bluuebunny/crossref_metadata_2025 huggingface dataset:
The Master Equation for the Dissociation of a Dilute Diatomic Gas. VII. Vibration–Dissociation Coupling in an Expansion Nozzle
Authors: Labib N. I. , McElwain D. L. S. , Pritchard H. O.
Published: May 2006

The normal-mode approach to the solution of the vibration–dissociation coupling problem for a dilute diatomic gas, which was described in Part III of this series, has been extended to the treatment of recombination in a steady supersonic nozzle expansion. This method of solution did not suffer from the familiar instabilities associated with parasitic eigenvalues which have so far impeded solution of this problem. We report a calculation on H + H + M → H2 + M (without V–V coupling) yielding simultaneously the temperature, density, velocity, and the populations of eachindividual vibrational level from 3900–1500 °K which was completed with acceptable accuracy along the zero-streamline in a few minutes of computer time.In the absence of V–V coupling effects, although grossly distorted vibrational population distributions were found, the populations were always monotonic with vibrational quantum number; however, it was possible to generate absolute overpopulations of one vibrational state with respect to another by simulating vibrational coupling effects.The main conclusions of the calculation are that under these conditions (i) the rate constant for recombination is the normal phenomenological recombination rate constant; (ii) the vibrational relaxation time τvib appears to vary over several orders of magnitude depending on the approximation used to define the vibrational energy content, but if a proper measure of the vibrational energy is used, τvib can be correlated with the second eigenvalue of the relaxation matrix, and is therefore the same as that which would have been found in a shock-tube measurement.
Phosphonitrilic Chloride—The Dehydration of Amides to Nitriles
Authors: Graham John C. , Marr David H.
Published: May 2006

Phosphonitrilic chloride is found to dehydrate amides to nitriles rapidly and in high yields. A mechanism for the dehydration is proposed.
A Conformational Study of Lysergic Acid and iso-Lysergic Acid Dialkylamides by Proton Magnetic Resonance Spectroscopy
Authors: Bailey K. , Grey A. A.
Published: May 2006

The 220 MHz p.m.r. spectra of the dimethylamides of D-lysergic acid (3) and D-iso-lysergic acid (4) are reported. Extensive use of double resonance experiments and the presence of four long-range coupling constants provide an unambiguous assignment for the conformation of 3 in CDCl3. Its D ring is shown to exist in a half-chair form in which the 8-β amide function is pseudo-equatorial. Its epimer essentially exists in the other half-chair form with a pseudo-equatorial 8-α amide function. Data from the p.m.r. spectra of a series of N,N-dialkylamides of these acids are also presented.The spectrum of protonated 3 at 23 °C shows two forms of the 6-NCH3 and 8-CON(CH3)2 groups but only one for the epimer 4.
A Synthetic Study in the Tricyclovetivene Series
Authors: Deljac A. , MacKay W. D. , Pan Connie S. J. , Wiesner Karel J. , Wiesner K.
Published: May 2006

not available
Structure and Reactions of Cuprous Thiobenzoate
Authors: Ferretti Aldo
Published: May 2006

Cuprous thiobenzoate is capable of displacing I− from aliphatic and activated aromatic iodides, in alcoholic or alcohol–pyridine solution, with formation of thiolbenzoates in excellent yield. The reaction fails with other halogenated substrates. In these cases, the products of prolonged heating of the reaction mixture are ethyl benzoate, dibenzoyl disulfide, benzoic acid, thiobenzoic acid, hydrogen sulfide, and cuprous sulfide.
Urea – Boron Trihalide Adducts. II. Enhancement of Barriers to Rotation in sym-and unsym-Dialkylureas on BF3 Complexation
Authors: Hartman J. S. , Schrobilgen G. J.
Published: May 2006

N.m.r. evidence is presented for restricted rotation and oxygen donation in dialkylurea–boron trihalide adducts. Conformer populations in sym-dimethylurea.BF3 are not the same as in the previously reported sym-dialkylurea–SbCl5 adducts.
Studies of Rhenium β-Diketone Complexes. III. The Crystal and Molecular Structure of Bis(μ-O-1,3-diphenylpropane-1,3-dionatotricarbonylrhenium(I))
Authors: Barrick J. C. , Fredette M. , Lock C. J. L.
Published: May 2006

One of a series of compounds obtained by the reaction of chloropentacarbonylrhenium(I) with β-diketones has been shown by single crystal X-ray diffraction to be bis(μ-O-1,3-diphenylpropane-1,3-dionatotricarbonylrhenium(I)). The crystals are monoclinic with lattice parameters a = 11.988(A) Å, b = 14.441(9) Å, c = 10.298(7) Å, β = 115.25(7)°. The space group is P21/c and there are two dimers per unit cell. A total of 1563 independent reflections were measured on a single crystal X-ray diffractometer and the structure was refined by least squares analysis to a weighted R2 value of 0.0427. The dimer units are held together by two bridging oxygen atoms, one from each of the β-ketoenolate groups; the distance of the bridging oxygen from the rhenium atom to which it is chelated (2.162(9) Å) is shorter than the distance to the other rhenium atom (2.204(7) Å). The main part of the β-ketoenolate ring is 37° from the OReO plane.
Retardation of AlH2Cl Hydrogenolysis of the Ethylene Ketals of 5-Norbornen-2-one and 2-Norbornen-7-one Due to the Presence of the Double Bond
Authors: Davis H. A. , Brown R. K.
Published: May 2006

The double bond in either 5-norbornen-2-one ethylene ketal or 2-norbornen-7-one ethylene ketal provides no anchimeric assistance in the hydrogenolysis of these ketals by AlH2Cl in ether. Instead, a marked retardation of reaction occurs, a result considered to be due to competitive association of the Lewis acid, AlH2Cl, with the π bond.Attack of the AlH2Cl on the former ketal occurs from the exo direction to give only the endo-5-β-hydroxyethoxy product, whereas the latter ketal reacts with AlH2Cl to give a 2:1 mixture of the syn and anti 7-β-hydroxyethoxy products. A rationale is provided to account for the results.
Conductance and Conductometric Titrations of Picric Acid in Sulfolane at 30°
Authors: Eller P. M. P. , Caruso Joseph A.
Published: May 2006

Conductance of picric acid solutions in sulfolane resembles the behavior seen in several other aprotic solvents and is suggestive of complex solution equilibria. The effect of water on equivalent conductance of picric acid is large for concentrations greater than about 0.3 M. Picric acid behaves as a weak acid in conductometric titrations.
The Hydrolysis of Disubstituted Alkyl Phosphorochloridates and N,N,N′,N′-Tetra-stibstituted Phosphorodiamidic Chlorides in Water and Deuterium Oxide: Heat Capacity of Activation and Kinetic Solvent Isotope Effects
Authors: Ko E. C. F. , Robertson R. E.
Published: May 2006

The pseudo-thermodynamic parameters, ΔH≠, ΔS≠, and ΔCp≠ and the kinetic solvent isotope effects have been determined for the three alkyl-phosphorochloridates, where the alkyl group is ethylisopropyl and n-propyl; for tetra-methyl and tetra-ethyl phosphorodiamidic chlorides; the di-n-propyl and di-isopropyl analog, the di(isopropylmethylcarbinyl)phosphorochloridate and the tetra-ethylthiophosphorodiamidic chloride. These compounds have a potential relationship to compounds used as insecticides and as polymers. The mechanism of reaction is discussed on the basis of these data.
Vibrational Spectra, Vibrational Analysis and Stereochemistries of the Pentacoordinate Molecules SiCl3X•N(CH3)3 and SiCl3X•N(CD3)3 where X = H, F, Br, or I
Authors: Boal D. , Ozin G. A.
Published: May 2006

The thermally unstable compounds SiCl3X•N(CH3)3 and SiCl3X•N(CD3)3 where X = H, F, Br, or I are studied at −196 °C by infrared and Raman spectroscopy. The data are compatible with molecular five coordinate compounds having a trigonal bipyramidal stereochemistry with the ligand trimethylamine always in the axial position. Using the vibrational data and normal coordinate analyses in both the Cs and C3v configurations, X is suggested to be equatorial for H and F and axial for Br and I. The factors influencing the position of X in the compounds are discussed.
Studies Relating to Aziridine Antitumor Antibiotics. Part I. Asymmetric Syntheses. Part II. Chiral Aziridines and their Conversion to α-Aminoacids
Authors: Lown J. W. , Itoh T. , Ono N.
Published: May 2006

Separable diastereomeric cis-l-menthyl 2-phenyl-3-aziridinecarboxylates (4 and 5) were prepared by the Gabriel reaction. N-Acylation with p-nitrobenzoyl chloride or p-anisoyl chloride of 4 and 5 gives 7 and 8, and 23 and 24, respectively. Sodium iodide-catalyzed rearrangement of the N-acylated aziridines is regiospecific with exclusive attack at C-2 and from 8 is obtained the chiral 2-oxazolines cis-9 and trans-10 in a ratio of 30:70 together with the unsaturated amide 11. The structure of the latter was proven by independent synthesis. The intermediate l-menthyl N-p-nitrobenzoyl-3-iodophenyl-alaninate (18) was isolated at lower temperatures and shown to form the equilibrium mixture of 9 and 10 with triethylamine owing to partial racemization by a Finkelstein identity reaction. Use of an N-p-anisoyl substituent in the aziridine improves the yield of chiral 2-oxazolines by preventing the formation of 11, and allows the separation of pure cis- and trans-oxazolines for characterization. The aziridines bearing N-p-anisoyl substituents display a greater sensitivity to attack by weaker nucleophiles than the p-N-nitrobenzoyl analogs.Acid hydrolysis of 9 and 10 gives D-allo-β-phenylserine in an optical yield of about 17% from which 5 and 8 are tentatively assigned the 2R,3R configuration. Similar acid hydrolysis of the 2-p-anisyl-2-oxazoline (26b) allowed the isolation of the intermediate l-menthyl O-anisoyl-allo-β-phenylserinate (30a), hydrolysis of which gave D-allo-β-phenylserine in about 18% optical yield. The isolation of allo-β-phenylserine only from cis- and trans-2-oxazolines is attributed to acid-catalyzed inversion at the benzylic center to the conformationally more stable allo form.
Radical Intermediates In Chloramine and N-Chloroimide Reactions
Authors: Edwards Oliver Edward , Paskovich Donald H. , Reddoch Allan H.
Published: May 2006

Nitrogen-centered radicals produced by the action of Ag(0) or Ag(I)-amine systems on N-chloroazacyclononane, N-chloropiperidine, and N-chlorosuccinimide have been trapped using 2-methyl-2-nitrosopropane. The resulting nitroxides exhibited e.p.r. spectra consistent with structures 1, 2, and 3. Hydrogen gas evolved during reaction of the chloramines with Ag(0) was shown to arise completely from the amine derivatives.Excess Ag(0) reduced the succinamidyl radical to give the silver salt of succinimide.
Pyrrole Chemistry. XV. The Chemistry of Some 3,4-Disubstituted Pyrroles
Authors: Groves John Kington , Cundasawmy Niven Eddy , Anderson Hugh John
Published: May 2006

The syntheses of a variety of 3,4-disubstituted pyrroles including the antimitotic agent Verrucarin E are described. 3,4-Pyrroledicarboxylic esters were prepared through a Diels–Alder reaction. Partial hydrolysis of the diesters gave the 4-ester-3-acids which were modified to achieve the synthesis of a variety of unsymmetrically 3,4-disubstituted pyrroles. Raney nickel reduction of a thiolester gave hydroxymethyl under conditions which left acyl or carbalkoxy substituents unaffected. Pyrrole reactions involving carbanionic reagents are complicated by 1-proton abstraction. Therefore, when necessary, the nitrogen was protected by an N-benzyloxymethyl substituent which can be cleaved to the N-hydroxymethyl derivative by aluminum chloride or by hydrogenolysis. Subsequent treatment with benzyltrimethylammonium hydroxide gave back the pyrrole.
Alcohol to Ester Rearrangement. II. Diphenylphosphine and Hexafluoroacetone
Authors: Janzen Alexander Frank , Vaidya Om Chand
Published: May 2006

The reaction of diphenylphosphine with hexafluoroacetone gives (C6H5)2PC(OH)(CF3)2 which is readily oxidized to (C6H5)2P(O)C(OH)(CF3)2 and, in the presence of base catalyst, undergoes rearrange ment to the isomeric (C6H5)2P(O)OCH(CF3)2. Reaction of hexafluoroacetone with diphenylarsine gives (C6H5)2AsC(OH)(CF3)2 while reaction with diphenyl phosphonate gives (C6H5O)2P(O)C(OH)(CF3)2 which rearranges to (C6H5O)2P(O)OCH(CF3)2.
Scandium(III) Complexes of 8-Hydroxyquinoline and Derivatives
Authors: Corsini A. , Toneguzzo F. , Thompson M.
Published: May 2006

Under the conditions specified, scandium(III) and 8-hydroxyquinoline react in aqueous solution to give Sc(C9H6NO)3•H2O and not the adduct, Sc(C9H6NO)3•C9H7NO, as previously reported. The adduct is formed by reaction of the aquo tris chelate in molten 8-hydroxyquinoline and the anyhdrous tris chelate is obtained by thermal decomposition of the adduct. The 2-chloro, 4-chloro, and 5-methyl and 5-nitro derivatives also yield aquo tris chelates from aqueous solution while the 2-methyl and 4-methyl derivatives give adducts.
Crystal and Molecular Structure of Hexakis(dimethylamino)cyclotriphosphazene, [NP(NMe2)2]3
Authors: Rettig Steven J. , Trotter James
Published: May 2006

Crystals of the title compound are monoclinic, a = 15.539(4), b = 9.061(1), c = 16.707(6) Å, β = 107.19(5)°, Z = 4, space group P21/c. The measured and calculated densities are 1.19 and 1.180(1) g cm−3, respectively. The structure was determined by direct methods and refined by electron-density and full-matrix least-squares procedures to R = 0.047 for 2503 observed reflections. The six-membered phosphazene ring is slightly, but significantly, non-planar, the conformation being that of a distorted boat. The molecule has approximate D3 symmetry. The ring P—N bonds are all equal, mean P—N = 1.588(3) Å, and the relatively short exocyclic P—N bonds, mean 1.652(4) Å, indicate the presence of exocyclic π-bonding in the molecule. The N—C bonds range from 1.417(7) to 1.471(5) with a mean of 1.45(2) Å. The mean endocyclic N—P—N and P—N—P angles are 116.7(4) and 123.0(4)°, respectively, while the exocyclic N—P—N angles average 101.5(8)°.
Base-catalyzed Degradations of Carbohydrates. V. The Conversion of 3-Deoxyhex-2-enopyranoses into 2-Furoic Esters
Authors: Aspinall G. O. , Khan R. , King R. R. , Pawlak Zofia
Published: May 2006

Condensation of 2,3,4-tri-O-acetyl-α-D-xylopyranosyl bromide and benzyl 2,3,4-tri-O-methyl β-D-glucopyranoside (2), followed by removal of protecting groups, affords 2,3,4-tri-O-methyl-6-O-(β-D-xylopyranosyl)-D-glucopyranose (5). Alkaline degradation of the disaccharide 5, followed by treatment with dilute acid, furnishes 5-β-D-xylopyranosyloxymethyl-2-furaldehyde (8), which is converted by oxidation and esterification, followed by acetylation, into methyl 5-(2,3,4-tri-O-acetyl-β-D-xylopyranosyl-oxymethyl-2-furoate (11), whose structure has been confirmed by direct synthesis.
Heterogeneous Isomerization of Ethylene Oxide to Acetaldehyde
Authors: Bernardini O. O. , Cherniak E. A.
Published: May 2006

Surface catalyzed isomerization of (CH2)2O to CH3CHO occurs in a small, Pyrex reactor containing 15 or 230 Torr (CH2)2O at temperatures in the range 339.2 °C to 461.4 °C. Ro(CH3CHO), the initial rate of formation of CH3CHO, depends on the number of successive pyrolyses and on the evacuation time between pyrolyses, which is not true of the initial rates of formation of H2, CO, CH4, CH2CO, and C2H6. Ro(CH3CHO) also depends on the reactor S/V and on pretreatment of the reactor with product gases, particularly H2. The reproducible and limiting values of Ro(CH3CHO) are independent of the (CH2)2O pressures used. Above 385 °C these initial rates exhibit an Arrhenius temperature dependence while below 385 °C they pass through a maximum.Analysis of the Langmuir–Hinshelwood, low surface coverage mechanism shows that the T > 385 °C isomerization is partially or totally controlled by CH3CHO desorption and that −ΔHads < (55 ± 10) kcal mol−1, for CH3CHO on this surface.Ea = 57 kcal mol−1 for the homogeneous first order decomposition of (CH2)2O, in the 15 Torr pyrolysis at temperatures in the range 374.0 to 406.7 °C, and any vibrationally excited CH3CHO, formed in the gas phase at this pressure (and possibly even at 230 Torr), dissociates into chain initiating radicals.
The Pyrolysis of Trimethylthallium and Evaluation of D[(CH3)2Tl—CH3]
Authors: Price S. J. , Richard J. P. , Rumfeldt R. C. , Jacko M. G.
Published: May 2006

The pyrolysis of trimethylthallium has been studied in a mercury free toluene carrier flow system (452–536 °K, total pressure 6.7–39.3 mm, contact time 0.9–5.1 s, 5.4–90.2% decomposition). In a vessel cleaned with boiling concentrated HNO3 and coated by decomposing 0.1 g Tl(CH3)3 no heterogeneous reaction could be detected. The extent of reaction measured by product analysis (CH4, C2H6, C6H5C2H5) assuming three CH3 per Tl(CH3)3 undergoing reaction 1
Some Observations on the Hydrolysis of the Amides of Primary α-Acetylenic Amines
Authors: Gardner John Nicholson
Published: May 2006

Some amides of primary α-acetylenic amines were made from the corresponding α-acetylenic alcohols by the Ritter reaction. Depending upon the other substituents on the carbon atom bearing nitrogen and the ethynyl group, hydrolysis resulted in formation of the α-acetylenic amine or in hydration of the triple bond to yield a ketone.
Substituent Interactions in Di- and Tri-acyl Derivatives of cis- and trans- 2-Hydrazinocyclopentanol
Authors: Campbell J. A. , Mackay Donald
Published: May 2006

The action of thionyl chloride followed by an alkaline work-up quantitatively isomerizes trans-1,2-dibenzoyl-1-(2-hydroxylcyclopentyl)hydrazine(5) to cis-2-benzoyl-1-(2-benzoyloxycyclopentyl)hydrazine (3). One equivalent of tosyl chloride in pyridine converts 5 to an intermediate which can be hydrolyzed to a mixture of 3 and 5 or can be transformed to the N-tosyl derivative 13 by tosylation and then hydrolysis. Oxazolidine structures are suggested as intermediates for these reactions.The alcohol 2 can also be isomerized to 3, using 0.8 N aqueous ethanolic hydrochloric acid, to which 5 is inert. The ester 3 is again the major product in the hydrolysis by this acid mixture of the cis-tribenzoyl derivative 17, the cis-N1-p-anisoyl derivative 21a and the cis-N1-acetyl derivative 21b, the amide group being cleaved much more rapidly than the ester, especially in the case of 21b. A mechanism involving ester participation by way of an oxazolidinium cation is proposed for these amide hydrolyses, and this is supported by tracer studies.The trans-esters 24a and b hydrolyze mainly at the ester group with retention of configuration.Polymorphism is a common phenomenon among the title compounds.
ortho Diquaternary Aromatic Compounds. IV. Acid-catalyzed Rearrangements of Polyalkyltetralones and Related Ketones
Authors: Barclay Lawrence Ross Coates , Young Robert Hayworth , Adams Keir Leigh , Foote Helen Mary
Published: May 2006

The ketones 1,1,4,4-tetramethyl-2-tetralone (1a), 1,1,4,4,7-pentamethyl-2-tetralone (1b), and 1,1,4,4,6-pentamethyl-2-tetralone (1c) undergo rearrangement on heating with aluminum chloride or ferric chloride in tetrachloroethane or nitromethane into mixtures of their respective isomeric ketones, 1-acetyl-1,3,3-trimethylindane (2a) and 2,2,4,4-tetramethyl-1-tetralone (3a) from 1a, 1-acetyl-1,3,3,6-tetramethylindane (2b) and 2,2,4,4,7-pentamethyl-1-tetralone (3b) from 1b, and 1-acetyl-1,3,3,5-tetramethylindane (2c) and 2,2,4,4,6-pentamethyl-1-tetralone (3c) from 1c. A quantitative study using g.l.c. of the distribution of the ketones with time shows that the sequence of the rearrangement is: [Formula: see text]. A methyl group homologously para to the carbonyl (1c) accelerates the rearrangement. The same kind of rearrangement takes place during Friedel–Crafts cyclialkylation with 2,2,5,5-tetramethyltetrahydrofuranone. A unifying reaction mechanism is postulated to account for the rearrangements. This mechanism also accounts for the rearrangement and fragmentation products from treatment of 1,1,4,4-tetramethyl-2,3-dioxotetralin (9) with aluminum chloride or sulphuric–acetic acids. The products from 9 include 1-acetyl-1,3,3-trimethyl-2-indanone, 1,1,3-trimethyl-2-indanone, and, from the aluminum chloride – catalyzed rearrangement, 5(or 6)-acetyl-1,1,3-trimethyl-2-indanone.
Isothiazolopyridines. I. Synthesis and Spectra of Isothiazolo[3,4-b]-, 3-Amino-isothiazolo[4,3-b]-, Isothiazolo[5,4-b]-, and 3-Methylisothiazolo[5,4-c]pyridines. Preparation and Spectra of Some 2,3- and 3,4-Disubstituted Pyridines
Authors: Taurins Alfred , Khouw Virginia Tan
Published: May 2006

Isothiazolo[3,4-b]pyridine was synthesized from 2-aminonicotinonitrile in three steps: by the reaction with ammonia and hydrogen sulfide to produce 2-aminothionicotinamide; oxidative cyclization with hydrogen peroxide to give 3-aminoisothiazolo[3,4-b]pyridine, followed by diazotization and reduction with hypophosphorous acid. 3-Aminoisothiazolo[4,3-b]pyridine was prepared in a similar way from 3-aminopicolinonitrile via 3-aminothiopicolinamide. Isothiazolo[5,4-b]pyridine was synthesized from 2-chloronicotinonitrile in three steps: by the reduction with formic acid in the presence of Raney nickel to obtain 2-chloronicotinaldehyde; transformation of the latter into 2-thiocyanonicotinaldehyde; and finally cyclization with ammonia to obtain isothiazolo[5,4-b]pyridine. 3-Methylisothiazolo[5,4-c]pyridine was prepared by cyclization of 4-acetyl-3-thiocyanopyridine with ammonia. N.m.r. and u.v. spectra of the isothiazolopyridines, their derivatives, and the pyridine intermediates were recorded and interpreted.
13C Nuclear Magnetic Resonance Studies. 29. 13C Spectra of Some Alicyclic Methyl Esters
Authors: Gordon M. , Grover S. H. , Stothers J. B.
Published: May 2006

The shielding effects of the carbomethoxyl group on neighboring carbons in the cyclohexane and trans-decalin ring systems have been characterized by 13C n.m.r. examination often model compounds. The data show that sufficient differences are exhibited by axial and equatorial groups to permit stereochemical assignments in related systems. The observed trends are compared with those produced by other functional groups. The three-, four-, and five-membered ring cycloalkae carboxylic acid esters were also examined.
Stereospecific Conjugate Alkenyl Group Transfer to α,β-Enones Using Vinylalane Reagents
Authors: Hooz John , Layton Robert B.
Published: May 2006

trans- Alkenyl alanes (easily prepared by hydroalumination of an acetylene) promote the stereospecific 1,4- delivery of the olefinic unit to conjugated ketones. This new conjugate addition reaction provides easy access to trans-γ,δ-unsaturated ketones which would otherwise be available with difficulty.
Proton Magnetic Resonance Studies of Rotational Isomerism in Halotoluene Derivatives. IX. Rotational Barriers and Conformational Energy Differences in α,α,α′,α′,α″,α″, 2,4,6-Nonachloromesitylene
Authors: Peeling J. , Goodwin B. W. , Schaefer T. , Rowbotham J. B.
Published: May 2006

The activation parameters for the rotation of the dichloromethyl groups in the two conformations of α,α,α′,α′,α″,α″,2,4,6-nonachloromesitylene are reported for solutions in toluene-d8 and in methylene chloride. In addition, free energies of activation are given for solutions in bromochloromethane, tri-chloroethylene, and in carbon disulfide. The free energies of activation are lower in the toluene solution than in the other solutions. The entropies of activation are near zero, perhaps slightly negative. The symmetrical conformation is more stable than the unsymmetrical one in all the solvents.
On the Unimolecular Decomposition of the tert-Butoxy Radical
Authors: Yip C. K. , Pritchard H. O.
Published: May 2006

It is argued that a large apparent pressure dependence in the rate of decomposition of the tert-butoxy radical should not be interpreted in terms of unimolecular reaction theory; the effect is probably heterogeneous in origin.
Solvation of Cl− and O2− with H2O, CH3OH, and CH3CN in the gas phase
Authors: Yamdagni R. , Payzant J. D. , Kebarle P.
Published: May 2006

Determination of the temperature dependence of the equilibrium constants Kn,n−1 for the reactions A −Bn = A −Bn−1 + B where A− equals Cl− and O2− and B is HOH, CH3OH, or CH3CN leads to the corresponding ΔH0n−1, ΔG0n−1,n, and ΔS0n−1,n values. The experimental technique is based on mass spectrometric detection of ions escaping from a high pressure ion source. At n = 1, Cl− is solvated most strongly by methanol, then CH3CN and HOH. At higher n a cross over is observed with water becoming the best solvent. These results are in agreement with the positive transfer enthalpies and free energies for Cl− from the liquid solvents HOH → CH3OH and HOH → CH3CN reported in the literature.O2− is solvated more strongly than Cl− appearing thus as an ion of "size" intermediate between Cl− and F− Again CH3OH gives the highest interaction for n = 1, however for n > 1 water gives stronger interactions.
The Oxidation of Benzyldimethylamine by Bromine
Authors: Lee Donald G. , Srinivasan R.
Published: May 2006

The rates of oxidation of several substituted benzyldimethylamines by bromine in 50% aqueous acetic acid have been determined spectrophotometrically. Electron-withdrawing substituents decrease the rate of reaction with the Hammett ρ value being −0.95. The reaction is subject to general base catalysis and substitution of deuterium in the α-position decreases the rate of reaction by approximately 30%, thus indicating that the α-C—H bond is cleaved in the slow step of the reaction. All results are consistent with a mechanism which involves, in the rate determining step, loss of an α-hydrogen atom as a proton with concomitant transfer of electrons from nitrogen to the oxidant.
A Comparative Proton Magnetic Resonance Study of the Molecular Conformation of Uracil and 6-Aza Uracil Nucleosides and Nucleotides
Authors: Wood Donald J. , Hruska Frank E. , Mynott Richard J. , Sarma Ramaswamy H.
Published: May 2006

Proton magnetic resonance data for uridine and uridine-5′-monophosphate, and the corresponding 6-azauracil analogs, are presented and discussed in terms of their overall three dimensional conformations in aqueous solution. The data reveal a destabilizing influence of the 6-aza base upon the gog and g′–g′ conformation of the ribose phosphate moiety.
Crystal Structure of α-VPO5
Authors: Jordan Byron , Calvo Crispin
Published: May 2006

α-VPO5 crystallizes in the tetragonal space group P4/n with a = 6.014(7) and c = 4.434(2) Å. The structure, isotypic with that of α-VSO5, was refined by full-matrix least-squares method to an R value of 0.089 using 239 independent reflections. The vanadium ion lies on a crystallographic four-fold axis, as does one of the oxygen atoms, and the P on a site of [Formula: see text] symmetry. A second oxygen atom, as a result of disorder, occurs in two positions which are mirror reflected with respect to the ac plane. The structure consists of highly distorted VO6 groups with bond lengths along the c axis of 1.580(11) and 2.853(11) Å while the remaining four V—O bond lengths are all 1.858(8) Å. The P—O bond lengths in the PO4. tetrahedron are 1.541(8) Å with the PO4 groups bridging across four chains of VO6 groups.
N.M.R. Studies of Anhydrous Hydrogen Fluoride Solutions
Authors: Shamir Jacob , Netzer Aharon
Published: May 2006

Solutions of anhydrous HF and SO2 and electrolytes in anhydrous HF have been studied by n.m.r. Both 1H and l9F chemical shifts were studied as a function of concentration and temperature. The dimerization constant and the enthalpy of the reaction [Formula: see text] were calculated.The results for electrolyte solutions were interpreted on the basis of two effects, ionization and the H-bond breaking effect. A linear relationship exists between δ0, the molal chemical shft, and the ionic crystallographic radii. A temperature effect was also observed and interpreted. Solutions of salts of Lewis acids were also studied but results are less conclusive; it was shown, however, that their δ0 values are smaller than those of alkali fluorides.
Binary Dioxygen Complexes of Nickel, Palladium, and Platinum, M(O2) and (O2)M(O2), in Low Temperature Matrices
Authors: Huber H. , Klotzbücher W. , Ozin G. A. , Voet A. Vander
Published: May 2006

The cocondensation reactions of nickel, palladium, and platinum atoms with gaseous oxygen or dilute oxygen–argon mixtures at 4.2–10 °K give rise to binary transition metal dioxygen complexes. Variable concentration and diffusion controlled warm up studies, 16O/18O isotopic substitution studies, normal coordinate and isotope intensity calculations establish the complexes to be of the types M(O2) and (O2)M(O2). Both the mono- and bisdioxygen complexes contain the dioxygen molecules coordinated to the metal atom in a side-on fashion, with a unique D2d "spiro"-type structure favored for the bis-complexes. Frequency and bond stretching force constant trends within the series of complexes are examined and suggest that the O—O and M—O values increase with increasing coordination number, and thus with an increase in partial positive charge on the metal. This trend in O—O stretching frequencies is not in accord with the evaluation of metal–dioxygen bond strengths as based on the degree of reversibility of dioxygen coordination.
The Reactions of Organometallic Compounds Involving Silicon. Reactions of Methyldiphenyl-, Triphenylsilyl-sodium, -potassium, -rubidium, and -caesium with 9-Methylfluorene in Tetrahydrofuran
Authors: Hamid Muhammad Abdul
Published: May 2006

The reactions of triphenylsilyl-sodium(Ph3SiNa), diphenylmethylsilyl-sodium(Ph2MeSiNa), triphenylsilyl-potassium (Ph3SiK), triphenylsilyl-rubidium (Ph3SiRb), and triphenylsilyl-caesium (Ph3SiCs) with 9-methylfluorene in tetrahydrofuran (THF) were studied using the stop-flow technique at low temperatures. The rate constant k (1 mol−1 s−1) depends on the nature of the cation; at −50 °C k is 11.5 for Ph3SiNa, 29.5 for Ph2MeSiNa, 26.8 for Ph3SiK, 35.6 for Ph3SiRb, and 47.9 for Ph3SiCs. It seems that the organosilylalkali–metal compounds (R3SiM) exist in the form of contact ion-pair and therefore the reactivity of an ion-pair is determined by the Coulombic binding energy of the pair. The thermodynamic constants of activation for these reactions were calculated for −50 °C and compared with the corresponding values of triphenylsilyl-lithium Ph3SiLi reaction with 9-methylfluorene in THF. The plots of log k, ΔS≠, and ΔH≠ against 1/(rc + 2) and ΔS≠ against ΔH≠ were drawn to show that Li+ due to its existence as solvent separated ion-pair behaves differently to its Na+, K+, Rb+, and Cs+ counterparts.The electronic spectra of R3SiM, 9-methyl-fluoren-9-yl-sodium, -potassium, -rubidium and -caesium were determined at temperatures varying from 20 to −80 °C. A red shift was observed in spectra of R3SiNa at low temperatures; this was attributed to the increase in dipole moment which occurs during the electronic transition. The spectra of 9-methylfluoren-9-yl-sodium, -potassium, -rubidium, and -caesium were compared with their lithium counterpart to explain the effects of gegenion on the solvation of these species.
Proton Transfer Reactions of Carbon Acids. III. Effect of Solvent Change on the Equilibrium and Kinetic Parameters of the Reaction of Di-(4-nitrophenyl)methane with Alkoxide Bases
Authors: Kim Jae-Hang , Leffek Kenneth T.
Published: May 2006

The equilibrium constants, the second-order rate constants, and the activation parameters have been determined for the proton transfer from di-(4-nitrophenyl)methane to ethoxide ion in a series of mixed solvents containing various amounts of acetonitrile in ethanol. The quantities have been interpreted in terms of the general postulates of the Miller–Parker theory of solvation effects.
The Structure of Thiobinupharidine
Authors: Wróbel J. T. , Bobeszko B. , Martin T. I. , MacLean D. B. , Krishnamachari N. , Calvo C.
Published: May 2006

The spectroscopic properties of thiobinupharidine and its isomer, neothiobinupharidine, of established structure, have been examined and compared. From this study it was possible to deduce the structure and relative configuration of the alkaloid. The structure has been firmly established and the absolute configuration determined by the study of the crystal structure of thiobinupharidine dihydrobromide dihydrate, C30H42O2N2S•2HBr•2H2O. The crystals are orthorhombic with space group C2221, a = 25.128(6), b = 9.869(2), c = 26.380(6) Å, and Z = 8. The structure was refined, using full-matrix least-squares techniques with 1934 reflections, to a final R value of 0.097. The thiobinupharidine moiety hydrogen bonds to one of two types of H2O–Br–H2O spiral chains in the structure. The tetrahydrothiophene ring is distorted from planarity, and this together with the nonequivalence of the S and C atoms in the ring causes the molecule to deviate from C2 symmetry
Some Synthetic Interconversions in the Nitrocyclohexane System
Authors: Baer Hans H. , Shields Douglas C. , Dawson Geoffrey G.
Published: May 2006

Several transformations starting from trans, trans-2-nitrocyclohexane-1,3-diol (1) and its diacetate (2) were carried out as model reactions for synthetic work on nitro sugars. They included methylation with diazomethane, dehydration, dehydroacetylation, nucleophilic elimination–additions with alcohols, and bromination. The monomethyl ether of 1 (3), the monomethyl ether acetate (5), the dimethyl and dibenzyl ethers (4 and 9), bromonitro compounds derived from 1 and 4 (13 and 14), and four 3-substituted 2-nitro-cyclohexenes with methoxyl, ethoxyl, acetoxyl, and hydroxyl groups as substituents (6, 8, 7, and 11, respectively) were obtained in these studies. The nitronate formation of 1 and 4 and attendant production of nitroolefins was investigated by u.v. spectroscopy.
Diterpenoid Metabolites of Cyathus helenae. Cyathin B3 and Cyathin C3
Authors: Ayer William A. , Carstens Leslie L.
Published: May 2006

Cyathin B3, a metabolite of Cyathus helenae is shown to possess structure 3a. Cyathin C3 is 1,2-dehydrocyathin B3 (4a). Cyathin B3 has been correlated with cyathin A3 (1) and cyathin C3 with allocyathin B3 (2).
Further Studies in the Reactions of Triethylaluminum with Bis-(diphenylphosphino) amines
Authors: Clemens Donald F. , Smith Jr. Robert B. , Dickinson John G.
Published: May 2006

Triethylaluminum reacts with bis(diphenylphosphino)-n-propylamine and bis(diphenylphosphino)-n-butylamine to form the 1:1 adducts in which the aluminum atom is pentacoordinate. Triethylaluminum does not react with other bis(diphenylphosphino)amines in which the third substituent on the nitrogen atom is α-methylbenzyl, benzyl, or 1,1-dimethylamine. The formation of adducts from straight-chain hydrocarbons and the total lack of reactivity for the Lewis bases containing bulky groups leads to the postulation that steric hindrance prevents the free pair of electrons on the phosphorus atoms from being available to the triethylaluminum.
Na+ and K+ Binding by Fulvic Acid
Authors: Gamble Donald S.
Published: May 2006

The electrostatic binding of Na+ and K+ by fulvic acid in aqueous solution has been measured with cation electrodes at 25.00 °C ± 0.05. The binding equilibria were followed during the course of acid–base titrations, and have revealed distinct binding regions in the titration curves. In one of these regions Na+ is more strongly bound than is K+. The standard free energies of binding were 11.7 × 103 to 20.5 × 103 J/mol ± 2% for Na+, and 11.5 × 103 to 17.8 × 103 J/mol ± 1%, for K+.
Binary Dinitrogen Complexes of Rhodium, Rh(N2)n (where n = 1–4), in Low Temperature Matrices
Authors: Ozin Geoffrey A. , Voet Anthony Vander
Published: May 2006

The products of the cocondensation reactions of Rh atoms with N2 and N2/Ar mixtures at 10 °K are investigated by matrix isolation infrared spectroscopy and are shown to be binary dinitrogen complexes of the form Rh(N2)n. Examination of the reaction products in pure 14N2, 15N2, 14N2/15N2, and in dilute Ar/14N2, Ar/14N2/15N2, and Ar/14N2/14N15N/15N2 matrices establish the values of n to be 1–4. Isotopic frequencies are computed for the NN stretching modes of the individual dinitrogen complexes on the basis of the Cotton–Kraihanzel (C.K.) force field approximation and are found to be in close agreement with observed values. Trends in the best fit C.K. force constants for Rh(N2)n (n = 1–4) and the thermodynamic stabilities of the individual complexes as indicated by the function ΔHcn, a measure of the enthalpy of decomposition, are discussed. Comparisons are made between Ni(N2)n and Rh(N2)n (where n = 1–4). The structure of Rh(N2)4 in solid nitrogen is shown to be that of a distorted tetrahedron. Calculations show that a site symmetry of D2d for Rh(N2)4 satisfactorily accounts for all of the spectral lines observed for the complex in nitrogen. In solid argon, Rh(N2)4 appears to have an approximately regular tetrahedral structure. The relationship between RhN2 and N2 chemisorbed on Rh metal is discussed and compared with the analogous Ni–, Pd–, and Pt–nitrogen systems.
On the Thermodynamically Controlled Epimerization of Deoxynitroinositol Monomethyl Ethers
Authors: Kovář Jan , Baer Hans H.
Published: May 2006

1-Deoxy-4-O-methyl-1-nitro-scyllo-inositol (1), its myo-1 epimer (2), 3-deoxy-6-O-methyl-3-nitro-epi-inositol (3), and its muco-3 epimer (4) in the presence of excess base give nitronates (1′ from 1, 2′ from 2, and 3′ from 3 and 4) which are mutually interconverted by epimerization. The equilibrium constants were determined, revealing the order of thermodynamic stabilities of the nitronates to be 3′ > 2′ > 1′. In the presence of a catalytic amount of base, the nitro inositols epimerize also, and the order of stability of the free nitro compounds is [Formula: see text]. The connection between these epimerizssation equilibria and the pKa values of the compounds is discussed. The results are explained in terms of conformational analysis, whereby the importance of the A(1,3) strain is reasserted and good agreement with calculated conformational energy data is obtained.
Maleic Anhydride – Triethylamine Complex
Authors: Mayahi Mahmood F. , El-Bermani M. F.
Published: May 2006

Reaction of triethylamine with maleic anhydride (MA) forms first a yellow solution, which immediately turns into a dark brown product with a large increase in temperature. The addition product is a 1:1 open chain inner salt [Formula: see text]. The spectral properties of this salt are reported.
Etude par Spectroscopic Infrarouge de la Solvatation Préférentielle du Cation Li+
Authors: Regis André , Corset Jacques
Published: May 2006

The analysis of the infrared spectra of ternary mixtures LiClO4–S1–S2 shows a preferential solvation of the Li+ ion by ammonia and methylamines (S2) in acetonitrile or tetrahydrofuran (S1) and by acetonitrile (S2) in nitromethane (S1). The appearance of wide bands in the "ion-cage" vibration region is related to the formation of different species [Li(S1)n − i(S2)i]+. The variation of their relative concentration when ρ = [S2]/[LiClO4] increases explains the frequency shift of the bands. The interaction energy Li+ ion – solvent molecule decreases when the number of S2 molecules in the first solvation shell increases and does not seem to depend on the dielectric constant of the surrounding medium. The mean composition of the first solvation shell is obtained from intensity measurements of absorption bands of the S2 molecules not bonded to the ions; in favorable cases (S2 = ND3, CH3CN) solvation number of the Li+ ion in the pure solvent could be estimated. The solvating power of the different bases used is shown to decrease in the order NH3 > CH3NH2 > (CH3)2NH > (CH3)3N > CH3CN > CH3NO2 and involves both donor–acceptor and ion–dipole interactions.
A Revision of the Stereochemistry of Lactucin
Authors: Bachelor Frank William , Itô Shô
Published: May 2006

On the basis of circular dichroism measurements on lactucin, hydroxyachillin, and acetoxyachillin the stereochemistry of the C-5 hydrogen has been revised to the 5α configuration. The reasons for the former erroneous assignment are reexamined and the structures of several hexahydrolactucin derivatives are reinterpreted.
The Reduction of Acetamidopentaamminecobalt(III) by Chromium(II)
Authors: Balahura Robert J. , Hutley Lynda
Published: May 2006

The reduction of nitrogen bonded acetamidopentaamminecobalt(III) by chromium(II) has been studied. The acetamido complex is a reasonably strong acid attributed to the equilibrium[Formula: see text]which has a pKa of 2.16 ± 0.08 at 25.0° and μ = 0.01 M. The reduction process has the rate law[Formula: see text]For reduction of the conjugate base k = kNHKa and kNH = 5.23 × 10−2 M−1 s−1 at 25.1°, with ΔH = 14.5 ± 2 kcal mol−1 and ΔS = 16 ± 6 e.u. respectively. The rate law is indicative of an inner-sphere process. The orientation of the ligand is thought to be important for the reduction of the acetamido and the related carboxylato complexes, and this is discussed.
Acid Ionizations of Nitroalkanes in Aqueous Solution
Authors: Matsui Takeki , Hepler Loren G.
Published: May 2006

not available
The Carbon-13 Nuclear Magnetic Resonance Spectra of 2-Acetamido-2-deoxy-D-hexoses and some Specifically Deuteriated, O-Acetylated, and Phosphorylated Derivatives
Authors: Bundle D. R. , Jennings H. J. , Smith Ian C. P.
Published: May 2006

The 13C n.m.r. spectra of the 2-acetamido-2-deoxy-D-hexoses and some 3-O-acetyl and 1-phosphate derivatives are assigned and discussed. To facilitate the interpretation of the spectra, an initial assignment of the resonances in the spectrum of 2-acetamido-2-deoxy-D-glucose was required. For this purpose, both the 3-2H and 4-2H derivatives of this acetamido-hexose were synthesized. These syntheses are reported together with those of 2-acetamido-3-O-acetyl-2-deoxy-D-glucose and 2-acetamido-2-deoxy α- and β-D-glucose-1-phosphate. These model compounds were used to study substituent effects related to the 2-acetamido-2-deoxy-D-hexose-containing polysaccharide antigens of N. meningitides.
Methyl Isocyanide as a Key Molecule in Thermal Explosion Theory
Authors: Pritchard Huw O. , Tyler Brian J.
Published: May 2006

Thermal explosion limits have been measured in the temperature range 285–351 °C for methyl isocyanide and at 351 °C for mixtures of methyl isocyanide and methyl cyanide. We suggest that the methyl isocyanide isomerization is potentially the best reaction system against which to test thermal explosion theories, but at the present time certain kinetic, thermochemical, and thermodynamic data are not available with sufficient accuracy.
Hydrogen–Water Deuterium Exchange over Graphon Supported Group VIII Noble Metals
Authors: Sagert Norman Henry , Pouteau Rita Mary Louise
Published: May 2006

Specific activities of Group VIII noble metals supported on Graphon have been determined for hydrogen–water deuterium exchange. Metal surface areas, which are required to calculate specific activities, were measured by hydrogen chemisorption, and by reaction of hydrogen with chemisorbed oxygen. For the second triad metals, ruthenium, rhodium, and palladium, and in the temperature range 140 to 225 °C, the variation of activity was Ru < Rh > Pd. For the third triad metals, osmium, iridium, and platinum, the variation of activities was Os < Ir < Pt in the same range of temperature. Apparent activation energies were measured over this temperature range, and orders of reaction with respect to hydrogen and water were measured at 160 °C (200 °C for Pt). From these data, activation energies for the surface exchange reaction were calculated. In the second triad the activation energies decrease slightly with increasing atomic number, but in the third triad they decrease quite markedly with increasing atomic number. A good correlation was obtained between the activation energy for surface exchange and the thermionic work function of the metal. This supports our earlier suggestion that Graphon is able to donate electrons to the metal and thus lower the activation energy for the surface exchange.
Quaternary Nitrogen Heterocycles. III. Kinetic and Thermodynamic Control of Pseudobase Formation from the 1-Methyl-3-nitroquinolinium Cation
Authors: Bunting John W. , Meathrel William G.
Published: May 2006

A kinetic study of the formation and decomposition of the pseudobase of the 1-methyl-3-nitroquinolinium cation has revealed that although 1,4-dihydro-4-hydroxy-1-methyl-3-nitroquinoline is the predominant product at equilibrium, the kinetically controlled product is the isomeric pseudobase, 1,2-dihydro-2-hydroxy-1-methyl-3-nitroquinoline. This less stable isomer has been identified from its u.v-visible spectrum, and the pKROH value for its formation (9.16) has been measured by the stopped-flow technique.
Electrochemical Synthesis of Deuterio Organic Compounds. I. Electrochemical Reduction of 1-Halonaphthalenes and Synthesis of 1-Chloro-4-methylnaphthalene
Authors: Renaud Roger N.
Published: May 2006

Electrochemical reduction of 1-chloro-, 1-bromo-, 1-iodo-, 1-chloro-4-methyl-, and 1-bromo-4-methyl naphthalene was done in presence of deuterated water. The deuterium content of the naphthalene obtained reveals that the mechanism for the bromo and the iodo derivatives might involve either a simultaneous transfer of two electrons or an organometallic intermediate, while reduction of the chloro derivative might proceed at least partially via a radical intermediate.The synthesis of 1-chloro-4-methylnaphthalene from 1-chloro-4-chloromethylnaphthalene was achieved either by selective sodium borohydride reduction or by selective electrochemical reduction.
Microwave Spectrum of N-Methyl Morpholine
Authors: Dass S. C. , Kewley R.
Published: May 2006

The microwave spectrum of N-methyl morpholine has been investigated within the 8 to 40 GHz region. The observed rotational constants for the ground vibrational state are (in MHz), A = 4821.235(0.077), B = 2342.579(0.004), and C = 1719.452(0.003). The dipole moment components have been determined as (in D), μa = 1.21(0.02), μc = 0.10(0.03), and μ= 1.21(0.02). The values of these parameters show that the observed spectrum is due to the chair form with an equatorial methyl group. The 14N nuclear quadrupole coupling constants have the values (in MHz), χaa = 2.4(0.1), χbb =.6(0.3) and χcc = −5.0(0.2). Sets of rotational transitions due to six excited vibrational states have also been assigned.
Electron Mobilities and Ranges in Liquid C1–C3 Hydrocarbons and in Xenon: Effects of Temperature and Field Strength
Authors: Robinson Maurice G. , Freeman Gordon R.
Published: May 2006

Electron mobilities were measured in ethane, ethylene, propane, cyclopropane, and propylene to complete the studies of the lower hydrocarbons. The effect of temperature on the mobilities in these liquids and in methane, n-butane, and xenon were also measured. Examples of the data are given in the order mobility (cm2/Vs), temperature (K), Arrhenius temperature coefficient (kcal/mol): methane, 430, 140, −0.16; ethane, 0.97, 200, ∼3; ethylene, 0.0030, 170, —; propane, 0.55, 238, ∼3; n-butane, 0.073, 250, ∼4; cyclopropane, 0.0043, 234, ∼4; propylene, 0.008, 234, ∼4; xenon, ∼1200 at 40 V/cm, 198, 0. The mobilities in the C2–C4 hydrocarbons are independent of applied electric field strength E up to 20 kV/cm; that in methane is independent of E up to 2 kV/cm; that in xenon decreases as E−1/2 between 33 and 300 V/cm and decreases slightly more rapidly at higher field strengths. The density-normalized ranges of the secondary electrons in each of the liquids is independent of temperature. The correlation between the ranges of the secondary electrons and the mobilities of thermal electrons observed in other liquids (ref. 2) persists for the simple hydrocarbons.
The Preparation and Properties of 1-Cyano-2,3,4-triamnine(ethylenedianine)cobalt(III) Chloride
Authors: Norris Albert Richard
Published: May 2006

The i.r., u.v.–visible, and p.m.r. spectral characteristics of a cyanotriammine(ethylenediamine)cobalt(III) chloride are described and compared to the corresponding spectral characteristics of the related compounds cis-[NH3CN]Cl2, trans-[Coen2NH3CN]Cl2•H2O, and [Co(NH3)5CN]Cl2. Evidence is presented to support the formulation of the [Coen(NH3)3CN]Cl2 complex as a 1-cyano-2,3,4-triammine(ethylenediamine)cobalt(III) chloride.