Sur diverses possibilités de formation de pyrimidines à partir de formyl-3 chromone

Guanidine transforms the following: (a) 3-formylchromone into a mixture of 2-amino-5-(2-hydroxybenzoyl)pyrimidine and 2-amino-5H-[1]-benzopyrano[4,3-d]pyrimidine; (b) the diacetate of 3-methylidyne-chromone into 2-amino-5-hydroxy-5H-[1]benzopyrano[4,3-d]pyrimidine; and (c) the oxime of 3-formylchromone into 2-amino-5H-[1]benzopyrano-[4,3-d]pyrimidin-5-one. Thiourea, acetamidine and nitroguanidine can also generate pyrimidines of the same type with 3-formylchromone, the diacetate of 3-methylidynechromone or 3-(1,3-dioxolan)chromone.     

La solution solide Cr1−xIrxO2

A new solid solution Cr_1?xIr_xO₂ (0 ≤ x ≤ 1) has been prepared using oxidizing agents under pressure. The magnetic study shows the importance of the spin-orbit coupling and the weakening of the ferromagnetic interactions with increasing iridium content.     

Two unexpected effects concerning perturbations of the B3Π0u+ state of molecular iodine

We present in this paper two new effects observed in the state of molecular iodine: a very high diamagnetic correction in the vibrational level υ′ = 62 and an important orientation of the optically excited molecules due to predissociation. Both effects can be interpreted by taking into consideration the perturbation of the B state by other electronic states.     

Structure cristalline de SmZrF7. Relations structurales avec le type ReO3

The crystal structure of the fluorozirconate SmZrF₇ has been determined from single crystal X-ray data; the final R value is 0.028. In this compound, isotypic with all the fluorozirconates LnZrF₇ (Ln = rare earth), the symmetry of the cell is monoclinic (space group: P₂₁). The Zr atoms are surrounded by six fluorine atoms forming an almost perfect octahedron: the average distance ZrF is 2.006 Å. The Sm atoms are surrounded by a 8 fluorine atoms polyhedron, the distances SmF lie from 2.221 to 2.411 Å. The association of these two polyhedra by sharing corner forms slabs with an approximately ReO₃ type arrangement: the thickness of the slabs is two octahedra.These slabs with the composition M₂X₇ are held together so that the top fluorine atoms at the surface of a slab increase the coordination of the Sm atom of an adjacent slab. This MX_3.5 phase corresponds to a new structural type between MX₃ (ReO₃ type) and MX₄ (SnF₄ type).     

On the Correlation between Ionization Potentials and Excitation Energies,part III: Pyrazine

A recently suggested scheme for relating ionisation potentials (IP) to excitation energies (E) has been applied to pyrazine and 2,6-dimethylpyrazine. The results indicate that in these systems the energy gap (ΔE) between the two lowest lying ¹n,π*-states is significantly smaller than that (ΔIP) between the corresponding ²n-states of the parent radical cations. The values estimated for ΔE on the basis of ΔIP, measurable by photoelectron spectroscopy, disagree with those calculated theoretically but seem to be supported by the experimental evidence available. Since ΔE = ΔIP would normally be expected, the relationship ΔE < ΔIP actually present in these systems is discussed and related to the different shape of the n-MO's involved in the ionization and excitation processes.     

Microtitration of weak organic acids in nonaqueous solvents

Summary The applicability of nonaqueous titrimetry to the microdetermination of weak organic acids has been established.Phenols have been found to be titrable in dimethylformamide. Those containing one or more chlorine, hydroxyl, or carbonyl groups can be titrated to a thymol blue endpoint and those containing amino or alkyl groups to an azo-violet endpoint.Sulfonamides, barbiturates, enols, imides, and some hydrazides have also been titrated in dimethylformamide. The scope extends to compounds with a pK_a of about 9 for visual titrations and 10.5 for potentiometric titrations in dimethylformamide.Pyridine may be used as a solvent for the visual titration of weak acids with pK_a of up to about 10.5. Methyl-isobutanone may be used for the visual titration of acidic compounds with a pK_a of about 9 and lower by using thymol blue as the indicator.The hydrazides give better results in potentiometric titrations; the visual endpoints are poorly defined for practical purposes.

---

Zusammenfassung Die Maßanalyse in nichtwäßrigem Milieu wurde für die Mikrobestimmung schwacher organischer Säuren herangezogen.Phenole lassen sich in Dimethylformamid titrieren. Enthalten sie ein oder mehr Chloratome bzw. Hydroxyl- oder Carbonylgruppen, so können sie gegen Thymolblau als Indikator titriert werden; Amino- oder Alkylgruppen tragende Phenole werden gegen Azoviolett titriert.Sulfonamide, Barbiturate, Enole, Imide und einige Hydrazide werden gleichfalls in Dimethylformamid titriert: Verbindungen mit einem pK_s bis etwa 9 durch visuelle Endpunktbestimmung, bis 10,5 auf potentiometrischem Weg.Pyridin eignet sich als Lösungsmittel für die visuelle Titration schwacher Säuren mit einem pK_s bis etwa 10,5, Methylisobutanon hingegen für saure Verbindungen mit einem pK_s von etwa 9 und weniger, wobei Thymolblau als Indikator dient.Hydrazide werden besser potentiometrisch titriert; die visuelle Endpunktbestimmung eignet sich für praktische Zwecke nur wenig.

---

Rèsumè La possibilité d'application de la titrimétrie non aqueuse au microdosage des acides organiques faibles a été établie par les auteurs. Ils ont trouvé que les phénols étaient susceptibles d'être titrés dans la diméthylformamide. Ceux qui contiennent un ou plus d'un groupement chlore, hydroxyle ou carbonyle peuvent être titrés en présence de bleu de thymol comme indicateur de point final, et ceux qui contiennent des groupements amines ou des groupements alcoyles à l'aide de l'indicateur violet azoïque. Les sulfamides, les barbiturates, les énols, les imides et quelques hydrazides ont été également titrés dans la diméthylformamide. Le domaine de dosage s'étend à des composés dont le pK_a est voisin de 9 pour les titrages visuels et de 10,5 pour les titrages potentiométriques dans la diméthylformamide. Il est également possible d'utiliser la pyridine pour les titrages visuels d'acides faibles dont le pK_a est voisin de 10,5. On peut employer la méthylisobutanone pour des titrages visuels de composés acides dont le pK_a est inférieur à 9 ou voisin de cette valeur; on utilise alors le bleu de thymol comme indicateur.Il est préférable d'utiliser les titrages potentiométriques dans le cas des hydrazides car les points finaux de titrages sont mal définis dans la pratique courante lorsqu'on les détermine visuellement.

     

Chemical ionization desorption mass spectrometry of some quaternary ammonium salts

The ammonia chemical ionization desorption spectra of N,N-dimethyl quaternary ammonium iodides in addition to high protonated molecular ion [M + H]⁺ intensity, show signals for an ion radical composed of N-methyl abstracted salt cation and ammonia [C + NH₃? CH₃]^+˙. These ions corresponding to the cation +2 show increased importance in the chemical ionization mode, using the same reagent gas. The technique of chemical ionization desorption appears suitable for the analysis of salts, and thus for the determination of the molecular weight of both anion and cation.     

Synthesis of some isomeric 4,11-dihydro-5H-[1]benzoxocino[4,3-d] or [3,4-c]isoxazol-5-ones and isomeric 4,5,10,11-tetrahydrobenzo[5,6]-cycloocta[2,1-d] or [1,2-c]isoxazol-5-ones

The title compounds were prepared by acid-catalyzed cyclization of aryloxymethyl- or (2-arylethyl)-4-carboxymethylisoxazoles which in turn were synthesized from aryloxymethyl- or (2-arylethyl)isoxazole-4-carboxylic acids by Arndt-Eistert homologation.     

Electroorganic synthesis. Reductive alkylation of functionalized 1,2-dithiole-3-thiones

Two-electron reduction of some substituted 1,2-dithiole-3-thiones 1 followed by alkylation of the dianionic intermediates leads through electrosynthesis to mixture of Z and E isomers of the corresponding substituted alkyl-(3-thioalkyl)-2-propenedithioates 2, 3 in satisfactory yield. The structure of those products was established by ¹³C and ¹H nmr and mass spectroscopy. The isomers ratios were determined by nmr spectroscopy.