Pyridine In Methanol Research Articles

The mechanism of alkylation reactions. Part 1. The effect of substituents on the reaction of phenacyl bromide with pyridine in methanol

Rate constants have been determined for the reaction of p-bromophenacyl bromide with pyridine and three substituted pyridines in methanol at 313.2 K. The reaction of phenacyl bromide in methanol at 313.2 K was investigated for pressures up to 100 MPa and the effect of substituents on the volume of activation, ΔV*, determined. From the partial molar volumes of reactants and products, the values of ΔV* were interpreted in terms of the intrinsic volume of the transition state, solvent electrostriction in the transition state and differences in hydrogen bonding between the initial and the transition state. The results support a transition state in which (a) bond forming leads over bond breaking and (b) considerable charge dispersal occurs. A priori calculations of ΔV and ΔV* are compared with experimental values and their utility discussed.

Thermodynamic study of the transfer of pyridines from the gas phase to solution in methanol

Enthalpies of solution of eleven pyridines in methanol are combined with vaporization data to obtain enthalpies of transfer of the pyridines from the gas phase to solution in methanol. The data reflect specific solvation effects involving substituent groups and the electronic and steric influence of substituent groups on hydrogen-bonding interactions between methanol molecules and the pyridine nitrogen atom. Free energies of transfer of pyridine, 2-methylpyridine and 2,6-dimethylpyridine from the gas phase to methanol are compared with the effects of 2-methyl and 2,6-dimethyl substitution on the free energy of solvation of the pyridinium ion.

Thermodynamic study of the acid dissociation of substituted pyridinium ions in methanol

Standard Gibbs' free energies, enthalpies and entropies of dissociation of the pyridinium ion and thirteen substituted pyridinium ions in methanol have been measured. The electronic effects of substituents on the thermodynamic data are discussed in terms of specific solvation around the substituent groups and of changes in solute–solvent interactions at the pyridine N atom or the pyridinium ion +NH group charge centre. Reference to gas-phase data for the dissociation of pyridinium ions and to enthalpies of solvation of neutral pyridines in methanol has allowed separation of substituent effects involving the pyridines and the pyridinium ions. The steric effects of 2-t-butyl and 2,6-di-t-butyl substitution on solute–solvent interactions are assessed and compared with corresponding effects involving the addition of t-butyl substituents on the acid ionization of phenol. An acidity function for hydrogen chloride in methanol is defined.

Light Scattering in pyridine—n-hexane and pyridine—methanol mixtures

Light Scattering in pyridine—n-hexane and pyridine—methanol mixtures

Base-induced benzoyl migrations in Diels–Alder adducts of benzoyl-1,4-benzoquinones

Addition of buta-1,3-diene and trans-penta-1,3-diene to substituted benzoyl-1,4-benzoquinones affords the corresponding 4a-benzoyl-4a,5,8,8a-tetrahydro-1,4-naphthoquinones which in pyridine and pyridine–methanol, undergo [1,5] and [1,2] benzoyl shifts to give 2-benzoyl-5,8-dihydro-1,4-dihydroxynaphthalenes; the effects of para-substituents in the benzoyl group on the kinetices and regiospecificity of the migration are described.

Acyl migrations in Diels–Alder adducts of acyl-1,4-benzoquinones

Treatment of several 4a-acyl-4a,5,8,8a-tetra-hydro-1,4-naph thoquinones with boiling acetic anhydride gives the 1,4-diacetoxy-2-acyl-5,8-dihydronaphthalenes, and the corresponding 1,4-dihydroxy-compounds are formed when acetic acid is used, but the latter are more readily obtained, via the Δ8a,1enols, by treatment with pyridine or pyridine–methanol, these basic reagents cause deformylation of the 4a-formyl analogues, but transfer of the formly group to the oxygen at C-4 can be effected with imidazole.

1,5] and [1,2] Acetyl shifts in Diels–Alder adducts of 2-acetyl-6-methyl-1,4-benzoquinone

Treatment of the Diels–Alder adduct 4a-acetyl-4a,5,8,8a-tetrahydro-3-methyl-1, 4-naphthoquinone with pyridine–methanol or acetic anhydride leads to a [1,5] acetyl shift to the 3-position which can be followed by a [1,2] acetyl shift to the 2-position (adduct numbering).

Light Scattering in pyridine—n-hexane and pyridine—methanol mixtures

Light Scattering in pyridine—n-hexane and pyridine—methanol mixtures

Mechanism of the oxidative coupling of phenols: Influence of pH upon the electrochemical oxidation of xylenol in methanol

AbstractIn acidic methanol, xylenol undergoes a bielectronic one step oxidation leading to the phenoxonium cation. Above pH 5,2 the reaction takes place in two monoelectronic steps, the first of which leading to a free radical. CC coupling, leading to quinones, occurs with the cation, whereas the free monomeric radical undergoes polymerization by CO coupling. The influence of the pyridine concentration upon the orientation of the coupling may be explained by the coincidence between the pKA of pyridine in methanol and the pH which favours disproportionation of the monomer radical.

ChemInform Abstract: IONIZATION CONSTANTS AND VOLUMES OF HIGHLY HINDERED PYRIDINES IN METHANOL

Chemischer InformationsdienstVolume 6, Issue 32 Heterocyclic Compounds ChemInform Abstract: IONIZATION CONSTANTS AND VOLUMES OF HIGHLY HINDERED PYRIDINES IN METHANOL W. J. LENOBLE, W. J. LENOBLESearch for more papers by this authorT. ASANO, T. ASANOSearch for more papers by this author W. J. LENOBLE, W. J. LENOBLESearch for more papers by this authorT. ASANO, T. ASANOSearch for more papers by this author First published: August 12, 1975 https://doi.org/10.1002/chin.197532269Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume6, Issue32August 12, 1975 RelatedInformation

Kinetics of reactions in solutions under pressure. XXXI. Ionization constants and volumes of highly hindered pyridines in methanol

Kinetics of reactions in solutions under pressure. XXXI. Ionization constants and volumes of highly hindered pyridines in methanol

ChemInform Abstract: DOPAQUINONE AND RELATED COMPOUNDS, THE REACTION WITH CYCLOPENTADIENE

AbstractDie Cyclopentadien‐Addukte der bei der Oxidation der Resorcinderivate (I) mit Chloranil entstehenden o‐Chinone werden als Acetylderivate (II) isoliert.

Dopaquinone and Related Compounds. The Reaction with Cyclopentadiene

Abstract The trapping of o-quinones produced during the oxidation of 4-substituted catechols(I, R=CH3, CH2CH2CO2H, CH2CH2NH3Br, CH2CH(NH3Cl)CO2CH3) in the presence of cyclopentadiene affords adducts, which are changed into 8-substituted 5,6-diacetoxy-1,4-dihydro-1,4-methanonaphthak nes(IV, R=CH3, CH2CH2CO2H, CH2CH2NHCOCH3, CH2CH(NHCOCH3)COCH3) by treatment with acetic anhydr de-pyridine Dopaquinone (IIe) is trapped with cyclopentadiene, followed by acetylation and methylation with acetic anhydride–pyridine–methanol (13 : 2 : 2) to give the N-acetyl-2-(5,6-diacetoxy-1,4-dihydro-1,4-methanonaph-thyl-8)-l-alanine methyl ester (IVd).

The formation of Δ 2-pyrrolines by base catalysed nitrile dimerisation

The reaction of (1-bromocyclohexyl)methylidenemalonitrile and 2-bromo-2-methylpropylidenemalonitrile with sodium methoxide in methanoi has been shown to give high yields of Δ 2-pyrrolines in a Thorpe reaction involving two initially formed nitrile products. The by-products formed, (hexahydrobenzaldehyde dimethyl acetal]-1-malonitrile and 1,1-dicyano-2,2-dimethyl-3,3-dimethoxy propane, respectively, were shown to be the only products when the malonitriles were treated with pyridine in methanol. On the action of acid, the Δ 2-pyrrolines aromatised to yield 1,2-dihydro-3H-pyrrolizineproducts. Structure det different reaction paths have been discussed.

A fluorophotometric method for the determination of amino acids by using pyridoxal and zinc(II) ion

A procedure for the determination of amino acids has been developed based on their interaction with pyridoxal and Zn 2+ ion in pyridine methanol to yield highly fluorescent chelates. This fluorescence procedure is 20–100 times more sensitive than the colorimetric procedure. N-Pyridoxylidene amino acid-Zn(II) chelate contains a 1:1 molar ratio of ligand to metal ion.

Separation and detection of water-soluble acid dyes on polyamide thin layers

A method is described in which twenty water-soluble acid dyes, isolated from food products by means of DEAE-Sephadex, were detected by thin-layer chromatography using polyamide plates.The isolation procedure involved shaking samples with the Sephadex and then eluting the dyes by column chromatography. In polyamide thin-layer chromatography, the solvent system suitable for the separation of the dyes was pyridine—methanol—28% aqueous ammonia—water (5:6:1:16).This is a simple and rapid method for the detection of acid dyes in cellulosic and proteinaceous samples, especially when the dyes are present in low concentrations.

Selective Hydrogenation of Methyl Oleate Ozonolysis Products by Palladium in Pyridine—Methanol Solvent1

Selective Hydrogenation of Methyl Oleate Ozonolysis Products by Palladium in Pyridine—Methanol Solvent¹