanol
Authors: Buncel Erwin , Norris Albert Richard , Russell Kenneth Edwin , Wilson Harold
Published: May 2006

The reactions of 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrotoluene fully deuterated at the methyl position (TNT-d3) with sodium and potassium t-butoxide in t-butanol have been studied. With TNT as the substrate, proton abstraction by ion-paired sodium or potassium t-butoxide appears to be the predominant reaction in solution. With sodium t-butoxide as base, the forward rate constant for proton abstraction at 30.0 °C (Kf,ip) is 6000 ± 400 M−1 s−1 while ΔH≠ and ΔS≠ for the reaction are 4.2 ± 0.3 kcal mol−1 and −27 ± 2 cal deg−1 mol−1, respectively. With TNT-d3 as the substrate, formation of a TNT-d3-t-butoxide ion σ-complex occurs simultaneously with deuteron abstraction. Specific rate constants for the two processes have been determined at 30.0 °C. Initial rate studies establish a hydrogen-deuterium kinetic isotope effect of 8 ± 1 for the formation of the anion in t-butanol.
Studies Relating to Aziridine Antitumor Antibiotics. Part II. 13C and 1H Nuclear Magnetic Resonance Spectra of Mitomycin C and Structurally Related Streptonigrin
Authors: Lown J. William , Begleiter Asher
Published: May 2006

Double irradiation experiments in the 100 MHz n.m.r. spectrum of mitomycin C allowed determination of vicinal coupling constants which provide information on the conformation of the antibiotic in solution. The natural abundance 13C spectrum and comparison with selected model compounds allowed assignment of the carbon resonances of mitomycin C. The 13C chemical shifts of the quinone ring carbons in mitomycin C have a bearing on the proposed stabilization in vivo. Similar studies on the antitumor antibiotic streptonigrin bearing the common aminoquinone moiety gave indications of conjugative interactions similar to those established for mitomycin C.
L'oxydation chromique et les esters chromiques
Authors: Richer Jean-Claude , Hachey Jean-Marie
Published: May 2006

Rates of decomposition of chromic acid esters derived from secondary alicyclic alcohols and rates of oxidation of these cyclanols by chromic esters derived from tertiary alcohols have been measured in anhydrous benzene. The results obtained are compared to those of other workers for reactions held in polar solvents. A mechanism is suggested to explain the observed results.
Hydride Reductions of 1-Phenyl-1-nonen-3 -one: Mass Spectrometry of 1-Phenyl-1-nonen-3-ols and Relative Stereochemistry of the Diastereoisomeric 4-Dimethylaminomethyl-1-Phenyl-1-nonen-3-ols
Authors: Taylor Wesley Gordon , Dimmock Jonathan Richard
Published: May 2006

The metal hydride reduction products of some styryl ketones and dimethylaminomethyl Mannich bases have been investigated. Sodium borohydride selectively attacked the carbonyl carbon atom to give the desired allylic alcohols. Reduction of 1-phenyl-1-nonen-3-one with lithium aluminum hydride gave 1-phenyl-3-nonanol which represents the conjugate addition product. Fragmentations of 1-phenyl-1-nonen-3-ol were compared to the modes of mass spectral breakdown of 4-phenyl-3-buten-2-ol, an allylic alcohol which is known to behave like a saturated ketone on electron bombardment. Peaks corresponding to the McLafferty ion and the loss of a methyl radical from this rearrangement product were observed. Certain Mannich bases were reduced to diastereoisomeric allylic amino alcohols. The separation, 1H n.m.r. spectroscopy, and relative stereochemistry of the diastereoisomers are discussed.
Champ de force de valence et modes normaux de vibration de la glycylglycine et du monochlorhydrate monohydrate de glycylglycine
Authors: Destrade Christian , Dupart Eliane , Joussot-Dubien Monique , Garrigou-Lagrange Chantal
Published: May 2006

The valence force field and normal modes of vibration of α-glycylglycine have been calculated using the vibrational spectra of ten isotopic derivatives, selectively labeled with deuterium or nitrogen-15. It is shown that this force field permits the determination of the frequencies of glycylglycine-hydrochloride in the solid state, despite a structure very different from that of the zwitterion. The agreement is particularly satisfying for those modes of vibration most sensitive to molecular conformation. It is thus possible to use this type of calculation to determine the conformation of an oligopeptide.
Entropy Production in Chemically Reacting Systems
Authors: Pritchard Huw O. , Labib Nabil I. , McElwain D. L. Sean
Published: May 2006

Numerical integration of the gasdynamic equations describing the coupling between vibrational relaxation and dissociation for a hydrogen–helium mixture in a plane shock wave shows that the total entropy is a completely monotonic function of time; this is found to be the case whether the system is considered to be isolated, or whether there is loss of energy or mass from the flow.
The Stereospecificty of α-Thiohemiaminal Reduction. A 300 MHz Proton Magnetic Resonance Investigation of Deuteride Reduction Products from 6,6′-Dihydroxythiobinupharidine and 6-Hydroxythiobinupharidine
Authors: LaLonde Robert T. , Wong Chun F. , Das Kala C.
Published: May 2006

Thiobinupharidine-6-d1 and thiobinupharidine-6,6′-d2, products obtained earlier from the sodium borodeuteride reduction of 6-hydroxythiobinupharidine and 6,6′-dihydroxythiobinupharidine, were examined in perdeuteriobenzene solution by 300 MHz p.m.r. Thiobinupharidine-6-d1 was found to contain 84% equatorial deuterium and 16% axial deuterium at the C-6 position. Thiobinupharidine-6,6′-d2 was found to contain 82% equatorial deuterium and 18% axial deuterium at C-6.
Systèmes aromatiques à 10 électrons π dérivés de l'aza-3a-pentalène. XI. Etude par résonance magnétique nucléaire de l'imidazo [1,2-b] pyrazole et du pyrazolo [1,5-a] benzimidazole
Authors: Elguero José , Fruchier Alain , Knutsson Leif , Lazaro René , Sandström Jan
Published: May 2006

Nuclear magnetic resonance spectroscopy has allowed us to determine the annular tautomerism in two [5,5]-heteroaromatic systems and the position of the acetyl group in their acetyl derivatives. In each case, the more stable compound is the one in which the imidazolic nitrogen atom is bearing H or COCH3. We have also found unusual couplings with the N—H in the N-unsubstituted compounds and abnormally high barriers for the azolides. These observations agree well with the hypothesis of a decrease in the aromaticity of the imidazolic part.
An Electron Spin Resonance Study of the Arylsilyl Adducts of Phenyl tert-Butyl Nitrone and Their Decomposition Kinetics
Authors: Adeleke Babatunde B. , Wong Sau-King , Wan Jeffrey K. S.
Published: May 2006

The formation and the stability of some arylsilyl adducts of phenyl tert-butyl nitrone were studied in a photochemical system using di-tert-butyl peroxide as solvent. The β-proton splittings of all the arylsilyl adducts, ranging from 5.6 to 8.3 G, are relatively larger than their carbon analogs, which are usually less than 4 G. The arylsilyl adducts are found to decompose in di-tert-butyl peroxide solvent by a first-order kinetics. The activation energy involved in the decomposition of a series of arylsilyl adducts varies from about 14 to about 9 kcal/mol, as the size of the silyl group increases. In all cases, very low values of the A factors (between 106 and 1010) were observed.
Infrared Spectra of Water in Crystalline Hydrates: KSnCl3•H2O, an Untypical Monohydrate
Authors: Falk Michael , Huang Chung-Hsi , Knop Osvald
Published: May 2006

Infrared spectra of polycrystalline KSnCl3•H2O were recorded between 4000 and 300 cm−1 at different degrees of deuteration and at temperatures between 30 and −160 °C. At low temperatures the spectra show a complexity indicative of the presence of several crystallographically distinct water molecules. These molecules occupy sites with nearly identical environments and at room temperature are spectroscopically indistinguishable. The environment of each of these molecules is asymmetric. Hydrogen bonds are very weak and probably highly bent. The water molecules are less separated from one another than in K2SnCl4•H2O and may share their potassium neighbors.
Reactions of Sodium Tetrahydroborate and Cyanotrihydroborate With Divalent Co, Ni, Cu, Pd, and Pt Chlorides In the Presence of Tertiary Phosphines
Authors: Holah David G. , Hughes Alan N. , Hui Benjamin C. , Wright Ken
Published: May 2006

The reactions of divalent Co, Ni, Cu, Pd, and Pt chlorides with NaBH4 and NaBH3CN in the presence of tertiary phosphines under inert atmosphere conditions have been examined. The nature of the product varies enormously depending upon reaction conditions, and compounds obtained include complexes involving coordinated BH4− and BH3CN− of the type MLn, MBLn, and MHBLn, (L = phosphine, B = BH4− or BH3CN−, n = 2, 3, or 4). The first univalent nickel and cobalt BH4 complexes are reported. Platinum abstracts the CN group from BH3CN− to form the species PtH(CN)L2. Infrared spectral data are reported and appear to indicate two types of bonding (M—N and M—H) between BH3CN− and metals. Some electronic reflectance spectra and magnetic properties are also reported, including those of Co(I) and Ni(I) species. Attempts are made to rationalize the data in terms of a suggested mechanism for the reduction of metal halides by NaBH4.
Partition Function Ratios of the Methyl Halides Differing Only in Isotopic Substitution
Authors: Bron Jan
Published: May 2006

By using the best available spectroscopic data for the force fields and geometries of the methyl halides, partition function ratios for these species are evaluated as a function of temperature. These ratios are of the type q(AXYZB)/q(12CH3B) in which q is the partition function; A is 12C, 13C, or 14C; X, Y, and Z are either 1H, 2H, or 3H; and B stands for either F, Cl, Br, or I. To the logarithm of these functions at the various temperatures (200–500 K) a curve is fitted with the equation [Formula: see text] All ratios are determined with respect to the unsubstituted 12CH3B molecule. Examples of the utility of the partition function ratios are given.
A Study of d-Orbital Effects in Esters of Trifluorothiolacetic Acid. A Comparison of Evidence from Dipole Moment and Kinetic Data
Authors: Bock E. , Queen A. , Brownlee S. , Nour T. A. , Paddon-Row M. N.
Published: May 2006

The dipole moments of a series of esters of trifluoroacetic acid and trifluorothiolacetic acid have been determined in benzene solution at 25 °C. The results are consistent with conjugative and hyperconjugative electron release by the hydrocarbon groups to the d-orbitals of sulfur. This conclusion is supported by data for the hydrolysis of these compounds in water or aqueous acetone.
Dielectric Behavior of the Aniline–Cyclohexane System in the Consolute Region
Authors: Lubezky I. , McIntosh R.
Published: May 2006

Measurements of ε′ and ε″ at 5 kHz are reported for the system aniline–cyclohexane in the region of the consolute temperature. No anomalously large values of ε′ and ε″were found in the region of concentration where the binodal curve is essentially flat. Traces of water increase the temperature for phase separation. An explanation in terms of the formation of molecular clusters is offered for the difference of behavior of this system and that of nitrobenzene – trimethyl pentane.
Isoxazole Hydrate
Authors: Gough S. R. , Garg S. K. , Ripmeester J. A. , Davidson D. W.
Published: May 2006

X-Ray, n.m.r., and dielectric studies show that the hydrate of isoxazole is a typical type II clathrate hydrate in structure, in reorientation rates of host and guest molecules, and in composition.
The Methyl Ethers of 2-Amino-2,6-dideoxy-D-galactopyranose (D-Fucosamine)
Authors: Perry Malcolm B. , Daoust Virginia
Published: May 2006

The 3-, 4-, and 3,4-dimethyl ethers of 2-amino-2,6-dideoxy-D-galactose (D-fucosamine) have been synthesized. 2-Amino-2,6-dideoxy-3,4-di-O-methyl-D-galactose was made by the methylation of methyl 2-acetamido-2,6-dideoxy-α-D-galactopyranoside to its 3,4-di-O-methyl derivative which was hydrolyzed to yield pure 2-amino-2,6-dideoxy-3,4-di-O-methyl-D-galactose hydrochloride. 2-Amino-2,6-dideoxy-3-O-methyl-D-galactose was made from methyl 2-acetamido-2-deoxy-3-O-methyl-α-D-galactopyranoside by conversion of its 6-sulfonate to the 6-deoxy-6-iodo derivative, followed by reduction to the 6-deoxy derivative which, on hydrolysis, gave 2-amino-2,6-dideoxy-3-O-methyl-D-galactose hydrochloride. 2-Amino-2,6-dideoxy-4-O-methyl-D-galactose was made from methyl 2-acetamido-2-deoxy-3,6-di-O-(p-tolylsulfonyl)-α-D-galactopyranoside which was methylated to yield the 4-O-methyl derivative and subsequent conversion of the latter compound to its 6-deoxy derivative, via its 6-deoxy-6-iodo derivative, followed by detosylation, gave methyl 2-acetamido-2,6-dideoxy-4-O-methyl-α-D-galactopy-ranoside convertible by acid hydrolysis to 2-amino-2,6-dideoxy-4-O-methyl-D-galactose hydrochloride.
Molecular Size Distribution in Random Polyfunctional Condensation with or without Ring Formation: Computer Simulation
Authors: Falk Michael , Thomas Ruth E.
Published: May 2006

We have re-examined the polymer size distribution in a model system initially composed of N0 monomeric units RAƒ, where each unit R carries ƒ identical functional groups A. Self-condensation is postulated to proceed at random by the formation of [Formula: see text] bonds until the fraction α of A groups have reacted. The controversy regarding the applicability of the Flory–Stockmayer (F.S.) and the Whiteway–Smith–Masson (W.S.M.) expressions to this model has been resolved. Two variants of this model are distinguished, depending on whether ring formation is allowed or forbidden. It is shown that in the limit of an infinite system the incidence of rings in the ringsallowed model tends to zero below the critical value of α, αc = 1/(ƒ − 1 ). Consequently, the limiting polymer size distributions for the rings allowed and ringsforbidden models coincide over the range [Formula: see text], and are both described by the F.S. expression. For the ringsforbidden model, the F.S. equation fails above αc, but for the rings allowed model it continues to apply over the entire accessible range [Formula: see text] The W.S.M. equation represents the limiting distribution for the polymerization process in which one functional group per monomer is singled out (A*) and bonding is restricted to [Formula: see text] pairs. In that process, and in the limit of an infinite system, rings are not formed over the entire attainable range of α, from 0 to 2/ƒ.
Azatropolones. Part II. The Schmidt Reaction of 2-Methoxy-5-methylbenzoquinone
Authors: Hughes Colin G. , Lewars Errol G. , Rees Alun H.
Published: May 2006

2-Methoxy-5-methylbenzoquinone undergoes reaction with sodium azide in sulfuric acid to give (a) 3-hydroxy-6-methyl-1H-azepin-2,5-dione, which undergoes ring contraction with base to give 5-methyl-4-pyridone-2-carboxylic acid; (b) 4-methoxy-7-methyl-1H-azepin-2,5-dione, which reacts with phosphorus oxychloride to give methyl 2-chloro-6-methylpyridine-4-carboxylate, not 2-chloro-4-methoxy-7-methyl-5H-azepin-5-one; (c) 7-methoxy-4-methyl-1H-azepin-2,5-dione. The reactions of these compounds are discussed and the evidence for their structures is presented.
The Product of Homotropylium Cation Photolysis
Authors: Christensen P. A. , Huang Y. Y. , Meesters A. , Sorensen T. S.
Published: May 2006

The product of homotropylium ion photolysis is the 1,2-dihydro-4H+-pentalenyl cation. CNDO/2 and analogies to cyclopentenyl cation rearrangements allow one to rationalize the formation of this product.
The Mass Spectrometry of the Pyrolysis Products of Some Tetraalkylammonium and Bistetraalkylammonium Bromides
Authors: Verrall Ronald E. , Burns John A.
Published: May 2006

The mass spectra of three tetraalkylammonium bromide salts and two series of bistetraalkylammonium bromide salts, one saturated and the other unsaturated, have been studied. Substitution is the major process which occurs in the pyrolytic decomposition of these quaternary ammonium bromides when placed in the probe of the mass spectrometer. This leads to the production of a tertiary amine and an alkyl halide. The substitution reactions which occur are influenced by the proximity of the bromide anion(s) to the positively charged quaternary nitrogen centers in the crystal lattice. As well, a shorter distance between the positive nitrogen centers favors substitution reaction by means of an electron inductive effect.
Some Rhodium(III) Complexes of Linear Tetraamines
Authors: Halliday Robert W. , Court Richard H.
Published: May 2006

We report the preparation of rhodium(III) complexes of 2,3,2 tet; 3,2,3 tet, 3,3,3 tet, and 3,4,3 tet. In the case of the [Rh(2,3,2 tet)Cl2]Cl complex, both the cis-&([a-z]+); and trans forms were isolated. In the remaining cases, only the trans form was isolated.
Reaction of Cuprate Reagents with Pyridine in the Presence of Chloroformate. A Novel Synthesis of 1,4-Dihydropyridine Derivatives
Authors: Piers Edward , Soucy Marcel
Published: May 2006

Reaction, under appropriate conditions, of lithium dialkyl- or diarylcuprates with pyridine in the presence of methyl chloroformate afforded, in good yields, 1-carbomethoxy-4-alkyl (or aryl)-1,4-dihydropyridines. Also formed, in limited but varying amounts (∼2–11%), were the corresponding 1,2-dihydropyridine derivatives.
Preparation, Infrared Spectra, Electronic Spectra, and Magnetic Moments of Copper(II) Complexes of N-Acetylglycine and Their Amine Adducts
Authors: Marcotrigiano G. , Pellacani G. C.
Published: May 2006

Compounds of the type [CuA2•H2O]2 and [CuA2•4H2O]2 have been prepared, where A is N-acetylglycine (aceturic acid). Amine adducts of the type CuA2B (B = piperazine, 2,2′-bipyridine, and 1,10-phenantroline) and CuA2B2 (B = N-methylpiperazine, piperidine, morpholine, pyridine, and ethylenediamine) were obtained by reaction of the amines with CuA2•4H2O. Each complex was characterized by elemental analysis, infrared spectrum, electronic spectrum, and magnetic moment. For the piperazine and ethylenediamine adducts a square-planar pattern of coordination about copper(II) ion is probable, while for the other amine adducts a square-pyramidal structure is proposed. For all the complexes the coordination of the N-acetylglycine occurs only through the terminal carboxyl oxygen in a monodentate arrangement.
The Crystal and Molecular Structure of Dichloro(acetylacetonato)-2,2′-bipyridylindium(III)
Authors: Contreras J. G. , Einstein F. W. B. , Tuck D. G.
Published: May 2006

The molecular structure of dicholoro(acetylacetonato)-2,2′-bipyridylindium(III) has been determined from three dimensional X-ray data collected by counter methods. The structure has been refined by least-squares techniques to a conventional R factor of 4.3% for the 3524 observed reflections. Crystals of Cl2In(acac)(bipy) are monoclinic, a = 11.340(3), b = 12.198(3), c = 14.330(3) Å, β = 120.25(2)°, z = 4, space group P21/c. The chloride ligands are cis, with In—Cl at distances of 2.443(1) and 2.394(1) Å; the In—O bond lengths are 2.124(3) and 2.164(3) Å, and the In—N bond distances are 2.276(4) and 2.299(4) Å.
Acid and Base Catalysis in the Oxidation of 6,7,8-Trimethyllumazine. I. Products of the Reaction
Authors: Oyama Kiyotaka , Stewart Ross
Published: May 2006

The permanganate oxidation of 6,7,8-trimethyllumazine (1), a pteridine derivative, is subject to catalysis by acids and bases. Above pH 3.5, the reaction products are 6,8-dimethyl-7-oxolumazine and formaldehyde. Below pH 3.5, the reaction products are hydroxybiacetyl and the methylamide of alloxanic acid.Oxidation of 1 by potassium trans-1,2-diaminocyclohexanetetraacetatomanganate(III) at pH 6.0 under an oxygen atmosphere gave the oxolumazine and formaldehyde. Under a nitrogen atmosphere coupled products were obtained, indicating that radical intermediates are formed with this oxidant.
Sulfur-free Penicillin Derivatives. VI. Synthesis of the 1-Oxacephem Ring System
Authors: Wolfe Saul , Ducep Jean-Bernard , Tin Kam-Chung , Lee Shui-Lung
Published: May 2006

The title compound has been synthesized by ring closure of an alkyl 2-(2′-chloro-3′-S-phthalimido-4′-oxo)azetidinyl-3-methyl-4-hydroxy-trans-2-butenoate using SN1 experimental conditions. The required E-allylic alcohols were obtained in two ways starting with an alkyl 2-(2′-chloro-3′-S-phthalimido-4′-oxo)azetidinyl-3-methyl-2-butenoate. The first involves allylic bromination with 1 molar equiv. of N-bromosuccinimide, conversion of the mixed Z- and E-allylic bromides into the mixed Z- and E-allylic formates, and deformylation to a mixture of E-alcohol and lactone. The alcohol was separated from the lactone via its tetrahydropyranyl derivative, and then regenerated. In the second route, allylic bromination was performed with 2 molar equiv. of N-bromosuccinimide and the resulting dibromo compound was converted into the β,γ-unsaturated olefin with zinc in acetic acid. Epoxidation with peroxytrifluoroacetic acid followed by exposure to triethylamine again afforded a mixture of E-alcohol and lactone. The u.v. spectrum of a 1-oxacephem shows a maximum at 266 nm.
Production de O2(b1∑g+), &([a-z]+);′ = 0, 1 et 2 par la reaction O(21D2) + O2(X3∑g−)
Authors: Gauthier Michel J. E. , Snelling David R.
Published: May 2006

The emissions of the 0–0 and 1–1 bands of the O2(b1∑g+→X3∑g− transition have been observed at 762 and 771 nm respectively in the photolysis of O3/O2/Ar mixtures at 253.7 nm. From the dependence of these emissions on the concentration of oxygen for various ozone concentrations the following conclusions can be drawn: one-quarter to one-half of the O2(b1∑g+) molecules formed in the energy transfer from O(21D2) to O2(X3∑g−) are in the vibrational state &([a-z]+);′ = 1, the remainder being in the &([a-z]+);′ = 0 state. Furthermore, it is shown that O3 deactivates O(21D2) eight times more effectively than O2. The relative rates of the reactions of O2(b1∑g+), &([a-z]+);′ = 1 with O2 and O3 are also discussed and approximate values of 0.6 and 1.0 are determined relative to the rate of the reaction of O2(b1∑g+), &([a-z]+);′ = 0 with O3.
A Study of the Effect of Solvent and Temperature on the Electron Paramagnetic Resonance Parameters and Linewidths of Copper(II)bis(Diethyldithiocarbamate)
Authors: Herring F. Geoffrey , Tapping Robert L.
Published: May 2006

The effect of varying solvent and temperature on the e.s.r. parameters and linewidths of copper(II) bis(diethyldithiocarbamate) has been studied. The temperature and solvent dependences of the isotropic hyperfine coupling constant (a0) have been interpreted in terms of vibronic and axial ligation effects. The rotational correlation time, τR, of Cu(DEDC)2 has been measured in the solvents employed. The values of τR measured at 300 K have been used to obtain the anisotropic interaction parameter, κ, which is found to correlate roughly with the dipole moment and molar refractivity of the solvent.
Synthesis and Crystal and Molecular Structures of the N,N-Dimethylethanol-aminogallane and N,N-Dimethylethanolaminogallium Dimethyl Dimers
Authors: Rettig Steven J. , Storr Alan , Trotter James
Published: May 2006

Crystals of the N,N-dimethylethanolaminogallane dimer 1a are monoclinic, a = 8.540(1), b = 7.0433(7), c = 12.227(6) Å, β = 92.94(3)°, Z = 2, space group P21/c and crystals of the N,N-dimethylethanolaminogallium dimethyl dimer 1b are orthorhombic, a = 15.608(3), b = 11.655(2), c = 10.266(2) Å, Z = 4, space group Pccn. Both structures were determined by Patterson and Fourier syntheses and were refined by full-matrix least-squares procedures to final R values of 0.039 and 0.053 for 1062 and 1155 reflections with 1 ≥ 3σ(I) respectively. Both structures feature well-separated centrosymmetric dimeric units occurring via the formation of four-membered Ga2O2 rings. The five-coordinate gallium atoms have distorted trigonal bipyramidal geometry. Steric interactions between methyl groups in 1b are believed responsible for the lengthening of the axial Ga—N distance from 2.279(3) in 1a to 2.471(4) Å in 1b. Other bond distances are: for 1a; Ga—O (axial), 2.053(3), Ga—O, 1.911(3), Ga—H, 1.50(7) and 1.73(5), O—C, 1.369(5), N—C, 1.466 – 1.485(6), C—C, 1.512(7), and mean C—H, 1.05; for 1b; Ga—O (axial), 2.078(3), Ga—O, 1.913(3), Ga—C, 1.936(6) and 1.948(7), O—C, 1.382(7), N—C, 1.452–1.482(7−8), C—C, 1.516(9), and mean C—H, 1.01 Å.
Electrochemiluminescence of Phenanthrene-d10: A Possible Case of Efficient Triplet–Triplet Annihilation
Authors: Periasamy N. , Santhanam K. S. V.
Published: May 2006

Electrochemiluminescence (e.c.1.) of mixed phenanthrene(Ph)-d10-oxidant and Ph-h10-oxidant systems have been studied. Emission from excited singlet state of Ph-d10 or Ph-h10 is observed. On the basis of energetics of the electron transfer reaction, triplet-triplet annihilation is postulated to give the excited singlet state of Ph. Comparison of these results with photoluminescence of Ph-d10, shows efficient triplet–triplet annihilation occurs in e.c.1.
The Catalysis of Proton Exchange in Creatinine by General Acids and General Bases
Authors: Srinivasan R. , Stewart Ross
Published: May 2006

The rate of exchange of methylene protons in creatinine has been followed in D2O by means of proton magnetic resonance spectroscopy over a range of acidity from pD 12.22 to DA –4.24. A plot of the logarithm of the rate against acidity function is in the form of a "W", one wing of which involves reaction of neutral creatinine with hydroxide ion, and the other diprotonated creatinine with water. The central peak represents reaction of protonated creatinine with a molecule of creatinine acting as base. The reaction is subject to catalysis by buffers.The activation of exchange produced by protonating the substrate is designated protonactivatingfactor, p.a.f., and factors affecting its size are discussed in terms of structure.
Isotopic Scrambling and Mass Spectral Fragmentation Studies with 2-Ferrocenylethyl and 2-Ferrocenylethyl-1,1-D2 Systems
Authors: Lee Choi Chuck , Chen Shi-Chow , Sutherland Ronald G.
Published: May 2006

In a number of reactions including the solvolysis of 2-ferrocenylethyl-1,1-d2 tosylate (1—OTs-1-d2) in 60% et OH, HCOOH, or CF3CH2OH, the reaction of 1—OH-l-d2 with SOCl2 in tetrahydrofuran or toluene, and the treatment of 1—Cl-1-d2 with AlCl3 in CH2Cl2, no scrambling of the D-label from C-1 to C-2 was observed, indicating the absence of any 1,2-ferrocenyl shifts in any of these SN1 type of reactions. In the mass spectral fragmentation of 1—X and 1—X-1-d2, where X = OTs, OH, OCHO, OCH2CF3 and Cl, a number of common features were observed, including [Formula: see text] and [Formula: see text]
Chemistry of Proximal π-Bond Systems. Part III. Synthesis of Substituted Benzopolycyclic Hydrocarbons
Authors: Butler D. N. , Snow R. A.
Published: May 2006

A series of 21 bridged, vicinal, exocyclic dimethylene hydrocarbons (1–21) have been converted to the related benzopolycyclic dimethyl esters (C1–C21) by oxidation of their respective dimethyl acetylenedicarboxylate Diels–Alder adducts (B1–B21).This synthetic sequence represents an excellent, general route to aromatic ring-substituted benzopolycyclic hydrocarbons.
Substrate Inhibition in the Hydrolysis of Hippuric Acid Esters by Carboxypeptidase A
Authors: Murphy Joe , Bunting John W.
Published: May 2006

The dependence of initial velocity upon substrate concentration has been examined in the carboxypeptidase A catalyzed hydrolysis of the following hippuric acid esters (at pH 7.5, 25°, ionic strength O.5): C6H5CONHCH2CO2CHRCO2H: R=CH3; CH2CH3;(CH2)2CH3; (CH2)3CH3; (CH2)5CH3; CH(CH3)2; CH2CH(CH3)2; C6H5; CH2C6H5. All of these esters display marked substrate inhibition of their enzymic hydrolyses. With the exception of R=CH3, the velocity-substrate concentration profiles for each of these esters can be rationalized by the formation of an E.S2 complex which, independent of the alcohol moiety of the ester, reacts approximately 25 times more slowly than the E.S complex. For most of these esters, the formation of E.S2 approximates ordered binding of the substrate molecules at the catalytic and inhibitory sites. While binding at the catalytic site is markedly dependent on the nature of the R group, binding of a second substrate molecule to E.S is not significantly affected by the nature of the R side chain. For R=C6H5, the D ester is neither a substrate nor a competitive inhibitor of the hydrolysis of the L-ester but can replace the L-ester at the binding site which is responsible for substrate inhibition. The kinetic analysis suggests that this behavior of D and L -enantiomers is also typical of the other esters examined (except possibly R=CH3). For R=CH3 only, substrate activation also seems to occur prior to the onset of substrate inhibition at higher substrate concentrations.
An Epitetrathiodioxopiperazine with 3S,6S Configuration from Hyalodendron sp.
Authors: Strunz George M. , Kakushima Masatoshi , Stillwell Merlyn A.
Published: May 2006

(3S,6S)3-Benzyl-6-hydroxymethyl-1,4-dimethyl-3,6-epitetrathiopiperazine-2,5-dione has been isolated from cultures of Hyalodendron sp. The same compound is produced when hyalo–dendrin is heated with methanol–hydrochloric acid.
Protonation du N,N-diméthylformamide: étude par spectrométries vibrationnelle et électronique
Authors: Combelas P. , Costes M. , Garrigou-Lagrange C.
Published: May 2006

Infrared and Raman spectra of acidic (hydrochloric or sulfuric) aqueous solutions of dimethylformamide indicate the existence of a single protonation equilibrium.[Formula: see text]The pK for this reaction was evaluated as −1.35 ± 0.05 from u.v. spectra; a less precise value (−1.1 ± 0.5) was obtained from Raman spectra. This result disagrees with earlier conclusions which favored the existence of two ionization equilibria for dimethylformamide. [Journal translation]
Sulfur-Free Penicillin Derivatives. V. Preparation, Hydrolysis, and Oxidative Rearrangement Of Fused Oxazoline–Azetidinones
Authors: Wolfe Saul , Lee Shui-Lung , Ducep Jean-Bernard , Kannengiesser Gérard , Lee Wha Suk
Published: May 2006

Chlorinolysis of an anhydropenicillin affords a 2-(2′-chloro-3′S-amino, -acylamino or -phthalimido-4′-oxo)azetidinyl-3-methyl-2-butenoyl chloride, as a mixture of 2′R (cis) and 2′S (trans) epimers in which the 2′R epimer usually predominates. Hydrolysis of the acid chloride and treatment of the carboxylic acid with aqueous bicarbonate causes cyclization, in the case of a 3′-acylamino substituent, to a 2R-6-(1′-carboxy-2′-methyl-prop-1-enyl)-1-oxa-3,6-diaza-4S,5R-bicyclo[3,2,0]hept-2-ene-7-one. The mechanisms of these transformations are discussed, and alternative routes to such fused oxazoline–azetidinones are also presented.The oxazolines undergo ready hydrolysis to sulfonic acid salts of 2-(2′R-acyloxy-3′S-amino-4′-oxo)azetidinyl-3-methyl-2-butenoates upon treatment with the hydrate of a sulfonic acid in acetone solvent. Neutralization of these salts proceeds without O → N acyl transfer, because acylation yields a diacylated azetidinone in which the new acyl substituent is attached to nitrogen. Monobromination of the allylic methyl groups of these salts, followed by treatment with 2 molar-equiv. of triethylamine, leads to a deep-seated rearrangement, in high yield, to an oxazinone. The mechanism of this rearrangement and, in particular, the role of acylimines in this and related reactions, including the biosynthesis of penicillin, are discussed.
Allowed and Forbidden Reaction Paths for the H2 + D2 Exchange Reaction
Authors: S. Wright James
Published: May 2006

Symmetry arguments and abinitio s.c.f. calculations (double-zeta basis set) are used to show that the exchange reaction H2+ D2 → 2HD could proceed in a concerted fashion through a six-center transition state. The computed barrier height of 90 kcal/mol for this process lies below the experimental dissociation energy of H2 (but above the computed dissociation energy) and also below the energy required for exchange through a four-center transition state. Either the termolecular(2 + 2 + 2 ) or bimolecular(4 + 2 ) cycloadditions are thermally allowed. The presence of a transition metal would allow the reaction to proceed through a four-center geometry, leading to the formation of a possibly stable metal-H4 complex.
The Structure and Stability of Ni(II) Complexes of Thiourea and Related Ligands
Authors: Eaton D. R. , Zaw K.
Published: May 2006

A number of Ni(II) complexes of thiourea, N-methylthiourea, N,N′-dimethylthiourea, N-naphthylthiourea, N,N′-diethylthiourea, and ethylene thiourea have been studied in acetone solution by proton magnetic resonance, magnetic susceptibility measurements, and conductivity measurements. In solution these complexes have tetrahedral, square planar, and octahedral geometries. In many cases equilibria between compounds with different geometries exist. Such equilibria have been studied as a function of temperature. The factors determining the relative stability of Ni(II) compounds with different geometries are discussed. In the present series of compounds it is concluded that the charge on the metal ion has the predominant influence in determining geometry. Some qualitative results on ligand exchange rates and mechanisms are also reported.
Aril Azines. II. Hydrogenation of p-Tolil Monoazine
Authors: Yates Peter , Levi E. M.
Published: May 2006

Hydrogenation of p-tolil monoazine (1b) over palladium-on-charcoal gives as the major product 4,5-dihydro-5-(p-toluyl)-3,4,5-tri-(p-tolyl)-1H-pyrazol-4-ol (2b), which has previously been obtained by treatment of 1b with sodium methoxide. Several minor products are formed, which include p-tolualdehyde, p-toluic acid, and p-toluamide, p-tolunitrile, p-tolualazine, and 3,4,5-tri-(p-tolyl)-4H-pyrazo-4-ol (9). The structure of the last compound, which is also formed on reduction of 1b with sodium borohydride, was established by its independent synthesis from 1,2,3-tri-(p-tolyl)-1,3-propanedione by oxidation with lead tetraacetate followed by treatment with hydrazine. It is suggested that 2b arises via reduction of a C=N bond of 1b and aldol ring closure. The minor hydrogenation products are of interest in that their formation involves C—C hydrogenolysis; it is suggested that this is initiated by addition of a hydrogen atom to a carbonyl carbon atom of 1b.