The loss of CH3⋅ from some unsaturated dithioesters

The mechanism for the loss of CH₃? (and C₂H₅?) from the molecular ions of some unsaturated dithioesters of the type with n=0, 1, 2, has been studied. Based on first field free region metastable ion characteristics it is proposed that 1,3-dithiolium type product ions are generated. Deuterium labelling experiments indicated that the molecular ions of the 2-alkenyl alkanedithioates undergo a rearrangement prior to fragmentation which resembles the [3,3]sigmatropic rearrangement in solution chemistry.     

Fluorsulfonylstickstoffverbindungen

The reactions of fluorosulfonylurea derivatives with phosphorus pentachloride in carbon tetrachloride leads to and . These compounds are easily fluroinated by arsenic trifluoride to the corresponding fluorosulfonyl derivatives. It was shown that PCl₅ is reliable for the fluorine-chlorine exchange. Isocyanate esterchlorides as well as carbonyl-fluoride derivatives react with compounds which have an active hydrogen atom. By this way were prepared: . By hydrolysis of , is probably formed as the first reaction product. The acid could be trapped with tetraphenylphosphoniumchloride as a well-cristalline salt. Fluorosulfonyl isocyanate reacts with aldehydes to the following compounds: FSO₂N ? CHCH₃, FSO₂N ? CHC₂H₅, FSO₂N ? CH? CH(CH₃)₂ and FSO₂N ? CHC₆H₅. The physical and chemical properties as well as IR and NMR spectra of the compounds are described and, in part, compared and discussed.     

Roberta Sessoli

“My most exciting discovery to date has been that molecules can have a magnetic memory. The biggest challenge facing scientists is to find renewable and sustainable energy sources…?” This and more about Roberta Sessoli can be found on page 2265.

     

Massenspektrometrische Untersuchung organischer Stickstoffverbindungen. XXVII—Intramolekulare Redoxreaktionn bei ionisierten ortho-substituierten Nitroaromaten

Collisional activation demonstrates that the stable ions from o-nitrobenzaldehydedimethylacetale possess the structure of ionized o-nitroso benzoic acid methyl ester. Contrary to previous conclusions it is demonstrated that the structure of the stable ions (m/e 135) from different precursors [i.e. o-nitrobenzyl alcohol o-nitrobenzyl cyanide and o-nitrobenzaldoxime is best represented by 2,1-benzisoxazoline-3-one. Ionized o-nitrosobenzaldehtde rearranged to 2,1-benzisoxazoline-3-one prior to collision induced decomposition, whereas 2-benzoxazolinone and 3-hydroxy-1,2-benzisoxazole do not rearrange within 10^?5 s.     

Oxazolidines versus schiff bases

The formation of oxazolidines from propionaldehyde and aliphatic β-aminoalcohols is complicated by the appearance of appreciable amounts of unsaturated Schiff bases. The simple Schiff base, often the dominant species when aromatic aldehydes react with amines, could not be detected in the present aliphatic systems. We conclude that in aliphatic systems the order of stability is and . The gem-dimethyl group α to nitrogen stablizes the heterocyclic ring remarkably.     

Darstellung und Eigenschaften von Ti-substituierten N-Heterocyclen

Preparation and Properties of Ti-substituted N-Heterocycles The compounds (x = 2 to 6) have been prepared by transamination of Ti(NMe₂)₄ with the heterocyclic amines and have been characterised by elemental analyses and ¹H NMR and IR spectroscopy. The dependence on both x and n of the thermal decomposition has been studied for the series and . The results can be interpreted in terms of the steric strain of the R₂N and substituents. Apart from the piperidido groups none of the ligands exhibit protective group properties comparable to the R₂N groups.     

Synthese „anorganischer”︁ Tintenfisch-Moleküle

Inorganic Pode-Type Molecules The reaction of monosubstituated polyethylenglykoles [m = 0—4, R = Cl, OCH₃, OAs(CH₃)₂, OSi(CH₃)₃] with amino compounds (CH₃)_xE[N(CH₃)₂]_y(E = Si, x = y = 2; E = Si, x = 1, y = 3; E = P, x = 0, y = 3; E = As, y = 0, y = 3) results in the formation of pode-type molecules of the formula . The synthesis and rearrangement of these compounds by heating is described.     

Transition Metal Complexes with Bidentate Ligands Spanning trans-Positions. XII. Steric effects in the kinetics and mechanism of substitutions at hydride and methyl bisphosphine platinum (II) complexes

Ligand substitution reactions on square-planar platinum (II) complexes of the types trans-[PtRXL₂], trans-[PtR(4-PADA)L₂][BF₄], trans-[PtRX( ) and trans-[PtR(4-PADA)( )][BF₄] R=H, Me; X=Cl^?, I^?; L=PEt₃, bis(3-trifluoromethyl-phenyl)benzylphosphine ( 4 ), =the trans-spanning 2,11-bis[bis(3-trifluoro-methylphenyl)phosphinomethyl]benzo [c]phenanthrene ( 3 ); 4-PADA (=pyridine-4-azo-4′-(N, N-dimethyl)aniline have been studied at 30° using stopped-flow and conventional spectrophotometry, methanol as solvent, and 2.5 × 10^?2 M ionic strength (LiClO₄ as supporting electrolyte). 4-PADA was used as indicator ligand, as its absorption spectrum differs from those spectra where it is complexed. The expected steric effects of the bulky ligands, especially of 3 , on the rates and mechanisms of all the reactions studied are small. All reactions take place by the usual two-term rate law. Noteworthy, for the complexes with the bulky ligands 3 and 4 , the direct reaction path with the entering nucleophile is predominant. There is no preference for a solvent or dissociative path. The reactivity order for the hydride complexes is trans-[PtHX (PEt₃)₂]<trans-[PtHX( 4 )₂]<trans-[PtHX ( 3 )]. However, for the corresponding methyl complexes, there is some retardation by ligand 3 , probably due to an interaction between the methyl group and the hydrocarbon moiety of 3 , which inhibits the fluxional behavior of this ligand. The results have some relevance for the understanding of olefin-insertion reactions of hydride complexes containing these phosphine ligands.     

N‐Alkylation of imides using phase transfer catalysts under solvent‐free conditions

N‐Alkylation of imides in the reaction of imides and alkylhalides, catalyzed by PT catalysts under solvent‐free conditions, has been developed. The reaction occurs in the presence of K₂CO₃, and in many cases it takes place spontaneously. In the N‐benzylation reaction, it has been recognized that TBAB (tetrabutylammonium bromide) and TBATFB (tetrabutylammonium tetrafluoroborate) show highest catalytic effect. Versatility and synthetic capacity of the solvent‐free alkylation has been confirmed by N‐benzylation and N‐ethylation of various imides. The developed procedure gives easy access to N‐(ω‐bromoalkyl)imides.     

Kinetics of recombination,dismutation, and disproportionation reactions involving neutral ketyl radicals and radical anions

The kinetics of fast elementary recombination of neutral ketyl radicals of benzophenone and its four derivatives (BPH?), the dismutation of benzophenone radical anions, the disproportionation between BPH? and stable nitroxyl radicals, ( ), and the electron transfer have been investigated in both individual solvents and binary mixtures of different viscosities. Reaction (1) for unsubstituted BPH in water, water glycerol, and n-hexane is controlled by diffusion with 2k₁ ? k_diff. In aliphatic alcohols and toluene, which form solvation complexes with BPH?, reaction (1) is diffusion-enhanced and activation-controlled, respectively, with 2k₁ < k_diff. In a viscous solvent such as 1-propanol–glycerol mixture (100 ? η ? 450 cP) reaction (1) is diffusion-controlled. Reaction (2) in alkaline 1-propanol and alkaline 1-propanol–glycerol mixture is activation controlled. The rates of reactions (3) and (4) for benzophenone radicals and nitroxyl radicals of the imidazoline series decrease as the viscosity of the water–glycerol and 1-propanol–glycerol mixtures is increased. The reactions are molecular mobility limited; nevertheless, the numerical values of k₃ (k₄) are 2–6 times as small as the corresponding k_diff values due to the low steric factor of the reactions (therefore called pseudodiffusion-controlled reactions). The theoretical estimates of k₃ (k₄) are in good agreement with the experimental results. The elimination of spin forbiddance in the process of radical recombination in viscous solvents is discussed.     

Effect of gegen ion in cationic polymerization and copolymerization of trioxane

p-Chlorophenyldiazonium hexafluorophosphate has been reported to be a superior catalyst for cationic polymerization and copolymerization of trioxane as compared to boron trifluoride dibutyl etherate (BF₃·Bu₂O)¹. In the present investigation the effect of anions derived from elements in Group VA, AsF and SbF, has been ascertained. It has been concluded that p-chlorophenyldiazonium hexafluoroarsenate is also a superior catalyst to boron trifluoride dibutyletherate (BF₃·Bu₂O), while p-chlorophenyl-diazonium hexafluoroantimonate is inferior. Copolymers with the highest polymer yield (>95%) and molecular weight (intrinsic viscosity = 4 to 5) were obtained with Simple dependences on catalyst concentration have been observed to hold for a wide catalyst concentration range ([M]/[C]) = (1 to 20) × 10⁵: For the same relationships hold. However, the polymer yield (75%) and molecular weights (intrinsic viscosity ?1) are considerably lower while the extent of chain transfer is higher. Furthermore, the polymerization proceeds with explosive violence. The quantitative aspects resulting from polymerization, for the most part, can be interpreted in terms of the extent of dissociation of the propagating ions.     

The pyrolyses of tri- and tetramethylethylene in the presence of nitric oxide

The pyrolyses of trimethylethylene and tetramethylethylene have been investigated in the presence and absence of nitric oxide. It appears that apart from a unimolecular split, e.g., a disproportionation reaction such as may play an important role in initiation. Nitric oxide had no effect on H₂ production, which is probably a molecular process. There was similar behavior of both compounds in the presence of NO, indicating that the olefinic hydrogen atom does not play a decisive role. Other aspects of the mechanisms are discussed.     

Critical Enhancements of MRI Contrast and Hyperthermic Effects by Dopant‐Controlled Magnetic Nanoparticles

Doped up : The incorporation of Zn²⁺ dopants in tetrahedral sites leads to the successful magnetism tuning of spinel metal ferrite nanoparticles (see picture). (Zn_0.4Mn_0.6)Fe₂O₄ nanoparticles exhibit the highest magnetization value among the metal ferrite nanoparticles. Such high magnetism results in the largest MRI contrast effects (r2=860 mm^?1 s^?1) reported to date and also huge hyperthermic effects.

     

Mechanism of inhibiting action of quinones in oxidizing polymers and model compounds

Quinones (Q) do not affect the liquid-phase oxidation of hydrocarbons and retard the solid-phase oxidation of polymers terminating chains in reactions with alkyl macroradicals. This difference is the result of specific influence of a polymer matrix on the kinetics of free radical reactions. Quinones were found to terminate chains in oxidizing polypropylene containing hydroperoxide groups by the reaction with hydroperoxyl radicals. This is the result of peroxide group's decomposition with hydrogen peroxide production and chain termination in the following reactions: The equilibrium reaction between hydroquinone (QH₂) and quinonimine (QI) was evidenced to proceed as a chain reaction with chain propagation in reactions of •QH with QI and HQI• with QH₂. Analysis of the reactions of quinone with phenols (ArOH) proved that it can be important as an additional way of chain termination in oxidizing polymers and hydrocarbons at elevated temperatures.     

Chlorine Dioxide as an Electron-Transfer Oxidant of Olefins. Preliminary Communication

The kinetics and product studies of oxidation of eight olefins 1 - 8 by ClO₂ in H₂O in the pH range 3-7 are described. The reaction is faster as the pH decreases. At pH < 4, ClO₂ reacts equimolarly with olefins to yield isomeric mixtures of chlorohydrines and 1,2-dioxygenated products, following the equation: The order of reactivity is: (E)-stilbene > indene > β-methylstyrene > acenaphthylene > α-methylstyrene > styrene > cyclohexene > allylbenzene. A multi-stage radical-cation mechanism is proposed, in which an initial reversible protonation: is followed by an electron-transfer stage (rate-determining): The cation-radical thus produced, adds rapidly an additional ClO₂ to form dioxygenated products. The chlorohydrines most likely arise from HClO additions to the olefinic double bonds, which, in turn, generate from dismutation of 2 HClO₂ into HClO + H⁺ + ClO.     

Conformational energy surfaces of triplet-state isomeric methyloxiranes

A conformational study was carried out on the three ring-opened structures of triplet methyloxirane with a minimal Gaussian basis set, within the unrestricted Hartree–Fock framework. For the two structures energy surfaces E(θ₁, θ₂) were generated, where θ₁ measures the methyl rotation and θ₂ is associated with the torsion about the other C? C bond. For the third structure an energy hypersurface E(θ₁, θ₂, θ₃) was generated, where energy was a function of methyl rotation θ₁ and two nonequivalent C? O rotations θ₂ and θ₃. Analysis of the surfaces revealed the locations and relative energies of the critical points (minima, saddle points, and maxima). The overall stereochemical finding was that these ring-opened triplet C₃H₆O species possessed rather flexible structures.     

Anthracene‐Containing Wide‐Band‐Gap Conjugated Polymers for High‐Open‐Circuit‐Voltage Polymer Solar Cells

The synthesis, characterization, and photophysical and photovoltaic properties of two anthracene‐containing wide‐band‐gap donor and acceptor (D–A) alternating conjugated polymers ( P1 and P2 ) are described. These two polymers absorb in the range of 300–600 nm with a band gap of about 2.12 eV. Polymer solar cells with P1 :PC₇₁BM as the active layer demonstrate a power conversion efficiency (PCE) of 2.23% with a high V_oc of 0.96 V, a J_sc of 4.4 mA cm⁻², and a comparable fill factor (FF) of 0.53 under simulated solar illumination of AM 1.5 G (100 mW cm⁻²). In addition, P2 :PC₇₁BM blend‐based solar cells exhibit a PCE of 1.42% with a comparable V_oc of 0.89 V, a J_sc of 3.0 mA cm⁻², and an FF of 0.53.

     

[2, 3] Sigmatropic Rearrangements on Lithiation of Some Allyl Sulfides. Preliminary communication

In five cases, [2,3] sigmatropic rearrangement of the type has been observed.     

Gold Nanorod/Fe3O4 Nanoparticle “Nano‐Pearl‐Necklaces” for Simultaneous Targeting,Dual‐Mode Imaging,and Photothermal Ablation of Cancer Cells

Perlen auf Gold : Neuartige multifunktionelle Nanopartikel bestehen aus einzelnen Amin‐modifizierten Goldnanostäbchen, an denen Fe₃O₄‐„Perlen“ mit Carboxyendgruppe angebracht sind. Die Partikel eignen sich zur simultanen Erkennung, dualen Bildgebung und photothermischen Ablation von Brustkrebszellen.

     

The mass spectra of some chlorinated aromatic pesticidal compounds

Mass spectral studies of some chlorinated aromatic pesticidal compounds are reported. The compounds studied include substituted diphenyl derivatives of methane, ethene and methanol. The diphenylmethanes are characterized by a relatively intense peak at m/e 165. Comparison of their low voltage spectra with 9-dichloromethylfluorene indicates that this ion has a fluorenyl ion structure. The structure of the base peak (m/e 246) of the diphenylethenes was investigated by comparing competitive metastable transitions with 9-dichloromethylenefluorene and utilizing defocusing metastables. Additional studies of model compounds suggest that the m/e 246 ion is very complex and is probably comprised of a number of structures. The mass spectra of the diphenylmethanols are significantly different from the other two groups. The hydroxyl group markedly affects the fragmentation process for these compounds; the characteristic peak is presumably the chlorobenzoyl ion and is probably precursor for other fragment ions. Mass spectral correlations of pesticidal compounds of similar structure are needed to obtain enough background to facilitate interpretation of the mass spectra of their metabolites. Furthermore, such studies make feasible the identification of characteristic product ions formed by rearrangement processes during ionization of organic molecules in the gas phase. This information can be a nucleus for correlating the other significant mass spectral data of an unknown compound. Intensive studies of carbamates,¹ organophosphorus² and bridged polycyclic chlorinated pesticidal³ compounds were invaluable in identifying metabolites of the aforementioned pesticides.^4,5,6 The compounds in this Work are chlorinated aromatic pesticidal compounds which consist of a diphenylemthane, a diphenylethylene, or a diphenylmethanol structure. The compounds p,?-DDE were briefly discussed by Jorg, Houriet and Spiteller.⁷ The compounds examined are listed in Table 1. Treatment of data. The mass spectra of the pesticides are presented as bar graphs in Figs 1 to 12 It a metastable peak is observed, the metastable transition is indicated by m^* on the figures and also by (m^*) when confirmed or identified using the defocusing technique.⁸ Since the relative abundances of the metastable peaks for these compounds are very small (<0.1%) on special effort was made to establish their presence unless they wre pertinent.