Vinylic Molecules Research Articles

Carbon–Carbon Bond Coupling of Vinyl Molecules with an Allenyl Ligand at a Diruthenium Complex

The room-temperature reactions of the diruthenium μ-allenyl complex [Ru2Cp2(CO)2(NCMe){μ-η1:η2-CH═C═CMe2}]BF4, 3-NCMe, with a series of alkenes, RCH═CH2, afforded the complexes [Ru2Cp2(CO)2{μ-η3:η2-CH(R)CHC(Me)C(Me)CH2}]BF4 (R═Ph, 4; 4-C6H4Me, 5; Me, 6; nBu, 7; CO2Me, 8; and H, 9), containing an uncommon pentacarbon alkenyl-allyl ligand. Cross experiments with deuterated reagents, i.e., [Ru2Cp2(CO)2(NCMe){μ-η1:η2-CD═C═CMe2}]BF4 (3b-NCMe) and CD2═CD(C6H5) (styrene-d3), revealed that the formation of 4–9 is initiated by an attack of the alkene to the central carbon of the allenyl moiety, triggering two distinct C–H activation processes. Compounds 4–9 were characterized by analytical and spectroscopic methods and by single-crystal X-ray diffraction in the cases of 4, 7, and 8. Reported here is the clean coupling on a metallic scaffold between two C2 and C3 functions invoked in Fischer–Tropsch mechanistic models.

Functional Thin Films Resulting from Parylene–Vinyl Copolymerization

Quantum and kinetic studies of novel materials based on parylene polymers and variously substituted vinyl molecules are presented and discussed. It is demonstrated that the thin films which are the products of the copolymerization reactions can be prepared (i) within the parylene CVD process on active vinyl substrates or (ii) employing the same process but involving an additional source of vinyl molecules transported to the reaction chamber. Both methods lead to differently functionalized microstructures, primarily dominated by the parylene units, while the vinyl molecules appear relatively seldom (depending on the nature of the substituents used). The copolymerization is shown to be independent of penultimate monomers in linear chains and to undergo composition drift within certain scope. Namely, it is found that even a small amount of p-xylylene monomers in feed leads to the formation of long blocks of pure parylene while the substituted vinyl molecules are expected to appear occasionally in chains. Fin...

Structure of associates of vinyl molecules and maleic anhydride in CCl4 solution

The self-association of styrene, acrylonitrile, methylmethacrylate, N-vinylpyrrolidone, and maleic anhydride molecules is considered in dependence on the nature of the monomer, i.e., on the conjugation between functional groups. The AM1, Hartree-Fock (RHF), and density functional theory (DFT) methods of calculation are used in our investigations. Charge distributions on the atoms of interacting groups and contributions from overlapping molecular orbitals to the energy of formation of self-associates are found. The calculated parameters are compared with experimental data on absorption band shifts in IR spectra and on chemical shifts ΔH and ΔC for the hydrogen and carbon atoms of =CH, =CH2, C=O groups of bound molecules in 1H and 13C NMR spectra. The formation of π-H, CH…O, and CH…N bonds is proved. Analysis of CCl4/monomer dependences shows that dimers are present in dilute solutions, while the presence of trimers in concentrated solutions cannot be excluded. Self-association constants are determined along with the degree of self-association, which lies within the range of 40–60% for 50 mol% of a monomer in solution.

The electronic structure of p-xylylene and its reactivity with vinyl molecules

The electronic states of p-xylylene molecule were described at the multi-configurational CASSCF/MRMP2 level of theory. The closed-shell singlet state representing the quinoidal p-xylylene molecule was predicted to be the ground electronic state whereas the triplet (benzoidal) and the singlet open-shell states were found to be much higher in energy (by 159 and 423 kJ/mol, respectively, as found at the CASSCF(8,8)/6-31+G(d) level). The reactions of p-xylylene with variously substituted vinyl molecules (i.e., CH 2 CH 2, CH 2 CHCl, CH 2 CHCN, CH 2 CHNO 2, CH 2 CHCF 3, CH 2 CHC 6H 5, CH 2 CHCOOC 6F 5, and CH 2 C(CN) 2) were investigated with the DFT (using the B3LYP and MPW1 K functionals) and MP2 methods using the 6-31++G(d,p) basis set and the activation barriers in the 33–113 kJ/mol range were predicted. Since some of the activation barriers found are smaller than the energy required to initialize the parylene polymerization (63 kJ/mol) the reactions of the p-xylylene with vinyl molecules is postulated to be competitive with the polymerization process.

Influence of substituents in vinyl groups on reactivity of parylene during polymerization process

The MCSCF calculations indicate that both triplet and singlet state of biradical di- para-xylylene can exist during polymerization of parylene in gas phase and both can potentially react with vinyl molecules. The singlet-state open-shell dimer turned out to exhibit multiconfigurational character. In the case of triplet state of the dimer two mechanisms of the reactions with various species containing vinyl groups have been examined at the B3LYP/6-31G level. The kinetic and thermodynamical barriers have been estimated for the reaction path involving the π-bond cleavage as well as for the route describing the hydrogen atom transfer. It was found that the overall reactions are thermodynamically favorable, whereas appropriate kinetic barriers for certain derivatives are very small (close to 0 kcal/mol) which in turn makes allowances for easy reactivity under accessible conditions. The calculated mechanisms indicate the influence of substituents in vinyl groups for reactivity of parylene during LPCVD process.

Alkenyl‐functionalized precursors for renewable hydrogels design

AbstractA library of crosslinking chemistries for the hydrogel synthesis based on the hemicellulose acetylated galactoglucomannan (AcGGM) has been developed, demonstrated, and evaluated. A three‐step route was elaborated including (1) the carbonyldiimidazole activation of primary hydroxylated vinylic molecules such as acrylates, vinyl alcohols, and vinyl ethers, (2) the covalent coupling of the alkenyl precursors to the polysaccharide backbone hydroxyls, and (3) the radical crosslinking of pendant vinyl functionalities affording a hydrophilic network. Crosslinking strategies explored include redox initiation and photo initiation, with an effort to adapt the suggested synthesis routes to benign conditions. The different functionalization strategies were shown to influence the resulting gel's properties. Varying the crosslinking media was found to be a strong tool to tune the properties of the gels. Modifications were in all cases verified by means of NMR and FTIR, and the gels were characterized with respect to swelling capacity and rheological parameters. It was shown that by adjusting the synthesis parameters, the resulting properties of the AcGGM gels could be custom‐made for a given performance. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3595–3606, 2009

Free radical polymerization with catalytic chain transfer: Using NMR to probe the strength of the cobalt–carbon bond in small molecule model reactions

AbstractThis work examines cobalt–carbon bond formation between the cobalt (II) macrocycle, (tetrakis(p‐methoxyphenyl)porphyrinato)cobalt (II), (TAP)Co, and a variety of radicals derived from vinyl compounds to facilitate a better understanding of the various factors affecting the cobalt–carbon bond strength in catalytic chain transfer polymerization. The reaction of (TAP)Co with the following vinylic molecules was studied: methacrylonitrile, cyclohexene, methyl methacrylate, styrene, methyl acrylate, vinyl acetate, vinyl benzoate, methyl crotonate, cis‐2‐pentenenitrile, and ethyl α‐hydroxymethacrylate. Different concentrations of each vinylic compound were added to (TAP)Co and 2,2′‐azobis(isobutyronitrile) in CDCl3 at 60 °C. The ratio of Co(III) to Co(II) and the nature of the radical bound to the cobalt macrocycle were determined via nuclear magnetic resonance measurements. Several factors are shown to affect the reaction of the radical and the cobalt (II) species (and hence the strength of the cobalt–carbon bond in the resulting compound). These factors are as follows: the number of pathways by which a radical may be derived from the vinyl compound; the variety of radicals that can be produced from the vinylic molecule; the stability of the radical(s) generated; and the relative propagation rate of the vinyl compound. A discussion on the relevance of this study to the behavior of different monomers in catalytic chain transfer reactions is included. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6171–6189, 2006

Study of the simultaneous electro-initiated anionic polymerization of vinylic molecules

In this work, we study the simultaneous polymerization of vinylic monomers initiated via the electrografting of suited precursors on metallic substrates. The outcome of this work is to be able to obtain, in one step, new modified substrates with various surface properties brought by the combination of both polymers. For that purpose, two different vinylic monomers were simultaneously submitted to electro-initiated grafting on metallic electrodes, which mechanism is now well documented. We studied several couples of monomers chosen among four molecules: acrylonitrile, methacrylonitrile, methyl methacrylate and glycidyl methacrylate. In order to achieve simultaneous electrografting of both monomers, it is necessary to take into account the following molecular parameters: (i) the respective reduction potentials of the two monomers, (ii) the relative nucleophilicity of the anions propagating the reaction, (iii) the molecular structure of the neutral molecules. In this work, we discuss the influence of all of these parameters thanks to cyclic voltammetry, chronoamperometry, infrared measurements and quantum chemistry computational calculations. Association of experimental and computational results leads to a better understanding of the process.

Intracluster electron transfer from a metal atom/cluster followed by anionic oligomerization of vinyl molecules

Intracluster electron transfer and oligomerization reaction were investigated by mass spectrometry of clusters of alkali metal atom (M) with acrylonitrile (AN; CH2=CHCN). In the photoionization mass spectra of M(AN)n, magic numbers were clearly observed at n = 3k (k = 1-4 for M = Na and K, k = 1 for M = Li). The results of photodissociation of neutral K(AN)n indicate that the n = 3 cluster has an anomalous stability relative to other sizes of clusters. The C=C bond in vinyl molecules is also found to be necessary to form the magic numbers by measuring the photoionization mass spectrum of K atom with propionitrile. These results strongly support the intracluster anionic oligomerization reaction initiated by electron transfer from the alkali atom. The quantum chemical calculations have revealed that the evaporation induced by excess energy generated by intracluster oligomerization is important to form the magic numbers in the present clusters.

Coupled chemistry revisited in the tentative cathodic electropolymerization of 2-butenenitrile

2-Methyl 2-propenenitrile (methacrylonitrile) and 2-butenenitrile (crotononitrile) are vinylic molecules which differ only in the position of a methyl group on the double bond. By combining gas chromatography coupled to chemical ionization mass spectrometry, steric exclusion chromatography and infra-red spectroscopy, along with quantum chemistry based calculations of standard Gibbs energy changes of plausible reactions, we demonstrate that the protons of the methyl group in crotononitrile are acidic in anhydrous acetonitrile, while those of methacrylonitrile are not. In this way, we bring a definite explanation to the fact that methacrylonitrile forms homogeneous films of polymethacrylonitrile (PMAN) on a working electrode subjected to a cathodic polarization in anhydrous acetonitrile, while crotononitrile does not.

An ab initio study of the electric field influence on the electron distribution of HCN, CH 3CN, CH 2CHCN, and CH 2C(CN) 2

To assess the role of the monomer polarizability in the course of electropolymerization reactions, an ab initio study of the influence of an intense electric field (10 9 V m −1) on the dipole moment and total atomic charges of HCN, CH 3CN, CH 2CHCN, CH 2C(CN) 2 and CH 2CHCCH has been developed at the STO-3G, 3-21G and 6-31 G* levels. The calculated polarizabilities of the three vinylic molecules are high, the induced dipole moment being 10% of the permanent one. The decrease of the atomic charge observed on the vinylic CH 2 group is insufficient for it to be solely responsible for the increase in its electrophilic character.