Studies on the Diels-Alder reaction of maleic anhydride and β-trans-ocimene

The structure of the by-product, obtained in the Diels-Alder condensation of maleic anhydride with β-trans-ocimene followed by distillation of the adduct formed, has been established as 2-isopropylidene-4-methyl-7-carboxy- ,3,3a,6,7,7a-hexahydroindanone (IVa) and the mechanism of its formation from the adduct (II) discussed. Some hitherto unreported reactions of the maleic anhydride adduct (II) and its derivatives are described. These throw light on the stereochemistry of the adduct and derived products.

The specificity of the colour reaction between ammonia and 3-phenyl-2-thiohydantoin

The colour reaction between 3-phenyl-2-thiohydantoin and ammonia is studied quantitatively. Determinations of 0.1–0.6 μmoles of 3-phenyl-2-thiohydantoin are possible with a precision close to 2%. In analyses of amino acid mixtures for glycine after conversion to 3-phenyl-2-thiohydantoin, only derivatives of serine and threonine interfere to a slight extent. The specificity of the primary colour reaction with ammonia, and the structural requirements for it are discussed; a structure for the pigment species is proposed.

Quinone studies—Istar, open: Evidence for a new type of substitution reaction of phenanthrene-9,10-quinone derivatives

The para orientation by the carbonyl groups in the bromination of phenanthrenequinone derivatives has been explained on the basis of an excited state resulting from thermal excitation of the quinone and/or from a n→π* transition of the nonbonding electrons of the oxygen atoms. A general preparative method for the syntheses of 3-bromophenanthrenequinone derivatives has been developed. The structure of 2-nitro-6-bromophenanthrenequinone has been established by degradation. Synthesis of 2-nitro-6-bromofluorenone is described. Direct bromination of phenanthrenequinone to 2-bromo and 2,7-dibromo derivatives has also been described.

Reactions of tetrahalogeno-1,2-benzoquinones. Part III. Reaction of tetrachloro-1,2-benzoquinone with tetralones and naphthols: Pathway to the condensates

With a view to understanding the mechanism of the formation of 6-methoxy-2,2-(tetrachloro--phenylenedioxy)-naphthalen-1 (2H)-one (IIIa) in the reaction of 6-methoxy-1-tetralone (Ia) with tetrachloro-1,2-benzoquinone (II), the reaction of (II) with various tetralones and naphthols has been studied. Reaction with either α-tetralone or α-naphthol gives 2,2-(tetrachloro-o-phenylenedioxy)naphthalen-1 (2H)-one (IIIb), whereas reaction with either β-tetralone or β-naphthol gives a mixture of (IIIb) and ,1-(tetrachloro-o-phenylenedioxy)-naphthalen-2 (1H)-one (IX), with the former predominating. Further, reactions of (II) with 7-methoxy-3,4-dihydrophenanthren- 1 (2H)-one and m-methoxyphenol gave respectively 7-methoxy- ,2-(tetrachloro-o- phenylenedioxy)phenanthren-1 (2H)-one (VII) and 3-methoxy-6,6-(tetrachloro-o- phenylenedioxy)cyclohexa-2,4-dien-1-one (VIII). Structures of all these compounds have been proved on the basis of i.r. and n.m.r. data. The pathway to the formation of the condensates (III) is discussed.

Reaction of carbon disulfide with azide ion

Carbon disulfide reacts with azide ion to form the 1,2,3,4-thiatriazolinethionate ion and not the acyclic azido dithiocarbonate ion as previously reported. A series of salts of thiatriazoline have been prepared and none shows evidence for the presence of the azido group. Esters of thiatriazolinethione prepared by the reaction of the sodium salt with alkyl or acyl halides have been found to be either 5-(substituted) mercapto-1,2,3,4-thiatriazoles or 4-substituted 1,2,3,4-thiatriazoline-5-thiones. These structures have been assigned on the basis of degradative and spectroscopic evidence. The chemistry of the so-called azidodithiocarbonates has been reinterpreted in terms of the thiatriazole structure.

Pd and Pt ions as highly active sites for the water-gas shift reaction over combustion synthesized zirconia and zirconia-modified ceria

Noble metal substituted ionic catalysts were synthesized by solution combustion technique. The compounds were characterized by X-ray diffraction, FT-Raman spectroscopy, and X-ray photoelectron spectroscopy. Zirconia supported compounds crystallized in tetragonal phase. The solid solutions of ceria with zirconia crystallized in fluorite structure. The noble metals were substituted in ionic form.The water-gas shift reaction was carried out over the catalysts.Negligible conversions were observed with unsubstituted compounds. The substitution of a noble metal ion was found to enhance the reaction rate. Equilibrium conversion was obtained below 250 degrees C in the presence of Pt ion substituted compounds. The formation of Bronsted acid-Bronsted base pairs was proposed to explain the activity of zirconia catalysts. The effect of oxide ion vacancies on the reactions over substituted ceria-zirconia solid solutions was established. (c)2010 Elsevier B.V. All rights reserved.

Mechanism of the addition of alcohols to substituted phenylisothiocyanates : Electrical effects of the substituents on the reaction

The addition reaction of alcohols to substituted phenylisothiocyanates is found to be a second-order reaction. The reaction is catalysed by triethylamine. First-order rate constants of the addition reaction have been determined in excess of ethanol, for a number of substituted phenylisothiocyanates and the rate data give a satisfactory linear correlation with Hammett σ constants of groups. While the energies of activation vary randomly with substitution, the entropies of activation bear a linear relationship to the energies of activation. Infra-red spectra indicate that the thiourethanes which are the products of the addition reaction exist in the thioamide form. The most prominent resonance form which can satisfactorily explain both the kinetic and infrared data, has been suggested.

Reaction of benzisoxazolium cations with cyclic β-diketones

Reaction of 2-ethylbenzisoxazolium fluoborate (III) with dimedone, dihydroresorcinol, 2-methyldihydroresorcinol and 2-methylcyclopentane-1,3-dione in the presence of base leads to the formation of amides VIII, XI, X and XIII respectively, via the benzoketoketenimine intermediate (IX) and an intramolecular migration. The 7-hydroxy-2-ethylbenzisoxazolium salt (IV) gives the amide (XIV) by double migration. Amides VIII, XI, X and XIII undergo intramolecular Michael reaction to furnish the benzoxazinones (XVI, XVIII, XVII and XXVI). Stereochemistry of this addition is discussed and the conformation in which the CN bond at C-1′ is attached equatorially to the cyclohexanone ring is assigned to the Spirans (XX, XXX and XXVIII). Effect of acids and bases on the amide (VIII) and the spiran (XVI) is described.

Aspects of tautomerism. Part III. A new dimerisation reaction of pseudo-acid chlorides

Pseudo-acid chlorides of five 4′-substituted o-benzoylbenzoic acids are converted into a mixture of dilactones with sodium iodide in acetone. The meso-isomer is always formed to a larger extent than the (±)-mixture. These results imply that the radicals involved are not planar.

The reaction of the nuclei of the vegetative cells and zygotes of Saccharomyces carlsbergensis to some staining techniques

Vegetative cells and zygotes of Saccharomyces carlsbergensis fixed in iodine formaldehyde acetic acid solution and stained after acid hydrolysis in hæmatoxylin, Feulgen and Giemsa show a remarkable similarity in the size and orientation of the structures in the nuclear matrix with reference to the nuclear membrane. The nucleolus described by Guilliermond may either be the chromocenter or the nucleolar equivalent.

Reaction of dialkyl 2-butynoate with aniline and formaldehyde: revision of the structure of the product

Dimethyl 3-(aryl)-3,6-dihydro-2H-1,3-oxazine4,5-dicarboxylate structure assigned for the products obtained in the Bronsted acid catalyzed reaction of dimethyl but-2-ynoates with anilines and an excess of formaldehyde in methanol has been revised to methyl 1-(aryl)-3-(methoxymethyl)-4,5-dioxopyrrolidine-3-carboxylate. (C) 2010 Elsevier Ltd. All rights reserved.

A study of the slow reaction in Al-5 wt.% Ag alloy by resistivity measurements

The slow reaction in an Al-5 wt.% Ag alloy has been investigated by resistivity measurements. The "slope change" method gave an activation energy of 1.25 eV for silver diffusion during the slow reaction. The existence of an excess concentration of vacancies in equilibrium with the dislocation loops seems to be responsible for the slow reaction. The presence of silver inhibits the nucleation of dislocation loops by holding up the quenched-in vacancies in solution. There is no indication of the presence of a third stage in the low-temperature ageing process of this alloy.