Dipolmomente 1, 6-überbrückter [10]- Annulene

The dipole moments of 1, 6-bridged [10]-annulenes of type I (X = CH₂, O, NH) and of bromo derivatives with X = CH₂, O are in agreement with the previously established structure of these compounds if a partial moment of approximately 0,8 D is assigned to the non-planar π-electron system.     

Durch Nachbargruppenbeteiligung induzierte (1,2)-Chlorwasserstoff-Eliminierung aus ionisiertem 2-(β-Chloräthyl)- benzoesäuremethylester

By using deuterium labelled compounds and collisional activation spectra the mechanism of the unusually intensive HCl elimination from 2-(β-chloroalkyl)benzoic acid methyl ester as well as the structure of the product ion have been elucidated. It can be shown that the structure of the stable ion (lifetime τ～10?5 s) is best represented by 2-vinyl benzoic acid methyl ester whereas the reactive ion (lifetime τ<10^?6 s) at least partially rearranges to a cyclic ion. The hydrogen chloride elimination from 2-(β-chloroalkyl)benzoic acid is apparently a simple 1,2 process. A closer examination reveals that the reaction represents a further example of an unusual neighbouring group participation of the ester function.     

Kinetics of the First Order Autocatalytic Decomposition Reaction of Nitrocellulose （13.86% N）

The kinetics of the first order autocatalytic decomposition reaction of nitrocellulose (NC, 13.86% N) was studied by using DSC. The results show that the DSC curve for the initial 50% of conversion degree of NC can be de scribed by the first order autocatalytic equation dy/dt =-10^16.3 exp (-181860/RT)y-10^16.7ex(-173050/RT)y(1-y) and that for the latter 50% conversion degree of NC described by the reaction equations dy/dt=-10^16.4exp(-154820/RT)y (n=1) and dy/dt=-10^16.9 exp(-155270/RT) y^2.80(n≠1).     

Amino-phosphane. X. Einige Additionsreaktionen von N-Diphenylphosphinotetraphenyldiphosphin-imid

Diphenylphosphorous chloride and methyl iodide add readily to the N-bonded P(III)-atom of (C₆H₅)₂P? P(C₆H₅)₃?N? P(C₆H₅)₂ forming the salts [(C₆H₅)₂P? P(C₆H₅)₂ N P(C₆H₅)₂? P(C₆H₅)₂]Cl and [(C₆H₅)₂P? P(C₆H₅)₂ N P(C₆H₅)₂. CH₃]I, respectively. A similar behaviour is observed with sulfur: Under mild conditions (C₆H₅)₂P? P(C₆H₅)₂?N? P(C₆H₅)₂ = S is formed but forcing conditions are required to produce S = P(C₆H₅)₂? P(C₆H₅)₂?N? P(C₆H₅)₂?S. The monosulfide is also obtained by treating (C₆H₅)₂P(S)N[Si(CH₃)₃]₂ with diphenylphosphorous chloride, indicating the favoured formation of the phosphazene system as compared with the phosphazane system Confirmation of the structures comes from ³¹P nmr and IR data, and for the sulfides also from their degradation with bromine.     

Phosphates d'enols. XII—Etude en Spectrometrie de Masse de Derives Diethyliques et di-n-Butyliques

The mass spectrometric fragmentations of diethyl phosphates (1) and di-n-butyl phosphates (2) are influenced by the nature of the substituents R, R′ and R″ fixed on the double bond When R = H, the loss of ethylene or 1-butene is mainly observed. When R = CH₃, the double rearrangement process occurs with alkyl group participation of the enolic chain.     

Photolysis of carbon tetrachloride in the presence of alkanes

The photolysis of carbon tetrachloride in the presence of a number of alkanes has been investigated in the gas phase. The products obtained from the photolysis experiments were those expected from a chain reaction in which trichloromethyl radicals abstract hydrogen atoms from the alkane. The data have been used to determine Arrhenius parameters for hydrogen abstraction from the series of alkanes CH₄, C₂H₆, C₃H₈, and i-C₄H₁₀ by trichloromethyl radicals, The rate data obtained are used to explain why termination reactions involving alkyl radicals become less significant as the alkane becomes more complex.     

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.     

Fragmentations of protonated acetophenones via intermediate ion–molecule complexes

Protonated acetophenones, substituted with a methoxymethyl group in the para and meta positions, have been generated by electron impact induced fragmentation of the correspondingly substituted 2-phenylpropan-2-ols. The metastable ions, formed in the second field-free region of a VG ZAb 2F mass spectrometer, react unimolecularly by elimination of CH₃OH, formation of CH₃CO⁺ and ions, loss of CH₃COOCH₃, and loss of CH₂O. The mechanisms of these fragmentations have been elucidated with the aid of deuterated analogues of the protonated acetophenones. It is shown that these reactions are initiated by an endothermic transfer of the proton at the carbonyl group of the protonated acetophenones to the benzene ring. A further migration of the proton to the ether O atom of the methoxymethyl side-chain leads eventually to the elimination of CH₃OH. Protolytic bond cleavages of either side-chain gives rise to the CH₃CO⁺ and ions. At low internal energies both these ions may be trapped by the aromatic neutral fragment in ion-molecule complexes. Reactions within these complexes result in the energetically favourable losses of CH₃COOCH₃ and CH₂O, respectively. With respect to these reactions, the protonated acetophenones behave analogously to the correspondingly substituted and protonated benzaldehydes.     

Modification of poly(vinyl alcohol) through reaction with phosphorus-containing reactants

Crosslinked products of the form: and have been formed from the interfacial condensation of phosphorus diacid halides with poly(vinyl alcohol). Product yield and amounts of phosphorus reactant included in the product increases as the amount of base increases. Product stability in aqueous systems decreases in the order neutral > base > acid.     

Practical Microwave Synthesis for Organic Chemists.Strategies,Instruments, and Protocols. Herausgegeben von C. Oliver Kappe,Doris Dallinger und Shaun Murphree.

Wiley‐VCH, Weinheim 2008. 300 S., geb., 59.00 €.—ISBN 978‐3527320974

     

Isomérie Polyédrique dans des Spirophosphoranes Possédant le Groupement P?H

We have studied the temperature dependence of NMR spectra of six spirophosphoranes of the general formula: Experimental data show intramolecular isomerism which was explained by pseudo-rotation mechanism (Berry, Lit. 1). In all cases except one we also observed tautomerism between spirophosphorane and phosphite forms.     

Bildung siliciumorganischer Verbindungen. LVI. Reaktionen Si- und C-chlorierter 1,3,5-Trisilapentane mit CH3MgCl

Formation of Organosilicon Compounds. LVI. Reactions of Si- and C-Chlorinated 1,3,5-Trisilapentanes with CH₃MgCl (Cl₃Si? CCl₂)₂SiCl₂ (1) reacts with an excess of meMgCl (me = CH₃) forming me₃Si? C?C? Sime₃ (2), Sime₄, H₂C?C(Sime₃)[CH(Sime₃)₂] (3) as main products and (me₃Si)₂C? CH(Sime₃) and as by-products. The cleavage reaction of (1) to (2) and (3) does not occur when the meMgCl-concentration is lowered. The reaction is started by the formation of a GRIGNARD reagent at a CCl-group in compound (1). Cl₃Si? CCl₂? SiCl₂? CH₂? SiCl₃ forms with ; me₃Si? CCl₂? SiCl₂? CHCl? SiCl₃ forms (me₃Si)₂C?CH(Sime₃). A reaction sequence is given.     

Zur Darstellung von Cyclophosphaten,Cyclophosphatophosphonaten, Diphosphonaten und Diphosphiten in Harnstoffschmelzen

Preparation of Cyclophosphates, Cyclophosphatophosphonates, Diphosphonates, and Di-phosphites in Urea Melts Ammonium cyclotriphosphate (NH₄)P₃O₉, ammonium cyclotetraphosphate [P^IV? P^IV ? O? ]₂, ammonium cyclotriphosphatophosphonates Ammonium organyldiphosphonates And ammonium diphosphites are prepared in high yields on heating acidic phosphates, phosphonates, and phosphites in urea or urea/ammonium nitrate melts. The mechanism of the dehydration of phosphorus compounds containing POH groups in molten urea is discussed.     

HNO,an Intermediate in (Light-induced) Rearrangement Reactions of Nitrosooxy Compounds and Nitrosamines

IR-spectroscopic investigations of light-induced rearrangement reactions of nitrosooxymethane (CH³ONO³), nitrosooxyethane (CH₃CH₂ONO) and N,N-dimethylnitrosamine ((CH₃)₂NNO) in low-temperature rare-gas matrices have established that these molecules are transformed in two photolysis steps to the previously unknown C-nitroso compounds nitrosomethanol (CH₂(OH)(NO)), 1-nitrosoethanol (CH₃CH(OH)(NO)), and methyl(nitrosomethyl)amine CH₂(NO)(NH)(CH₃). Evidence for a similar rearrangement reaction has been advanced for N-Nitrosopyrrolidine which is converted to C-nitrosopyrrolidine . The matrix-isolation technique in combination with wavelength-selective irradiation allowed to trap and characterize an intermediate of rearrangement which revealed to be nitroxyl (HNO) complex (CH₂…HNO, CH₃CHO…HNO, CH₃N = CH₂…HNO, and ). Since these findings have a close resemblance with rearrangement reactions of more complex nitrosooxy compounds, nitrosamines, or nitrosohydrazines used in organic synthesis, it is suggested that also in these reactions nitroxyl is present as an intermediate species.     

γ-Radiation-produced supported metal complex catalysts. 3. Phosphinated polypropylene supports

p-Styryldiphenylphosphine was grafted onto polypropylene by γ-radiation. However, olefinic phosphines in general do not readily undergo such grafting. Among the many other olefinic phosphines examined only 1-(4-diphenylphosphinophenyl)-prop-1-ene and vinyldiphenylphosphine were grafted successfully and both had low grafting yields. The optimum conditions for grafting involve low dose rates and high total doses of γ-radiation in dimethylsulfoxide as solvent. This grafting is sensitive to impurities and inhomogeneity in the product readily results, especially at high grafting yields. Oxygen must be rigorously excluded if oxidation of grafted phosphorus(III) to phosphorus (V) is to be avoided. Phosphine oxides can be reduced to phosphines when grafted to the polymer with trichlorosilane. Mass spectrometry has shown that more than one olefinic phosphine binds to a single site in the polymer. Solid-state, high-resolution ³¹P-NMR is a valuable technique for characterizing the grafted polymer. The preparation and characterization of the following hitherto unreported phosphines is described: In addition, the precursor halides none of which has been reported, were prepared and characterized.     

Electron impact studies. CVII—Negative ion mass spectra of the oxime group. Monoximes derived from α-dicarbonyl systems

Specific losses of water are observed from the molecular anions of monoximes of α-diketones. Labelling studies, kinetic energy release values and the +E spectra of ions have been used to aid in the elucidation of the fragmentation pathways. It is proposed that the majority of ions have α-keto nitrile structures.     

The reactions of CF3 and CD3 radicals with boron trimethyl

Hydrogen abstraction from boron trimethyl has been studied using the abstracting radicals CF₃ and CD₃, from the photolysis of the corresponding ketones over the temperature range of 150° to 300°C. The following Arrhenius parameters were obtained: The difference E – E in the case of BMe₃ is considered due, in part, to polar effects. An exchange reaction is proposed for both CF₃ and CD₃ in collisions with BMe₃: Radical combination of CF₃ and CH₂BMe₂ leads to a hot molecule which undergoes a β-fluoro rearrangement elimination process, or a stabilized molecule which can thermally decompose:      

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.     

Thermal decomposition of azoethane

The thermal decomposition of azoethane (AE) was studied by detailed product analysis in the temperature and pressure intervals 508–598 K and 2.7–13.3 kPa. Besides the hydrocarbon products, three characteristic and quantitatively important nitrogen-containing compounds were also determined: ethyl-2-butyldiimide, ethanal-diethylhydrazone, and tetraethyl-hydrazine. Apart from the predominant termination reactions of the ethyl radical with itself and with the μ₂ radical, the decomposition is characterized by a very short chain reaction. The measurements led to determination of the following rate constants and rate constant ratios: for the following reactions:      

New Star‐Shaped Metallo‐Polymeric Chromophores

The synthesis of new star‐shaped polymers, prepared by atom transfer radical polymerization of methyl methacrylate with tris(dialkylaminostyryl‐2,2′‐bipyridine) zinc(II) and iron(II) metalloinitiators, is reported. Their thermal and optical (absorption and emission) properties are discussed.

Structure of the star‐shaped polymers.