Synthesis of ortho- and meta-Re(I)-metallocarboranes in water

A series of metallocarboranes of the types rac-[M(CO)3(eta(5)-7-R-7,8-C2B9H11)]-, rac-[M(CO)3(eta(5)-7-R-8-R'-7,8-C2B9H11)]-, and rac-[M(CO)3(eta(5)-7-R-7,9-C2B9H11)]- (M=Re) were prepared by reacting [NEt4]2[Re(CO)3Br3] or [Re(CO)3(OH2)3]Br with the corresponding carboranes in the presence of aqueous solutions of either alkali metal or tetraalkylammonium fluoride salts. Carborane derivatives that were investigated included those containing pyridine, amino, carboxylic acid, carbohydrate, and aryl substituents. During the course of the research, it was discovered that Re metallocarboranes can be prepared directly from the respective closo-clusters under similar reaction conditions used with nido-carboranes. Reaction yields ranged from modest to excellent depending on the carborane isomer and the nature of the cage substituent(s). A crystal structure of an amine-substituted Re metallocarborane was obtained where the complex crystallized in the orthorhombic space group P2(1)2(1)2(1) with a=8.982(2) A, b=11.563(3) A, c=16.811(4) A, alpha=beta=gamma=90 degrees, V=1746.1(7) A3, Z=4, and R1=0.0684.     

Furo[3,2-e]pyrrolo[1,2-α][1,4]diazepine and derivatives

The 5,10-dihydro-4H-furo[3,2-e]pyrrolo[1,2-α][1,4]diazepin-5-one ( 7 ) and furo[3,2-e]pyrrolo[1,2-α][1,4]diaze-pine ( 10 ) are synthesized from suitable isocyanates 3a,b in acetic acid. The reactivity of 10 (C- and N-alkyla-tion) is investigated.     

Solute-solvent interactions in water-tert-butyl alcohol mixtures. III. ΔG θ, ΔH θ, and ΔS θ for dissociation of aliphatic carboxylic acids in water-rich media

Standard Gibbs free energies, enthalpies, and entropies for the dissociation of various aliphatic carboxylic acids are obtained through potnetiometric and calorimetric measurements in water-tert-butyl alcohol mixtures. Results are discussed in terms of solvent structural effects for the proton exchange reaction and in terms of the compensation law to explain enthalpic and entropic effects.Part I, ref 4; Part II,Thermochimica Acta 6, 283 (1973).     

Interactions solutès-solvants dans les mèlanges eau-alcool tert.-butylique: V. enthalpie de dissolution des chlorures de sodium,potassium, rubidium et cesium

By using a calorimetric method, solution enthalpies of sodium, potassium, rubidium and cesium chlorides in mixtures containing from 0 to 45% by weight of alcohol are obtained. Standard enthalpies and transfer enthalpies are estimated. From previous data concerning Gibbs energies of transfer from water to the same solvent mixtures, transfer entropies are calculated. Enthalpies and entropies exhibit a maximum for molar fractions of about 0.07 of organic solvent. Results are discussed in terms of enhancement of the structuration of the aqueous network.     

Investigation of redox properties of different PtSn/Al2O3 catalysts.

Alumina-supported Sn and PtSn particles are studied by 119Sn M?ssbauer spectroscopy after oxidation and reduction under various conditions. The observed species of Sn(IV), Sn(II) and Sn(0) are grouped in several categories, each being characterised by distinct structural properties. Tin phases in contact with the support or with platinum are identified. The results are used to establish a model describing the phase transformations occurring in PtSn particles under oxidising or reducing conditions. Particular attention is paid to the reduction/reoxidation mechanisms governing H2/O2 double titrations. An increased reactivity of tin towards oxygen, induced by the contact with platinum, is demonstrated. It is shown that tin contributes to the oxygen uptake VO1 of a first titration cycle by platinum-catalysed transformation of Sn(II) into an oxometallic phase Pt(x)Sn(O). The oxygen titre VO2 of a second cycle is due to O2 chemisorption on platinum only.     

Modelisation of the Association Mechanism of a Series of Huperzine Derivatives Used for Alzheimer Disease with Human Serum Albumin: Effect of the Magnesium Cation

The role of the Mg²⁺ cation on huperzine molecule binding (drugs used for Alzheimer disease) on human serum albumin (HSA) was studied by affinity chromatography. The thermodynamic data corresponding to this binding were determined for a wide range of Mg²⁺ concentrations (x). For each solute, the huperzine binding on HSA was divided into two Mg²⁺ concentration regions. For a low x value, below x_c (1.2 mM), the binding decrease with x. For x above x_c the hydrophobic effect and van der Waals interactions between the huperzine molecule and the HSA implied a decrease in its binding. These results showed that for patients with Alzheimer disease, an Mg²⁺ supplementation during treatment with these huperzine molecules can increase the active pharmacological molecule concentration.     

Ultraviolet absorption spectra of some alkylchloramines

The ultraviolet spectra of six alkylchloramines are determined between 220 and 320 nm. The wavelengths of maximum absorption are 244 nm (? = 458 l mol^?1 cm^?1) for monochloramine, 252 nm (? = 372 l mol^?1 cm^?1) for methylchloramine, 251 nm (? = 378 l mol^?1 cm^?1) for ethylchloramine, 250 nm (? = 368 l mol^?1 cm^?1) for isopropylchloramine, 264 nm (? = 354 l mol^?1 cm^?1) for dimethylchloramine and 262 nm (? = 315 l mol^?1 cm^?1) for diethylchloramine.     

Nitroxydes 94 : decomposition thermique d'un radical oxazolidine-oxyle.

Pyrolysis of spiro ((4-t-butyl cyclohexane)-1,2′-(4′,4′-dimethyl oxazolidine-3′ oxyl)) $\text{1}$ leads to spiro ((4-t-butyl cyclohexane)-1,2′-(4′,4′ oxazolidine 3′-hydroxy)) $\text{2}$, 4-t-butyl cyclohexanone and 4-t-butyl cyclohexanoxime. Kinetic studies show that the reaction proceeds through an autocatalytic process.