bluuebunny/crossref_metadata_2025 huggingface dataset:
Etude de la formation d'exciplexes du 1,3,6,8-tetraphénylpyrène et du 1,2,3,4-tetraphénylnaphtalène
Authors: Rullière Claude , Denariez-Roberge Marguerite-Marie
Published: May 2006

We wish to report the formation of fluorescent complexes of 1,3,6,8-tetraphenyl-pyrene and 1,2,3,4-tetraphenylnaphtalene with N,N-dimethylaniline. The effect of substitution on the formation of and the possibility of laser action from this complex is discussed. An indirect measurement of the electron affinity is deduced.
Absorption Cross Sections of Stratospheric Molecules
Authors: Hudson R. D.
Published: May 2006

Photoabsorption cross sections necessary for calculations of the equilibrium conditions in the stratosphere fall into two distinct classes: cross sections for molecular oxygen and ozone, which control the transmission of solar radiation; cross sections for minor atmospheric species which are optically thin to solar radiation, and which are needed to calculate their rates of dissociation.The principal absorption features of molecular oxygen are absorption bands of the Schumann–Runge system between 175 and 200 nm and a weak dissociation continuum which extends from 175 to 260 nm. The band structure consists of many sharp rotational lines, and it is necessary to calculate cross sections using measured band parameters. Two measurements of the line widths for these bands have obtained large line widths (∼1 cm−1) indicating predissociation. The agreement between the two sets of data is good for only a few lines. This has implications in the calculation of the transmission of solar radiation to the lower stratosphere. The continua have been measured by four groups. The results agree, within the respective experimental errors, near 220 nm, but disagree near 250 nm.Ozone has a continuous absorption spectrum between 175 and 300 nm with band structure above 300 nm. Four sets of data are available which agree within ±2%. The cross section above 300 nm is temperature dependent. The cross sections for the minor species are in general not as well known. In nitric oxide, carbon monoxide, ammonia, and sulfur dioxide, band structure dominates the absorption spectrum, and cross sections have been measured at insufficient spectral resolution. Other species, such as nitric acid, hydrogen peroxide, water vapor, carbon dioxide, nitrous oxide, and nitrogen dioxide, have continua over the entire spectra range from 175 to 300 nm. Cross sections for these species have been measured; however, cross sections for many molecules, e.g., N2O5, NO3, etc., have not been studied.
Measurements of NO, NO2, and HNO3 in the Stratosphere
Authors: Schiff H. I.
Published: May 2006

Atmospheric models designed to predict the effect on the ozone budget of the injection of nitric oxide into the stratosphere by high-flying aircraft require a knowledge of the NO concentration in the unperturbed atmosphere. Moreover, a monitoring program will require a base line against which to measure the magnitude of any future stratospheric pollution. A number of measurements have recently been reported, not only on NO, but also on NO2, and HNO3 which are interconverted by stratospheric photochemistry. All the methods but two employ "remote-sensing" optical absorption or emission techniques. Infrared solar absorption using long optical paths at twilight has proven to be very sensitive in detecting trace atmospheric constituents but quantitative interpretation appears to be very difficult. Chemiluminescence and direct "particle" sampling have provided insitu measurements.The spread in the reported values of mixing ratios is very large for NO2, appreciable, but smaller for NO, and smallest for HNO3. Insufficient data are available to assess how much of this spread is due to measurement errors and how much is due to natural variability in the mixing ratios. Intercomparisons of the measurements for different nitrogen compounds are made by consideration of the principal chemical reactions governing their relative concentrations. Discrepancies exist which should diminish as more accurate chemical rate data and synoptic stratospheric measurements become available.
Infrared Measurements of Stratospheric Composition
Authors: Farmer C. B.
Published: May 2006

The observational techniques and results of i.r. measurements of the minor and trace molecular composition of the lower stratosphere are reviewed. Emphasis is given to those theoretical aspects of the formation of emission and absorption spectra which affect the quantitative interpretation of observational data in terms of the vertical distribution of observed molecular species.The principal experimental techniques currently being used are briefly reviewed, followed by a detailed summary of current knowledge of the abundances and spatial variability of the known minor constituents. The question of the determination of the minimum detectable concentration of a constituent molecule and its relationship to the instrumental parameters, the molecular transition intensities, and observation geometry is discussed; upper limit concentrations are given for some additional species of importance in current stratospheric studies.
Electronic Chemiluminescence in M + X2 Reactions: Dissociation Energies of the Alkaline Earth Monohalides MX (M = Ca, Sr, Ba; X = F, Cl, Br)
Authors: Menzinger Michael
Published: May 2006

Electronic chemiluminescence has been observed for nine reactions of Group IIa metal atoms (M = Ca, Sr, Ba) with dihalogen molecules (X2 = F2, Cl2, Br2).In all cases one or more electronically excited states of the monohalide MX* were observed. Continuum emission, presumably due to dihalides MX2*, was seen in all systems, and the emission intensity increased in the order F2 < Cl2 < Br2. Recombination to form MX2* appears thus to be a fairly general process in these systems.From the highest vibrational levels of MX populated in the upper electronic state(s) we have calculated the following lower limits to the ground state dissociation energies D0° (MX) (in kcal/mol):[Formula: see text]Information on the vibrational state distributions of the excited MX* is discussed from a qualitative point of view. Accordingly, the fluorides are formed with inverted vibrational distributions, which bear clear evidence of the direct nature of the interaction dynamics. The electronically excited chlorides and bromides, however, tend to be formed with monotonically decreasing, near-statistical distributions. This is consistent with the formation of long lived collision complexes. Reasons for these trends are discussed in terms of the energetics of the complete decomposition.
Some Reactions of Isothiazoline-3- and -5-thiones
Authors: Chauhan Mohinder S. , Hassan Mohamed E. , McKinnon David M.
Published: May 2006

Reactions of certain 3-bromothio-1,2–dithiolium bromides with primary amines produce isothiazoline-5-thiones. These compounds form adducts of varying stability with acetylenic reagents. Comparison of their reactivity with the isomeric isothiazoline-3-thiones indicates that while the former react rapidly to form only monoadducts, the latter react more slowly to form monoadducts which react more rapidly to form diadducts.
The Rates and Products of Addition of 4-Chlorobenzenesulfenyl Chloride to a Series of Side Chain Methyl Substituted Styrenes
Authors: Schmid George H. , Garratt Dennis G.
Published: May 2006

The rates of addition and the product compositions have been determined for the addition of 4-chlorobenzenesulfenyl chloride to a series of seven side chain methyl substituted styrenes in 1,1,2,2-tetrachloroethane at 25°. Unlike the addition to the corresponding series of methylated ethylenes, the effect of the methyl groups is not cumulative. The effect of the methyl groups depends upon whether or not the β-methyl group is cis to the phenyl. When it is cis, the rate of addition is decreased compared to styrene and substitution of additional methyl groups has only a small effect on the rate of addition. In compounds lacking a cis-β-methyl group the rate of addition more closely resembles that for addition to the methylated ethylenes. Steric hindrance between the cis-methyl and phenyl groups is believed to be the cause of this difference in behavior between the ethylene and styrene series.
Secondary Isotope Effects on the Ionization of 2-Nitropropane
Authors: Kresge A. J. , Drake D. A. , Chiang Y.
Published: May 2006

The equilibrium isotope effect on the acid dissociation of 2-nitropropane in wholly aqueous solution at 25° was found to be KH/KD = 1.23 ± 0.03 for complete deuteration of both methyl groups; the kinetic isotope effect for reaction of the same substrate with hydroxide ion, kH/kD = 1.09 ± 0.01; and the kinetic isotope effect for reaction with tris-(hydroxymethyl)-methylamine, kH/kD = 1.10 ± 0.01; both of the latter also refer to wholly aqueous solution at 25° and are for complete deuteration of both methyl groups. It is shown that the equilibrium isotope effect is largely, and the kinetic isotope effects probably partly, hyper conjugative in origin, thus supporting a hyper conjugative explanation of the anomalous effect of methyl groups on nitroalkane ionization.
Some Thermodynamic Properties of Indium Trichloride, Indium Hydroxide, and Indium Trioxide
Authors: Campbell Alan N. , Kartzmark Elinor M. , Bhatnagar Om N.
Published: May 2006

The equilibrium diagram of the system InCl3–H2O as been determined as far as it can be followed. From these freezing points, the activity coefficients at the freezing temperatures have been calculated. The heats of solution and of dilution of hydrated and of anhydrous indium chloride, in water, have been determined, as well as the heats of solution of indium hydroxide and of indium oxide (In2O3) in concentrated hydrochloric acid. From these data, the heat of the reaction: 2In(OH)3 = In2O3 + 3H2O and the molar enthalpies of InCl3 and In(OH)3 have been calculated.
Methyl Cyclopentadienecarboxylate Formation in the Methanol Quenched Vapor Phase Thermolysis of Methyl Salicylate
Authors: Mamer O. A. , Rutherford K. G. , Seidewand R. J.
Published: May 2006

Cyclopentadienylidenecarbonyl, the principle thermolytic fragment of methyl salicylate in the vapor phase, undergoes a rapid recombination with the methanol liberated in the initial fragmentation to yield monomeric methyl cyclopentadienecarboxylate. Reaction of this last ester with some dienophiles is reported, and, in the case of dimethyl acetylenedicarboxylate, adducts are obtained that suggest that the ester exists as a mixture of 1- and 2-substituted cyclopentadienes. No trace is found of a neutral fragment of mass 120 corresponding to the base peak in the 70 eV spectrum of methyl salicylate.
Oxidation of CO to CO2 in Melts Containing V2O5 and Alkali Oxides
Authors: Block-Bolten A. , Bertrand B. J. M. , Flengas S. N.
Published: May 2006

The conversion of CO to CO2 in the presence of V2O5 dissolved in a melt containing K2O and other alkali metal oxides was investigated in the temperature range 440 to 640 °C.The results indicate that CO may be oxidized to CO2 with a high overall reaction efficiency in a system of reactors connected in series. Molten salt solutions have the advantage, over solid "catalysts" in that they operate without being poisoned. The oxidizing capacity of these solutions is limited only by the depletion of V2O5 in the melts due to reaction and by the presence of large amounts of insoluble V2O4 solid which is a reaction product. The melts may be reactivated by treatment with oxygen.
Acid Catalyzed Rearrangements of Structurally Constrained Tricarbonyl(trans-pentadienyl)iron Cations
Authors: Jablonski C. R. , Sorensen T. S.
Published: May 2006

Both the tricarbonyl(1,4-dimethylene-cis, cis, trans, cis-hexa-1,3-dienyl)iron (secondary) and the tricarbonyl(1,4-dimethylene-5-methyl-cis, cis, trans-hexa-1,3-dienyl)iron (tertiary) cations, which cannot convert to a 5h-cis pentadienyl system via a simple bond rotation, can be prepared at low temperature in strong acid media from their related alcohol complexes. The secondary as well as the tertiary ions rearrange to give the thermodynamically more stable tricarbonyl-(1-alkylcyclohexa-1,3-dienyl)iron cation via an acid catalyzed pseudo first order process. The rate of rearrangement of the secondary ion is much faster than that of the tertiary ion indicating a substantial amount of residual positive charge on the exocyclic (β) carbon in the complexed trans-pentadienyl carbonium ions.
1,4-Diphenyl-1,4-butadiyl Diradicals from Thermolysis of cis- and trans-3,6-Diphenyl-3,4,5,6-tetrahydropyridazine
Authors: Kopecky Karl R. , Soler José
Published: May 2006

Reduction of 3,6-diphenyl-2,3,4,5-tetrahydropyridazine with sodium amalgam in ethylene glycol at 130° produces a 1:2 mixture of cis- and trans-3,6-diphenylpiperidazine (cis- and trans-4) from which trans-4 was obtained by fractional crystallization. Oxidation of cis- and trans-4 with oxygen gave cis- and trans-3,6-diphenyl-3,4,5,6-tetrahydropyridazine (cis- and trans-1). For thermolysis of trans-1 at 62.5° Ea = 25.3 ± 1.1 kcal/mol and ΔS≠ = 0.4 ± 3 e.u. At 63° the relative yields of styrene, cis- and trans-1,2-diphenylcyclobutane (cis- and trans-7) formed from cis-1 are 55.3, 30.1, and 18.6% and those formed from trans-1 are 59.1, 1.7, and 39.2%, respectively. For the 1,4-diphenyl-1,4-butadiyl diradical from thermolysis of cis-1kcleav/krot = 1.1 and kcyc/krot, = 1.5 whereas for that of trans-1kcleav/krot = 10 and kcyc/krot = 14. At 205° cis-7 decomposes to yield a 4.8:1 ratio of styrene: trans-7. This is near the ratio expected if the initial geometries of the diradicals produced from cis-1 and cis-7 are similar.
Aldol Type Condensations of β-Keto Ester Dianions
Authors: Huckin Stuart Nicholas , Weiler Larry
Published: May 2006

The dianion of methyl acetoacetate reacts with ketones and aldehydes to yield δ -hydroxy-β-keto esters. These hydroxy esters can be dehydrated to the corresponding γ,δ-unsaturated-β-keto esters which are useful in annelation reactions to form cyclic β-keto esters. The dianion of methyl acetoacetate does not appear to undergo conjugate addition to simple α,β-unsaturated ketones, instead only carbonyl addition occurs.
Methyl Radicals in Solid Acetonitrile: Decay or No Decay
Authors: Sargent Frederick Peter , Bailey Marshall Grant , Gardy Edward Michael
Published: May 2006

A comparison of both the e.s.r. spectra and the thermal stability of the radicals produced in γ radiolysis and 185 nm photolysis of acetonitrile shows that the former are not free methyl radicals. The initial species formed by γ radiolysis can be converted by photobleaching into a methyl radical weakly associated with a cyanide ion. The methyl radical of this CH3---CN−pair decays via hydrogen abstraction, whereas the free methyl radicals produced by 185 nm photolysis of acetonitrile are quite stable at 77 K. We ascribe the low energy of activation for the hydrogen abstraction reaction in the γ irradiated samples not primarily to quantum mechanical tunnelling but to perturbation by the cyanide ion.
Virial Partitioning of Charge Distributions and Properties of Diatomic Hydrides; NaH ↔ HCl
Authors: Bader R. F. W. , Messer R. R.
Published: May 2006

The virial partitioning method is applied to the ground states of the AH diatomic hydrides (A = Na, Mg, Al, Si, P, S, Cl) in their neutral and charged forms. This is a spatial partitioning of a molecular system, the partitioning surfaces, which in this instance divide each molecule into an (A) and an (H) fragment, being determined by the topographical features of the electronic charge distribution. The kinetic and potential energies of the virial fragments are well-defined quantities and in addition, satisfy the quantum mechanical virial relationship. Most important, virial fragments faithfully reflect the chemistry of the individual elemental components of molecular systems, the fragments and their properties remaining nearly constant or changing when in different systems, in accordance with chemical expectations.The populations of (H) in combination with (A) are used to order the first- and second-row elements (neutral and charged) in their abilities to abstract or donate charge relative to hydrogen. This ordering is of general interest as the population of (H) in AH changes little on passage to the general (most stable) polyatomic AHn. The virial equations are used to relate the kinetic energy of binding in AH to the changes in the potential energies and total energies of each fragment. One finds, in comparison of first- and second-row results, that the nature of the most important stabilizing interactions in the formation of AH change in a similar manner across the two rows of elements, but the change in the second-row set occurs two members to the right with respect to the first-row set.
Réactions des ions iso-C4H8+ et t-C4H9+ avec l'isobutène en phases liquide et gazeuse
Authors: Collin G. J.
Published: May 2006

The radiolysis of neopentane has been studied in gas and liquid phases. It was shown that, in the liquid phase, the iso-C4H8+ ion reacts at least as quickly with isobutene as with methylcyclopentane. The t-C4H9+ ion reacts at least 10 times more rapidly with isobutene and the main reaction is one of resonant transfer of a proton with isotubene; fewer than 5% of the t-C4H9+ ions add to isobutene. In the gas phase, the condensation reaction is more important than that of resonant proton transfer since proton transfer represents only 30% of the total reaction: [Formula: see text] Finally, the resonant transfer of a deuteron occurs about 2.9 more slowly than proton transfer. [Journal translation]
Cis–Trans Conformational Dependence of the Carboxylate pK in Glycylsarcosine
Authors: Morton R. A. , Danyluk S. S.
Published: May 2006

A study is reported of the influence of pD upon the 220 MHz proton n.m.r. spectrum of the dipeptide glycylsarcosine (Gly-Sar) in D2O at 23 °C. Variation of pD produces characteristic changes in chemical shifts for Gly-Sar and an analysis of the pD–chemical shift curves shows that the carboxyl pK differs significantly in cis and trans conformers, having values of 3.01 ± 0.03 and 3.39 ± 0.03, respectively. From a consideration of molecular models and theoretical calculations, it is concluded that the pK difference arises from a closer juxtaposition of terminal carboxyl and amino groups in the cis isomer.
The Behavior of 1-Phenyl-2-benzimidazolinethione and 1-Phenyl-2-benzimidazolinone upon Electron Impact and Pyrolysis
Authors: Lin Denis C. K. , Thomson Michael L. , DeJongh Don C.
Published: May 2006

The mass spectra of 1-phenyl-2-benzimidazolinethione (3) and 1-phenyl-2-benzimidazolinone (4) have been compared with their pyrolysis products and similarities have been found. In the 70 eV mass spectrum of 3, the base peak results from the loss of H•; at low ionizing voltages, this path and a competing path, loss of S, are the only ones which remain. At 650° in a stream of N2, 1-phenylbenzimidazole (8, 20%) formed from the loss of S and benzimidazo-[2,1-b]benzothiazole (5, 11%) formed by loss of H2. The major fragmentation paths in the mass spectrum of 4 are loss of CHO• and NCO•. At 950°, phenazine (6, 35%) formed by loss of CH2O, and carbazole (7, 14%) formed by loss of HNCO. In each pyrolysis, 65–70% of the starting material was recovered or accounted for.
Electronic and Vibrational Relaxation in Sulfur Dioxide Vapor
Authors: Caton Robert B. , Gangadharan A. R.
Published: May 2006

Vibrational relaxation in the A1B1 and a3B1 excited electronic states of sulfur dioxide vapor has been observed by direct spectroscopic means. The effects of vibrational relaxation on the phosphorescence quantum yield have been investigated in the pressure range from 0.6 to 200 mTorr of pure sulfur dioxide and in mixtures of sulfur dioxide with He, N2, CO2, and SF6. Phosphorescence persists at the lowest pressure reached for excitation at 302.0 or 313.1 nm, contrary to previous reports. The mechanism for the production of sulfur dioxide phosphorescence for the wide bandwidth excitation used here (185–370 cm−1) is consistent with recent evidence for two fluorescing species provided by Brus and McDonald from laser-excitation experiments.
Polymorphism in n-Alkylammonium Halides. A Wide Line Nuclear Magnetic Resonance Study of the Chlorides C11—C15
Authors: Tsau J. , Gilson D. F. R.
Published: May 2006

Wide line n.m.r. studies of the n-alkylammonium chlorides C12—C15 show a nonreversible behavior which parallels that observed using differential scanning calorimetry. For samples which have been heated above the nonreversible transition the temperature dependence of the line width and second moment resemble that of the shorter chain compounds of this series; one transition due to the onset of chain rotation and a second higher temperature transition due to more extended motion probably of a translational nature. A change in crystal structure is proposed in order to explain the nonreversibility.
The Hydrogen Bond Energies in ClHCl− and Cl−(HCl)n
Authors: Yamdagni R. , Kebarle P.
Published: May 2006

The equilibrium constants for the gas phase reactions: Cl−(HCl)n = Cl−(HCl)n−1 + HCl, (n, n−1) were measured at different temperatures with a pulsed electron beam high pressure mass spectrometer. This allowed determination of ΔGn,n−10, ΔHn,n−10, and ΔSn,n−10 for reactions with n = 1 to n = 4. The enthalpy change for the reaction: (ClHCl)− = Cl− + HCl was ΔH1.00 = 23.7 kcal/mol. This value is much higher than the literature value of 14.2 kcal/mol based on Born cycles. The stabilities of the Cl−(HCl)n clusters are compared with those of OH−(H2O)n and Cl−(H2O)n measured earlier. It is found that the (ClHCl)− is nearly as stable as the (HOHOH)− species but that the stabilities of the higher Cl−(HCl)n clusters decreases much more rapidly than that of OH−(H2O)n. The initial strong interaction in (ClHCl) is assumed to be due to the high polarizability of Cl. For large n this effect becomes unimportant. Cl−HOH is much more weakly bound than (ClHCl)−, however, at high n the Cl−(H2O)n interactions become more favorable.
The Nucleophilic Displacement of the Nitrate Group. 1. The Hydrolysis of a Series of Benzyl Nitrates in Water
Authors: Koshy Kalavelil Matthew , Robertson Ross Elmore
Published: May 2006

The temperature dependence of the rates of hydrolysis of a series of substituted benzyl nitrates in water provided estimates of the heat capacities of activation. These values varied with the substituent over a wide range (−28 → −101 cal mol−1 deg−1).An approximate parallelism has been found to exist between the ΔCp≠ values and kinetic α-deuterium effects obtained for the nitrates and chlorides.While recognizing the existence of specific factors contributing to individual differences, the relative values of these parameters for the individual members of the two series provide a useful measure of the ionic character of the transition state.
The Near-ultraviolet Absorption Spectrum of Diimide in Liquid Ammonia and its Decomposition between −65 and −38 °C
Authors: Back R. A. , Willis C.
Published: May 2006

The near-ultraviolet absorption spectrum of diimide in liquid ammonia at −50 °C is shifted about 500 Å to the red compared with the gas-phase spectrum, with λmax = 4000 Å. The spectrum is also broadened and the vibrational structure largely obscured. It is suggested that hydrogen bonding is responsible for these changes.Diimide is much more stable in liquid ammonia between −65 and −38 °C than in the gas phase at room temperature. A first-order decay is observed with Arrhenius parameters of A = 1.9 × 103 s−1 and E = 6.6 kcal/mol; this is always preceded by a more rapid, higher-order initial decay which may be related to the rapid decomposition observed during vaporization.
Characterization of Monohalogen and Monopseudohalogen Derivatives of Dimethylgermane
Authors: Barker Geoffrey K. , Drake John E. , Hemmings Raymond T.
Published: May 2006

The high yield syntheses of Me2GeHX (X = F, Cl, Br, I) and Me2GeHPs (Ps = CN, N3, NCO, NCS, OAc) are reported. The dimethylgermane derivatives are identified and characterized by various physical methods and by cleavage reactions where appropriate. A normal coordinate analysis based on a modified valence force field provides confirmation of the assignments for all the fundamental frequencies, except the torsional modes, in the vibrational spectra of the monohalogeno(dimethyl)germanes, Me2GeHX.
The Effect of Bond Function Polarization on the l.c.a.o.–m.o.–s.c.f. Calculation of Bond Angles and Energy Barriers
Authors: Jarvie John O. , Rauk Arvi , Edmiston Clyde
Published: May 2006

The effect of including polarization into a flexible s, p basis set by use of bond functions is studied in the systems H2O, NH3, H2O2, and N2H4. In all cases a decrease and subsequent improvement in calculated bond angles is found. Barriers to nitrogen inversion are also significantly improved. Bond function polarization alone does not account for the anti rotation barrier in H2O2 although it does lead to stabilization of the gauche form relative to the anti form. The effect on molecular charge distributions is to allow movement of charge into the bonding regions. The results indicate that bond functions are an efficient means of introducing polarization into a basis set and lead to an improved agreement between calculated and experimental geometric and energetic parameters.
Mass Spectra of C-Amino- and C-Azido-l,2,4-triazoles
Authors: Heitke Bruce T. , McCarty C. Gordon
Published: May 2006

A study of low resolution mass spectra of 1,2,4-triazoles shows that fragmentations of C-amino-l,2,4-triazole nuclei are analogous to the three fragmentation modes reported for pyrrole. The extent to which these fragmentations account for the peaks in the mass spectra depends on the substituents of the 1,2,4-triazoIes. Mass spectra of C-azido-l,2,4-triazoles cannot be interpreted by the three modes found for pyrrole. Without exception, their mass spectra contain a base peak which is shown, with the aid of deuterium labeling, to represent an ion formed by the loss of four nitrogen atoms plus the substituent on the endocyclic nitrogen atom.
Studies on Theoretical Psychotogens. Synthesis of O-Methylated Analogs of Catecholamine Neurotransmitters and Metabolic Precursors
Authors: Butterick J. R. , Unrau A. M.
Published: May 2006

The catecholamine analogs (±)-1-(3,4-dimethoxyphenyl)-2-alanine (1), β-(3,4-dimethoxyphenyl)ethylamine (2), (±)-1-(3,4-dimethoxyphenyl)-2-amino propane (3), (±)-erythro, threo-α-aminomethyl-3,4-dimethoxybenzyl alcohol (4), and (±)-erythro, threo-α-methylaminomethyl-3,4-dimethoxybenzyl alcohol (5) have been synthesized and optimized yields are reported. The availability of certain carbon-14 compounds has dictated logical starting points in the synthesis of 14C-tagged analogs. These syntheses were designed for metabolic and disposition work in connection with a pilot project concerned with the aetiology of schizophrenia with particular reference to the Osmond–Smythies – Harley-Mason hypothesis (2) of 1952.
Electron Spin Resonance Studies in Aqueous Solution: Titanium(III) in the pH Region 1.0–3.5
Authors: Premović Pavle Ilija , West Paul Ronald
Published: May 2006

In aqueous solutions of titanium(III) between pH 1.0 and 3.5 a single line e.s.r. signal is recorded with g = 1.9408 ± 0.001 and linewidth 95 ± 3 G. Evidence is presented in support of a hydrolyzed metal ion complex [Ti(OH)2(H2O)4]+ as the likely active species.
The Synthesis and Reactions of Chiral Sulfonium Ylids
Authors: Campbell Stewart J. , Darwish D.
Published: May 2006

Treatment of (−)-ethylmethylsulfonium phenacylid, (−)-1, in THF at room temperature with 15 equiv. of benzoic anhydride, acetic anhydride or 1 equiv. phenyl isocyanate produces the corresponding (−)-ethylmethylsulfonium diacylmethylids, (−)-5, (−)-6, and (−)-8. Treatment of (−)-1 with dimethyl sulfate in acetone gives (Z)-(+)-ethylmethyl-α-methoxy-β-styrylsulfonium methyl sulfate, (+)-10. Resolution of (±)-10 via its DBT salt and conversion to perchlorate gives the corresponding vinyl perchlorates (+)- and (−)-13. Under the resolution conditions the ketal perchlorates, (−)- and (+)-ethylmethyl-2,2-dimethoxy-2-phenylethylsulfonium perchlorate, (−)- and (+)-14, are also obtained. The rates of racemization at 50° in benzene of 1, 5, 6, and 8 are 39.7, 55.5, 106, and 79.1 × 10−5 s−1 respectively. The rates of racemization at 50° in methanol of 10, 13, and 14 are 1.93, 2.08, and 5.64 × 10−5 s−1. Racemization is proposed to proceed via pyramidal inversion. The synthetic potential of chiral sulfonium ylids is discussed with respect to their ease of racemization.
Thyroid Hormone Stereochemistry. II. Molecular Structure of Thyronine HCl Ethyl Ester Monohydrate
Authors: Camerman Arthur , Camerman Norman
Published: May 2006

The three-dimensional structure of L-thyronine, the non-iodinated physiologically inactive analog of thyroxine, has been determined by single crystal X-ray diffraction and compared to the active thyroid hormones. The compound crystallized as the monohydrate of thyronine hydrochloride ethyl ester in the monoclinic space group P21 with cell dimensions a = 10.502, b = 5.165, c = 17.940 Å, β = 109.74°. The structure was solved by Patterson methods to find the chloride ion and iterative Fourier maps to locate the rest of the atoms. Refinement was by anisotropic full-matrix least squares to convergence at R = 0.048.The two phenyl rings adopt a twisted orientation with respect to each other with angles of −37° and −67° between the plane of the inter-ring ether linkage and the planes of the α- and β-rings, respectively. This orientation differs considerably from that found in the iodinated thyronines. The conformation of the alanine side chain is remarkably similar to that of the alanine in the iodinated thyronines.
Redox Interchange Reactions of Halogenoplatinum(IV) Complexes. pH Dependence of the Hexabromoplatinate(IV)–Iodide Reactions
Authors: Johnson David W. , Poë Anthony
Published: May 2006

Successive stages in the reaction of the complex [PtBr6]2− with iodide have been reexamined with particular attention to their pH dependence. A reassignment of two of the three stages is necessary although the intimate mechanism remains unchanged. Reoxidation of [PtBr4]2− produced by the slow reduction of [PtBr6]2− with iodide leads to a mixture of trans-[PtBr4I(OH2)]− and trans-[PtBr4I(OH)]2−. Rate constants for reaction of iodide with the aquo- and hydroxy-complexes have been determined, as well as a value of 3.7 for the pKa of the aquo complex.
Sur la réduction de polyméthyldihydro-2,3 phénalènones-1 par l'hydrure de lithium et d'aluminium
Authors: Costakis E. , Canonne P. , St-Jean R.
Published: May 2006

The reduction of some polymethyl-2,3-dihydro phenalen-1-ones by lithium aluminum hydride yields a mixture of cis and trans isomers; the percentage of each isomer depends to a considerable extent on its structure. Indeed, for some, the trans isomer predominates while for others the cis isomer is obtained in up to 88% yields. Moreover, in the particular case in which the trans isomer is formed in low yields, its preferred conformation is trans diaxial.The steric constraints which render certain transition states unfavourable during the attack of the hydride are discussed with the aid of spectroscopic data on the alcohols obtained. [Journal translation]
The Infrared and Raman Spectra of Trifluoronitrosomethane
Authors: Shurvell Herbert F. , Dass Shiv C. , Gordon Robert D.
Published: May 2006

The infrared spectrum of gaseous CF3NO has been studied in the region 4000–35 cm−1. The infrared spectrum of the condensed phase has also been recorded and a complete vibrational assignment is proposed. Attempts to record the Raman spectrum have been hampered by photolysis. A frequency of 50 cm−1 for the CF3 torsional mode has been estimated from combination and hot bands. This corresponds to a barrier to internal rotation of approximately 425 cal/mol (150 cm−1). A normal coordinate analysis has been carried out and potential energy distributions, and valence and symmetry force constants are reported.
Etude de l'oxydation des éthylènes RCH=CH2 et R1(R2)C=CH2 par le Tl(NO3)3 dans le méthanol
Authors: Grignon J. , Fliszár S.
Published: May 2006

The distribution of products formed in the oxidation by Tl(N03)3 of the olefins RCH=CH2 and R1R2C=CH2 in methanol has been studied. The monosubstituted ethylenes (R = alkyl) lead to a diether RCH(OCH3)—CH2OCH3 and to a ketone RC(O)CH3, the latter being formed in an amount of 40–55%; when R=CH2Cl only the diether is formed. With the disubstituted ethylenes R1R2C=CH2, the ratio of the rate constants for the formation of the isomeric ketones k1 (implying the migration of R1) and k2 (implying the migration of R2) is related to the polar Taft constants by the equation log (k2lk1) = ρ*(σ2* − σ1*) with ρ* = −4. This indicates that the migration of the better electron donor occurs preferentially. In addition to the ketone mixture (∼10–15%), ∼75–80% of the diether and ∼10–20% of the aldehyde are formed. [Journal translation]
Pulse Radiolytic Formation of Solvated Electrons, Ion-pairs, and Alkali Metal Anions in Tetrahydrofuran
Authors: Salmon G. A. , Seddon W. A. , Fletcher J. W.
Published: May 2006

Pulse radiolysis of solutions of alkali metal cations in tetrahydrofuran (THF) demonstrates the formation of solvated electrons es−, alkali metal cation-ion pairs (M+, es−), and alkali metal anions M−. This paper describes the spectra, extinction coefficients, and radiolytic yields of es−, lithium, sodium, potassium, and cesium species in THF. The reaction kinetics are complex but largely involve reactions A and B[Formula: see text]with the concomitant disappearance of all three species by reaction with radiolytically produced radicals. Rate constants and ion-pair dissociation constants for es− and the sodium and potassium species are presented and compared with data established from studies of blue solutions of alkali metals dissolved in THF.
Electron Mobilities and Ranges in Solid Neopentane: Effect of Liquid–Solid Phase Change
Authors: Shinsaka Kyoji , Freeman Gordon R.
Published: May 2006

The mobility of thermal electrons, the radiolysis free ion yield, and the penetration range of epithermal electrons in neopentane increase on going from the liquid to the solid phase at the triple point (257 K). The mobility is u = 71 cm2/V s in the liquid at 258 K and 154 cm2/V s in the solid at 257 K; the density normalized penetration range of the secondary electrons in X-radiolysis is bGPd = 1.25 × 10−6 g/cm2 in the liquid (296−258 K) and 1.72 × 10−6 g/cm2 in the solid (253−202 K). The increases at the triple point are presumably due to the greater degree of order in the solid. Electron mobility in the solid increases with decreasing temperature, u(solid) ≈ 6.8 × 105T−3/2 cm2/V s. The scattering length of neopentane is ∼8 Å in the solid and ∼9 Å in the liquid near the triple point.
SN2 Displacement at Tertiary Carbon
Authors: Edwards Oliver E. , Grieco Ciro
Published: May 2006

Evidence is presented for classical SN2 displacement of bromine by azide ion from a tertiary α-bromo lactone, a tertiary α-bromo ester, and two tertiary α-bromo ketones.
Stereochemical Implications from the Conformational Analysis of the Seven-membered Ring in 5-Oxabenzocycloheptene
Authors: Canuel Louis , St-Jacques Maurice
Published: May 2006

The computer analysis (LAOCN-3 program) of the p.m.r. spectrum of 5-oxabenzocycloheptene (3) at −105° has provided values for all coupling constants about the C3—C4 bond, while the complete line-shape simulation (DNMR program) has provided the following activation parameters: ΔG≠ = 9.5 kcal/mol (at −57°), ΔH≠ = 9.9 kcal/mol, and ΔS≠ = 1.5 e.u. A novel long distance (transannular) deuterium isotope effect has been discovered during the analysis of the spectrum of a partially deuterated derivative of 3. A comparison of the p.m.r. parameters for 5-oxabenzocycloheptene and benzocycloheptene provides the basic data from which stereochemical and conformational inferences can be made for more complex derivatives in this series.
The Reaction of Methyl Radicals with Molecular Hydrogen
Authors: Kobrinsky Peter C. , Pacey Philip D.
Published: May 2006

Mixtures of neopentane and hydrogen were pyrolyzed in a flow system at 826–968 K and 27–400 mm Hg. Measurements of the yields of CH4 and C2H6 at various conditions enabled calculation of the rate constant for[Formula: see text]at 926 and 829 K. The Arrhenius plot of these and earlier measurements from 372 to 1370 K is a curve, which can be represented by[Formula: see text]
New Route to Cyclic Azomethine Imines
Authors: Ip P. C. , Ramakrishnan K. , Warkentin J.
Published: May 2006

Cyclic azomethine imines, in which the ring is four-membered, have been synthesized by thermal decomposition of the readily available 2-hydrazono-Δ3-1,3,4-oxadiazolines. Possible mechanisms, involving the intermediacy of an iminooxirane, are discussed.
Arrhenius Parameters for Reaction of the tert-Butylperoxy and 2-Ethyl-2-propylperoxy Radicals with some Nonhindered Phenols, Aromatic Amines, and Thiophenols
Authors: Chenier J. H. Bernard , Furimsky Edward , Howard James Anthony
Published: May 2006

Preexponential factors and activation energies are reported for the transfer of a hydrogen atom from phenol, β-naphthol, aniline, β-naphthylamine, thiophenol, and β-naphthalenethiol to a tertiary alkylperoxy radical ((CH3)3COO• and C2H5C(CH3)2OO•). The A-factors fall in the range 2 × 104 to 2 × 107 M−1 s−1 and increase in the order C6H5SH ~ β-C10H7SH ~ β-C10H7NH2 < C6H5NH2 ~ β-C10H7OH < C6H5OH while the activation energies fall in the range 1 to 5 kcal mol−1 and increase in the order C6H5SH ~ β-C10H7SH < β-C10H7NH2 ~ β-C10H7OH < C6H5OH ~ C6H5NH2. Differences in activation energies and preexponential factors are not consistent with a reaction mechanism which attributes low activation parameters solely to an equilibrium between the reactants and a hydrogen bonded free radical – reactant complex, followed by H-atom transfer within the complex.
Catalytic Hydrogenation of Unsaturated Carboxylic Adds Using N,N-Dimethylacetamide Solutions of Ruthenium(I) Chlorides
Authors: Hui Benjamin C. , James Brian R.
Published: May 2006

N,N-Dimethylacetamide solutions of dimeric ruthenium(I) chlorides catalyze homogeneously the hydrogenation of ethylene and unsaturated carboxylic acids under mild conditions. Kinetic and mechanistic studies show that the catalysis involves a monomeric Ru(I) complex which forms reversibly a steady state concentration of a Ru(III)H2 species; this reacts with olefinic substrate to yield saturated product by two successive single hydrogen atom transfers with regeneration of the Ru(I) catalyst. The overall hydrogen addition to fumaric acid is cis. Hydrogenation of maleic acid is accompanied by an efficient isomerization to fumaric acid.
Synthesis of 4-O-β-D-Galactopyranosyl-L-rhamnopyranose
Authors: Bebault Gwendolyn M. , Dutton Guy G. S. , Funnell Norman A.
Published: May 2006

4-O-β-D-Galactopyranosyl-L-rhamnopyranose has been synthesized in 60% yield by condensation of 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl bromide with methyl 2,3-O-isopropylidene-α-L-rhamnopyranoside using mercuric cyanide in acetonitrile (Helferich reaction). The disaccharide is a syrup but the derived alditol and alditol peracetate are crystalline compounds.
Acid and Base Catalysis in the Oxidation of 6,7,8-Trimethyllumazine. II. Kinetics and Mechanism
Authors: Stewart Ross , Oyama Kiyotaka
Published: May 2006

The kinetics of the oxidation of 6,7,8-trimethyllumazine, 1, by permanganate in aqueous solution is examined. The pH–rate plot shows a minimum at pH 3.5 and there is catalysis by buffers. Above pH 3.5 the 7-keto compound, 5, is produced by a general base catalyzed route the rate of which is identical to that of the reaction that causes exchange at the 7-methyl group. The kinetic isotope effect for oxidation of the 7-CD3 compound is 6.89 at 31.4°.Below pH 3.5 scission of the pyrazine ring occurs, there is a small isotope effect, and the rate is somewhat faster than that observed for exchange of the 7-methyl group. There appear to be three routes leading to product; one, a permanganate-independent reaction catalyzed by general acids, a second which is also permanganate independent and involves hydration of the substrate, and a third which is permanganate dependent and involves attack by permanganate on the conjugate acid of the substrate.The utility of oxidation as a means of locating hydration sites in heterocyclic compounds is discussed and some comments are made on the mechanism of the enzymic oxidation of the ribityl analog of 1.
ω-Aldehydo Sugars Prepared by Ninhydrin Oxidation
Authors: Gibson Alan R. , Melton Laurence D. , Slessor Keith N.
Published: May 2006

The reaction of ninhydrin with 6-amino-6-deoxy-hexopyranosyl sugars has been investigated. 6-Aldehydocyclohexaamylose and 1,2:3,4-di-O-isopropylidene-α-D-galacto-hexodialdo-1,5-pyranose have been prepared by oxidative deamination of 6-amino-deoxycyclohexaamylose and 6-amino-6-deoxy-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose, respectively, using ninhydrin. The preparation of the two aldehydes by the ninhydrin reaction is compared with the method of photolysis of the corresponding azido sugars. The mass spectra of the perdimethylsilyl derivatives of cyclohexaamylose and O-methyl oxime of 6-aldehydocyclohexaamylose have been recorded.
The Molecular Structure of Trimethylindium by Vapor Phase Electron Diffraction
Authors: Barbe Gerald , Hencher J. Lawrence , Shen Quang , Tuck Dennis G.
Published: May 2006

The molecular structure of trimethylindium has been redetermined by vapor phase electron diffraction. The independent structural parameters assuming three-fold axial symmetry based on the rg distances and their estimated uncertainties (2σ) are r(InC) = 209.3 ± 0.6 pm, r(CH) = 114 ± 3 pm, and < HCIn = 112.7 ± 0.8°. A slight nonplanarity (3.0 ± 2.5°) was attributed to a shrinkage effect in [Formula: see text] of 0.4 pm. The analysis was insensitive to the rotational position of the methyl groups relative to the InC3 frame. The root mean square amplitudes were not accurate due to a problem with the indium phase factor.
Rearrangement Studies with 14C. XL. The Acetolysis of 2-Phenylethyl-1-14C Triflate
Authors: Lee Choi Chuck , Unger Don
Published: May 2006

2-Phenylethyl-1-14C triflate (1-OTf-1-14C) was synthesized by the inverse addition of equivalent amounts of 1-OH-1-14C and pyridine to trifluoromethanesulfonic acid anhydride. Solvolysis of 1-OTf-1-14C in unbuffered HOAc resulted in about 32% rearrangement of the 14C-label from C-1 to C-2, a value that is almost the same as that observed for the analogous acetolysis of 1-OTs-1-14C. Partial reaction of 1-OTf-2-d2 in HOAc-d4 showed that unreacted 1-OTf-d2 was isotopically scrambled, indicating the occurrence of ion-pair returns. Acetolysis of 1-OTf-1-14C in the presence of added NaN3 or NaN3 and NaOAc, however, gave results indicating differences in behaviors between 1-OTf and 1-OTs and it is concluded that the acetolysis of 1-OTf and 1-OTs are mechanistically similar but not identical.
Formation of Adducts in the Nitration of p-Xylene. Exchange and Rearomatization Reactions of p-Xylene Adducts
Authors: Fischer Alfred , Ramsay John Neilson
Published: May 2006

Nitration of p-xylene in acetic anhydride gives as the major product cis and trans isomers of the adduct 1,4-dimethyl-4-nitro-1,4-dihydrophenyl acetate (1) as well as 2-nitro-p-xylene. The acetoxynitro adducts 1a and 1b are stereospecifically cleaved to the hydroxynitro adducts 2a and 2b, respectively, by sodium methoxide. Acid-catalyzed exchange of OAc in 1 for OCH3, OCHO, OCH2C6H4CH3-p occurs and is nonstereospecific. Rearomatization of 1 gives 2-nitro-p-xylene, side-chain (benzylic) derivatives, and 2,5-xylyl acetate. The relevance of these reactions to side-chain substitution of arenes under electrophilic conditions is discussed.
Electrochemical Reduction of Pyrazines into Dihydropyrazines. Preparation of Dihydropyrazines
Authors: Armand Joseph , Chekir Khaled , Pinson Jean
Published: May 2006

The electrochemical reduction of several pyrazines in an alkaline hydroorganic medium leads to 1,4-dihydropyrazines too easily oxidizable to be isolated. These derivatives isomerize into 1,2- or 1,6-dihydropyrazines, the rate of this reaction depending among other things on the pH and on the cosolvent. The different chemical and electrochemical preparations of dihydropyrazines are discussed. It is shown that 3,6-dihydro-2,5-diphenylpyrazine and 1,6-dihydro-2,5-diphenylpyrazine are in thermodynamic equilibrium.
The Fluoridation of Nonstoichiometric Calcium Hydroxyapatite. An Infrared Study
Authors: Amberg C. H. , Luk H. C. , Wagstaff K. P.
Published: May 2006

Calcium deficient hydroxyapatites were impregnated to varying degrees with fluoride in very dilute solutions of NaF at room temperature. Ca/P ratios were determined before and after fluoridation. Phosphate loss upon fluoridation was consistent with an initial mechanism of OH− vacancy filling by F−, with equivalent amounts of PO43− ions escaping to restore charge balance. Infrared measurements confirmed previous evidence of OH/F exchange and the formation of [Formula: see text] hydrogen bonds, which increased with progressive thermal activation, considerable exchange having occurred already at 120 °C and possibly below. The first signs of lattice collapse occurred near 600 °C, with the fluorided sample exhibiting somewhat better stability.
Concertedness in the Thermolysis of Some 1-Pyrazolines
Authors: Crawford Robert J. , Ohno Masatomi
Published: May 2006

not available
The Photochemical Reactivity of Some Benzoylthiophenes. III. The Effect of an Adjacent Methyl Group on the Excited State Reactivity of 2-Benzoylthiophene
Authors: Arnold D. R. , Clarke Jr. B. M.
Published: May 2006

The ultraviolet absorption and phosphorescence emission spectra of 2-(2-methylbenzoyl) thiophene (1), 2-benzoyl-3-methylthiophene (2), 2-benzoyl-4-methylthiophene (3), and 2-benzoyl-5-methylthiophene (4) are reported and analyzed. Partial energy diagrams are constructed. The lowest triplet is assigned as a π,π* state of the 2-thienoyl chromophore in every case. Photocycloaddition of isobutylene to the carbonyl group was observed with 1 and 2. The oxetanes are thermally unstable; olefins 1-(2-thienyl)-1-(2-methylphenyl)-2-methylpropene (from 1) and 1-phenyl-1-(2-(3-methylthienyl))-2-methylpropene (from 2) were formed and characterized. Irradiation of 1 and 2 in O-deuteromethanol did not lead to incorporation of deuterium; no reaction was observed. These results are discussed in terms of the existing generalizations potentially useful for predicting photochemical reactivity.
The Far Infrared Spectra and X-Ray Powder Diffraction Patterns of the Structure I Hydrates of Cyclopropane and Ethylene Oxide at 100 °K
Authors: Bertie John E. , Bates Frances E. , Hendricksen David K.
Published: May 2006

This paper presents the far-infrared spectrum and X-ray powder diffraction pattern of the structure I hydrate of cyclopropane at 100 °K, and the powder diffraction pattern of the isostructural ethylene oxide hydrate at 100 °K. Between 360 and 100 cm−1 the absorption by cyclopropane hydrate is essentially identical to that by ethylene oxide hydrate, but is shifted to low frequency by about 2%. This shift is undoubtedly related to the hydrogen bonds being slightly longer in cyclopropane hydrate, whose cubic lattice parameter is 11.98 ± 0.02 Å compared to 11.89 ± 0.02 Å for ethylene oxide hydrate, both at 110 ± 20 °K. The absorption by cyclopropane hydrate below 100 cm−1 decreases rapidly with decreasing frequency; this confirms that the absorption plateau observed for ethylene oxide hydrate between 100 and about 50 cm−1 is due to primarily rotational vibrations of ethylene oxide. A recent statement, that the orientational disorder of the water molecules need not be invoked to explain the far infrared spectrum of ice 1 h, is disputed.
Conversion of Bicyclo[2.2.2]octane Systems into Tricyclo[3.2.1.02,7]octanes: A Third Synthesis of The Diterpenoid Trachylobane
Authors: Kelly Ronald B. , Beckett Barry A. , Eber Jeno , Hung Hing-Kwok , Zamecnik Jiri
Published: May 2006

The cyclization of bicyclooctane systems to tricyclooctane systems is discussed with particular reference to stereochemical aspects as encountered during the total syntheses of ishwarane and trachylobane. Of special interest are the homoallylic cyclizations. A third, convenient synthesis of trachylobane via a reductive homoallylic cyclization is reported.