bluuebunny/crossref_metadata_2025 huggingface dataset:
New Synthetic Routes to Δ2-Pyrazolin-5-ones
Authors: Nye M. J. , Tang W. P.
Published: May 2006

Three new synthetic routes to Δ2-pyrazolin-5-ones involving base-catalyzed molecular rearrangements are reported.
Kinetics and Mechanism of the Sulfonation of 2-Phenyl-1-ethanesulfonic acid
Authors: Koeberg-Telder (Mrs.) A. , Nienhuis (Mrs.) Z. R. H. , Cerfontain H.
Published: May 2006

The kinetics of the sulfonation of 2-phenyl-1-ethanesulfonic acid in 85.0–98.4% H2SO4 has been studied. The results are discussed in terms of sulfonation of the unionized sulfonic acid and its conjugated base, the sulfonate anion. Partial rate factors for the —CH2CH2SO3H substituent are reported.
The Conformational Equilibrium of 1,2,3-Tribromopropane in Solution
Authors: Ernst L. , Schaefer T.
Published: May 2006

The p.m.r. spectra of dilute solutions of 1,2,3-tribromopropane in carbon tetrachloride, acetonitrile, and dimethylsulfoxide as well as of the neat compound are examined. From the three- and four-bond spin–spin coupling constants and from a comparison between observed and calculated dipole moments it is concluded that in nonpolar solvents the title compound exists preferably in the enantiomeric conformations a and i. In polar solvents other rotamers contribute to the equilibrium but still seem to play only a minor role. Semiempirical calculations of conformational energies rule out contributions to the conformational equilibrium from rotamers having (1:3) bromine–bromine interactions, but otherwise are only in moderate agreement with experiment.
Oxodichlororhenium(IV), ReOCl2
Authors: Frais P. W. , Howard-Lock H. E. , Lock C. J. L.
Published: May 2006

The preparation and some physical and chemical properties of ReOCl2 are described.
The Alkylation of Cyclic Diketone Thallium(I) Salts
Authors: McIntosh John M. , Beaumier P. M.
Published: May 2006

The C/O alkylation ratios of a series of alkyl halides and α-haloesters with the thallium(I) salts of 1,3-cyclohexanedione and 1,3-cyclopentanedione have been investigated. Unlike the alkylation of acyclic diketone salts, the predominant process in most cases is O-alkylation.
Some Oxime and Amide Complexes of NiCl2
Authors: Stone M. E. , Johnson K. E.
Published: May 2006

[Ni(Aox)4Cl2] (Aox = acetaldoxime), [Ni(Acm)4(H2O)2]Cl2 (Acm = acetamide), Ni(Cy)3Cl2 (Cy = cyclohexanone oxime), and [Ni(cap)6]Cl2(Cap = caprolactam) have been prepared. Their solution electronic spectra indicate approximately octahedral environments for Ni(II) while solid Ni(Aox)4Cl2 shows a small tetragonal distortion. The i.r. spectra can be accounted for by oxime bonding to Ni via nitrogen and amide bonding to Ni via oxygen alone.
Use of N-Carboxyanhydrides in the Synthesis of Dipeptides. Factors Affecting the Yields of Several Alanine and Valine-containing Dipeptides
Authors: Grovestine Eric M. , Langlois Jean R. , Williams Ross E.
Published: May 2006

A series of dipeptides having aliphatic side chains have been prepared in aqueous solution from alanine and valine NCA. An organic base was used to establish and maintain the pH. After the reaction the amounts of unreacted amino acid nucleophile and the overall yields in the reaction were determined. Our observations have led us to propose that NCA stability, the pKa of the amino acid nucleophile and the stability of the carbamate all can play an important role in determining synthetic yields during these preparations.
Substituent Effects on the Acetyl Group Conformation and the Carbonyl Frequency in Acetophenones
Authors: Krueger P. J.
Published: May 2006

The fundamental carbonyl stretching frequencies for o-, m-, and p-substituted acetophenones in dilute CCl4 solution are correlated with the electrophilic substituent constant σ+ by the expression vc=o (cm−1) = 11.53σ+ + 1691.5 (n = 27, correlation coefficient = 0.988, standard deviation = 1.2 cm−1). The frequencies of carbonyl groups trans to an o-substituent follow this correlation, assuming σo+ ≈ σp+, while those oriented cis to the substituent generally do not. Deviations from this correlation are interpreted in terms of dipole–dipole interactions, steric hindrance to planarity, intramolecular hydrogen bonding, and non-additivity of σ+ values for some combinations of substituents. The carbonyl frequencies for singly m- and p-substituted acetophenones are also correlated with the polar and resonance components of σ+ by the expression vc=o (cm−1) = 15.66σI + 10.99σR+ + 1689.8 (n = 13, correlation coefficient = 0.981, standard deviation = 0.9 cm−1). Thus the sensitivity of the carbonyl frequency to the polar effect is greater than to the resonance effect. In ω-substituted acetophenones no precise correlation with polar substituent constants is observed.
Synthesis of 1,3,4-Dioxazoles from Hydroxamic Acids and Acetylenic Compounds
Authors: Chen F. M. F. , Forrest T. P.
Published: May 2006

Hydroxamic acids have been shown to undergo a base-catalyzed reaction with acetylenic compounds containing electron-withdrawing groups, to yield substituted 1,3,4-dioxazoles.
cis Virtual Coupling
Authors: Bancroft G. M. , Libbey E. T.
Published: May 2006

The proton n.m.r. spectra of the new compounds cis-Fe(NCS)2(PR3) (R = Me, MeO) consist of two identical triplets assignable to trans PR3 and cis PR3 linkages in the same complex.
The Surface Analysis of Nickel Chromia Catalysts by X-Ray Photoelectron Spectroscopy
Authors: McIntyre Norman Stewart , Sagert Norman Henry , Pouteau Rita Mary Louise , Proctor Warren George
Published: May 2006

The surface composition of a series of nickel–chromia catalysts has been examined by X-ray photoelectron spectroscopy. Correlation of the amount of available surface nickel with the activity of the particular catalyst for hydrogen water deuterium isotope exchange is very good. No significant alterations are observed in the valence band spectra as the surface composition changes.
Reductive Cleavage of Carbohydrate p-Toluenesulfonates with Sodium Naphthalene
Authors: Jarrell H. C. , Ritchie R. G. S. , Szarek W. A. , Jones J. K. N.
Published: May 2006

Carbohydrate p-toluenesulfonates are desulfonylated rapidly and in high yield, by treatment with sodium naphthalene in tetrahydrofuran, to regenerate the original hydroxyl groups. The method has been applied to carbohydrates containing up to three p-toluenesulfonate groups, to unsaturated sugars, and to a nucleoside derivative.
Carbon-13 Magnetic Resonance: the Stereochemistry of 1,2- and 1,3-Dimethyl-4-phenylpiperidine Derivatives
Authors: Jones Alan J. , Casy A. F. , McErlane K. M. J.
Published: May 2006

The carbon-13 magnetic resonance spectra of the diastereoisomers of 1,2-dimethyl- (1) and 1,3-dimethyl-4-phenylpiperidin-4-ol (2), their esters and corresponding hydrochlorides have been determined. The observed chemical shifts can be ascribed to charge polarization or steric effects. The latter is particularly important in establishing the axial configuration of the 4-phenyl group and 3-methyl group in the preferred conformations of α-1 and β-2, respectively, and consequently the stereochemistry of these systems. Substituent additivity effects are similar to those in the piperidones and cyclohexanes. Solvent effects on 13C resonances remove the ambiguities of conformational change suggested in earlier proton studies.
Carbon-13 Magnetic Resonance: the Stereochemistry of Pharmacologically Active 1,2,5-Trimethyl-4-phenyl-piperidine Derivatives
Authors: Jones Alan J. , Beeman C. P. , Casy A. F. , McErlane K. M. J.
Published: May 2006

The carbon-13 magnetic resonance spectra of three diastereoisomers of 1,2,5-trimethyl-4-phenylpiperidin-4-ol and their esters and corresponding hydrochlorides have been determined in deuterochloroform and/or dimethylsulfoxide-d6. Chemical shifts observed support the configurations t-2-Me, c-5-Me (γ), c-2-Me, t-5-Me (β), and c-2-Me, c-5-Me, r-4-OH (α) for the isomers specified in parentheses. Chair conformations are preferred for γ (eq-Ph) and β (ax-Ph) piperidinols while the α-form favors a skew-boat. Evidence is presented for conformational changes in the α- and β-forms after N-protonation. The γ- and β-esters have conformations similar to the parent 4-piperidinols while the α-acetate base and hydrochloride prefer chair conformations but with different 4-phenyl orientations (base ax-Ph, HCl eq-Ph).
The Conformation of Pyridine Nucleotides Studied by 31P and 1H Fast Fourier Transform Nuclear Magnetic Resonance Spectroscopy. II. The Backbone Conformation of Dinucleotides
Authors: Sarma Ramaswamy H. , Mynott Richard J. , Hruska Frank E. , Wood Donald J.
Published: May 2006

Using parameters derived from the component mononucleotides, β-NMN, 5′-AMP, and 5′-ADP, the 31P n.m.r. spectra of oxidized pyridine coenzymes, recorded in the presence of coupling from the ribose protons, are analyzed with the use of extensive computer simulations. It is shown that the spectra are compatible only with gauche–gauche conformation about the C5′—O5′ bonds on both the adenine and nicotinamide ends of oxidized pyridine coenzymes. The 1H and 1H–{31P} Fourier transformed 16K n.m.r. spectra of 5′-AMP and 5′-ADP are reported and their full analysis given, and it is shown that the nucleotides exist predominantly in the gauche–gauche conformation about the C4′—C5′ and C5′—O5′ bonds.
Photoelectron Spectra of Sulfuryl and Thionyl Halides
Authors: Chadwick D. , Frost D. C. , Herring F. G. , Katrib A. , McDowell C. A. , McLean R. A. N.
Published: May 2006

The HeI photoelectron spectra of some sulfuryl and thionyl halides have been found, and an attempt has been made to relate the results to the bonding in these molecules.
Pyrolysis of Trifluoroacetaldehyde
Authors: Liu Michael T. H. , Loucks Leon F. , Michaelson Robert C.
Published: May 2006

The thermal decomposition of trifluoroacetaldehyde has been studied over the 460–520 °C temperature range, and at pressures from 4 to 400 mm Hg. The experimental rate equation in the high-pressure region is of the form: Rate = k[CF3CHO]3/2 where[Formula: see text]The results are consistent with a mechanism initiated by a first order process and terminated by a second order recombination of two CF3 free radicals. At lower pressures (40 mm Hg), the ratio of kinit/kterm is pressure dependent and the overall order increases. The effects of added inert gas confirm this pressure dependence.
A Study of the Proton Nuclear Magnetic Resonance Spectra of Aryl and Mono- and Disubstituted N-Methylazoles
Authors: Butler Richard Noel
Published: May 2006

Proton n.m.r. spectra of 111 substituted azoles are compared. The influence of the azole ring on the chemical shifts of substituent phenyl protons is discussed. A correlation between N-methyl chemical shifts and the structural characteristics of the N-methyl group in mono- and disubstituted azoles is noted.
The Fragmentation Mechanism of Cyclobutanol
Authors: Holmes John L. , Rye Robin T. B.
Published: May 2006

The mass spectra of cyclobutanol and three 2H labelled analogs have been studied. The losses of C2H4 and C2H5• from the molecular ion involve specific fragmentations. Only CH3• loss from the α-cleaved molecular ion2 clearly involves hydrogen atom scrambling; this fragmentation also proceeds by a specific mechanism involving C-2 and hydroxyl hydrogen atoms. Loss of water from the molecular ion involves all the hydrogen atoms but in a complex, non-random manner.
The Cumulative Acceleration by Methyl Substituents on the Rate of Addition of 4-Chlorobenzenesulfenyl Chloride to Olefins
Authors: Schmid George H. , Garratt Dennis G.
Published: May 2006

The rate of addition of 4-chlorobenzenesulfenyl chloride to ethylene and all six of its methylated derivatives has been measured in 1,1,2,2-tetrachloroethane at 25° by means of the stopped flow and a competitive technique. A plot of log krelvs. the number of methyl groups on the carbon–carbon double bond is linear. This establishes that the methyl groups have a cumulative acceleration on the rate contrary to previous reports. The use of the competitive method of obtaining rates of arenesulfenyl chloride additions to olefins suffers from the fact that thermodynamically rather than kinetically controlled product mixtures are often formed.
Photoreactions of Nitroso Compounds in Solution. XXIII. A Novel Oxidative Photoreaction of Nitrosamines and Nitrosamides
Authors: Chow Y. L. , Tam J. N. S. , Colón C. J. , Pillay K. S.
Published: May 2006

Novel oxidations attending the photorearrangement of a nitrosamide and the photoaddition of nitrosamine are described and compared with the corresponding non-oxidative photoreactions. With proper filters, disproportionation during photorearrangement of N-nitrosohexylacetamide and tautomerization during nitrosopiperidine photoaddition to cyclohexene can be minimized to give improved yields of the anti-dimers of C-nitroso compounds. These side reactions are shown to be exclusively derived from secondary photoreactions of the C-nitroso compounds. In the presence of oxygen, the courses of the photoreactions are diverted cleanly to form nitrate esters. Oxygen reacts with nitric oxide, both in the free state and when paired with the C-radical thus diverting the course of the reaction. The rate constant of radical combination between a C-radical and nitric oxide is estimated to be in the range of 2 × 107 s−1.
Effect of Solute–Solute Interaction on Molecular Luminescence in Rigid Glasses: Anomalous Thioxanthenone Phosphorescence and Anthracene Fluorescence
Authors: Loutfy R. O. , Williams D. F. , Yip R. W.
Published: May 2006

The phosphorescence spectra and lifetimes of thioxanthenone in a number of rigid matrices at 77°K was found to be dependent on the concentration, rate of cooling of the glass, and on the wavelength of excitation. At 77°K and at concentrations greater than ~5 × 10−5 M, aggregates of thioxanthenone are believed to be responsible for a new phosphorescence band at 472 nm, and a corresponding absorption band at 390–395 nm.The formation of aggregates is also believed to be responsible for the variations, with excitation wavelength, of the fluorescence lifetime of anthracene in polymethacrylate at ambient temperatures.
Investigation of Factors Affecting Conformational Preference in Complex Haloethane Derivatives by Classical Energy Calculations
Authors: Reynolds William F. , Wood Donald J.
Published: May 2006

Classical energy calculations are used in combination with Abraham's electrostatic theory of solvation energy to estimate rotamer energy differences for haloethane derivatives. The calculations are tested by comparing experimental and calculated ΔE values for several di- and tetrahaloethanes. There is good agreement for chloro and bromo derivatives but poorer agreement for fluoro and iodo derivatives. ΔE values in solution are also estimated for l4 complex chloro- and bromoethanes which we have previously investigated by n.m.r. spectroscopy. The calculations generally parallel the experimental results as reflected by vicinal coupling constants. They are particularly useful for trends in conformational preference for closely related compounds and are used in conjunction with vicinal coupling constants to identify diastereomers produced by halogenation of alkenes. Steric interactions, dipole–dipole interactions and solvation energy are all important in determining conformational preference for complex haloethanes in solution.
Pseudo-thermodynamic Parameters and Isotope Effects for Hydrolysis of a Series of Benzyl Chlorides in Water
Authors: Koshy K. M. , Robertson R. E. , Strachan W. M. J.
Published: May 2006

The temperature coefficient of the enthalpy of activation (ΔCp≠) for the hydrolysis of p-methyl, p-chloro and p-nitro benzyl chlorides have been determined, as well as α-deuterium isotope effects and kinetic solvent isotope effects. These results are discussed in terms of probable mechanism of hydrolysis in water.
Photochemistry of Pivalaldehyde in Solution Studied by CIDNP
Authors: Chen Holger E. C. , Groen Arend , Cocivera Michael
Published: May 2006

The n.m.r. spectrum observed during irradiation of pivalaldehyde dissolved in perfluoromethylcyclohexane indicates the formation of several compounds whose hydrogens are spin polarized. These compounds are 2-methylpropane, 2-methylpropene, and pivalaldehyde. A mechanism involving radical reactions which is consistent with these results is presented. According to this mechanism, the primary photochemical step is cleavage of the bond between the carbonyl carbon and the tertiary carbon of the t-butyl group. In contrast, this step does not appear to be important for acetaldehyde. As a test of the proposed mechanism CCl4 is added to trap free radicals. In this case, one of the products is CCl3COH. A mechanism for the formation of this and the other products having nuclear spin polarization is presented.
Cimicine and Cimicidine, Lactonic Alkaloids from Haplophyton cimicidum
Authors: Cava M. P. , Lakshmikantham M. V. , Talapatra S. K. , Yates Peter , Rae I. D. , Rosenberger M. , Szabo A. G. , Douglas B. , Weisbach J. A.
Published: May 2006

Evidence is presented in support of the stereostructures 4 and 5 for cimicine and cimicidine, respectively. Alkaloids 4 and 5, as well as the lactonic bases aspidophytine (23) and haplophytine (1), are converted by alkaline hydrogen peroxide to the corresponding 10-oxo derivatives.
Spectrométrie de masse des cyclohexanones gem-diphénylées. II. Chaleurs de formation et structures possibles des principaux ions fragmentaires
Authors: Fortin Claude J. , Rousseau Yves
Published: May 2006

The energetics of the processes leading to the formation of the major ions of gem-diphenyl cyclohexanones and analogues were studied. Many of the ions coming from the electron impact induced decomposition of these products appear in quite a large number of aromatic compounds which can thus be used for comparisons. We are proposing structures to represent these ions while some are eliminated on the basis of their ionic heats of formation.
A Unique Menschutkin Reaction Involving Fragmentation and Cyclization
Authors: Ottenbrite Raphael M. , Myers G. Rodney
Published: May 2006

It was found that N,N,N′,N′-tetramethylmethylenediamine reacted with a number of dihalides to form the corresponding cyclic quaternary ammonium compound and dimethylamine hydrohalide. The process involves a Menschutkin reaction with fragmentation of N,N-dimethylmethyleneamine followed by a second Menschutkin reaction to form a cyclic compound. The reaction proceeds best in a polar solvent and the yields are moderate to good.
Crystal and Molecular Structure of Benzylidenimine Tetrasulfide, (C6H5CHN)2S4
Authors: Barrick James C. , Calvo Crispin , Olsen Fredric P.
Published: May 2006

The structure of the title compound has been determined. Crystals are monoclinic with space group P21/a, Z = 4, a = 13.83(1), b = 19.66(2), c = 5.983(5) Å, β = 101.4(1)°, dcalcd = 1.404, dobs = 1.40(1). A full-matrix least-squares refinement on 1085 unique reflections of positive intensity measure produced a conventional R of 0.066. The spiral arrangement of the S4 chains (nearly generating a 31 axis) is such that the two aromatic rings are eclipsed. Alternation in bond length along the sulfur chain was observed, the long inner bond being 2.083(4) Å and the shorter outer bonds averaging 2.026(3) Å in length. No intermolecular non-bonding interactions involving sulfur were found.
Estimation of Phenols by the 4-Aminoantipyrine Method. II. Products from para-Substituted Alkylphenols
Authors: Jones Peter F. , Johnson K. E.
Published: May 2006

4-Aminoantipyrine reacts with p-alkylphenols on oxidation with potassium ferricyanide to give yellow ortho-quinoneimides. These undergo a thermal and base-catalyzed rearrangement to benzodihydrooxazepines.
The Use of Polymer Supports in Organic Synthesis. III. Selective Chemical Reactions on One Aldehyde Group of Symmetrical Dialdehydes
Authors: Leznoff Clifford C. , Wong Jack Y.
Published: May 2006

An insoluble polymer support system incorporating a diol functional group was prepared. The symmetrical dialdehydes, terephthalaldehyde and isophthalaldehyde, were attached to the polymer through acetal formation, constituting a unique method of blocking one aldehyde group of symmetrical dialdehydes. The free aldehyde group was reacted with hydroxylamine to give the mono-oximes of the terephthalaldehyde and isophthalaldehyde upon acid cleavage from the polymer. Similarly, the polymer bound aldehydes were reacted with Wittig reagents to give p- and m-formylstilbenes and 1-p- and -m-formyl-phenyl-4-phenyl-1,3-butadienes. The crossed aldol condensation of acetophenone with the symmetrical dialdehydes gave the 3-p- and -m-formylphenyl-1-phenyl-2-propene-1-ones (formylchalcones) in high yield. The Grignard reaction of phenylmagnesium bromide on the polymer bound aldehyde gave(p- and m-formylphenyl)phenylcarbinol in quantitative yield. Reduction of the polymer bound free aldehydes with sodium bis(2-methoxyethoxy)-aluminum hydride gave p- and m-hydroxymethylbenzaldehydes. Similarly the mixed benzoin condensation of polymer bound terephthalaldehyde and isophthalaldehyde gave p- and m-formylbenzils.
Molecular Motion in Azulene and the Azulenes–(s)-Trinitrobenzene Molecular Complex in the Solid State
Authors: Fyfe C. A. , Kupferschmidt G. J.
Published: May 2006

Molecular motion of azulene in its own molecular crystal and in its complex with trinitrobenzene has been shown from wide-line n.m.r. and spin–lattice relaxation time measurements to occur in the solid state. Calculations of the n.m.r. spectral parameters based on a model where the azulene molecules are reorienting in their molecular planes by 180° jumps give satisfactory agreement with experimental values. The results are discussed with respect to the available X-ray data.
Cleavage of the Sulfur–Sulfur Bond in 2,4-Dinitrophenyl-4-substituted-phenyl Disulfides by trans-[IrCl(CO) (PPh3)2]. A Kinetic Study
Authors: Lam Chiu T. , Senoff Caesar V.
Published: May 2006

The kinetics of the reaction between trans-[IrCl(CO)(PPh3)2] and a series of 2,4-dinitrophenyl-4-substituted-phenyl disulfides, YC6H4SSC6H3(NO2)2 (Y = Br, F, H, CH3, or CH3O) have been investigated in toluene between 70 and 90°. These reactions were found to follow simple second order kinetics, rate = k2[IrCl(CO)(PPh3)2][YC6H4SSC6H3(NO2)2]. The rates of reaction were also found to be insensitive to the nature of the para substituent, Y. This fact together with the observed activation parameters, ΔH≠ ~ 17 kcal mol−1 and ΔS≠ ~ − 19 cal mol−1 deg−1, have been interpreted as indicating that the initial step in these reactions involves a nucleophilic attack by the iridium atom at the sulfur atom bonded to the 2,4-dinitrophenyl group, followed by the formation of a three-centered transition state. An overall mechanism for these reactions is presented and discussed.
Kinetics of Exchange of Dimethylsulfoxide between Hexakis(dimethylsulfoxide)chromium(III) and Solvent: Pressure Effect and Mechanism
Authors: Carle Debra Lynn , Swaddle Thomas Wilson
Published: May 2006

For the exchange of all six dimethylsulfoxide (DMSO) ligands in Cr(DMSO)63+ with perdeuterated DMSO solvent, the first-order rate constant (75°) = 5.5 × 10−5 s−1, while ΔH* = 23.1 kcal mol−1, ΔS* = − 11.8 cal deg−1 mol−1, and ΔV* = − 11.3 cm3 mol−1. These and other data are indicative of an associative interchange mechanism for substitution in Cr(III) DMSO complexes in DMSO.
Irradiation Studies. III. The Products from 4-Phenylterephthalophenone and Their Syntheses
Authors: Thiemann Douglas Paul , Pearson Donald E. , Thoennes David James
Published: May 2006

The photoreduction products of the irradiation of 4-phenylterephthalophenone in pyridine – isopropyl alcohol were 4-(4-phenylbenzoyl)benzhydrol (2) and the unexpected product, 4-benzoyl-4′-phenyl-benzhydrol (3). The structures have been confirmed by an independent synthesis of each. A possible mechanism is discussed.
Hydrolysis of Substituted Diphenylacetaldehyde Ethylene Glycol Cyclic Acetals in Aqueous Hydrochloric Acid
Authors: Jensen Bruce L. , Counsell Raymond E.
Published: May 2006

The chemistry of DDT and DDD derivatives was explored by studying the steric and electronic effects on the hydrolysis of a variety of substituted diphenylacetaldehyde ethylene glycol cyclic acetals. This investigation demonstrated that ortho substituents, p-nitro, and p-methoxy groups affect the product distribution in different ways. The mechanistic details of this work are discussed.
Water Soluble Steroids with Catalytic Substituents II. Synthesis of 3β-(4(5)-Imidazolyl)-5α-androstane-11β, 17β,-diamine and Comparison of its Catalytic Properties with Those of 17β-(4(5)-Imidazolyl)-5α-androstane-3β, 11β-diamine
Authors: Guthrie J. Peter , Ueda Yasutsugu
Published: May 2006

3β-(4(5)-Imidazolyl)-5α-androstane-11β,17β-diamine, 15, has been synthesized in a multistep process from adrenosterone, 2, starting with lithium ammonia reduction to give 11α,17β-dihydroxy-5α-androstan-3-one, 3, which was converted to its diacetate, 4. Ethynylation at the 3 keto group gave the ethynyl triol 5, purified as its11,17-diacetate 6. Acid catalyzed rearrangement of 6 gave 3-acetyl-5α-androst-2-ene-11α,17β-diol diacetate, 7. This was hydrogenated, and then subjected to base catalyzed hydrolysis and equilibration to give crystalline 3β-acetyl-5α-androstane-11α,17β-diol, 9, which was converted to 3β-acetoxyacetyl-5α-androstane-11α,17β-diol, 10, using lead tetraacetate. After hydrolysis to the triol, 11, the Weidenhagen reaction led to formation of 3β-imidazolyl-5α-androstane-11α,17β-diol, 12. Finally oxidation to the dione, 13, formation of the dioxime, 14, and hydrogénation give 15. As expected 15 is a better catalyst than 17β-(4(5)-imidazolyl-5α-androstane-3β,11β-diamine, 1, for the hydrolysis of aryl esters of acids with hydrophobic substituents, but the effect is small. With 1 there is a marked electrostatic rate enhancement or retardation when charged groups are present on the aryl esters; this effect is much smaller for 15.
The Synthesis of Songorine: A Simplified Synthesis of the Aromatic Intermediate
Authors: Wiesner Karel , Ho Pak-Tsun , Chang Ding , Lam Yiu Kuen , Pan Connie Shii Jeou , Ren Wu Yun
Published: May 2006

A simple conversion of the previously described (1) tricyclic ester 1 into the pentacyclic songorine intermediate 21 is described. The process is stereospecific and it operates in an overall yield of 7.8%.
A 19F Nuclear Magnetic Resonance Study of Polymeric Fluoroanions of Tin(IV) and Titanium(IV)
Authors: Dean P. A. W.
Published: May 2006

Fluorine n.m.r. has been used to demonstrate the existence of fluorine-bridged polymeric fluoroanions of tin(IV) and titanium(IV) in liquid sulfur dioxide solution. In the system TiF4−(Pr2nNH2)2TiF6 the species formed are: Ti2F113−; a species (TiF5)nn−, which has a structure consisting of cis fluorine-bridged TiF6 octahedra and is most probably Ti2F102−; Ti2F9−; other fluorine-bridged polymers. The spectra of (TiF5)nn− and Ti2F9− are complex due to the effects of magnetic nonequivalence; the spectrum of (TiF5)nn− has been analyzed in detail. Both Sn2F113− and (SnF5)nn−, which has a structure like (TiF5)nn− are formed in SnF4−(Pr2nNH2)2SnF6.
Unusual Long-Range Spin–Spin Coupling in Norbornane-2,3-diones. Proton Magnetic Resonance Spectrum and X-Ray Structure Analysis of 6-endo-Bromo-1,5,5-trimethylnorbornane-2,3-dione
Authors: Hambly G. F. , Leitch Jeanette , Yates Peter , Nyburg S. C.
Published: May 2006

Several norbornane-2,3-diones show in their proton magnetic resonance spectra an unusual long-range spin–spin coupling, 4J46λ = 1.0–1.5 Hz. An X-ray structure analysis of 6-endo-bromo-1,5,5-trimethylnorbornane-2,3-dione shows that the norbornane framework deviates only slightly from mirror symmetry. This makes it unlikely that the unusual coupling in the norbornane-2,3-diones is due to distortion of the norbornane framework and lends credence to the view that it is due to substituent effects.
An Electron Spin Resonance Method for Monitoring the Progressive Replacement of Fluorine by Alkoxy Groups in Perfluorobenzophenone
Authors: Sargent Frederick Peter , Bailey Marshall Grant
Published: May 2006

The use of electron spin resonance (e.s.r.) to follow the course of a chemical reaction which does not involve paramagnetic intermediates is reported. The principle of the method is the conversion of the reaction product into a paramagnetic species which may be characterized by e.s.r. In the present example, photoconversion of ketones into radical anions is used to follow the successive displacement of fluorine from perfluorobenzophenone.
Hydrogen Peroxide Oxidation of Coordinated Thiocyanate Ion in cis- and trans-[Coen2NH3NCS]2+: The Preparation and Properties of trans-[Coen2NH3CN]2+
Authors: Norris Albert Richard , Wilson James William Lennox
Published: May 2006

The hydrogen peroxide oxidation of thiocyanate ion in cis- and trans-[Coen2NH3NCS]2+ leads to the formation of the corresponding cis- and trans-cyanoammine- and diamminebis(ethylenediamine)cobalt-(III) complexes. The spectral properties of the previously unreported trans-[Coe2NH3CN]2+ are reported and compared to the spectral properties of the cis-isomer.Observations are made concerning the reaction conditions which favor a high percent conversion of trans-[Coen2NH3NCS]2+ to trans-[Coen2NH3CN]2+.
Kinetic Studies of the Reactions of Cyanide Ion and 1,3,5-Trinitrobenzene in Ethanol, n-Propanol, Isopropanol, and t-Butanol at 25.0 °C
Authors: Gan Leong Huat , Norris Albert Richard
Published: May 2006

The specific rate constants for the formation of the 1:1 1,3,5-trinitrobenzene – cyanide ion σ-complex in ethanol, n-propanol, isopropanol, and t-butanol are 442 ± 14,932 ± 30, 2.45 ± 0.10 × 103 and 1.06 ± 0.05 × 105 M−1 s−1, respectively. A plot of log kvs. Dimroth's solvent parameter Et is linear with slope −0.25. The kinetics of the reactions of cyanide ion and 1,3,5-trinitrobenzene in ethanol and n-propanol are complicated by alcoholysis of cyanide ion which yields the corresponding alkoxide ion and the 1:1 1,3,5-trinitrobenzene–alkoxide ion σ-complex.
Kinetic and Equilibrium Studies of the Reactions of Cyanide Ion with 1,3,5-Trinitrobenzene, 2,4,6-Trinitroanisole, and 2,4,6-Trinitrotoluene in Isopropanol
Authors: Gan Leong Huat , Norris Albert Richard
Published: May 2006

Equilibrium constants for the formation of 1:1 cyanide ion σ-complexes with 1,3,5-trinitrobenzene, 2,4,6-trinitroanisole, and 2,4,6-trinitrotoluene have been determined spectrophotometrically over a range of temperatures. Standard enthalpy (ΔH0) and entropy (ΔS0) changes associated with each reaction have been evaluated. The kinetics of formation of the σ-complexes have been investigated by means of a stopped-flow technique and the activation parameters characterizing the formation of each complex have been determined. Evidence is presented which indicates the cyanide ion – 2,4,6-trinitroanisole σ-complex formed in isopropanol contains the cyanide ion bonded exclusively at the C-3 position.
Crystallographic Studies of Cobalt Arsenate. III. Crystal Structure of Co6.95As3.62O16
Authors: Krishnamachari Narasimhan , Calvo Crispin
Published: May 2006

Crystals of Co7.0As3.6O16 (1.8 × 3.84 CoO.As2O5) are orthorhombic with unit cell parameters a = 10.526(5), b = 5.985(2), and c = 4.871(2) Å. The space group is Pnma with Z = 1 and, except for fractionally occupied cation sites, the crystals have a structure closely related to that of the mineral olivine. The structure was refined by full-matrix least-squares with isotropic thermal parameters, using 1175 independent reflections measured with MoKα radiation, to a final R value of 0.075. The composition was determined by site population analysis. The structure is based upon a hexagonally close-packed arrangement of oxygen layers with As in tetrahedrally and Co in octahedrally coordinated interstices. The mean As—O bond length is 1.676 Å and the mean Co—O bond lengths are 2.139 Å for the site with m symmetry and 2.174 Å for the site showing inversion symmetry. These bond lengths are uncorrected for the effects of fractional occupancy of some of the cation sites.
Homogeneous Gas-phase Pyrolyses using a Wall-less Reactor. IV. Comparative Surface-Nonsurface Effects with Cyclopropane
Authors: Kulich Donald M. , Taylor Jay E. , Hutchings David A.
Published: May 2006

The rates of pyrolysis of cyclopropane in nitrogen have been determined using a wall-less reactor at temperatures of 600–740 °C and a total pressure of 1 atm. In the presence of oxidized stainless steel. quartz, or carbon coated steel rods the rate of conversion to propylene is 1.9 times the rate under homogeneous conditions. A maximum in surface effect was observed at S/V = 0.6 cm−1. A small but increased amount of methane and ethene are formed under surface conditions as compared to homogeneous conditions. Several possible mechanisms for the rate enhancement by surface are discussed. The most likely possibility is surface interaction with the cyclopropane molecule to form the diradical followed by its surface promoted conversion to propene. The importance of determining surface effects by comparing surface rates with totally homogeneous rates is emphasized.
The Ultraviolet Flash Photolysis of Ozone and the Reactions of O(1D) and O2(1Σg+)
Authors: Snelling D. R.
Published: May 2006

The decomposition of ozone has been studied following a short duration u.v. light pulse. From an analysis of the O3 decomposition curves for O3:N2, O3:N2:O2 and O3:O2 mixtures it is shown that the relative rate constant for O(1D) deactivation by N2 and O2 is given by [Formula: see text]It is also shown that O2(1Σg+) is formed in at least 75% of the collisions in which O(1D) is deactivated by O2. The rate constants of the reactions O2(1Σg+) + O3 → 2O2+O and O + O2 + O2 → O3 + O2 are found to be (2.3 ± 0.5) × 10−11 cm3 molecule−1 s−1 and (5.0 ± 0.5) × 10−34 cm6 molecule−2 s−1, respectively, at (295 ± 1) °K.
The Molecular Structure of 2,5-Dihydrofuran from the Analysis of the Nematic Liquid Crystal Nuclear Magnetic Resonance Spectrum
Authors: Cole K. C. , Gilson D. F. R.
Published: May 2006

The nematic phase n.m.r. spectrum of partially oriented 2,5-dihydrofuran has been analyzed. Corrections to the structure for ring puckering and methylene rocking motions, according to the model due to Malloy, give improved agreement between experimental and calculated direct dipole–dipole coupling constants.
A CNDO/2 Calculation on the Reaction of Ground State Oxygen Atoms with Olefins
Authors: Koda Seiichiro
Published: May 2006

A molecular orbital study within the framework of the CNDO/2 method has been made of the reactions of ground state oxygen atoms with olefins. Calculated excitation energies confirm the existence of a certain correlation between those and the logarithm of the reaction rate constants. The location of minima in the simplified potential energy surfaces computed appear to correspond to the reaction intermediates suggested previously.
Association of a Europium Shift Reagent with Dialkylnitrosamines
Authors: Perry Richard A. , Chow Yuan L.
Published: May 2006

The Eu(fod)3 induced shifts of the n.m.r. signals of various nitrosamines were studied at a constant lanthanide concentration and also at constant nitrosamine concentration. The bound chemical shifts (ΔB) and binding equilibrium constants (K) were determined. The stoichiometry of the complexes appears to be 1:1 in CDCl3 in agreement with the criteria of two types of existing tests designed to determine Eu–substrate ratio. On the basis of the experimental ΔB values, the molecular geometry of Eu–nitrosamine complexes were computed according to the principle of pseudo-contact shift. It was concluded that the Eu atom complexed at the oxygen of the nitroso group and that the conformations of nitrosamines in the complexes were basically the same as those of uncomplexed nitrosamines.
Proton Magnetic Resonance Studies of Rotational Isomerism in Halotoluenes. X. Estimates of Conformational Preferences and Rotational Barriers in Benzal Fluoride and Some Dichloro Derivatives
Authors: Rowbotham J. Brian , Janzen Alexander Frank , Peeling James , Schaefer Ted
Published: May 2006

The synthesis of benzal fluoride and of its 2,6-, 3,5-, 3,4-, and 2,4-dichloro derivatives is followed by an analysis of their proton magnetic resonance spectra. The long-range spin–spin coupling constants are most consistent with a barrier to rotation about the sp2–sp3 carbon–carbon bond in benzal fluoride of less than 500 cal/mol, in semiquantitative agreement with an ab initio molecular orbital calculation. The 2,6-dichloro derivative has a conformation in which the C—H bond of the side chain lies in the plane of the aromatic ring. The 2,4-dichloro derivative favors a similar conformation, the C—H bond lying cis to the ring chlorine atom. In contrast to the long-range proton–proton couplings, the long-range proton–fluorine couplings are intrinsically sensitive to substituent effects from the ring chlorine atoms.
cis-Activation by Oxyanions Coordinated to Chromium(III): Aquation and Base Hydrolysis of Nitratopentaamminechromium(III) Ion
Authors: Guastalla Giovanni , Swaddle Thomas Wilson
Published: May 2006

The aquation of Cr(NH3)5NO32+ in acidic solutions yields not only Cr(NH3)5OH23+ (33%) but also more highly aquated species including cis-Cr(NH3)4(OH2)23+ and Cr(NH3)3(OH2)33+. In 0.1 M HClO4, several successive reactions of comparable rates are involved, but at pH 6 only the two competing initial reactions producing Cr(NH3)5OH2+ and cis-Cr(NH3)4(OH)NO3+ are rate-controlling, so that the overall reaction rate is first-order in substrate with the apparent parameters kA = 2.4 × 10−3 s−1(25°), ΔHA* = 20.4 kcal mol−1, and ΔSA* = −2.1 cal deg−1 mol−1. In alkaline solutions, the pseudo-first-order rate of hydrolysis at a given [OH−] is governed by kobs = kA + kOH [OH−], with kOH = 1.1 × 10−2 M−1 s−1 (25°), ΔHOH* = 25.2 kcal mol−1, and ΔSOH* = 17.0 cal deg−1 mol−1. The path characterized by kOH leads exclusively to Cr(NH3)5OH2+. In both aquation and base hydrolysis, it is the Cr—ONO2 bond that is broken. The production of more highly aquated species in the aquation reactions is attributed to transient chelation of NO3− at the expense of a ligand cis to it. The evidence for this mechanism, and for its operation when oxyanions other than nitrate are coordinated to Cr(III), is reviewed.
Chemistry of Transition Metals. IV. Reactions of Alkyl Halides with the Metals of the First Transition Period
Authors: Egan Robert W. , Harrod John F.
Published: May 2006

The reactions of 1-chloropropane (1) and 1-chloro-2-methylpropane (2) with clean, polycrystalline films of the metals Ti through Cu were studied at ambient and elevated temperatures. At ambient temperature all of the metals exhibited a complex pattern of behavior. Titanium was uniquely different from other metals in that no catalytic hydrogenation of product olefin by product hydrogen was observed.At elevated temperatures the two reactants exhibited the same dichotomy as previously reported for titanium in that 2 was catalytically dehydrochlorinated by all metals, whilst 1 underwent non-catalytic dehydrochlorination. Except in the cases of Ti and Mn, the halide deposited by reaction of 1 with the metal surfaces provided an effective diffusion barrier to further reaction. It is suggested that the rate-controlling step for both Ti and Mn in reactions with 1 is transport of metal atoms from the pure metal into the halide surface layer.
An Electron Spin Resonance Study of the tert-Butylsulfinyl Radical
Authors: Howard James A. , Furimsky Edward
Published: May 2006

The tert-butylsulfinyl radical, (CH3)3CSO•, can be prepared directly in the cavity of an e.p.r. spectrometer by photolysis of di-tert-butyl peroxide in a solution of tert-butylsulfenic acid in toluene or isopentane at low temperatures (−40° to−100°). The e.s.r. spectrum consists of a rather broad singlet (ΔHmis ∼ 1.9 G) with the field center at g = 2.0106.This radical undergoes self-reaction by a bimolecular process and a 2.5 × 10−7 M solution has a half-life of 0.07 s at −100 °C. It is, therefore, much shorter-lived than the iso-structural tert-butylperoxy radical, (CH3)3COO•.
13C Nuclear Magnetic Resonance Studies of Organometallic Compounds. III. cis-Methylplatinum(II) Derivatives
Authors: Clark H. C. , Ward J. E. H.
Published: May 2006

Eight new cis-methylplatinum(II) derivatives of the type DIARSPt(CH3)X (DIARS abbreviates o-phenylenebis(dimethylarsine), where X is an anionic substituent, and [DIARSPt(CH3)L]+PF6−, where L is a neutral ligand, have been prepared. Data derived from the 13C n.m.r. spectra of these complexes are discussed and compared with data derived from the 1H n.m.r. spectra of the complexes. Comparisons with the 13C n.m.r. parameters obtained from related series of trans-methylplatinum(II) derivatives reveal marked differences between the n.m.r. cis- and trans-influences. It appears that the n.m.r. cis-influence may in part be related to a ligand's "steric bulk".
Some Derivatives of 1-Benzazepine. Part II
Authors: Birchall G. R. , Rees A. H.
Published: May 2006

We have investigated the ring expansion of some substituted 1,4-naphthoquinones by hydrazoic acid to yield new 1-benzazepine derivatives of the "azatropolone" type. Ring contraction of those products, which are 2,5-dihydro-3-hydroxy-2,5-dioxo-1-benzazepines, gives 4-quinolone-2-carboxylic acids. Some of the reactions of the new benzazepine system were investigated. Attempts to prepare substituted derivatives suitable for making 1-benzazatrop-5-one were not successful.The effect of substituents on the ring expansion reaction is discussed and an anomalous ring expansion to a 2,5-dihydro-4-hydroxy-2,5-dioxo-1-benzazepine is described and explained mechanistically.
A Low Temperature Infrared Study on the Association of Thiols with Organic Oxygen Bases
Authors: Alencastro R. Bicca De
Published: May 2006

The infrared spectra of mixtures of propane-1-thiol and several oxygen-containing weak organic bases have been measured between 2500 and 2650 cm−1, in a 1:1 mixture of CCl3F and C2F4Br2 at temperatures ranging from 20 to –190 °C. Association of the [Formula: see text] type was observed between propane-1-thiol and 2-methyl-tetrahydrofuran, or cyclopentanone. This association is less important between the thiol and hexachloropropanone. In the case of a thiol–furan mixture association of the [Formula: see text] type is strongly indicated.
Carbon-13 Nuclear Magnetic Resonance Studies of ortho-Substituted Anisoles and Diphenyl Ethers
Authors: Buchanan Gerald W. , Montaudo Giorgio , Finocchiaro Paolo
Published: May 2006

Carbon-13 n.m.r. chemical shifts for 8 anisoles and 15 diphenyl ethers are reported. para-Carbon shieldings are found to be sensitive to the degree of steric interference to conjugative electron release by the ethereal oxygen atom. An empirical correlation between the para-carbon shifts and the average twist angle of the phenyl rings from a reference plane has been developed. Satisfactory agreement has been found between the angles of twist derived from carbon chemical shifts and those based on other physical measurements.
Routes to N-Aryl-N′-thioaroylhydrazines and Related sym- and unsym-Hydrazonyl Sulfides, and a Note on the So-called N-Phenyl-N′-thiobenzoyldiimide
Authors: Wolkoff P. , Hammerum S. , Callaghan P. D. , Gibson M. S.
Published: May 2006

Aromatic hydrazonyl halides (1), treated successively with triethylamine and hydrogen sulfide – triethylamine, give N-aryl-N′-thioaroylhydrazines (3) as primary products, which can be isolated in many cases. Depending on conditions, further reaction may occur to give sym-hydrazonyl sulfides.Both sym and unsym-hydrazonyl sulfides are available from reaction of appropriate hydrazonyl halides and N-aryl-N′-thioaroylhydrazines in presence of triethylamine.The product of oxidation of N-phenyl-N′-thiobenzoylhydrazine under various conditions is confirmed as the corresponding hydrazonyl disulfide rather than N-phenyl-N'-thiobenzoyldiimide.
Mechanism and Stereochemistry of the Hydrolysis of 4-Arylamino-1,2,3,4- tetrahydroquinaldines
Authors: Forrest T. P. , Dauphinee G. A. , Miles W. F.
Published: May 2006

Rates of acid-catalyzed hydrolysis of the benzylic amino group in stereoisomers of 4-arylamino-1,2,3,4-tetrahydroquinaldines have been determined by n.m.r. spectroscopy. Those isomers which have a pseudo-axial leaving group react more rapidly than those with a pseudo-equatorial leaving group, forming in each case the isomer with a pseudo-axial hydroxyl group as the kinetically controlled product. This product is converted in time to an equilibrium mixture of the two stereoisomeric alcohols. The reaction is inhibited by excess acid and appears to proceed through an intermediate carbonium ion which is stabilized by the heterocyclic nitrogen atom.
Reductive Cleavage of Acetals and Ketals by Borane
Authors: Fleming Bruce , Bolker Henry I.
Published: May 2006

Borane in tetrahydrofuran was found to reduce acetals and ketals to ethers, generally in good yield and under mild and convenient conditions. Cyclic acetals and ketals were converted by this reagent into hydroxy ethers. The mechanism appeared to resemble that of reduction with LiAlH4–AlCl3.
Drop Calorimetry of the Complex Compounds CsMnCl3, Cs2MnCl4, and Cs2ZrCl6
Authors: Kucharski A. S. , Flengas S. N.
Published: May 2006

Enthalpies of fusion, heat contents, and heat capacities, for the compounds CsMnCl3, Cs2MnCl4, and Cs2ZrCl6 have been determined by drop calorimetry. The following results were obtained for the enthalpies of fusion:[Formula: see text]The heat capacities were determined as[Formula: see text]
The Isolation of an Episelenurane from the Reaction of 4-Tolueneselenenyl Chloride with Ethylene
Authors: Garratt Dennis G. , Schmid George H.
Published: May 2006

The structure of the first product from the addition of 4-tolueneselenenyl chloride to 1–90% 13C ethylene in methylene chloride or chloroform has been assigned as 1-chloro-1-(4′-tolyl)selenocyclopropane (1) on the basis of its n.m.r. and c.m.r. data. In particular the chemical shifts and 13C–77Se spin–spin coupling constants serve to distinguish it from its isomer 2-chloroethyl 4-tolyl selenide (2) which is slowly formed from 1.
Structure cristalline et moléculaire du cyclopentadiényle-carbonyle-bistriphénylphosphine-manganèse (benzénate), MnC5H5CO[P(C6H5)3]2•C6H6
Authors: Barbeau Claude , Dubey Ram Janam
Published: May 2006

The crystal and molecular structure of cyclopentadienylcarbonyl-bis(triphenylphosphine)-manganese(benzenate), MnC5H5CO[P(C6H5)3]2•C6H6, has been obtained from analysis of three dimensional X-ray data obtained with a precession camera. The red, rectangular crystals are triclinic, space group [Formula: see text] and have a unit cell with the following parameters: a = 9.83(2) Å, b = 14.79(1) Å, c = 11.36(2) Å, α = 69.44(8)°, β = 66.48(8)°, γ = 67.57(10)°, and z = 2. The final residual factor is 0.087 for the 4554 independent reflections used in the least squares refinement. The structure consists of individual molecules of Mn(C5H5)CO[P(C6H5)3]2. The distance [Formula: see text] is 2.16(1) Å. The coordinate CO (Mn—C: 1.748(9) Å, C—O: 1.172(11) Å) is perpendicular to the plane of the phosphorous and manganese atoms.The important characteristic is the angle P—Mn—P of 104(1)° (Mn—P: 2.237(3) Å). The angular opening of 14° is considered to be a consequence of an electrostatic repulsion between the two donor P atoms. [Journal translation]