Homolytic dissociation of the carbon-element σ bonds by Grignard reagents

The reaction of 2-ethyl-3-tetrahydrofuryl thiocyanate (I) and triphenylacetonitrile (VIII) with methylmagnesium iodide in ether was studied using GC/MS, PMR and¹³C NMR spectroscopy. The reaction of (I) with CH₃MgI gives the product of the homolysis of the C-S bond, namely, bis(2-ethyl-3-tetrahydrofuryl) disulfide (II), in 81% yield. This reaction is assumed to be general in nature since triphenylacetonitrile (VIII) is also homolytically cleaved by the action of CH₃MgI to give triphenylmethane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2886–2888, December, 1991.     

Structure of phenolic stabilizers for polymers VIII. Crystal structure of 2,2′-methylenebis(4-methyl-6-ter-butylphenol) monoacrylate

L. Ya. Karpov Scientific-Research Physicochemical Institute. Scientific-Research Institute of Rubber and Latex Goods. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 5, pp. 162–164, September–October, 1991.     

Effects of stereoisomerism in the mass spectra of 2,4-disubstituted thiacyclohexanes

The mass spectra of cis- (Ia-c) and trans-2-methyl-4-R-thiacyclohexanes (IIa-c; a R = n-C₄H₉, b R = n-C₅H₁₁, c R = Ph) were studied. It was established that [M-CH₃]⁺ ions, which correspond to the loss of a methyl group from the 2 position, are formed more readily in the case of the less stable trans isomers IIa-c than in the case of cis isomers Ia-c. The three-dimensional structures of the substances have no effect on the degree of elimination of the R substituent. The relative ionization energies (RIE) for Ia,b and IIa,b and the relative appearance energies (RAE) of the [M-CH₃]⁺ ions were measured by the electron impact method. It was found that the RIE are almost 0.05 eV lower and that the RAE of the [M-CH₃]⁺ ions are 0.1 eV lower for trans isomers IIa,b than for cis isomers Ia,b.Communication 4 from the series Ionization and appearance energies in organic chemistry, See [1] for Communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 333–338, March, 1981.     

Configurational inversion and hexachloroethane chlorination of α-sulfonylcarbanions

The cis fused bicyclic sulfones 1a, 1c and 3a are lithiated in benzene with n-butyllithium under concomitant cis/trans isomerization of the ring fusion, involving intramolecular proton transfer. H/D exchange of the three α-hydrogens in protic solvents proceeds with retention of configuration. The lithiated sulfones are chlorinated with hexachloroethane (HCE) and show a strong preference for introduction of halogen at an equatorial α-position.     

The influence of solute-solvent interactions on the kinetics and stereospecificity of polymerization-the relevance of aromatic solvent shifts observed on the nmr spectrum of methyl methacrylate

The effect of certain aromatic compounds on the PMR spectrum of methyl methacrylate (MMA) was investigated. The magnitude of observed aromatic-induced shifts decreased in the order benzene ? styrene > chlorobenzene ≈ bromobenzene.Assuming that the interaction arises from a stoichiometric 1:1 complex, equilibrium parameters for the MMA-benzene interaction have been estimated. ΔH ± S.E. (ΔH) = ?(8 ± 4) kJ mol^?1. These effects are likely to have a small influence on the kinetics of copolymerization with aromatic monomers and polymerization in aromatic solvent. The stereochemistry of the solute-solvent interactions suggests that MMA takes a cis-conformation in solution, which is relevant to the mechanism of stereoregular polymerizations of this monomer.     

Amide-water interactions in cosolvent systems. I. Solubilities and apparent molar volumes of methyl paraben

Solubility and apparent molar volume data are used to demonstrate effects of amide alkylation on amide-water interactions at 25° C. Precise measurements were made of the apparent molar volumes of the amides in binary amide-water mixtures using a dilatometric technique. The results show that the apparent molar volumes of alkyl-substituted amides in water pass through a minimum at an amide concentration which varies inversely with the degree of alkylation. Further studies showed that the solubilities of methyl paraben (methyl-p-hydroxybenzoate) and naphthalene in various amide-water solvent systems increased in characteristic fashion with amide alkylation.     

Photoreactions of aromatic compounds—XXXV: Nucleophilic photosubstitution of methoxy substituted aromatic compounds. Monophotonic ionization of the triplet

Methoxy groups exert an activating and ortho/para directing influence in light induced nucleophilic substitution reactions (cyanation, hydroxylation, etc) of aromatic compounds in aqueous media. The first chemical step in these processes is monophotonic ionization of the aromatic compound in its lowest triplet state, followed by reaction of the radical cation with the nucleophile Quantum yields of photocyanation of 4-fluoro- and 4-chloroanisole indicate that in 99% (mole fraction) water virtually all triplets formed undergo electron ejection.This hypothesis is in agreement with the results of charge density calculations for the radical cations. It is directly supported by the similarity of the product composition of these photochemical substitutions with that of anodic substitutions, where the intermediacy of an aromatic cation is generally accepted. The presence of an oxidizing agent (oxygen, or persulphate) is required only when a hydrogen is replaced. The nucleophilic photosubstitution at electron rich aromatic systems in solvents as water can therefore be classified as an S_r⁺n¹(³Ar^*) process.     

Photometrische Bestimmung von Titan in molybd?nhaltigen St?hlen mit Tetrahydroxyphenazin

Zusammenfassung Tetrahydroxyphenazin (THP) bildet mit Titan im sauren Medium Komplexe mit sehr hohen Werten des Extinktionskoeffizienten. Es wird ein Bestimmungsverfahren für Titan in molybdänhaltigen Stählen beschrieben, bei dem die störenden Elemente mit einem Gemisch aus Tri-n-butylphosphat und Chloroform extrahiert werden. Das in der wäßrigen Phase verbleibende Titan wird mit THP photometrisch bestimmt. Die hochempfindliche Methode erlaubt Titanbestimmungen im Nanomol-Bereich. Bei Stahlproben mit 0,2–0,7% Ti (in Gegenwart von 0–2% Mo) ergab sich ein Variationskoeffizient von 0,4 bis 2,4%.

---

Photometric determination of titanium in molybdenum steels with tetrahydroxyphenazine

Complexes with very high molar extinction coefficients are produced in the reaction of tetrahydroxyphenazine (THP) with titanium in acid solution. In the method described titanium is determined photometrically by complexing with THP in the aqueous phase after extracting the interfering elements with a mixture of tri-n-butyl-phosphate and chloroform. This highly sensitive method is applicable for determination of titanium in the nanomolar region. With steel samples containing 0.2–0.7% of Ti (in presence of 0–2% of Mo) variation coefficients of 0.4 to 2.4% have been obtained.

---

---

Für die Durchführung dieser Arbeit wurden dankenswerterweise Forschungsmittel aus dem ERP-Sondervermögen bereitgestellt.Dem Verbande der Chemischen Industrie und der Deutschen Forschungsgemeinschaft, die diese Arbeit unterstützt haben, danken wir bestens.     

Hemmung der aktiven Bromidaufnahme durch Pflanzenzellen durch Glucose

Zusammenfassung Die Aufnahme von Bromid-Ion durch Chlorella pyrenoidosa, die durch aktiven Transport erfolgt, wird durch Glucose gehemmt, obwohl die Atmung stimuliert wird. Die Hemmung tritt bei Energielieferung durch Belüftung oder Belichtung ein. Galactose und Mannit wirken nicht wie Glucose. Offenbar hemmt die Glucose die Nutzbarmachung des Elektronenflusses bei dem System der Atmung oder Photophosphorylierung für die Bromid-Aufnahme.

---

The absorption of bromide ion by chlorella pyrenoidosa, which is due to active transport, is inhibited by glucose though respiration is stimulated. Inhibition is observed when energy is supplied either by aeration or by illumination. Galactose or mannitol do not act like glucose. Apparently glucose interferes with the utilization of electron flow in the respiration or photophosphorylation systems for the absorption of bromide.

---

---

Mit 3 Abbildungen.

---

Herrn Prof. Dr.F. Wessely zum 70. Geburtstag in Verehrung gewidmet.