The elimination of metal(I) hydride in the mass spectra of some metal(II) compounds

Metal(I) hydrides are eliminated as neutral species in the electron impact ionization mass spectra of copper(II) and palladium(II) complexes of ethylene-N,N′-3-benzoylprop-2-en-2-amine. Deuterium labelling shows that the hydrogen atom of the metal(I) hydride is derived predominantly from the ethylene bridge both for ion source reactions and for metastable ion transitions. Evidence supporting the proposed rationalization for elimination of metal(I) hydride is provided by the observation of an analogous reaction in the mass spectrum of (ethylene-N,N′-salicylaldiminato)copper(II). The mass spectrum of ethylene-d₄-N,N′-3-benzoylprop-2-en-2-amine shows an unusual rearrangement to give [C₇H₅D₂]⁺ ions involving a formal phenyl-to-methylene transfer.     

Oligomérisation anionique de l'ethylène. II. Etude des paramètres thermodynamiques

A kinetic study, as a function of temperature, of ethylene oligomerization by the n-BuLi–TMEDA complex allowed us to evaluate the thermodynamic parameters (ΔS^? < ?23.7 u.e.) and thus to support a transition state where the ethylene is coordinated to the lithium atom.     

Specific rearrangement reactions of acetylated lysine containing peptide bn (n = 4–7) ion series

Characterization of ε‐N‐acetylated lysine containing peptides, one of the most prominent post‐translational modifications of proteins, is an important goal for tandem mass spectrometry experiments. A systematic study for the fragmentation reactions of b ions derived from ε‐N‐acetyllysine containing model octapeptides (K_AcYAGFLVG and YAK_AcGFLVG) has been examined in detail. Collision‐induced dissociation (CID) mass spectra of b_n (n = 4–7) fragments of ε‐N‐acetylated lysine containing peptides are compared with those of N‐terminal acetylated and doubly acetylated (both ε‐N and N‐terminal) peptides, as well as acetyl‐free peptides. Both direct and nondirect fragments are observed for acetyl‐free and singly acetylated (ε‐N or N‐terminal) peptides. In the case of ε‐N‐acetylated lysine containing peptides, however, specific fragment ions (m/z 309, 456, 569 and 668) are observed in CID mass spectra of b_n (n = 4–7) ions. The CID mass spectra of these four ions are shown to be identical to those of selected protonated C‐terminal amidated peptides. On this basis, a new type of rearrangement chemistry is proposed to account for the formation of these fragment ions, which are specific for ε‐N‐acetylated lysine containing peptides. Consistent with the observation of nondirect fragments, it is proposed that the b ions undergo head‐to‐tail macrocyclization followed by ring opening. The proposed reaction pathway assumes that b_n (n = 4–7) of ε‐N‐acetylated lysine containing peptides has a tendency to place the K_Ac residue at the C‐terminal position after macrocyclization/reopening mechanism. Then, following the loss of CO, it is proposed that the marker ions are the result of the loss of an acetyllysine imine as a neutral fragment. Copyright © 2014 John Wiley & Sons, Ltd.     

Catalytic systems Me2SiCp*NtBuMX2/(CPh3)(B(C6F5)4) (MTi,XCH3, MZr,XiBu) in copolymerization of ethylene with styrene

Catalytic activity of Me₂SiCp*N^tBuMX₂/(CPh₃)(B(C₆F₅)₄) [MTi, XCH₃ (1); MZr, X=ⁱBu (2)] systems in the ethylene/styrene (E/S) feed was examined. Experimental data revealed high activity for the catalytic system (1) for copolymerization ethylene with styrene, whereas the system with enhanced catalytic activity for ethylene homopolymerization (2) was temporarily blocked in the styrene presence yielding, even at high styrene content, homopolyethylene as the final product. Properties of thus obtained polymers were analyzed. Catalytic system (1) occurred very sensitive to S/E ratio in the comonomers feed. The 10‐fold acceleration for ethylene consumption was shown in two experimental sets conducted at S/E = 1.3 ratio, 1 bar, and 7.5 bar ethylene pressure, respectively. The consequent enhancement in S/E ratio resulted in slowing down both ethylene consumption and catalyst deactivation rates. Atactic polystyrene was formed at high styrene content with the catalyst (1). Catalytic system (1) allowed design of products with the highest styrene content (20 mol %) at low ethylene pressure, moderate temperature, and high S/E ratio. The apparent activation energy estimated from the initial rates of ethylene consumption was 54.6 kJ/mol. Analysis of apparent reactivity factors (r_E = 9 and r_S = 0.04; r_E × r_S = 0.4) and ¹³C‐NMR copolymer spectra revealed an alternating tendency of the comonomers for active center incorporation. DSC measurements showed considerable decrease of melting points and crystallinity even for copolymers with low styrene content. The catalyst produced relatively high–molecular weight copolymers (140–150 kg/mol) even at 80°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1083–1093, 1999     

Facile synthesis of poly(l‐tryptophan) through polycondensation of activated urethane derivatives

A facile and phosgene‐free synthetic route to poly(l ‐tryptophan) 2 by the polycondensation of N‐phenoxycarbonyl‐l ‐tryptophan 1 is described. The monomer 1 was synthesized via the carbamylation of tetrabutylammonium salt of L‐tryptophan with diphenyl carbonate. The polycondensation proceeded smoothly at 60 °C in N,N‐dimethylacetamide in the presence of amines (n‐butylamine, diethylamine, and triethylamine) along with the elimination of phenol and carbon dioxide. The structural analysis of the obtained 2 by Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry revealed that n‐butylamine or diethylamine was successfully incorporated into the chain end of the polypeptide. Furthermore, we have demonstrated the synthesis of a diblock copolymer by utilizing amine‐terminated poly(ethylene glycol) as a source of the polyether segment. The chain length of the polypeptide segment was controlled by varying feed ratio between 1 and the amino group of poly(ethylene glycol). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4565–4571     

From poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide)‐block‐poly(N‐isopropylacrylamide) triblock copolymer to poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide) hydrogels: Synthesis and rapid deswelling and reswelling behavior of hydrogels

Poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide)‐block‐poly(N‐isopropylacrylamide) (PNIPAAm‐b‐PEO‐b‐PNIPAAm) triblock copolymer was synthesized via the reversible addition‐fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process with xanthate‐terminated poly(ethylene oxide) (PEO) as the macromolecular chain transfer agent. The successful synthesis of the ABA triblock copolymer inspired the preparation of poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide) (PNIPAAm‐b‐PEO) copolymer networks with N,N′‐methylenebisacrylamide as the crosslinking agent with the similar approach. With the RAFT/MADIX process, PEO chains were successfully blocked into poly(N‐isopropylacrylamide) (PNIPAAm) networks. The unique architecture of PNIPAAm‐b‐PEO networks allows investigating the effect of the blocked PEO chains on the deswelling and reswelling behavior of PNIPAAm hydrogels. It was found that with the inclusion of PEO chains into the PNIPAAm networks as midblocks, the swelling ratios of the hydrogels were significantly enhanced. Furthermore, the PNIPAAm‐b‐PEO hydrogels displayed faster response to the external temperature changes than the control PNIPAAm hydrogel. The accelerated deswelling and reswelling behaviors have been interpreted based on the formation of PEO microdomains in the PNIPAAm networks, which could act as the hydrophilic tunnels to facilitate the diffusion of water molecules in the PNIPAAm networks. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Spectres de masse des composés organiques. 5e communication. Perte de méthane et d'éthylène à partir des ions butyle

The loss of methane and ethylene in the mass-spectrometric fragmentation of different isomeric butyl ions which originate from butyl halides has been studied. The different carbon atoms in n-butyl are already equivalent after 10^?7 s, whereas the statistical distribution of the hydrogen atoms within the molecule can only be observed for the metastable peaks. A protonated cyclobutane structure is proposed as an intermediate product in the fragmentation of the n-butyl ion. The fragmentation of this model has been simulated by a computer. This allows prediction as to the time-scale of fragmentation. The comparison of this model fragmentation with that of isomeric butyl ions shows that, even in the decay of the tertiary butyl ion, the formation of the proposed rearranged cyclic structure competes favorably with the direct fragmentation.     

Electron-impact induced fragmentation of 3-hydroxy quinazoline-2,4(1H,3H) dione,pyridopyrimidine-2,4(1H,3H)diones,lumazine and alloxazine

Electron-bombardment of the N-3-hydroxy derivatives of the above-mentioned condensed uracils revealed that the major fragmentations involved the heterocyclic ring. The most intense ion proved to be the M-32 ion which was created by the loss of the NHOH radical from the molecular ion. Mechanisms for this transition are presented. Other fragmentations common to these systems are discussed and compared with those reported for the corresponding N-3 deoxy analogs of the title compounds. The mass spectral fragmentations of the O-methyl-, N-methyl- and O,N-dimethyl derivatives of 3-hydroxyquinazoline-2,4(1H,3H)dione were analyzed and were consistent with those expected from these structures. Electron bombardment of the 3-benzenesulfonyloxy derivatives of the title compounds resulted primarily in the scission of the sulfonate group in preference to that of the heterocyclic dione ring. These sulfonates also showed ions which indicated that a Lossen rearrangement had taken place in the mass spectrometer.     

Oligomérisation anionique de l'ethylène. I. Etude cinétique

A kinetic study of ethylene oligomerization in hexane, in the presence of n-BuLi–TMEDA complexes, allowed us to suggest a new mechanism for anionic ethylene oligomerization. n-BuLi and n-Bu(CH₂CH₂)Li species have the same reactivity. The RLi–TMEDA complex in a 1-to-1 stoichiometry is the active species. The following kinetic equation has been established: It reflects the intervention of associated species (n-BuLi–TMEDA)₂ as well as the influence of the concentration of the complexing agent on the kinetics of oligomerization.     

Synthesis of functional star‐shaped poly(ethylene oxide) using the macromonomer technique

Functional poly(ethylene oxide) stars were prepared by free‐radical copolymerization of poly(ethylene oxide) macromonomers with divinylbenzene in water. The poly(ethylene oxide) arm was prepared by anionic polymerization using 2‐[2‐(N,N‐dimethylamino)ethoxy]ethanol potassium alkoxide as the initiator. These functional stars were converted into peripherally charged stars by quaternization of the peripheral tertiary amino groups with methyl iodide.     

Preparation and Aggregation of Polypseudorotaxane from Dendronized Poly(methacrylate)‐Poly(ethylene oxide) Diblock Copolymer and α‐Cyclodextrin

Summary: Dendronized poly(methacrylate)‐poly(ethylene oxide) (PDMA₅₈‐b‐PEO₄₅) formed as a stoichiometric inclusion complex with α‐cyclodextrin. The incorporation of the rodlike PDMA blocks produced no apparent change in the crystal structure, but its steric hindrance on the PEO chain resulted in lower yield as compared with the pure PEO. Moreover, the architectural transition from rod–coil to rod–rod led to a morphological change from spindly aggregates to rods in a binary solvent mixture of N,N‐dimethylformamide and water.

Synthesis and self‐assembly of the α‐cyclodextrin‐[dendronized poly(methacrylate)‐poly(ethylene oxide)] (α‐CD‐PDMA‐PEO) polypseudorotaxane (PR).     

Der massenspektrometrische Zerfall isomerer Diacetamido-cyclo-hexane,ihrer N-Phenäthyl-Derivate und Bis (acetamidomethyl)cyclohexane. 32. Mitteilung über massenspektrometrische Untersuchungen,,

The Mass Spectral Decomposition of Isomeric Diacetamido-cyclohexanes, their N-Phenethyl-Derivatives and Bis(acetamidomethyl)cyclohexanes In the mass spectra of the six isomeric diacetamidocyclohexanes 2--4 (cis and trans each, Scheme 2) as well as of the six isomeric bis(acetamidomethyl)cyclohexanes 6--8 (cis and trans each, Scheme 5) are clear differences between the constitutional isomers, whereas cis/trans isomers show very similar spectra. The lack of stereospecific fragmentations is explained by loss of configurational integrity of the molecular ion before fragmentation. However, the mass spectral fragmentation of epimeric diamidocyclohexanes becomes very stereospecific by the introduction of a phenethyl group on one of the nitrogen atoms: this group avoids epimerization of the molecular ion prior to fragmentation. In the N-phenethyl derivatives 10, 11, 13 and 14 (Scheme 8) the typical fragmentations of the cis-isomer after loss of ·C₇H₇ from the molecular ion are the elimination of CH₂CO by formation of cyclic ions, and the loss of p-toluenesulfonic acid or benzoic acid, respectively, with subsequent elimination of CH₃CN (Scheme 9). In the trans-isomer the typical fragmentations are the loss of the side chain bearing a tertiary nitrogen atom, and the elimination of the tosyl or benzoyl radical, respectively, with subsequent loss of CH₃CONH₂ (Scheme 10).     

Diels–Alder modification of poly(ethylene terephthalate‐co‐anthracene‐2,6‐carboxylate) with N‐substituted maleimides

Dimethyl 2,6‐anthracene dicarboxylate is used as a comonomer in the synthesis of functional copolymers that are subject to modification with Diels–Alder reactions. The formation of poly(ethylene terephthalate‐co‐2,6‐anthracenate), containing less than 20 mol % of the anthracene‐2,6‐dicarboxylate structural units, provides materials that are tractable and soluble. The anthracene units of the copolymers undergo Diels–Alder reactions with N‐substituted maleimides. The grafting of N‐alkylmaleimides affords soluble, hydrophobic polymers, whereas grafting with maleimide‐terminated poly(ethylene glycol) affords hydrophilic polymers. Because this reaction proceeds below the melting point of the copolymers, the procedure can be applied to thin films, whereby the surface properties are modified. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3256–3263, 2002     

Oligomérisation anionique de l'ethylène. III. Application à la synthèse d'alcools à longue chaine

Living oligomers of ethylene obtained by n-BuLi complexed with TMEDA have been deactivated by ethylene oxide. The nuclear magnetic resonance study of the product obtained allowed us to follow the influence of TMEDA toward the functionalization. Three products have been characterized: By increasing the ratio [TMEDA]/[n-BuLi] one obtains a decrease of the functionalization reaction.     

Application of NMR spectroscopy of chiral association complexes. 8—Rotation about the C(sp2)–C(aryl) Bond in 2,6–disubstituted benzamides

The barrier to rotation about the C(sp²)? C(aryl) single bond in non-planar benzoyl compounds was investigated using N,N-dimethyl, N,N-tetramethylene and N,N-diisopropyl derivatives of 2,4,6-trimethylbenzamide and 2,6-dimethoxybenzamide and N,N-dimethyl derivatives of the corresponding thiobenzamides. Their ¹H and ¹³C NMR spectra were determined and assigned and the splittings in the ¹H spectra due to the addition of the optically active shift reagent (+)-Eu(hfbc)₃, are discussed. The free enthalpy of activation was calculated from the coalescence temperature of the ortho-methyl or -methoxyl signals and from a line-shape analysis. An exact equation for the determination of the rate constant at coalescence and a valid approximation which includes the line-width are presented. A distinct effect of the size of the N-substituent on the barrier to rotation in 2,6-dimethoxybenzamides was observed, while the π values for the 2,4,6-trimethylbenzamides studied are practically identical.     

Synthesis and crosslinking of poly (aryl ether)s containing 1,1-diphenylethylene moieties

Poly (aryl ether)s containing the diphenylethylene moiety, synthesized from 1,1-bis(4-fluo-rophenyl)ethylene or 1,1-bis(4-hydroxyphenyl)ethylene, are thermally crosslinkable. Char-acterization and crosslinking studies of these polymers were carried out by GPC, DSC, TGA, and NMR. The solvent resistance and T_g's of the resulting crosslinked networks increase after crosslinking. Thermogravimetric analysis shows that no significant mass loss accompanies the crosslinking reaction. © 1995 John Wiley & Sons, Inc.     

Donor property of cobalt(II) Schiff base complexes toward triphenyltin(IV)‐chloride: A kinetic study

In this study, some cobalt(II)tetraaza Schiff base complexes were used as donors in coordinating to triphenyltin(IV)chloride as acceptors; the kinetics and mechanism of the adduct formation were studied spectrophotometrically. Co(II)tetraaza Schiff base complexes used were [Co(amaen)][N,N′‐ethylene‐bis‐(o‐amino‐α‐methylbenzylideneiminato)cobalt(II)] ( 1 ), [Co(appn)] [N,N′‐1,2‐propylene‐bis‐(o‐amino‐α‐phenylbenzylideneiminato)cobalt(II)] ( 2 ), [Co(ampen)] [N,N′‐ethylene‐bis‐(o‐amino‐α‐phenylbenzylideneiminato)cobalt‐(II)] ( 3 ), [Co(cappn)][N,N′‐1,2‐proylene‐bis‐(5‐chloro‐o‐amino‐α‐phenylbenzylideneiminato)cobalt(II)] ( 4 ), and [Co(campen)] [N,N′‐ethylene‐bis‐(5‐chloro‐o‐amino‐α‐phenylbenzylid‐eneiminato)cobalt(II)] ( 5 ). The reactivity trend of the complexes in interaction with triphenyltin(IV)chloride was Co(amaen) > Co(appn) > Co(ampen) > Co(cappn) > Co(campen). The linear plots of k_obs versus the molar concentration of the triphenyltin(IV)chloride, a high span of the second‐order rate constant k₂ values, and large negative values of ΔS^≠ and low ΔH^≠ values suggest an associative (A) mechanism for the acceptor–donor adduct formation. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 635–640, 2012     

Die massenspektrometrische retro-Diels-Alder-Reaktion: 1, 2, 3, 4-Tetrahydroisochinolin und 1, 2, 3, 4-Tetrahydronaphthalin (Tetralin). 31. Mitteilung über massenspektrometrische Untersuchungen

The Mass Spectral retro-Diels-Alder-Reaction: 1,2,3,4-Tetrahydroisoquinoline and 1,2,3,4-Tetrahydronaphthaline (Tetraline) The retro-Diels-Alder reaction of 1,2,3,4-tetrahydroisoquinoline and of its N-acetyl derivative was confirmed on the basis of labelled derivatives (Scheme 2). Furthermore, the loss of ethylene was investigated with the 1,2,3,4-tetrahydronaphthalene- and 1,2,3,4-tetrahydronaphthalen-1-one-derivatives given in Schemes 4, 5 and 6. In the case of the 1,2,3,4-tetrahydronaphthalen-1-one-derivatives ethylene is lost via a retro-Diels-Alder reaction. The loss of ethylene from 1,2,3,4-tetrahydronaphthalene ( 1 ) and from its derivatives is a rather complex reaction (Scheme 8): 1/3 of ethylene is split off 1 ⁺ via a formal retro-Diels-Alder reaction, 2/3 are lost after a specific rearrangement. The ratio of these two fragmentation pathways depends very much on the substituents placed at the aliphatic and the aromatic rings, compare e.g. Table 4.     

Antimicrobial agents as photostabilizers for rigid poly(vinyl chloride)

Some amide derivatives of ethylene glycol‐bis(2‐aminoethylether)‐N,N,N^′,N^′‐tetraacetic acid (EGTA) have been prepared via their coupling with different aniline derivatives: amino, methyl, chloro, and hydroxy aniline. The EGTA amide derivatives were characterized, and their antimicrobial activities were evaluated. These antimicrobial agents have been investigated as photostabilizers for rigid poly(vinyl chloride) (PVC), suspension PVC, with a K value of 70. Their stabilizing efficiencies were evaluated by determining the percentage of weight loss, the intrinsic viscosities, as well as the amount of formed gel of the photodegraded PVC. The extent of discoloration and the change in the mechanical properties of the photodegraded polymer were also evaluated. The applied materials reduced the loss in weight that resulted from HCl evolution during photodegradation. Both viscosity and gel content measurements showed also a decrease in their values during the degradation process. The decrease in the percentage of gel formation upon applying the investigated photostabilizers reflects the lowering in extent of cross‐linking of the polymer, which implies preserving the mechanical properties of PVC. The extent of discoloration was also improved in the presence of the investigated compounds. The results have proved a greater stabilizing efficiencies of the antimicrobial EGTA amide derivatives than that of the phenyl salicylate ultraviolet (UV) absorber, which is commonly used as an industrial stabilizer. A radical mechanism was proposed to account for the stabilizing action of the investigated products. Copyright © 2011 John Wiley & Sons, Ltd.     

1,2‐Bis(8‐quinolyl­thio­methyl)­benzene

The title potentially tetradentate N,S,S,N‐donor ligand, C₂₆H₂₀N₂S₂, has been structurally characterized. The two S atoms adopt a trans conformation, lying above and below the benzene ring. The two quinoline rings are planar, with one parallel to the benzene ring and the other nearly perpendicular to it.