bluuebunny/crossref_metadata_2025 huggingface dataset:
Lanthanum ion catalysis of nucleophilic displacement reactions of monoesters of methyl phosphonic acid
Authors: Withey R. J.
Published: May 2006

The catalytic effects of lanthanum ion on the rate of hydrolysis of p-nitrophenyl hydrogen methylphosphonate in aqueous solution at pH > 7.0 are reported. Increases in rate by a factor of about 3.6 × 104 have been observed. No such catalysis was found for diesters of methylphosphonic acid.
Decomposition of lauroyl, decanoyl, and octanoyl peroxides in solution
Authors: Guillet J. E. , Gilmer J. C.
Published: May 2006

The thermal decomposition from 50 to 250° of lauroyl, decanoyl, and octanoyl peroxides in solution in a high molecular weight hydrocarbon was studied. These peroxides are convenient sources of C-11, C-9, and C-7 straight-chain aliphatic free radicals, whose reactions may be considered as models for the higher molecular weight radicals formed during thermal cracking of polyolefins.The ratio of disproportionation to combination for these radicals is about 0.2, which is very similar to the values obtained for lower alkyl radicals in the gas phase. This ratio appears to be relatively independent of temperature. Intramolecular chain transfer, which results in the isomerization of the radical, occurs at the higher temperatures, and the process has an apparent activation energy of about 2 kcal per mole.The product distribution indicates that at reaction temperatures up to 250° a statistically random distribution of alkyl radicals is never achieved in solution. Since the radicals are formed in pairs, they tend to react with each other rather than with radicals formed from other peroxide molecules. This is demonstrated by the near absence of cross-combination products when two different peroxides are decomposed in the same solution simultaneously at 70°. At 250°, some cross-product is formed but less than one-fifth of the amount expected if the radicals were uniformly distributed in the solution. The activation energy for the formation of cross-product is of the same order as that for diffusion. The significance of these results in terms of the classical picture of "cage reactions" is discussed.
Substitutional and solvation effects on conformational equilibria. Effects on the interaction between opposing axial oxygen atoms
Authors: Lemieux R. U. , Pavia A. A.
Published: May 2006

Evidence based both on nuclear magnetic resonance and rotation data primarily obtained from methyl 3-deoxy-β-L-erythro-pentopyranoside and a number of its derivatives is interpreted to show that the electrostatic repulsion between the oxygen atoms at the 2 and 4 positions is substantially less when these oxygens are linked to acyl groups than when in the form of either methyl ethers or as hydroxyl groups hydrogen bonded to solvent. Also, experimental evidence is presented which requires the hydrogen bridge between two axially disposed hydroxyl groups to be substantially strengthened by hydrogen bonding of the free hydroxyl by solvent.
Branched-chain sugar nucleosides. IV. 9-(3-Deoxy-3-C-"hydroxymethyl"-β(and α)-D-allofuranosyl and ribofuranosyl)adenine
Authors: Rosenthal Alex , Sprinzl Matej
Published: May 2006

Hydroboration followed by alkaline hydrogen peroxide oxidation of 1,2:5,6-di-O-isopropylidene-3-C-methylene-α-D-ribo-hexofuranose (2) yielded 3-deoxy-3-C-"hydroxymethyl"-1,2:5,6-di-O-isopropylidene-α-D-allofuranose (3) and partially hydrolyzed 3 in a total yield of 88%. Compound 3 was hydrolyzed selectively to the 1,2-monoisopropylidene derivative 5, which was converted via benzoylation followed by acetolysis into the 1,2-diacetate 7. Condensation of the latter compound with chloromercuri-N-benzoyladenine in the presence of titanium tetrachloride, followed by deblocking with methanolic sodium methoxide, yielded 9-(3-deoxy-3-C-"hydroxymethyl"-β(and α)-D-allofuranosyl)adenine in yields of 44 and 4% respectively, based on 7. The over-all yield of 10 based on 3 is 20%. Sodium metaperiodate oxidation of 10, followed by sodium borohydride reduction of the aldehydo-derivative, afforded 9-(3-deoxy-3-C-"hydroxymethyl"-β-D-ribofuranosyl)adenine (11) in 81% yield.Direct acetolysis of 3, followed by conversion of the mixture of peracetates into a mixture of glycosyl chlorides, and finally condensation of the latter with 8 gave the blocked crystalline β-D-nucleoside 9 in an over-all yield of about 9%, based on 3. Subsequent unblocking of 9 gave a nucleoside having the same physical constants as 10.
Observation of a large dose rate effect on the ozone yield in the radiolysis of gaseous oxygen
Authors: Boyd A. W. , Willis C. , Cyr R. , Armstrong D. A.
Published: May 2006

The ozone yield from the radiolysis of gaseous oxygen has been measured to be G(O3) = 12.8 ± 0.6 at 1026–1027 eV g−1 s−1 and to be G(O3) = 6.2 ± 0.6 at 1016 eV g−1 s−1. The latter result depends on a new determination of the stoichiometry of the oxidation of iodide by ozone. It is proposed that the difference in yields between the two dose rates is due to differences in ion-recombination processes.
Infrared spectra of acetonitrile sorbed on porous glass
Authors: Low M. J. D. , Bartner P. L.
Published: May 2006

Infrared spectra were recorded of acetonitrile sorbed on highly degassed porous glass as well as on silica and B-, Al-, and Zr-impregnated porous glass and silica. Most of the acetonitrile was weakly and reversibly adsorbed, becoming hydrogen-bonded to surface hydroxyls. A small amount of the adsorbate formed weakly bound surface complexes with Al- and Zr-, but not with B-impurities.
Reactions of 4-aroyl-4-oxazolines and 3-aroyI-4,5-dihydrofurans
Authors: Lown J. W. , Smalley R. K. , Dallas G. , Maloney T. W.
Published: May 2006

4-Aroyl-4-oxazolines undergo stereospecific [2 + 3] cycloaddition to olefinic dipolarophiles with the formation of 3-aroyl-4,5-dihydrofurans. The latter are also found to be reactive towards further [2 + 3] cycloaddition reactions. Possible mechanisms for these reactions are discussed and the synthesis of several new furans and dihydrofurans reported.
Single bond radius of trigonal nitrogen and the C(sp2)—N(sp2) single bond
Authors: Camerman Arthur
Published: May 2006

Estimation of p-π character in nitrogen–carbon bonding is dependent on a knowledge of the trigonal nitrogen – trigonal carbon single bond length. Recent experimental results indicate a value of 1.470 ± 0.005 Å for this bond distance and a value of 0.720 ± 0.010 Å for the trigonal nitrogen single bond radius; these values are suggested as criteria for estimating p-π character in trigonal N – aromatic C bonds.
Deuterium exchange of C-methyl protons in lumazine derivatives
Authors: McAndless J. M. , Stewart Ross
Published: May 2006

Proton magnetic resonance spectroscopy has been used to examine the deuterium exchange of the methyl protons in two lumazine derivatives. The exchange occurs at the C-7 methyl group in 6,7,8-trimethyllumazine (2) and at the C-6 methyl group in 1,7-dihydro-6,7,8-trimethyllumazine (3). The former reaction is subject to both general acid- and general base-catalysis but the latter only to general acid-catalysis. Plausible mechanisms for the reactions of both compounds are advanced, involving in the case of 3, acid-catalyzed addition of water across the C6—N5 double bond.
Length change – adsorption relations for the water – porous glass system to −40 °C
Authors: Feldman R. F.
Published: May 2006

Adsorption of water has been studied extensively above 0 °C, but the problem of the phase transition of adsorbates in porous materials is presented at temperatures below 0 °C. Experiments that show how phase transitions modify length change – adsorption relationships are described.Adsorption – length change measurements from −40 to −0.5 and isotherms at −20 and −0.5 °C were obtained. In another group of experiments different forms of isosteres were also obtained; the principle that water should be allowed to enter the sample at the low temperature was usually followed.Isotherms and length change – adsorption characteristics below 0 °C are qualitatively similar to those above 0 °C, but a decrease in adsorptive capacity and length change was observed. These results and those obtained from the isosteres lead to the conclusion that capillary condensation and menisci theories are operative and that a solid meniscus exists. It follows therefore that the saturated vapor pressure of frozen adsorbate is greater than that of bulk ice and that its volumetric expansion on freezing is similar to the bulk phase transition. It is shown how these phenomena can predict migration of water and generation of pressure within the porous body when it is subjected to cooling and warming cycles.
Signs of spin–spin coupling constants between aldehydic and ring protons in 2,6-dinitrobenzaldehyde. Evidence for a hyperconjugative contribution to JPH,CHO
Authors: Bell C. L. , Danyluk S. S. , Schaefer T.
Published: May 2006

not available
Kinetics of the reaction of glycine with N-ethylmaleimide
Authors: Leslie James
Published: May 2006

The rate law for the reaction of glycine with N-ethylmaleimide (NEM) has been determined to be −d(NEM)/dt = k(NEM)(glycine)/aH+, which is consistent with a rate-controlling reaction of an unprotonated amino group with the N-ethylmaleimide. The rate constant, k, has the value 3.7 × 10−11 min−1 at 25°.
Reactions of diphenylcyclopropenone with 1,3-dipoles
Authors: Lown J. W. , Maloney T. W. , Dallas G.
Published: May 2006

Diphenylcyclopropenone reacts with 1,3-diphenylisobenzofuran to give a benzotropone derivative 5, with 3-carboalkoxyaziridines to give trans-3-pyrrolines (e.g. 10), and with a 3-cyanoaziridine to give the pyrrole 20. Possible mechanisms of these reactions are considered and compared with previous 1,3-dipolar additions to cyclopropenones.
Assignments of configuration by nuclear Overhauser effects in some dibenzthiepin derivatives
Authors: Fraser Robert R. , Schuber Francis J.
Published: May 2006

The configuration of the benzylic protons responsible for each absorption in the nuclear magnetic resonance spectra of 1,11-dimethyl-5,7-dihydrodibenz(c,e)thiepin and its S-oxide and S-dioxide have been determined by nuclear Overhauser experiments. Successful application of the method was achieved by using partially deuterated derivatives for the purpose of removing undesirable relaxation mechanisms between protons. Triple irradiation of doublets was also usefully employed. The sulfoxide assignments arrived at herein reverse the tentative assignments put forth by us (1). It is noteworthy that all experiments on the sulfoxide failed when CDCl3 was used as solvent. In DMSO normal nuclear Overhauser effects were seen, presumably since sulfoxide dimers are not formed in this solvent. The sulfonium perchlorate derivative of the thiepin was also synthesized. The remarkable similarity of its n.m.r. spectrum to that of the sulfoxide is interpreted as evidence that the effect of the sulfoxide group on the shifts of neighboring protons is due primarily to the "lone pair" on sulfur.
Ion–molecule reactions in carbonyl sulfide – hydrocarbon mixtures
Authors: Džidić I. , Good A. , Kebarle P.
Published: May 2006

The major ion–molecule reactions occurring in pure COS and in mixtures of COS with methane, methyl iodide, ethane, and ethylene were investigated in a Nier-type mass spectrometer. In cases where two or more reactions could be postulated to account for the observed product ions, appearance potential data and graphical analysis were used to evaluate the contributions of the individual reactions. Phenomenological cross sections were obtained for the reactions studied and approximate rate constants were then calculated.An independent set of measurements were carried out in a high-pressure pulsed-beam mass spectrometer, in which the absolute rate constants for reactions occurring in COS were measured, using nitrogen as a carrier gas. The rate constants thus obtained were used to verify the validity of the rate constants calculated from the measured cross sections.
Volatilité du nitrate, chlorure et sulfure mercurique et préparation de sources radioactives de 203Hg
Authors: Grossoleil Jacques , Roy J. C.
Published: May 2006

With 203Hg as a tracer, the volatility of Hg(NO3)2 and HgCl2 in the presence of HNO3, HCl, H2S, Na2S, NaHS, Na2S2O3, and NH3 has been studied. The amounts of mercury varied between 1 and 50 μg and the other experimental conditions were those encountered in the preparation of radioactivity standards. We found that the losses of activity were large during the evaporation of solutions of Hg(NO3)2 in HNO3, that they were nil during the evaporation of solutions of HgCl2 in HCl, and that they were large again for the solid residues left after the evaporation of each one of these solutions. When using a solution of Hg(NO3)2 in HNO3, we found it very difficult to eliminate completely the losses by a HgS precipitation; we stopped them completely only by addition of a large excess of sulfide ion as Na2S and NaHS or of Na2S2O3. The precipitation of HgS from a solution of HgCl2 in HCl is much easier and stops the losses completely.The results can be explained by saying that the formation of the HgCl42− complex in a HCl medium greatly stabilizes the mercuric ion and renders it nonvolatile, whereas the formation of volatile Hg(NO3)2 molecules is favored in a HNO3 medium where no complex formation occurs.
Mass spectra of some deuterium labelled dimethylquinolines
Authors: Draper P. M. , MacLean D. B.
Published: May 2006

The mass spectra of several dimethylquinolines, labelled in the methyl group with deuterium, have been examined. The results are in agreement with the formation of ring-expanded molecular ions prior to fragmentation to the M—H and M—CH3 ions. Two ring-expanded ions may form since there are two methyl groups which can participate in the ring expansion process. Ring expansion through a methyl group located on the benzenoid ring is favored over ring expansion through a methyl group on the pyridine ring.
Internal rotation in the methyl esters of dimethylcarbamic acid and thio derivatives
Authors: Lemire Alberta E. , Thompson James C.
Published: May 2006

The kinetic parameters for hindered rotation about the C—N bond have been determined by total nuclear magnetic resonance line shape analysis for the methyl esters of N,N-dimethyldithiocarbamic acid, and N,N-dimethylmonothiocarbamic acid. A qualitative picture of the effect of substituents on the potential barrier in carbamate and thiocarbamate esters is presented.
Polar effects at solid/liquid interfaces
Authors: Lowe A. C. , Riddiford A. C.
Published: May 2006

Studies of the advancing contact angle of water upon several alkylchlorosilaned glass surfaces at 22 °C lead to the view that, at zero or very low interfacial velocities, the free energy per unit area of the solid/liquid interface is governed by both dispersive and polar forces. At higher velocities, the polar forces may be neglected.
Crystallographic studies of cobalt arsenates, I. Crystal structure of Co3(AsO4)2
Authors: Krishnamachari N. , Calvo C.
Published: May 2006

Co3(AsO4)2, an analogue of the mineral xanthiosite, crystallizes in the monoclinic space group P21/c with Z = 4. The unit cell parameters are a = 5.830(4) Å, b = 9.675(2) Å, and c = 10.34(2) Å with β = 93.42(5)°. The intensity of 2261 independent reflections were estimated either from integrated precession photographs or by direct measurement using a scintillation counter. The final value of the reliability index is 0.072 for a full matrix least-square refinement where all the atoms have anisotropic thermal parameters. The three independent cations are surrounded octahedrally by oxygen atoms with mean Co—O bond lengths of 2.12 Å and a range from 1.99 to 2.29 Å. One of the arsenate ions, AsO44−, is a nearly regular tetrahedron with a mean As—O bond length of 1.70 Å; while the second, with an angular irregularity primarily introduced by one oxygen atom, shows a mean As—O bond length of 1.69 Å. This structure consists of nearly hexagonally close packed layers of oxygen atoms normal to the b axis repeating every four layers.
A fluorine magnetic resonance study of the solid addition compounds SF4•AsF5 and IF7•AsF5
Authors: Barr M. R. , Dunell B. A.
Published: May 2006

A broad-line fluorine magnetic resonance study of the solid addition compounds SF4•AsF5 and IF7•AsF5 shows that each has two types of chemically distinct fluorine in the ratios of 1:2 and 1:1, respectively. The fine structure and the second moments of the spectra are consistent with the ionic formulations SF3+AsF6− and IF6+AsF6−. Bond lengths in the iodine compound are discussed in relation to the observed second moment at liquid-nitrogen temperature and the calculated rigid-lattice second moment based on the detailed sodium-chloride-type crystal structure of Beaton. The chemical shifts of the fluorines in the three ionic species are measured relative to trifluoracetic acid and to HF. Reorientations of the ions in the solid state are discussed on the basis of the change in second moment with temperature for each compound. A very rough estimate of the anisotropy of chemical shift in IF6+AsF6− is made from the slope of the second moment vs. field-squared line at liquid-nitrogen temperature.
Acid-catalyzed rearrangement of 3-carene-2,5-dione (3,7,7-trimethylbicyclo[4.1.0]hept-3-ene-2,5-dione)
Authors: Still I. W. J. , Nathan G. W.
Published: May 2006

The reaction of 3-carene-2,5-dione (2) with acetic anhydride–concentrated sulfuric acid at 25° has been shown to lead exclusively to the formation of 2-methyl-6-isopropenylhydroquinone diacetate (3b).
Electron transference in hemolytic aromatic substitution reactions
Authors: Davis Dennis D. , Ahmed Fauzia Y.
Published: May 2006

The selectivity of methyl radicals in the homolytic substitution reaction on naphthalene was studied as a function of solvent. The selectivity decreases as the solvent dielectric increases. A possible explanation of these effects based upon a charge-transfer contribution to the transition state leading to σ-complex formation is offered.
Neutral terpenes from the bark of Sitka spruce [Piceasitchensis (Bong.) Carr.]
Authors: Rogers I. H. , Rozon L. R.
Published: May 2006

Four of the minor components of the neutral triterpene fraction of Sitka spruce bark have been isolated and characterized as 3β,21α-dihydroxy-Δ14-serratene (1) (serratenediol), 3α,21 β-dimethoxy-Δ14-serratene (2), 3α-methoxy-21-keto-Δ14-serratene (3), and 3β-hydroxy-21-keto-Δ14-serratene (4). 13-Epimanool was characterized as its 3,5-dinitrobenzoate derivative.
Protonated cyclopropanes. IV. Trifluoroacetolysis of 1-14C-1-propyl tosylate
Authors: Lee C. C. , Chwang W. Kao-Ying
Published: May 2006

The trifluoroacetolysis of 1-14C-1-propyl tosylate was carried out either with or without the presence of an equivalent of sodium trifluoroacetate. Both 1-propyl and 2-propyl trifluoroacetates were obtained, the latter being the major product if the sodium salt was not present. Isotope position rearrangements from C-1 to C-2 and C-3 were observed in the 1-propyl trifluoroacetate to the extent of about 2 and 17%, respectively, for the reactions effected with and without sodium trifluoroacetate. The rearranged 14C label was about equally distributed at C-2 and C-3. It is proposed that these rearrangements may be explained on the assumption that part of the overall reaction proceeds through equilibrating protonated cyclopropane intermediates.
Nuclear magnetic resonance spectra of the epihalohydrins: II. Spectral analyses and structural correlations for all the epihalohydrins
Authors: Macdonald C. J. , Reynolds W. F.
Published: May 2006

Complete analyses of the proton magnetic resonance spectra of propylene oxide, epifluorohydrin, epibromohydrin, and epiiodohydrin shows that in all cases the cisoid coupling constants over four bonds are negative, and the transoid coupling constants positive. Dipole moments, together with the vicinal coupling constants of the CH—CH2X moiety, are used to establish the probable conformations for all the epihalohydrins. Conformational factors appear to obscure any possible relationship between substituent electronegativity and long-range coupling constants.
Correlation of the intramolecular nuclear Overhauser effect with internuclear distance
Authors: Bell R. A. , Saunders J. K.
Published: May 2006

A linear relationship between the intramolecular nuclear Overheauser effect (n.O.e.) and the sixth power of the internuclear distance for protons in reasonably compact organic molecules in deuterio-chloroform solution is derived. Examples of H—H and CH3—H interactions from this work and the literature have been used to demonstrate the validity of this relationship. It is shown that application of the observed n.O.e. between two protons or between a proton and a methyl group can be used to determine internuclear distances in unknown structures.
Structure of a galactomannan from seed of Crotalariamucronata
Authors: Unrau A. M. , Choy Y. M.
Published: May 2006

A galactomannan, purified by repeated complexation with copper acetate, was shown to be composed of D-mannose and D-galactose in a molar ratio of 3:1. Methylation of the polysaccharide followed by hydrolysis gave 2,3,4,6-tetra-O-methyl-D-mannose, 2,3,4,6-tetra-O-methyl-D-galactose, 2,3,6-tri-O-methyl-D-mannose, 2,4,6-tri-O-methyl-D-mannose, 3,4,6-tri-O-methyl-D-mannose (from 1 → 2-linkages), and 2,3-di-O-methyl-D-mannose (molar ratio 1:23:28:11:4:26). Periodate degradation further indicated that the galactose units occupied single unit branch points linked (1 → 6). One in every 6 mannose units was resistant to periodate attack further suggesting the presence of (1 → 3)-linkages. An approximately equimolar occurrence of 2-O-β-D-mannopyranosyl-D-erythritol and O-β-D-mannopyranosyl-(1 → 3)-2-O-β-D-mannopyranosyl-D-erythritol indicated a significant frequency of isolated and consecutive (1 → 3)-linkages. In conjunction with results from methylation experiments a relatively simple structure may be assigned.
Thermal decomposition of methyl azide
Authors: O'Dell Jr. M. S. , Darwent B. deB.
Published: May 2006

The thermal decomposition of gaseous methyl azide has been investigated at conversions of less than 1% at 155, 170, and 200 °C. The reaction has been shown to be homogeneous and unimolecular, the first-order rate constant being kun1 = 2.85 × 1014 exp − (40 500/RT). The decomposition results in the formation of CH3N(X3∑−) and N2(X1∑g+). The CH3N(X3∑−) do not react with CH3N3 to produce N2, but do form a polymer of composition similar to hexamethylene tetramine and also react with olefins. The major products are N2 and polymer; small amounts of H2 and CH4, but no C2H6, are formed.
Oxidation of ascorbic acid by osmium(VIII)
Authors: Mehrotra U. S. , Mushran S. P.
Published: May 2006

Reduction of osmium(VIII) by ascorbic acid has been studied in the presence of hydrochloric acid. The reaction is found to be directly proportional to the concentration of ascorbic acid and osmium(VIII) and to the reciprocal of the hydrogen ion concentration. In the proposed mechanism, the reacting species have been shown to be perperosmic acid and ascorbate ion; this was supported by the negligible effect of the ionic strength. Influence of temperature was studied in the range 25–40 °C, and the energy and entropy of activation were calculated as 14.1 ± 0.2 kcal mole−1 and −8.6 ± 0.1 e.u., respectively. Osmium(IV) was found to be a product of the reaction.
Radiation-induced oxidation of 2-propanol by hydrogen peroxide in aqueous solutions
Authors: Burchill C. E. , Ginns I. S.
Published: May 2006

The radiation-induced oxidation of 2-propanol by hydrogen peroxide in neutral deaerated aqueous solution has been investigated. 2-Propanol is oxidized to acetone, and hydrogen peroxide reduced in stoichiometrically equivalent high yields. The yields are independent of hydrogen peroxide concentration in the range 5 × 10−2 to 10−3 M and linearly dependent on alcohol concentration in the range 0.13 to 1.05 M. The reaction yields increased with decreasing dose rate.The results are explained by a chain mechanism in which initiation occurs via H-atom abstraction from 2-propanol to form either (CH3)2ĊOH (1) or CH3 CHOH ĊH2 (2). 1 reacts with H2O2 in a chain propagating reaction[Formula: see text]2 may abstract the α hydrogen from the parent alcohol[Formula: see text]or undergo bimolecular termination. A lower limit of 53 ± 101mole−1 s−1 is estimated for the rate constant for this radical conversion reaction.
Hydrogen bonding and long-range proton coupling constants in some ortho disubstituted aniline derivatives. Intramolecular proton exchange and degree of nonplanarity of the amino group
Authors: Wasylishen R. , Schaefer T.
Published: May 2006

Long-range spin–spin coupling constants over five bonds between the two amino protons and the ring protons are reported for some ortho disubstituted aniline derivatives in cyclohexane and benzene-d6 solutions. Equal coupling of both amino protons to the meta protons in unsymmetrically ortho disubstituted aniline derivatives indicates the occurrence of intramolecular exchange of the amino protons. The absence of any observable coupling over six bonds to the para proton places an upper limit on the degree of nonplanarity of the amino group in the 2,6-dibromo- and 2,6-dichloroanilines. A relatively basic compound like 2,4,6-trimethylaniline does not display long-range couplings of the amino protons, very likely because intermolecular proton exchange occurs.
Hydrogen abstraction from toluene by methyl radicals and the pressure dependence of the recombination of methyl radicals
Authors: Dunlop A. N. , Kominar R. J. , Price S. J. W.
Published: May 2006

Using dimethylzinc, dimethylmercury, and trimethylbismuth as sources of methyl radicals, values of k1/k21/2[Formula: see text]have been calculated from 338 to 610 °C over the pressure range 4.5–204 mm. M is predominantly toluene. The observed pressure dependence of reaction [2] is in agreement with that found when M = benzene, but is somewhat greater, and the fall-off occurs at higher pressures, than for ethane dissociation. However, reasonable agreement is obtained if it is assumed that the efficiency of toluene as a third body in reaction [2] is about 1/10th that of ethane.Extrapolation to infinite pressure, where it is assumed that E2 = 0and A2 = 1013.34 cm3 mole−1 s−1, gives E1 = 8.0 ± 0.3 kcal mole−1 and A1 = 1011.07 cm3 mole−1 s−1.
Etude cinétique de la réduction des ozonides de styrènes substitués dans le noyau par la triphénylphosphine
Authors: Carles J. , Fliszár S.
Published: May 2006

The rates of reduction k[ozonide][triphenylphosphine] have been studied, in chloroform solution, for ozonides of ring-substituted styrenes. The second order rate constants k fit the Hammett equation with ρ = 0.72, thus confirming that the reduction proceeds via a nucleophilic attack of the triphenylphosphine on the ozonide ring. The absence of any significant kinetic solvent effect indicates that the rate determining step is in the formation of an unstable six-membered ring oxyphosphorane intermediate.
Reactions of some 2-aminophenyl- and 2- and 4-nitrophenyl sulfones in aqueous sodium hydroxide solution
Authors: Shaw K. B. , Miller R. K.
Published: May 2006

When 2-aminophenylsulfonylacetic acid (3) was heated under reflux in an excess of dilute sodium hydroxide solution, the only product identified was 2-methylsulfonylaniline (6). When 2-nitrophenyl-sulfonylacetic acid was treated under the same conditions, the major products identified were 2-methyl-sulfonylnitrobenzene (7), 2-nitrophenol (8), and orthanilic acid (13); minor products of this reaction were 6 and 3-methylsulfonyl-3′-nitro-4-amino-4′-hydroxybiphenyl (12). The same products were obtained although the yields were different when 7 was boiled with alkali, but the reaction of 4-methylsulfonyl-nitrobenzene (15) with alkali was less complex and 4-nitrophenol (16) was the only major product. The biphenyl 12 was also formed in small yield when N-(2-methylsulfonylphenyl)hydroxylamine (19) was treated with alkali and its formation in these reactions was investigated in detail. It was concluded that 12 arises from 7 and 19, but it could also be prepared from 19 and 2-chloro- or better, 2-fluoronitrobenzene, in alkaline solution, and based on all these observations, a mechanism for its formation is suggested. The genesis of the various other products is also discussed. Reference is made to the infrared spectra of sulfones.
Radiation chemistry of gaseous oxygen: experimental and calculated yields
Authors: Willis C. , Boyd A. W. , Young M. J. , Armstrong D. A.
Published: May 2006

The yield of ozone from the radiolysis of gaseous oxygen has been measured at 1026–1027 eV g−1 s−1 to be G(O3) = 12.8 ± 0.6, in reasonable agreement with the value of 13.8 of Ghormley, Hochanadel, and Boyle (2a). At 1016 eV g−1 s−1, our results and re-examination of previous data give G(O3) = 6.2 ± 0.6. The same value is obtained at the high dose rates by the addition of electron scavengers. The difference in yields on going from high to low dose rates and the decrease with electron scavengers at the high dose rate is explained by differences in ion neutralization processes. These are supported by computer calculations. The mechanism of the neutralization steps is discussed in terms of the applicability of the electron jump theory and the effect of clustering of the ions.The proportion of energy lost to ionization, excitation, and subexcitation electrons is calculated. This is based on the W value, relative cross sections for ionization, and the potential energy curves for O2+ ions. A predicted yield on this basis is G(O3) = 14.0 ± 0.9, in fairly good agreement with the experimental yield.
Reaction of conjugated enones with divinylcopperlithium tri-n-butylphosphine complex. A new preparation of γ,δ-unsaturated ketones
Authors: Hooz John , Layton Robert B.
Published: May 2006

A new synthesis of γ,δ-unsaturated ketones is reported, based on the reaction of α,β-unsaturated ketones with a vinyl ate complex.
Yield of free-ions in the radiolysis of formamide, a liquid of very high dielectric constant
Authors: Head D. A. , Walker D. C.
Published: May 2006

Solutions of N2O in liquid formamide (dielectric constant 109) gave a yield of N2 during γ-radiolysis of G(N2) = 3.3 ± 0.3. Competition between N2O and other scavengers, including water, ethanol, acids, AgNO3, and CdI2 strongly resembled the pattern of reactivity characteristic of solvated electrons found in other polar liquids. Furthermore, the yield obtained (3.3) was consistent with the high dielectric constant and predicted for the free-ion yield by Freeman's model assuming a total ionization of 4.7. However, the absence of an absorption band in nanosecond pulse radiolysis experiments suggests that solvated electrons were not present 10−9 s after the passage of the ionizing radiation. It is quite possible that in this system "solvent anions" (or other reactive reducing ions) were formed in yield equal to the "free-ion" yield. This presupposes that formamide anions readily reduce N2O and Ag+, are inactivated by H+ and do not react with water and alcohols.The high dielectric constant apparently leads to large yields of comparatively long-lived (> 10−7 s) reducing ions (free-ion yield of 3.3) accompanied by rather small yields of H atoms and simple molecular decomposition products. In these respects the radiolysis decomposition of formamide resembles that of water.
Thermal [2 + 3] cycloaddition of N-trichloroacetyldiphenylcyclopropenimine to 3-aroylaziridines and 3-carbomethoxyaziridines
Authors: Lown J. W. , Westwood R. , Moser J. P.
Published: May 2006

N-Trichloroacetyldiphenylcyclopropenimine reacted with either cis- or trans-3-benzoyl-1-cyclohexyl-2-m-nitrophenylaziridine in a [2 + 3] cycloaddition to the C=N bond of the imine to form (a) 5-benzoyl-2-m-nitrophenyl-4-(spirodiphenylcyclopropene)-3-(trichloroacetylhydrate)-imidazolidine and (b) 1-cyclohexyl-4-(cis-1,2-diphenylvinyl)-3-dichloroacetyl-2-m-nitrophenylimidazoline. Similar reactions with other 3-aroylaziridines gave analogous imidazolidines and imidazolines. Isolation of an unhydrated imidazolidine of type (a) in the corresponding addition with 3-carbomethoxy-1-cyclohexyl-2-phenylaziridine gave direct spectroscopic proof for the cyclopropene moiety in these adducts. The orientation of the 1,3 dipolar additions was confirmed by a reaction using a specifically 3-deuterated aziridine.The isolation of these adducts of type (a) strongly supports the previously suggested intermediacy of an oxazolidine in the analogous addition of 3-aroylaziridines to diphenylcyclopropenone.
Pyrolysis of ethane in the presence of hydrogen sulfide. Rates of formation of ethylene, hydrogen, and methane
Authors: McLean P. R. , McKenney D. J.
Published: May 2006

Rates of formation of ethylene, hydrogen, and methane have been measured at 630 °C for the thermal decomposition of ethane at pressures between 100 and 620 Torr, with various pressures (approximately 1 to 100 Torr) of added hydrogen sulfide. The effect of the H2S was to increase the rate of methane formation and to decrease the rate of ethylene and hydrogen formation. Rates of formation of all three of these gases decreased with increasing hydrogen sulfide pressures. The quantitative data obtained and the partial product analysis indicate that a complex mechanism is operative. Possible qualitative explanations for the observations are discussed.
Stereospecific synthesis of two epimeric 2-chlorodeoxy pentoses involving anomeric chlorine participation
Authors: Jennings H. J.
Published: May 2006

A simple procedure has been developed for the stereospecific synthesis of some 2-chloro-2-deoxy pentoses. Treatment of β-D-xylopyranosyl chloride 2,3,4-tri(chlorosulfate) with aluminum chloride (> 1 mole equivalent) resulted in specific chloro-displacement of the C-2 chlorosulfate group via a mechanism involving anomeric chlorine migration, which occurred to the extent of almost 100%. The resultant crystalline 2-chloro-2-deoxy-α-D-lyxopyranosyl chloride 3,4-di(chlorosulfate) when treated with sodium iodide yielded crystalline 2-chloro-2-deoxy-D-lyxose. Similarly α-D-lyxpoyranosyl chloride 2,3,4-tri(chlorosulfate) yielded 2-chloro-2-deoxy-a-D-xylopyranosyl chloride 3,4-di(chlorosulfate) from which pure 2-chloro-2-deoxy-D-xylose was obtained by a modified procedure. The structures of these compounds have been confirmed and the mechanism is discussed.
Reaction of carbon disulfide with nickel(II)–amine complexes
Authors: McCormick B. Jack , Kaplan Roy I.
Published: May 2006

The reaction of carbon disulfide with a variety of nickel(II)–amine complexes has been carried out. It has been found that dithiocarbamate complexes are readily formed under the proper conditions, and the synthetic procedures presented provide a convenient and direct route to such compounds. Complexes having hydroxyl and mercaptide groups in addition to amine groups have been found to give exclusively dithiocarbamate complexes, rather than xanthates or trithiocarbonates. The infrared and optical spectra of the complexes have been measured and are discussed in terms of the proposed structures of the complexes.
Biosynthesis of lycopodine from lysine and acetate. The pelletierine hypothesis
Authors: Castillo M. , Gupta R. N. , MacLean D. B. , Spenser Ian D.
Published: May 2006

The biosynthesis of lycopodine (5) was studied in intact plants and in excised shoots of the clubmoss Lycopodiumtristachyum Pursh. Specific incorporation of label from lysine and from acetate was demonstrated by partial degradation. The observed distribution of activity was incompatible with a polyketide origin of lycopodine. The incorporation pattern is consistent with the hypothesis that lycopodine is a modified dimer of pelletierine (4), which, in turn, is derivable from lysine and acetate.
Effect of thorium on the reactions of iron(II) and iron(III) at a platinum electrode
Authors: Breckenridge J. H. , Harris W. E.
Published: May 2006

The effect of thorium perchlorate on the iron(III)–iron(II) couple was studied by the use of current–voltage data and chronopotentiometry. It is suggested that the primary effect of thorium on the ferric–ferrous couple is exclusion of iron from the double layer and the blocking of active sites on the electrode surface with a resultant decrease in the exchange current for the iron couple.
Alkaloids of Shepherdiaargentea and Shepherdiacanadensis
Authors: Ayer W. A. , Browne L. M.
Published: May 2006

Tetrahydroharmol (3) was isolated from Shepherdiaargentea. Tetrahydroharmol (3), serotonin (12), and a new alkaloid shepherdine (2a) were isolated from Shepherdiacanadensis; and evidence was obtained for the presence of 6-hydroxytryptamine in S. canadensis.
Anionic polymerization of styrene in oxepane (hexamethylene oxide)•counter-ion, sodium
Authors: Löhr G. , Bywater S.
Published: May 2006

The propagation reaction in the anionic polymerization of styrene in oxepane has been studied as a function of temperature and concentration of polystyrylsodium. Conductance measurements on polystyrylsodium were also made together with determinations of density, viscosity, dielectric constant, and dipole moment of oxepane itself. The measurements enabled the propagation rate constant to be determined of the polystyryl anion at 30 °C and of the ion-pair over a wide temperature range. The results have been compared with those obtained in tetrahydrofuran and tetrahydropyran.
The kinetics of oxygen exchange between the sulfite ion and water
Authors: Betts R. H. , Voss R. H.
Published: May 2006

Oxygen of mass 18 was used as a stable tracer to measure the rate of exchange between the sulfite ion and water as a function of pH and total sulfite concentration. A value for the rate constant of hydration of SO2 in aqueous solution was determined. The gross rate constants k1 and k−1 for the overall reaction[Formula: see text]at 24.7 °C and ionic strength = 0.9 were evaluated from exchange results to be [Formula: see text]Also, for the first time, rate constants for the pyrosulfite equilibrium[Formula: see text]Were obtained[Formula: see text]at 24.7 °C and ionic strength = 0.9
Studies on microcapsules. VI. Effect of variations in polymerization condition on microcapsule size
Authors: Shigeri Yoshimichi , Koishi Masumi , Kondo Tamotsu , Shiba Motoharu , Tomioka Suiichi
Published: May 2006

The effect of variations in polymerization condition on the size of microcapsules prepared by the interfacial polycondensation method was studied. Factors lowering the rate and degree of polymerization, such as a decrease in temperature or monomer concentration, were found to increase the microcapsule size. A mechanism was proposed for the formation of large microcapsules in the polycondensation step.
Cyclopropylcarbinyl-oxo-carboniumions. A solvolytic basis for the cyclopropylcarbinyl-oxo-carbonium ion
Authors: Fraser-Reid Bert , Radatus Bruno
Published: May 2006

Hydrolysis of 4,6-O-benzylidene-3-deoxy-3-C-(iodomethyl)-D-allal (1) in neutral buffered medium with or without silver ion assistance gives the cyclopropyl aldehyde 4 as the only product. Methanolysis of 1 gives an equal mixture of the α and β anomers of methyl 4,6-O-benzylidene-2,3-C-methylene-2,3-dideoxy-D-allopyranosides (6 and 7). These results indicate that the cyclopropylcarbinyl-oxo-carboniumion (2), is produced with unit efficiency in solvolyses in neutral media, and the formation of both diasteriomers (6 and 7) requires the complete absence of bicyclobutonium ion (9) resonance contribution to the stabilized intermediate, and implies a strong contribution from the oxo-carbonium ion 10. In basic media compound 1 undergoes quantitative dehydroiodination to the conjugated diene, 4,6-O-benzylidene-1,2,3-trideoxy-3-C-methylene-D-ribo-hex-1-enopyranose(8).
Photo-initiated reactions of thiols and olefins. V. Inhibition of butene-2 isomerization by oxygen: a new method for determining relative reactivities
Authors: Graham D. M. , Soltys J. F.
Published: May 2006

Investigation of the kinetics of oxygen inhibition of the thiyl radical catalyzed isomerization of cis-butene-2 has yielded an estimate for the relative rates of oxidation (k7) and decomposition (k3) of the CH3S and olefin adduct radical. At 25 °C, k7/k3 = 7 × 104 l mole−1, and E3 − E7 = 11.8 ± 2.5 kcal. Making use of these results, a new method has been developed for determining relative reactivities of olefins, and some preliminary results have been obtained.
Nuclear magnetic resonance study of carbethoxypyrroles
Authors: Roomi M. W. , Dugas H.
Published: May 2006

The chemical shifts and the ring proton coupling constants of various substituted carbethoxypyrroles are reported.The electron-withdrawing effect of the carbethoxy groups shifts the resonances of the ring substituents to low field while the inductive and mesomeric effects of the methyl groups shift the resonances to higher field. The deshielding effect is more pronounced with 2-carbethoxypyrroles than for 3-carbethoxypyrroles. The ring proton spin–spin coupling constants depend on the nature of substituents and increase with the electronegativity of the substituents. In some cases long-range coupling between the methyl side-chain protons and ring protons could be observed.
Anion exchange resin solvent selectivity and anion solvation: a nuclear magnetic resonance study
Authors: Frankel Lawrence S.
Published: May 2006

Nuclear magnetic resonance has been utilized to study solvent selectivity of anion exchange resins in aqueous dimethyl sulfoxide and aqueous acetonitrile. Solvent selectivity data in the chloride ionic form is in qualitative agreement with independent preferential solvation studies of chloride ion. The importance of solvent activity coefficients is demonstrated for aqueous acetonitrile.
Biosynthesis of dendrobine
Authors: Edwards O. E. , Douglas J. L. , Mootoo B.
Published: May 2006

The incorporation of 4-14C-mevalonate into dendrobine, the major alkaloid of Dendrobiumnobile (Orchidaceae), is consistent with a biosynthesis involving successive intermediates with trans-cis farnesol, germacrane, and cadalane skeletons.
Studies on metal hydroxy compounds. X. Thermal analyses, decomposition kinetics, and infrared spectra of lead halide (Cl, Br, I) derivatives
Authors: Ramamurthy P. , Secco E. A. , Badri M.
Published: May 2006

The thermal analyses, thermogravimetry (TG), and differential thermal analysis (DTA) of PbOHCl, PbOHBr, and PbOHI reveal that the initial mode of decomposition is via dehydroxylation. Calorimetric measurements along with related enthalpy values for the decomposition reaction are given.The infrared spectra of these compounds are interpreted in terms of folded bands of (PbOH+)n tied together by halide ions consistent with their crystal structures.The kinetics of thermal decomposition of lead hydroxyhalides follow a diffusion-type rate equation which is in contrast to the simple first-order rate equation observed for most Cd, Zn, and Cu compounds. These two distinct rates are interpreted in terms of mobile OH or H species in the dehydroxylation step.
Application of proton magnetic resonance to rotational isomerism in halotoluene derivatives. III. α,α-Dichloro-2,4,6-tribromotoluene
Authors: Peeling J. , Schaefer T. , Wong C. M.
Published: May 2006

At room temperature the proton magnetic resonance spectrum of α,α-dichloro-2,4,6-tribromotoluene is ABX where the methine proton in the sidechain is X and is lying in the plane of the aromatic ring. At higher temperatures the ring proton spectrum, AB, broadens and eventually collapses to yield an A2X spectrum. From an analysis of the ring proton line shapes the barrier to rotation of the dichloromethyl group about the sp2–sp3 carbon–carbon bond is obtained; ΔG* = 17.5 ± 0.1 kcal/mole at 304°K, ΔH* = 15.67 ± 0.08 kcal/mole, ΔS* = −7 e.u., Ea = 16.38 ± 0.08 kcal/mole, log A = 11.78 ± 0.23 where the least squares errors given should probably be multiplied by a factor of from 3 to 5 to take possible systematic errors into account. The barrier is about 2 kcal/mole higher than in α,α,2,4,6-pentachlorotoluene. The barrier to rotation arises from the conformation in which chlorine and bromine atoms are eclipsed.
Studies on nucleation from solution of some soluble inorganic salts
Authors: Velazquez J. A. , Hileman Jr O. E.
Published: May 2006

Vonnegut's droplet technique in combination with selective extraction of solvent is reported as a new method for the study of nucleation from solution of soluble substances at constant temperature. The method is applied to studies on NH4Cl, NH4NO3, NH4SCN, (NH4)2Cr2O7, and K2Cr2O7,. The results are reported and various nucleation parameters are calculated and discussed in terms of the limitations of the Becker–Doring model of nucleation when it is applied to crystal nucleation from solutions of electrolytes.
Unsaturated derivatives of the 1,2;5,6-di-O-isopropylidene-D-hexofuran-3-uloses
Authors: Slessor K. N. , Tracey A. S.
Published: May 2006

The formation of the two 3-O-acetyl-1,2;5,6-di-O-isopropylidene-D-hex-3-enoses from the four 1,2;5,6-di-O-isopropylidene-D-hexofuran-3-uloses is reported. Treatment of the two enol acetates with hydrogen or deuterium in the presence of palladium or platinum leads to rearrangement as well as reduction and reductive hydrogenolysis of the acetoxy group. This rearrangement makes the enol acetates unsuitable as intermediates in the stereospecific synthesis of deuterated sugars of high isotopic purity.
Radiation-induced oxidation of 2-propanol by hydrogen peroxide in aqueous solutions
Authors: Burchill C. E. , Ginns I. S.
Published: May 2006

not available
The Raman spectrum and molecular structure of Me3SiOReO3 in the solid, liquid, solution, and gaseous phases
Authors: Boal D. H. , Ozin G. A.
Published: May 2006

The Raman spectrum of Me3SiOReO3 is found to be essentially the same in all of the above phases, proving that the non-linear SiORe bridged structure found in the solid phase is retained in the other phases and is not just the result of crystal packing requirements. The interpretation of the spectrum of Me3SiOReO3 is found to be particularly straightforward as the vibrational data can be considered to be intermediate between that of the parent, non-linear molecules (Me3Si)2O and (O3Re)2O. In the present work, assignments for the ReO and SiO bridge stretching modes are proposed.
Vibrational spectra of phosphorus ligand derivatives of some alkyltricarbonyl-π-cyclopentadienylmolybdenum compounds
Authors: Craig P. J.
Published: May 2006

Raman and infrared spectra of a series of complexes RCOMo(CO)2[L]π-C5H5 (R = Me, Et, σ-C3H5, CH2Ph; L = PPh3, P(OCH2)3CCH3) and of ClMo(CO)2[PPh3]π-C5H5 and HW(CO)2[P(OPh)3]π-C5H5 have been recorded. In this complementary study of complex metal carbonyl compounds, assignments are suggested for metal–carbon–oxygen deformation, metal–carbon stretching, metal–ring, and metal–phosphorus stretching vibrations. It is thought that the latter occur in the range 240–200 cm−1, frequencies for phosphite complexes being lower than for the corresponding phosphine derivatives.
Trimethylsilyl-substituted cyclopentadienes
Authors: McLean S. , Reed G. W. B.
Published: May 2006

An account is given of the migratory behavior of the silyl group and of hydrogen in trimethylsilyl-substituted cyclopentadienes. The reaction of trimethylsilylcyclopentadiene with dimethyl sulfoxide is described.