L'isomérie géométrique d'amidines mono-substituées de l'acide benzothiazole-carboxylique-2. Isomères anti à carboxyle normal,isoméres syn à carboxyle énolisé

The condensation of methyl benzothiazole-2-iminicarboxylate with α-amino-acetic esters gives rise to amidines possessing only one (I) of the two possible tautomeric structures. Both syn and anti isomers have been characterized of the single tautomer. This is the first demonstration of geometrical isomerism around the imine group in amidines. The carboxylic esters and the free acids of the syn fro exist exclusively as the enol, whereas the anti derivatives prefer the carboxyl structure. The existence of these isomers has been confirmed by their IR., UV., and NMR. spectra as well as by the inversion of their configuration and the formation of cyclic derivatives.     

Living cationic polymerization of 2-chloroethyl vinyl ether: Kinetics,mechanism and application to polymer synthesis

The cationic polymerization of 2-chloroethyl vinyl ether initiated by HI/weak Lewis acid (I₂ or ZnI₂) systems has been studied from both a kinetic-mechanistic and a synthetic viewpoint. At low temperature and in toluene as solvent, the polymerization proceeds via a living process and the kinetic order with respect to monomer varies according to the nature of the Lewis acid activator. This behaviour can be explained by the coordination of the Lewis acid with both the monomer and the chain-end, the latter leading to a strong activation of the -I bond towards monomer insertion. The living polymerization obtained from divinylether precursors leads to -I ended telechelics, and their transformation into dihydroxytelechelic oligomers has been performed. The chemical modification of chloroalkyl side groups by phase transfer catalysis allows the attachment of specific groups without consumption of-OH ends.     

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.     

Synthesis and characterization of 4‐aryl‐5‐(1‐aryl‐2‐methyl‐2‐nitropropyl)‐1,2,3‐selenadiazoles

The synthesis of a new set of selenadiazoles, 4‐aryl‐5‐(1‐aryl‐2‐methyl‐2‐nitropropyl)‐1,2,3‐selenadiazoles ( 4 ) derived from 2‐[4‐methyl‐4‐nitro‐1,3‐diarylpentylidene]‐1‐hydrazinecarboxamide ( 3 ) has been reported. THF has been found to be the solvent of choice for this reaction. Structural features of 3 and 4 have been analyzed by NMR and X‐ray techniques.     

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.     

Reactivity of Diamine Monomers in Non‐Equilibrium Copolycondensation Toward Aromatic Copolyamides

Based on the Hammett equation, a general method is established to relate the polycondensation monomer reactivity with both the monomer structural parameters and the properties of the solvent used for the non‐equilibrium ternary copolycondensation to give copolyamides. Linear plots of the logarithm of the monomer reactivity ratio, log r, versus structure parameter ΔpK could be represented by the equation log r = ρΔpK.

Relationship between log r and ΔpK using THF as the solvent.     

Interfaces between coexisting phases in polymer mixtures: What can we learn from Monte Carlo simulations?

Symmetric binary polymer mixtures are studied by Monte Carlo simulation of the bond fluctuation model, considering both interfaces between coexisting bulk phases and interfaces confined in thin films. It is found that the critical behavior of interfacial tension and width is compatible with that of the Ising model, as expected from the universality principle. In the strong segregation limit, only qualitative but not quantitative agreement with the self-consistent field (SCF) theory is found. It is argued that the SCF theory requires but for the short chains studied (N = 32 effective monomer units per chain), the limit is only reached for close to unity. Also, the effective χ-parameter decreases in the interface. It is shown that the interfacial width w does not increase by the adsorption of block copolymers as long as their areal density is still dilute (“mushroom” regime). But a broadening of interfaces does occur for thin films confined between walls at distance D, due to fluctuations that lead to for short-range forces, in agreement with experiment.     

Darstellung und Stabilität von Aroxy-fluor-silanen

Preparation and Stability of Aroxy-fluoro-silanes. Different possibilities for preparation of aroxy-fluoro-silanes (esp. substituted phenoxy-fluoro-silanes) are investigated. The reaction was proved as the best method of preparation. The aroxy-fluoro-silanes are disposed to dismutation reactions.     

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.     

Salt effect in the base-catalyzed polymerization of unsaturated amide compounds. IV. Polymerization of p-vinylbenzamide in the presence of LiCl/N,N,N′,N′-tetramethylethylenediamine

In the presence of lithium chloride and N,N,N′,N′-tetramethylethylenediamine, p-vinylbenzamide was polymerized in basic media to form a polymer with structure consisting of units due to both proton transfer and vinyl type polymerization, whereas in the presence of the salt alone the monomer underwent exclusively vinyl type of polymerization to give a polystyrene derivative:      

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.     

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.     

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.     

3‐Ethylated N‐Vinyl‐2‐pyrrolidone with LCST Properties in Water

The monomer 3‐ethyl‐1‐vinyl‐2‐pyrrolidone ( 3 ) and the homopolymer poly(3‐ethyl‐1‐vinyl‐2‐pyrrolidone) ( 5 ) have been synthesized. Polymer 5 is soluble in water and shows a critical temperature (T_c) of 27 °C. The presence of cyclodextrin causes a slight shift of the T_c. The lower critical solution temperature (LCST) could be varied between 27 and 40 °C by copolymerization with N‐vinyl‐2‐pyrrolidone. A linear correlation between the T_c and the copolymer composition is observed.

     

Étude des Paramètres de Résonance Magnétique Nucléaire et de la Stéréochimie de Thiono-2 R-2 Dithiaphosphorinanes-1,3,2

The ¹H, ¹³C and ³¹P n.m.r. spectra of eleven 2-R-2-thiono-1,3,2-dithiaphosphorinanes with various R groups attached to the phosphorus atom have been recorded and analysed. In the compounds where R=Cl, OMe or N, the molecule adopts a chair conformation with the R group axially oriented. When the molecule adopts a chair conformation with equatorially oriented R. In the case of the derivatives with R=phenyl, Me, N(Me)₂ or NHt-Bu, a chair–chair conformational equilibrium was observed. The hindered rotation about the P? N bond was also examined in the derivative with      

Competition entre les réactivités dipolarophiles et nucléophiles des pyrazolines-2 dans l'action de l'oxyde de benzonitrile. Synthèse,identification, comportement chimique des tétrahydropyrazolo-[4,5-b] oxadiazoles-1,2,4

The reaction of benzonitrile oxide with different series of Δ²-pyrazolines provides evidence for the three reactive centers of compounds i.e., the dipolarophile reactivity of the C = N-bond, and the presence of the two the other nucleophilic sites: the N₁ nitrogen atom and the C₃ carbon atom for unsubstituted pyrazolines at these corresponding positions. Furthermore the regiospecificity of the cycloaddition reaction leading to new series of condensed heterocycles is well demonstrated.     

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.