bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional-group and substituent effects, both steric and electronic, upon the ultraviolet absorption spectra of some conjugated heteroenoid compounds
Authors: Currie D. J. , Lough C. E. , Silver R. F. , Holmes H. L.
Published: May 2006

The positions of the long-wavelength maxima in the spectra of some 300 compounds of generalized formula I may be accommodated by assuming that the observed maximum is equal to that of styrene + Δλ (the conjugative effect of A) + Δλ′ (the inductive effect of B) + ΣΔλ″ (the sum of the steric effects of the A, B, and phenyl groups) + D (an empirical parameter related to X and Y). These arguments have been extended to the spectra of II. Δλ′ is related to the σ value for meta-substituted benzene derivatives or to σ*. D for meta- and

[Formula: see text]para-substituted derivatives roughly correlates with the appropriate σ+ values, whereas D for ortho-substituted derivatives is related to a simple function involving the D value for para substitution and the steric substituent constant, ES. For compounds of generalized formula III, the electronic effects of the A and B groups cancel but the steric effects are additive.Multiple bands occur in the long-wavelength region of the spectra for compounds containing halogen, alkoxy, or amino groups. These groups are highly polarizable and are considered to function both as electron donors and electron sinks.
Amino group stretching vibrations in primary acid amides
Authors: Krueger P. J. , Smith D. W.
Published: May 2006

Most primary alkyl, primary α-substituted alkyl, and primary aromatic acid amides exhibit three sharp concentration and temperature dependent absorption bands at 3 518 ± 3, 3 504 ± 4, and 3 486 ± 8 cm−1, in dilute (0.003 M or less) CCl4solution, just below the fundamental antisymmetric NH2stretching vibration. These are tentatively assigned to the shifted antisymmetric NH2stretching vibration in cyclic dimers, cyclic trimers, and cyclic tetramers respectively, with increasing NH … O hydrogen bond strength. In all alkyl amides the antisymmetric NH2band intensity exceeds the symmetric band intensity. Conjugation of the CONH2group with π-electron systems reverses this intensity relationship, except where the acidic NH2group can form intramolecular hydrogen bonds. These observations substantiate the previously published views on the nature of the vibrational mechanism of the NH2group. No evidence is found for enolization of amides in CCl4solution.
Kinetics of the hydrolysis of acyl chlorides in pure water
Authors: Queen A.
Published: May 2006

The activation parameters ΔH≠, ΔS≠, and ΔCP≠ for the hydrolyses of a series of alkyl chloroformates and dimethylcarbamyl chloride in water have been determined. The results indicate that, with increasing electron donation to the chlorocarbonyl group, the mechanism changes from bimolecular to unimolecular (SN1) displacement at this position. For isopropyl chloroformate, some concurrent alkyl–oxygen bond fission is also indicated. The bimolecular mechanism involves reversible addition of water to the carbonyl group followed by ionization of the carbon–chlorine bond.
Europium tartronate and mandelate ion association in water
Authors: Manning P. G.
Published: May 2006

Stepwise stability constants have been determined for the 1:1 and 1:2 Eu3+:mandelate− and Eu3+:tartronate2− complexes in water. Measurements were made at low ionic strength and the temperature was 25 °C. The solvent-extraction–radiotracer method was used.For the mandelate system at an ionic strength of 0.104, K1 = 5.0 × 102, K2 = 1.58 × 102, and K1:K2 = 3.1. The K1:K2 ratios suggest monodentate ligandcy.The stepwise stability constants for the two stages of tartronate ion association are: K1 = 7.1 ( ± 15%) × 104 and K1K2 = 4.2 ( ± 5%) × 108. The magnitudes of the stability constants suggest that tartronate is a tridentate ligand. The stability constant ratios are discussed with reference to the ratios for piperidinedicarboxylate and iminodiacetate complexes.
Radiolysis of methylcyclohexane. IV. Effects of carbon tetrachloride and nitrous oxide in the vapor phase
Authors: Holtslander W. J. , Freeman G. R.
Published: May 2006

There is a radiation-induced chain reaction in methylcyclohexane (MCH) – CCl4mixtures in the vapor phase at 110° and 380 Torr. The chain-propagation products are chloroform and methylcyclohexylchloride (Gmax ≈ 40) and the chain-termination products are mainly methylcyclohexene (MC), bimethylcyclohexyl (C14), and hexachloroethane, depending on the composition of the mixture. At CCl4concentrations < 1 mole%, HCl is formed mainly by reaction of Cl−with positive ions, e.g. Cl− + C7H14+ → HCl + C7H13. The value of the ratio G(MC)/G(C14) is 8 ± 1 in pure MCH and in the mixtures up to 44 mole% CCl4.There is a radiation-induced chain reaction in MCH–N2O mixtures in the vapor phase. At 110° and 380 Torr, G(N2) = 22, G(MC) = 16, and G(C14) = 1.6, independent of N2O concentration between 2 and 10 mole%. The G-values are independent of MCH pressure between 50 and 520 Torr. Product formation is inhibited by the addition of SF6or DI. The half-life of the ion N2O−with respect to decomposition to N2 + O−is 10−4–10−3s under these conditions. It is suggested that the mechanism contains the reactions

[Formula: see text]

[Formula: see text]Reaction [24] is slightly exothermic. Reaction [25] is exothermic if the electron affinity of N2O is greater than that of C7H13.
Temperature dependence of the 35Cl nuclear quadrupole resonance frequencies of the trimeric and tetrameric phosphonitrilic chlorides
Authors: Kaplansky M. , Whitehead M. A.
Published: May 2006

The 35Cl nuclear quadrupole resonance frequencies of the trimeric and tetrameric phosphonitrilic chlorides have been studied as a function of temperature. Two forms of the tetramer were used and the differences in their spectra ascribed to crystallographic effects. Correlation of each of the lines in the trimer to a set of chlorine atoms in the unit cell were attempted using crystallographic data.
Spectres infrarouge et Raman de KSCN à l'état cristallin
Authors: Savoie R. , Pézolet M.
Published: May 2006

The Raman spectrum of potassium thiocyanate has been recorded at various temperatures between − 195 and 185 °C. The predicted factor-group splitting of the C—N stretching vibration in the crystal at room temperature has been observed. The spectra of the two crystalline phases differ mainly in the lattice region. The far-infrared spectrum has also been recorded, and the existence of lattice modes at 25–30 cm−1 is shown to be doubtful.
The mechanism of the iodination of aminochromes
Authors: Mattok G. L. , Wilson D. L.
Published: May 2006

The kinetics of the iodination of several aminochromes by iodine in aqueous potassium iodide, to form the 7-iodo derivatives, have been studied. The rate of iodination is directly dependent on the concentrations of the aminochrome and iodine and varies inversely with the first power of the iodide ion concentration. The rate of reaction is independent of pH, but the reaction is subject to general base catalysis. A mechanism for the iodination of aminochromes is proposed. The reactive species are molecular iodine and the zwitterionic form of adrenochrome, and the reaction proceeds via a quinonoid intermediate. The rate-controlling process is the removal of the C-7 proton.
The antifungal factors in barley. IV. Isolation, structure, and synthesis of the hordatines
Authors: Stoessl A.
Published: May 2006

Careful fractionation of extracts prepared from barley coleoptiles gave small amounts of pure hordatines A and B and substantial amounts of a mixture of their glucosides. The structures of the hordatines were deduced by degradative and spectroscopic studies and by the synthesis of some degradation products. A synthesis of racemic hordatine A analogous to its probable biogenesis was achieved by the oxidative coupling of coumaroylagmatine.The possible role of the hordatines in lignification is briefly discussed.
Reaction of Grignard reagents with β-dicarbonyl compounds. II. Synthesis of β-hydroxyketones from 2,4-pentanedione
Authors: Canonne P. , Leitch L. C.
Published: May 2006

Several new β-hydroxyketones having the formula CH3R′C(OH)CH2COCH3 have been prepared by the action of Grignard reagents on 2,4-pentanedione. With benzyl-, o-xylyl-, p-xylyl-, 3,4-dimethylbenzyl-, 2,5-dimethylbenzyl-, 3,5-dimethylbenzyl-, and α-naphthylmethyl-magnesium chlorides, 60 to 75% yields of the β-hydroxyketones were obtained. Phenyl-, p-tolyl-, and p-trifluoromethylphenyl-magnesium bromide and 2,4-dimethylbenzylmagnesium chloride gave lower yields, whereas with α-naphthylmagnesium bromide no β-hydroxyketone was formed. The β-hydroxyketones were separated from non-ketonic by-products by means of Girard's reagent T or P. Solid derivatives of the β-hydroxyketones could not be prepared.
Studies of the solvent effect on the chemical shifts in n.m.r. spectroscopy. II. Solutions of succinic anhydride, maleic anhydride, and the N-substituted imides
Authors: Matsuo Taku
Published: May 2006

Proton magnetic resonance spectra of succinic anhydride, maleic anhydride, and the N-ethyl- or N-(p-chlorophenyl)-imides have been investigated in various media. In benzene solution, a specific interaction between the π-electron cloud of the solvent and the moiety of the protons alpha to the carbonyl groups is suggested. The strength of the interaction is considered to be in the order of (i) maleic anhydride, (ii) succinic anhydride, and (iii) the N-substituted imides. The interaction may be due to both the large electron affinity and the polarization of the carbonyl group. The low-field shifts in strongly polar solvents, such as acetone or dimethyl sulfoxide, are ascribed to the preferential associations of the lone-pair electrons of polar solvents to the electron-deficient sites of solute molecules. In some cases, however, the solvent effects on the chemical shifts are opposite to those expected from the donor properties of the solvents. An explanation may be available from the anisotropic magnetic susceptibilities of the polar groups of the solvent molecules.
Ionization of methane and its electronic energy levels
Authors: Collin Jacques E. , Delwiche Jacques
Published: May 2006

The retarding potential difference (r.p.d.) efficiency curves of methane obtained with two different types of mass spectrometers are presented and discussed. It is shown that a Jahn–Teller splitting could explain some of the experimentally observed energy levels. Pre-ionization is shown to occur at 14.4, 16, and 19.5 eV. In particular, the latter value is rediscussed in terms of the second ionization potential of methane. It is concluded that the recent explanation of Ehrhardt and Linder, according to which the 19.5 eV level is a forbidden pre-ionized state, is compatible with our results and that the second ionization potential of methane should be around 24 eV. Ion–molecule reactions are shown to be of small importance around 19.5 eV, contrary to a hypothesis suggested by Sjögren.
Thiele acetylation of substituted benzoquinones
Authors: Wilgus H. S. , Gates,Jr J. W.
Published: May 2006

The treatment of substituted quinones with acetic anhydride under acid catalysis gives substituted triacetoxybenzenes. Previous work on this reaction is summarized, and the reaction has been extended to include quinones having electron-withdrawing groups, and two quinones which had previously been reported as inactive.
Synthesis of 2,2-disubstituted-6-cyanocyclohexanones
Authors: Kulp Stuart S.
Published: May 2006

The synthesis of a series of 2,2-disubstituted-6-cyanocyclohexanones by hydrolysis of the precursor 3,3-disubstituted-2-amino-1-cyanocyclohexenes (2,2-disubstituted-6-cyanocyclohexanoneimines) is described. The appropriate disubstituted acetonitriles reacted with 1-chloro-4-bromobutane to give the chloro nitriles, which were converted into the 2,2-disubstituted-heptanedinitriles for cyclization. The cyclic imino nitriles (enamines) hydrolyzed to keto nitriles, keto amides, or ketones depending on the reaction conditions. The new compounds possess the following substituents: dimethyl, diethyl, ethyl phenyl, and diphenyl. The enolization of the β-keto nitriles is discussed.
Cyclobutadiene–metal complexes. X. Reactions of tetramethylcyclobutadienenickel chloride with iron carbonyls
Authors: Bruce R. , Moseley K. , Maitlis P. M.
Published: May 2006

Tetramethylcyclobutadieneiron tricarbonyl has been obtained in 25–37% yield from the reaction of triiron dodecacarbonyl with either 3,4-dichlorotetramethylcyclobutene or tetramethylcyclobutadienenickel chloride dimer. The latter reaction also gave small amounts of another complex, Me8C8NiFe(CO)3. The reaction of [Me4C4NiCl2]2 with iron pentacarbonyl gave Me4C4Fe(CO)3 together with two other complexes. The structures of these new complexes are discussed in the light of their nuclear magnetic resonance, mass, and infrared spectra.
Correlation of isotope effects in substitution reactions with nucleophilicities. Secondary α-deuterium isotope effect in the iodide-131 exchange of methyl-d3 iodide
Authors: Seltzer Stanley , Zavitsas Andreas A.
Published: May 2006

The secondary α-deuterium isotope effect in iodide-131 exchange of methyl-d3 iodide is kH/kD = 1.05 ± 0.01 in methanol and 1.10 ± 0.04 in water at 20°. A correlation of secondary α-deuterium and 13C effects, in bimolecular nucleophilic substitution reactions, with the difference of E values between nucleophile and leaving group is presented.
Electrochemical reactions at PbO2 electrodes. Part II. The exchange reaction at β-PbO2 electrodes
Authors: Hampson N. A. , Jones P. C. , Phillips R. F.
Published: May 2006

The results of short time galvanostatic polarization experiments are described in which the maximum potential excursion is limited to ± 10 mV about the equilibrium potential.Exchange currents have been evaluated both geometrically and iteratively. The charge transfer reaction

[Formula: see text]is slow. The dependence of the exchange current on the concentration of Pb(II) is consistent with a charge transfer coefficient of 0.2 in agreement with the arithmetical analysis of current–potential data.There is evidence for an adsorbed layer of hydrogen ion at the electrode.
Sound velocity in the inert gas liquids and the law of corresponding states
Authors: Aziz R. A. , Bowman D. H. , Lim C. C.
Published: May 2006

Velocity of sound was measured to an accuracy of 0.1% in liquid argon, krypton, and xenon under saturated vapor conditions by a resonance ultrasonic technique. Measurements in argon and krypton were from their normal boiling points to close to their critical points, while those in xenon were from its triple point to close to its critical point. Adiabatic compressibilities of these liquids were calculated in the temperature regions for which density data were available.Analysis of the results indicates that such velocity data can provide a precise test of the principle of corresponding states, in its classical and quantum forms. The corresponding states principle holds quite well in the above liquids when subjected to this test.The velocity data in all cases agree more closely with tunnel model calculations than with cell model calculations.
Intramolecular hydrogen bonds and the orientation of amino groupsin o-phenylenediamines
Authors: Krueger P. J.
Published: May 2006

The infrared absorption spectra of partially deuterated o-phenylenediamine and 4,5-di-methyl-, 4-methyl-, and 4-chloro-o-phenylenediamine in dilute CCl4 solution show double intramolecular

[Formula: see text] hydrogen bonds in which the two NHD groups are equivalent and each group acts as both a proton donor and a proton acceptor. The ring substituent effect on this interaction in these compounds is small. In 4-methoxy-o-phenylenediamine, the amino groups are not equivalent, but double intramolecular hydrogen bonds are still present. In 4-nitro-o-phenylenediamine, only one intramolecular

[Formula: see text] hydrogen bond appears to exist. The effect of N-substitution on some of these observations is discussed.
The constitution of isamic acid
Authors: Mayo P. de , Ryan J. J.
Published: May 2006

The structure of isamic acid, prepared by the reaction of isatin with ammonia, has been established. It is that of the ylid XIIa or XIIc, different from the ylid XIIb first suggested by the present authors in an earlier communication. The difference lies in an unsuspected exchange of nitrogen functions.The nature of the oxidation products with hydrogen peroxide (VII), with nitric acid, and with potassium permanganate (XXVII) has been elucidated; these do not differ from those suggested earlier.In the Appendix the action of diazomethane on N-acetyl isatoic acid is described. Three molecules of reagent are consumed in esterification, homologation, and epoxide formation.
The stereochemistry of nitrate esters. II. Symmetric stretching frequencies of the nitrato group in nitrate esters of l,4;3,6-di-anhydrohexitols (4,8-dihydroxy-cis-2,6-dioxabicyclo[3.3.0]octanes)
Authors: Hayward L. D. , Livingstone D. J. , Jackson M. , Csizmadia Valerie M.
Published: May 2006

In the infrared spectra of mono- and di-nitrate esters of the l,4;3,6-dianhydrides of d-mannitol, d-glucitol, and l-iditol in benzene solution (0.04 M in nitrato groups), the frequencies of the va(NO2) and v(ON) bands (singlets) were 1 645 ± 3 and 843 ± 3 cm−1, respectively, whereas the vs(NO2) band occurred at frequencies characteristic of either an endo (1 282 ± 1 cm−1) or an exo (1 274 ± 1 cm−1) configuration of the nitrato group; the ratios of the band areas were 1.5:1.0:1.0, respectively.The stereospecific frequency of the vs(NO2) band was attributed to non-bonded intramolecular interaction between the nitrato group and vicinal oxy groups on the basis of the spectra run in a series of solvents and the molecular conformations determined by X-ray crystallography. This new stereochemical probe permitted the assignment of the structure, configuration, and conformation in a series of nitrate esters.
Kinetics of formation of sodium chlorozirconate
Authors: Dutrizac J. D. , Flengas S. N.
Published: May 2006

The kinetics of formation of sodium hexachlorozirconate from sodium chloride single crystals and zirconium tetrachloride vapor at about 600 Torr have been investigated by the weight-gain method. Analysis of the results showed the formation reaction to be diffusion controlled, with zirconium tetrachloride being the most probable diffusing species. The apparent energy of activation has been determined for this reaction from the variation of the rate constant with temperature, and it was found to be 12.3 ± 3 kcal/mole. The Arrhenius rate equation for the formation of Na2ZrCl6 from NaCl and ZrCl4 at 600 Torr pressure, in the temperature range 400 to 500 °C, is

[Formula: see text]where the units of the parabolic rate constant, K, are (g(Na2ZrCl6))2 cm−4 h−1.
Use of conductimetric titrations in dilute oleum to determine the reactions of complex electrolytes in sulfuric acid
Authors: Robinson E. A. , Quadri S. A. A.
Published: May 2006

The use of conductimetric base–acid titrations in dilute oleum to confirm the modes of reaction of solutes in sulfuric acid that have been established by the methods of cryoscopy and electrical conductivity in 100% acid is discussed and compared with Leisten's method of "cryoscopic mixtures".
Behavior of carboxylic acids and carboxylic anhydrides in sulfuric acid
Authors: Robinson E. A. , Quadri S. A. A.
Published: May 2006

The behavior of some carboxylic acids and anhydrides in sulfuric acid has been investigated by cryoscopic and conductimetric measurements in 100% H2SO4, cryoscopic measurements in aqueous H2SO4, and conductimetric titrations in dilute oleum.The previously established behavior of acetic anhydride in dehydrating sulfuric acid,

[Formula: see text]is confirmed, and glutaric anhydride is shown to behave similarly.For succinic acid the second stage of protonation is incomplete, whereas glutaric and adipic acids are fully diprotonated. Fumaric acid is less protonated in the second stage than is succinic acid.For succinic acid, maleic acid, and phthalic acid the equilibrium

[Formula: see text]is important. For succinic acid and its anhydride the equilibrium favors substantial formation of carboxylic-acidium ion even in dilute oleum, whereas for maleic and phthalic acids and their anhydrides formation of the anhydrides is favored in 100% H2SO4 and dilute oleum.Maleic anhydride molecules behave essentially as nonelectrolytes in sulfuric acid; phthalic acid is a very weak base; and naphthalene 1,8-dicarboxylic anhydride is a strong base.
Energy distribution in electronically excited CH and C2 in low pressure hydrocarbon flames
Authors: Ndaalio Gaspar , Deckers Jacques M.
Published: May 2006

A study has been made of the rotational energy distribution of electronically excited CH and of the vibrational energy distribution of electronically excited C2 radicals in low pressure (0.2 to 35 Torr) hydrocarbon flames. The rotational energy of the CH radical in the A2Δ (ν = 0) state has been found to be statistically distributed in the levels with quantum numbers 14 to 21. This distribution can be described by a temperature which has, however, no thermodynamic significance. In the methane–oxygen flame this temperature has been found to be independent of both the composition of the gas mixture and the pressure, whereas in the ethylene–oxygen system it varies with these parameters. Hydrogen–methane–oxygen flames behave as ethylene flames. Inert diluents such as nitrogen and carbon dioxide do not affect the temperature at very low pressures. This indicates that the energy distribution is not perturbed measurably by collisions before emission takes place. In order to explain these observations we have to accept that at least two reactions produce CH* in ethylene flames.The cross section for energy transfer out of the high rotational levels of CH(A2Δ) to flame gases is found to be smaller than 0.6 Å2 and that for transfer to CO2 is about 2 Å2.A statistical distribution also has been observed in the vibrational energy distribution of electronically excited C2. The corresponding temperature is about 6 500 °K and is independent of the composition of the gas mixture and of the fuel. It decreases very slowly with increasing pressure above 3 Torr. Inert diluents added to the gas mixture do not alter this temperature.The cross section for de-excitation of C2(A3πg) is found to be smaller than 2.5 Å2.
The thermal decomposition of t-alkyl N-arylcarbamates. I. The effect of ring substituents
Authors: Thorne M. P.
Published: May 2006

A series of t-butyl N-arylcarbamates in which the aryl group is a phenyl or a meta- or para-substituted phenyl ring has been prepared. Decomposition of these compounds in diphenyl ether at 177.5 °C has shown that the reaction is essentially first order, yielding carbon dioxide, isobutylene, and the corresponding amine. The rates of decomposition increase with increasing electronegativity of the substituent on the aromatic nucleus, and give a Hammett plot with a slope of 0.54. A cyclic mechanism is proposed for the decomposition reaction.
Photochemistry of nitroso compounds in solution. IX. Steric effects in the photoaddition of N-nitrosodialkylamines to olefins. Magnetic non-equivalence of methylene protons caused by a distant asymmetry
Authors: Chow Y. L. , Colón Carlos J.
Published: May 2006

The photoreactions of various N-nitrosodialkylamines were studied in the presence of an olefin. Steric hindrance of the nitrosamino group could retard the efficiency of the addition. For N-nitroso-1,2,3,4-tetrahydroisoquinoline, the photodecomposition itself is so fast that no photoaddition takes place even in the presence of a reactive olefin such as styrene. The methylene group attached to the oximino group in IIa, IIIa, and VIa was magnetically non-equivalent, exhibiting AB quartet signals. The causes of this magnetic non-equivalence are discussed.
Substituent effects in the catalytic hydrogenation of steroidal Δ4- and Δ5-3,3-ethyleneketals
Authors: Liston A. J. , Howarth M.
Published: May 2006

A number of isomeric Δ4- and Δ5-3,3-ethylenedioxy steroids were prepared to study the substituent effects on the relative amounts of 5α and 5β ketals formed during catalytic hydrogenation. Hydrogenation of Δ5-3,3-ethylenedioxy steroids with palladium on charcoal as catalyst yielded 5α steroids exclusively. The Δ4-3,3-ethylenedioxy compounds yielded mixtures of 5α and 5β ketals in which slightly more 5β product was formed than was obtained by catalytic hydrogenation of the equivalent Δ4-3-oxo steroid. Substituents in the C-11 position of the Δ4 ketals diminish the amount of 5β steroid formed during hydrogenation.
Nucleation of calcium phosphate from solution
Authors: Walton A. G. , Bodin W. J. , Furedi H. , Schwartz A.
Published: May 2006

A method of determining the stoichiometry of metastable phases from nucleation characteristics is described and is applied to calcium phosphate precipitation. The stoichiometric ratio [Ca]/[P] is shown to be 1.49 ± 0.02 in the pH range 7.0–9.1, indicating that it is not hydroxyapatite which normally forms first in the physiological pH region. Characterization of the product by radio isotopes and by infrared spectroscopy and electron diffraction confirms the stoichiometry and indicates that the calcium phosphate nucleated from solution at high pH is an amorphous or soft metastable material. Some biological implications of these findings are pointed out.
Cyanide complex of 1,3,5-trinitrobenzene in nonaqueous solvents
Authors: Norris A. R.
Published: May 2006

The initial reversible interaction of 1,3,5-trinitrobenzene and cyanide ion has been studied spectrophotometrically in a number of nonaqueous solvents and found to result in the formation of a complex containing 1,3,5-trinitrobenzene and cyanide ion in a 1:1 ratio. At 25.3 °C, the equilibrium constants for complex formation (K) and the molar extinction coefficients (ϵ) of the complex were found to be 1.44 ± 0.15 × 105 l mole−1 and 2.24 ± 0.05 × 104 l mole−1 cm−1 and 3.35 ± 0.35 × 105 l mole−1 and 2.24 ± 0.05 × 104 1 mole−1 cm−1 respectively for acetone and chloroform solutions. The second-order rate constant governing formation of the complex in chloroform was found to be 2.25 × 102 l mole−1 s−1 at 25.0 °C. On the basis of the visible and infrared absorption data obtained for the complex in chloroform and 1,2-dimethoxy-ethane, the complex is considered to be a Meisenheimer-type complex rather than a "charge-transfer" complex.
Configuration of methyl formate in benzene and carbon disulfide solutions
Authors: Bock E.
Published: May 2006

The dipole moment of methyl formate in dilute benzene and carbon disulfide solution at 25 °C was determined. The obtained value for the dipole moment was compared with the measured value of β-butyrolactone derived from dilute benzene solution. It is concluded that the preferred configuration of methyl formate in CS2 solution does not correspond to that assumed by Pendred et al. in their calculations of spin-lattice proton relaxation times in methyl formate dissolved in CS2, but to that postulated by Curl, Jr. from microwave data.
Photometric analysis of trace amounts of hydrazine with p-dimethylaminobenzaldehyde. Chemical equilibria
Authors: Gamble Donald S. , Hoffman I.
Published: May 2006

An equilibrium scheme is proposed for aqueous acid solutions containing hydrazine, p-di-methylaminobenzaldehyde and p-dimethylaminobenzaldazine. The quinoidal cation form of the latter has an absorbance peak at 455 mμ, for which

[Formula: see text] (±2.1%). In 0.4 m to 1 m H+, 10−5 m benzaldazine is practically all in the quinoidal cation form. The acid attenuation of absorbance at 455 mμ is caused by protonation of the dimethylamino group of unreacted aldehyde. Semiquantitative equilibrium data are presented for the reaction between hydrazine and p-dimethylaminobenzaldehyde.
Epoxide ring opening of methyl 2,3-anhydro-4-azido-4-deoxy-pentopyranosides
Authors: Dick A. J. , Jones J. K. N.
Published: May 2006

Epoxide ring opening reactions of methyl 2,3-anhydro-4-azido-4-deoxy-pentopyranosides with hydroxide ion and methoxide ion are described. The products obtained by reactions of the epoxides with hydroxide ion are related, by preparation of their 2,3-di-O-methanesulfonyl derivatives, to known compounds or their enantiomers. Opening of the α-d(and l)-ribo epoxides with methoxide ion gave monomethylated products which were characterized by nuclear magnetic resonance analysis of their acetates. The relative yields of the two major products obtained in each case are not accounted for, in some cases, by consideration of only steric and inductive effects.
Some reactions of hexafluorobutyne-2 with phosphines and amines
Authors: Cullen W. R. , Dawson D. S.
Published: May 2006

The addition reaction R2EX + CF3C≡CCF3 → R2EC(CF3)=C(CF3)X has been investigated further (E = P and N); 1:1 adducts have been obtained from (C2H5)2PH, (CF3)2PH, (C6H5)2P—P(C6H5)2, and (CH3)2NCl, but not from (CH3)2PCl or (CH3)2P—P(CH3)2. (CF3)2PH also gives a 2:1 adduct. Triphenylphosphine causes the butyne to polymerize at − 78°. A similar but slower reaction takes place with trimethylamine. In the presence of water, trimethylamine and the butyne give the bis(butenyl) ether cis,trans (CF3CH=CCF3)2O as the major product.
The photodimerization of 3-phenyl-2-cyclohexenone
Authors: Yates Peter , Eğe Seyhan N. , Büchi G. , Knutsen D.
Published: May 2006

Ultraviolet irradiation of 3-phenyl-2-cyclohexenone has been found to give a single photo dimer, whose structure has been established as the cis–anti–cis head-to-head cyclobutane derivative X.
Electron spin resonance studies of γ-irradiated aqueous alkaline solutions of acrylamide at 77 °K
Authors: Seddon W. A. , Smith D. R.
Published: May 2006

The γ radiolysis of acrylamide in 8 M NaOH solutions in H2O and D2O at 77 °K results in the formation of

[Formula: see text]and

[Formula: see text]radicals, with a maximum yield

[Formula: see text] = 1.9 molecules/100 eV. Since in the absence of acrylamide the yield of trapped electrons, G0(e−t), = 1.9, it appears that the precursor of

[Formula: see text] is a radical anion

[Formula: see text], which then abstracts a proton from the solvent according to

[Formula: see text]In support of this interpretation we find that Hm1· is also formed in similar media as a result of (a) "photo-bleaching" of trapped electrons or (b) photo-detachment of electrons from ferrocyanide ion with light of wavelength 2 537 Å. This is confirmed by the electron spin resonance (e.s.r.) spectra obtained from methacrylamide and acrylonitrile in γ-irradiated alkaline ice. The concentration dependence of electron scavenging by acrylamide indicates that the electrons diffuse over distances of up to 170 Å prior to trapping or capture by the solute.
Determination of the activity coefficients of methanol and ethanol in benzene solutions by gas chromatography
Authors: Pollak Peter , Cave G. C. B
Published: May 2006

A rapid gas-chromatographic method is described for the quantitative analysis of the equilibrium vapor phase over a solution. A vapor pump has been designed for the purpose and is described. The method should be particularly useful at low concentrations of volatile solutes, alone or in mixtures. As an example of the application of the method, the vapor concentrations of methanol and of ethanol over benzene solutions at 25 °C have been measured. The precision of the data is also reported. The activity coefficients of the alcohols in the benzene solutions were calculated.
Importance of heterogeneous termination in the pyrolysis of ethane
Authors: Lin M. C. , Back M. H.
Published: May 2006

It is shown that the increase in the order of the thermal decomposition of ethane that is observed below about 200 mm is partly the result of the changes in the order of the unimolecular dissociations of ethane and the ethyl radical that occur in the same range of pressures, and partly the result of the increasing importance of a heterogeneous termination process as the pressure is lowered.
Unimolecular decomposition of methyl chloride. II. Some refinements of the calculations
Authors: Forst W. , St. Laurent P.
Published: May 2006

The quantum version of the statistical collision theory is applied to the unimolecular decomposition of methyl chloride in the second-order region using an improved computational procedure and a more realistic physical model. An attempt is made to determine active degrees of freedom, i.e. degrees of freedom participating in intramolecular energy transfer, by rational argument. These considerations point to at least one overall rotation as active, in addition to all nine vibrations as active. Conservation of angular momentum is explicitly considered in the case of one active rotation and an appropriate correction factor is included in the calculated rate constant, as is a correction for anharmonicity. The theoretical rate constant so computed is within less than a factor of two of the experimental value.
Dipole moments of substituted chloroformates in dilute benzene solutions
Authors: Bock E. , Iwacha D.
Published: May 2006

The dipole moments of methyl, ethyl, n-propyl, n-butyl, amyl, and phenyl chloroformate as well as n-butyl formate in dilute benzene solution at 25 °C were determined. The experimental results suggest that the configuration of the chloro-esters differs from the configuration of the unchloroinated esters, viz. the ester hydrocarbon group and the chlorine atom are cis to each other.
Reaction mechanism studies. 5. The mechanism of the diaxial → diequatorial rearrangement of β-chlorothioethers
Authors: King J. F. , Abikar K.
Published: May 2006

p-Methoxy- and p-nitro substituted analogues (1b and 1c) of the diaxial β-chlorothioether 2β-chloro-3α-(phenylthio)-5α-cholestane (1a), have been prepared and found to undergo the diaxial → diequatorial rearrangement. The rates of rearrangement of these compounds show the sequence p-methoxy > H > p-nitro. It is concluded that the transition state for the rearrangement is polarized in the sense of a sulfonium chloride (3). The rearrangement of 1a is 1600 times faster in butanol than in decalin (at 110°). There is thus no inherent insensitivity to solvent change in a rearrangement in which there may be a "four-atom arrangement" in the transition state, a conclusion relevant to previous work on the diaxial → diequatorial rearrangement of 1,2-dibromides (1). It was further found that the nitro group slowed the rearrangement (at 110°) more in butanol than in decalin, an observation regarded as consistent with, but not requiring, the incursion of a merged ion-pair, cyclic concerted mechanism.
Photochemical synthesis.19. The flash photolysis of unsaturated sultones
Authors: Charlton J. L. , Mayo P. de
Published: May 2006

The hypothesis that the irradiation of unsaturated sultones gives the final products, the ketosulfonic esters, via a sulfene intermediate has been reexamined. In the case of sultone (4), it has been shown that, if such a species be an intermediate, it must have a lifetime, in cyclohexane solution, of less than 20 μs. The consequenes of this observation are discussed.The flashing of sultone (4) in methanol generates the enol of the keto ester end product (13) which decays with a half life of about 20 s
Steroid 16,17-furoxan derivatives
Authors: Reimann Hans , Schneider Helen
Published: May 2006

The syntheses of 3-methoxy-l,3,5(10)-estratrieno[16,17-c]furoxan (3) and 3-keto-4-androsteno[16, 17-c]furoxan (8) from 16-oximinoestrone methyl ether and 16-oximino-5-androsten-3β-ol-17-one, respectively, are described.
A rapid, mild procedure for the preparation of alkyl chlorides and bromides
Authors: Hooz J. , Gilani S. S. H.
Published: May 2006

Primary and secondary alkyl chlorides have been conveniently prepared by the reaction of tri-n-octylphosphine with carbon tetrachloride solutions of the corresponding alcohols. This rapid, high yield reaction proceeds with inversion of configuration. By using carbon tetrabromide the method has been extended to the synthesis of alkyl bromides.
Coordination compounds of norbornadiene with silver tetrafluoroborate
Authors: Quinn Harold W.
Published: May 2006

Crystalline complexes of norbornadiene with silver tetrafluoroborate have been obtained both from anhydrous and aqueous solution. While both solutions yield complexes of stoichiometry AgBF4•C7H8 and 2AgBF4•3C7H8, those from the aqueous solutions also contain water of crystallization. The infrared spectra show that norbornadiene is similarly complexed in both the anhydrous and hydrated complexes but that the coordination in the 1:1 complex is different from that in the 2:3 complex. The anhydrous and hydrated 1:1 complexes have the same X-ray diffraction powder patterns while those of 2:3 complexes are different.
Nature of the coordination bond in metal complexes of substituted pyridine derivatives. II. The far infrared spectra and metal–ligand force constants of copper complexes of 4-substituted pyridines
Authors: Wong Patrick T. T. , Brewer D. G.
Published: May 2006

Infrared spectra, including the lower frequency region, of copper (II) complexes of the type [CuL2Cl2], where L = 4-methylpyridine, 4-carbinylpyridine, pyridine, 4-acetylpyridine, 4-pyridinecarboxamide, 4-carbomethoxypyridine, and 4-cyanopyridine have been measured. The substituent effect upon the copper–nitrogen (ligand) and copper–chlorine stretching frequencies has also been examined. It was found that the substituents on the pyridine ring not only affected the nature of copper–nitrogen bond, but also the copper–chlorine bond. It appears that an entirely delocalized system exists, involving the chlorine atoms and the substituents in the complexes. Force constants associated with the coordination bond between copper and the nitrogen of the ligands have been calculated by means of an IBM 1620 computer. By comparison of the copper–nitrogen stretching frequencies with the corresponding force constants, and the heats of coordination, it may be concluded that the magnitude of the metal–ligand stretching frequency is directly related to the metal–ligand coordination bond strength for the systems under study.
The role of Hg 63P0 atoms in mercury photosensitization. IV. Origin of the 4850 Å and 3350 Å bands
Authors: McAlduff J. E. , Drysdale D. D. , Roy D. J. Le
Published: May 2006

The continuous emission bands at 4850 Å and 3350 Å, attributed to the decay of electronically excited mercury molecules, have been studied in a flow system in which Hg 63P1 atoms were generated in the presence of nitrogen. The mechanism presented to account for the formation and decay of these eximers incorporates the assumption that these bands are derived by spontaneous emission from the A30u− and A31u states of the mercury molecule respectively. It is proposed that the A31u state is the precursor of the A30u− state.
Tumbling of methyl radicals adsorbed on a silica gel surface studied by electron spin resonance
Authors: Gardner C. L. , Casey E. J.
Published: May 2006

The electron spin resonance spectra of CH3 and CD3 adsorbed on a silica gel surface at 77 °K are characterized by a marked dependence of the line width on nuclear spin quantum number. This dependence can be interpreted in terms of the tumbling of the radicals on the surface, anisotropies in the hyperfine and g tensors giving rise to a relaxation mechanism dependent on MI. A quantitative comparison of the spectra with the theory of this relaxation mechanism developed by McConnell, Kivelson, and Freed and Fraenkel enables the tumbling frequencies, 2.0 × 107 s−1 and 1.3 × 107 s−1 for CH3 and CD3 respectively, to be determined.
Recoil studies of the reaction 12C(p,pn)11C from threshold to 85 MeV
Authors: Hontzeas S.
Published: May 2006

In order to survey the features of the simple 12C(p,pn)11C reaction from threshold to 85 MeV, data were obtained for average projected ranges of 11C along and perpendicular to the beam direction. The data from threshold to 45 MeV provide evidence for a large momentum transfer mechanism of the compound nucleus type. In the 45–85 MeV energy region the data were analyzed in terms of a vector model consistent with the cascade–evaporation mechanism. More detailed information regarding differential ranges and angular distributions are needed if the recoil parameters are to provide conclusive results.
Molar excess volumes of binary n-alcohol systems at 25 °C
Authors: Pflug H. D. , Benson G. C.
Published: May 2006

A dilatometer suitable for measuring small changes in volume associated with the mixing of liquids is described. The apparatus was used to measure the excess volumes of 11 binary n-alcohol systems at 25 °C.
Organic and biological spectrochemical studies. XXV. Properties of the p-bis(methylthio)benzene and p-bis(ethylthio)benzene cation radicals
Authors: Forbes W. F. , Sullivan P. D.
Published: May 2006

The electron spin resonance spectra of the sulfur analogs of the p-dimethoxy and p-diethoxy benzene cation radicals, i.e. the cation radicals of p-bis(methylthio)benzene (1) and p-bis(ethylthio)benzene (2), were investigated in aluminium chloride – nitromethane. The spectra are interpreted in terms of cis–trans isomerism. Empirical molecular orbital calculations support this assignment and yield qualitatively correct spin densities at the ring positions. Comparison of the spectral properties of these species with corresponding compounds containing oxygen atoms indicates changes which can be associated with the greater tendency of the sulfur atom to attract spin density. There is also evidence from the β-alkyl proton splitting constants that the conformation of the radical of 2 differs from that of its oxygen analog. Slightly different g values are again observed for the cis and trans isomers, as previously noted for related compounds.
Organic and biological spectrochemical studies. XXVI. E.s.r. spectra of the 4,4′-dimethoxybiphenyl cation radical
Authors: Forbes W. F. , Sullivan P. D.
Published: May 2006

The electron spin resonance (e.s.r.) spectrum of 4,4′-dimethoxybiphenyl in aluminium chloride–nitromethane is remarkably temperature dependent. The changes are explained by postulating the rapid interconversion of conformational isomers, leading to line-width alternation.
Disubstituted hydroxamic acids and the determination of vanadium
Authors: Cassidy R. M. , Ryan D. E.
Published: May 2006

A number of disubstituted hydroxamic acids were investigated as possible replacements for benzoylphenylhydroxylamine in the determination of vanadium; none is superior. At 378 mμ., p-phenylazobenzoylphenylhydroxylamine shows a marked sensitivity increase but selectivity is poor. In the visible region, there is an increase in molecular extinction coefficient as the reagent π system is extended; how ever, complete coplanarity of the aromatic and metal chelate rings is not possible and the increase is not large enough to be of much practical value.
The synthesis of 2-amino-2-deoxyhexoses: D-glucosamine, D-mannosamine, D-galactosamine, and D-talosamine
Authors: Lemieux R. U. , Nagabhushan T. L.
Published: May 2006

Methods for the preparation of the hydrochlorides of 2-amino-2-deoxy-D-glucose (D-glucosamine) and 2-amino-2-deoxy-D-mannose (D-mannosamine) from tri-O-acetyl-D-glucal and of 2-amino-2-deoxy-D-galactose (D-galactosamine) and 2-amino-2-deoxy-D-talose (D-talosamine) from tri-O-acetyl-D-galactal are described. The reactions involve addition of nitrosyl chloride to the acetylated glycal followed by conversion of the adduct to acetylated derivative of the 2-oximinohexose and reduction of the oxime to amine.
The chemistry of ylids. XVI. The acidifying effects of 'onium groups
Authors: Johnson A. William , Amel Ronald T.
Published: May 2006

An examination of the pKa's of a series of phenacyl 'onium salts has indicated that the acidifying effects of the 'onium groups increase in the order arsonium < phosphonium < sulfonium. The acidifying effects of the 'onium atom substituents increase in the order methyl < n-butyl < phenyl. These observations have been accounted for in terms of pπ–dπ overlap between the carbanion and the heteroatom of the 'onium group.
Preparation of cis-crotonyl chloride
Authors: Hocking M. B.
Published: May 2006

Published methods for the preparation of cis-crotonyl chloride were found to give a product contaminated with appreciable proportions of the trans isomer. Separation of these two isomers was found to be impossible because of the small boiling point difference and the readiness with which the cis acid chloride isomerizes to the trans. Herein are outlined the precautions necessary to obtain pure cis-crotonyl chloride contaminated only with the free acid, from which it is readily separated by cold distillation.
Analysis of the n.m.r. spectrum of pentafluorobenzene
Authors: Schaumburg K. , Gillies D. , Bernstein H. J.
Published: May 2006

The 1H and 19F spectra of pentafluorobenzene (PFB) have been analyzed, and spectral parameters obtained by iteration using least squares criterion. A number of solutions were found by this procedure. The physical solution was selected by "tickling" experiments.
Dipole moments of some molecules in dilute benzene solutions
Authors: Bock E. , Iwacha D.
Published: May 2006

The dipole moments of bromochloromethane, bromodichloromethane, bromotrichloromethane, dimethylcarbamyl chloride, dimethylcarbamyl fluoride, vinyl formate, phenyl chlorothiolformate, γ-valerolactone, and 2-iodopropene were determined in dilute benzene solutions at 25 °C. The observed magnitudes of the dipole moments are rationalized in terms of molecular electronic charge distributions.
Photolysis of HNCO vapor in the presence of NO and O2
Authors: Back R. A. , Ketcheson R.
Published: May 2006

The effect of NO at pressures up to 380 Torr on the photolysis of HNCO vapor (4.5 Torr) by light from an unfiltered medium-pressure mercury lamp has been studied at 37 °C. The yield of CO was reduced to about half its original value, which is attributed to reactions of NH and NCO with NO. The yield of N2 showed a steady increase with increasing NO pressure, probably due to reactions of NO(A2∑+) excited by absorption of light. The hydrogen yield fell rapidly to zero as the NO pressure was increased.Added oxygen at pressures up to 5 Torr had no effect on the CO and N2 production at 37 °C; at 110 °C the CO yield decreased somewhat while the N2 remained unaffected. These observations suggest that NH and NCO do not react readily with O2. The production of H2 fell rapidly to zero with increasing O2 pressure at both temperatures. The suppression of H2 formation by both NO and O2 supports the belief that it is formed by reactions of hydrogen atoms.