Selective reduction of the N-O bond in n-oxides and in nitrones by sodium hydrogen telluride

Sodium hydrogen telluride reduces $\text{tert}$.-amine $\text{N}$-oxides to the corresponding amines in very high yield, but does not reduce sulphoxides. This reagent also reduces nitrones to $\text{sec}$.-amines at pH6 and to imines at alkaline pH (10–11).     

Reactions of triphenylarsine oxide with aqueous hydrogen fluoride: Crystal structure of bis(triphenylarsine oxide)hydrogen(I) tetrafluoroborate

Fluorination of triphenylarsine oxide by aqueous hydrogen fluoride (1–40%) in the absence of glass readily gives triphenylarsine difluoride. When the reaction with dilute (1%) aqueous hydrogen fluoride is carried out in borosilicate glass apparatus, the glass participates in the reaction resulting in the formation of the crystalline 2:1 adduct 2Ph₃AsO·HBF₄. Crystals of this compound are monoclinic, $\text{P}$2₁/$\text{c}$, $\text{a}$ = 12.926(4), $\text{b}$ = 17.819(6), $\text{c}$ = 14.994(4) Å, β = 98.97(3)°, Z = 4. The structure contains cations [(Ph₃AsO)₂H]⁺ in which $\text{O}\text{?}$O is 2.44(2)Å, and anions BF₄^?.     

Polar radicals XVIII. On the mechanism of chlorination by N-Chloroamines: Intermolecular and intramolecular abstraction

The photochlorinations of the $\text{n}$-butyl, $\text{n}$-pentyl, and $\text{n}$-hexyltrimethyl-ammonium chlorides, using molecular chlorine in hexachloroacetone or 15% CD₃CO₂D/85% H₂SO₄, or using N-chlorodimethylamine in the acid solvent are described. The ammonium group exerted a strong polar directing effect upon the site of substitution. This effect was found to be more pronounced in the more polar protic solvent. The reagent, N-chlorodimethylamine, generated the dimethylamminium radical, whose reaction showed a polar sensitivity toward hydrogen abstraction similar to that of the chlorine atom, but exhibiting a much greater secondary/primary selectivity. Comparison of the isomer distributions obtained from the self photochlorination reactions of N-chloro-$\text{n}$-hexylmethylamine and N-chloro-$\text{n}$-pentylmethylamine in the acid solvent, with the distribution pattern obtained for the chlorinations of the ammonium salts with N-chlorodimethylamine, suggested that the self chlorinations of the N-chloroamines proceed by the intramolecular hydrogen abstraction mechanism suggested previously.     

Solution of hydrogen in palladium/copper alloys

The solution of hydrogen in $\text{Pd}\text{Cu}$ fcc substitutional alloys has been examined in the region of low hydrogen contents. Relative partial molar enthalpies of absorption at infinite dilution are found to be somewhat less exothermic for the alloys than for palladium but the change with X_Cu is small. Partial excess entropies of absorption decrease with X_Cu but not as markedly as for the other Pd/group IB alloys. Relative electrical resistance relationships for $\text{Pd}\text{Cu}$ alloys have been determined as a function of their hydrogen contents. Interstitial hydrogen increases the relative electrical resistance to a lesser extent with increase of X_Cu, but the absolute increase of resistance is nearly invariant with X_Cu.     

The replacement of vinylic hydrogen by fluorine

In 3$\text{H}$, 4$\text{H}$-tetrafluoro-3-thiolen and 1$\text{H}$,2$\text{H}$-octafluorocyclohexene, the conversion of -CHCH- into -CHCF- by fluorination over KCoF₄ takes place by saturation to -CHFCHF- followed by dehydrofluorination, and not by direct replacement of a vinylic hydrogen.     

The invention of new radical chain reactions. part X: High yield radical addition reactions of αβ-unsaturated nitroolefins. An expedient construction of the 25-hydroxy-vitamin D3 side chain from bi

Radicals derived from thiohydroxamic esters $\text{3}$ readily add to nitroolefins $\text{5}$ (Z = NO₂) to give good yields of α-nitrosulphides. These adducts, where the structure permits, are easily oxidised to carboxylic acids $\text{8}$ by treatment with alkaline hydrogen peroxide. Reductive cleavage to the corresponding aldehydes or ketones $\text{9}$ is efficiently carried out by the action of TiCl₃. Addition of methyl magnesium iodide to the methyl ketone derived from 3α-acetoxy 11-oxo cholanic acid gives steroid $\text{10}$ possessing the 25-hydroxycholesterol side chain of the vitamin D₃ metabotites. Radical additions to 1-phenylthio-2-nitropropene $\text{11}$ have been briefly studied.     

Synthesis,Reactions and Catalytic Activities of a Cationic Acrylonitrile-Rhodium(I) Complex

Reaction of RhCl (CO)(Ph₃P)₂(Ph₃P = triphenylphosphine) with AgClO₄ in acrylonitrile at 30°C produces a new cationic rhodium(I) complex, [Rh(CH₂CHCN)(CO) (Ph₃P)₂]ClO₄ ($\text{1}$) and AgCl. The ¹H-NMR and IR spectra of $\text{1}$ suggest that acrylonitrile is coordinated to rhodium through the π-system of the vinyl group. The complex $\text{1}$ reacts with molecular hydrogen to give a propionitrile-rhodium(I) complex, [Rh(CH₃ CH₂CN) (CO)(Ph₃P)₂ClO₄($\text{2}$) where the coordination of propionitrile through nitrogen is suggested by the ¹H-NMR and IR spectral data. The coordinated acrylonitrile in $\text{1}$ is readily replaced with triphenylphosphine and propionitrile to give [Rh(CO)(Ph₃P)₃] ClO₄ and $\text{2}$, respectively. The complex $\text{1}$ is catalytically active for the hydrogenation and polymerization of acrylonitrile at 25°C under the atmospheric pressure of hydrogen.     

Chemistry in hydrogen fluoride V. Catalysts for reaction of HF with halogenated olefins

Tantalum pentafluoride, niobium pentafluoride, titanium tetrachloride, and molybdenum pentachloride catalyze the addition of hydrogen fluoride to $\text{tetra}$- and $\text{tri}$chloroethene and related compounds. Hydrogenation of tetrachloroethene to 1,1,2,2-tetrachloroethane was observed using hydrogen, methylcyclopentane, and TaF₅ in HF.     

Selective formation of peroxy-p-quinolato Co(III) complexes in the oxygenation of 4-alkyl-2,6-di-t-butylphenols with Co(II)-Schiff's base complexes

The oxygenation of 4-alkyl-2,6-di-$\text{t}$-butylphenols ($\text{2}$) with Co(II)-Schiff's base complexes in aprotic solvents such as CH₂Cl₂, THF, Py, and DMF leads to highly selective formation of the corresponding peroxy-$\text{p}$-quinolato Co(III) complexes. The reaction proceeds by mechanism involving a rate determining hydrogen abstraction by superoxo Co(III) species from $\text{2}$ giving phenoxy radical, rapid step of electron transfer from Co(II) complex to the phenoxy radical, and dioxygen incorporation into phenolato Co(III) complex thus formed.     

The reactions of trifluoromethyl and trichloromethyl radicals with conjugated and methylene-interrupted dienes and enynes

The photochemical addition of CF₃I to buta-1,3-diene and vinylacetylene in the gas phase gave 1,4-adducts as the main products. In gas phase reactions only products derived from hydrogen abstraction were detected in the CF₃I/penta-1,3-diene system, but the 1,4-adducts again predominated in the liquid phase. CCl₃Br similarly gave a mixture of 1,2- and 1,4-adducts, the latter predominating, on photochemical reaction with penta-1,3-diene. The 1,2-adduct was the main product from the CCl₃Br/pent-1-en-4-yn reaction, but some hydrogen abstraction was observed. The preference shown by conjugated dienes to give 1,4-adducts in the $\text{trans}$- configuration is interpreted in terms of steric factors and the propensity of dienes to adopt the $\text{s}$-$\text{trans}$ conformation.     

The X-ray crystal structure of a 1:1 complex between 1,3:1′, 3′:4,6:4′,6′-tetra-O-methylene-2,2′:5,5′-bis-O- oxidiethylenedi-D-mannitol and water

In the crystalline complex referred to in the title, the host molecule $\text{DD}$-$\text{1}$ has crystallographic C₂ symmetry with the hydrogen bonded guest water molecule straddling the two-fold axis.     

Thermodynamics of solid solution of hydrogen in M2C type carbides of vanadium and niobium

Equilibrium hydrogen pressures in the systems V₂CH₂ and Nb₂CH₂ have been determined at several temperatures in the range 400–650°C. Hydrogen pressure data were treated to obtain various thermodynamic quantities for the solutions of hydrogen in V₂C and Nb₂C. It has been found that the enthalpies of the reaction $\text{H(S.S.)}\text{=}\text{1}\text{2}\text{H}{}_2\text{(}\text{g}\text{)}$ are similar but slightly less endothermic compared to the respective metal hydrogen solid solutions. Entropies of dissolved hydrogen in V₂C and Nb₂C are also found to be similar to those of hydrogen in the respective metals.     

Amino acid derivatives that stabilize secondary structures of polypeptides : II. The most stable conformation of peptides containing 3-amino-2-piperidone-6-carboxylic acid (Acp)

From ¹H NMR evidence, the conformation of the piperidone ring of 3-amino-6-carboxyl-2-piperidone (ACP) in the derivatives Ac-Acp-NHET. Cbz-Gly-Acp-OEt, Cbz-Gly-Acp-Gly-OEt, Boc-$\text{L}$-Phe-$\text{LL}$-Acp-$\text{L}$-Ala-OCH₃, and Boc-$\text{L}$-Phe-$\text{DD}$-Acp-$\text{L}$-Ala-OCH₃ is shown to be a chair with the RCONH function equatorially and the CONHR′ function axially disposed. An internal hydrogen bond of the β-turn type is proposed for these amide derivatives.     

The 18-electron electrocyclisation of vinylogous fidecene. an unusual sequence of pericyclic processes

Upon thermal activation the vinylogous fidecene $\text{1}$ is isomerised into the pentacyclic indenoid hydrocarbon $\text{13}$ (benzene, t_{$\text{1}\text{2}$} (150°C) ca. 5 min), the formation of which is explained by an initial conrotatory (“symmetry-forbidden”) 18-electron electrocyclisation followed by two fast hydrogen migrations ([1.9], [1.5]) and 14π-electrocyclisation.     

Reversible nethide shifts in the 2-tert-butyl-2-adamantyl cation

Treatment of either 3-$\text{tert}$-butyl-2-adamantanol or 2-isopropenyl-2-methyladamantane with acid in the presence of a reducing agent (hydrogen iodide or tri-$\text{2}$-hexylsilane) yielded 2-$\text{tert}$-butyladamantane as the major or exclusive product. Both precursors gave the 2-$\text{tert}$- butyl-2-adamantyl cation at ?78°C in FSO₃H-SbF₅-SO₂ClF.     

Electron transfer reactions between pentafluorobenzoyl peroxide and dimethoxybenzenes

Pentafluorobenzoyl peroxide (FBP) reacted rapidly with dimethoxybenzenes in F₁₁₃ (CCl₂FCClF₂) with kinetics of first order in each component. High yields of ring-substituted esters of $\text{m}$-dimethoxybenzene ($\text{m}$-DMB) and $\text{p}$-dimethoxybenzene ($\text{p}$-DMB) were obtained, whereas for 2,5-di-$\text{t}$-butyl-1,4-dimethoxybenzene (DBDMB), the $\text{t}$-Bu group was simultaneously eliminated. For 2,5-dimethyl-1,4-dimethoxybenzene (DMDMB), the benzylic hydrogen was substituted. Rate and product studies both indicate a rate-determining electron transfer step leading to radical ion pairs which collapse to products.     

Photoreduction de benzophenones par les lactames etudiee par p.a.n.i.c.

CIDNP signais are observed during the photoreaction of p,p$\text{-}\text{?}$dichlorobenzophenone with lactams and amides in C₆D₆. The reaction intermediates are the radical pairs resulting from hydrogen abstraction α to nitrogen by the triplet p,p$\text{-}\text{?}$dichlorobenzophenone. They lead to the adducts between lactam and ketone. Attempts to trap radicals by CCl₄ prove that a part of the recombination proceeds in the solvant cage. Polarization of the ketone can only be explained by considering this product as an escape product.     

A Raman spectral analysis of the ammonium iodide—dioxane complex

The solid state complex between ammonium iodide and 1,4-dioxane has been found by TGA studies to be a ($\text{1}\text{1}$) adduct rather than a ($\text{1}\text{2}$) adduct as previously formulated. The laser Raman spectra of NH₄I· dioxane and ND₄I· dioxane in the N-H and N-D stretching regions show decreases in frequency compared to NH₄I and ND₄I which are consistent with hydrogen bonding of the N-H · O variety as a means of incorporation of the dioxane into the salt crystal lattice.     

Note on a theoretical interpretation of the isotopic ratio vOH/vOD versus vOH in isotopically diluted HDO molecules in solid hydrates

A simple intra- and inter-molecular potential for water molecules engaged in hydrogen bonding has been used in a one-dimensional approximation for a theoretical interpretation of the experimental correlation $\text{v}$_OH/$\text{v}$_OD versus $\text{v}$_OH in solid hydrates. The variation in the equilibrium OH(D) distance has also been considered.     

Determination of hydrogen ion activities in various ternary water/methanol/dioxane solvent systems

The practical pH values for solutions in ternary water/methanol/dioxane solvents measured by a pH meter standardized with aqueous buffer solutions do not lie on the conventional scale of hydrogen ion activity referred to the standard state in the corresponding medium (pa^*_H). These values can be converted to pa^*_H by the introduction of a correction term δ = $\text{E}\text{?}$_j ? log(_mγ_H) (where $\text{E}\text{?}$_j is a term incorporating the liquid junction potential, which depends on the solvent composition and _mγ_H is the medium effect on hydrogen ion). Values of δ were determined for various ternary solvents at 25°C and were found to be constant in each medium independent of the solute composition.