Co-condensates

The key initiation step in cationic polymerization of alkenes is the formation of a carbocationic intermediate, which can then interact with excess monomer to start propagation. We studied in some detail the initiation of cationic polymerization under superacidic, stable ion conditions. Carbocations also play a key role, as I found not only in the acid-catalyzed polymerization of alkenes but also in the polycondensation of arenes as well as in the ring opening polymerization of cyclic ethers, sulfides, and nitrogen compounds. Superacidic oxidative condensation of alkanes can even be achieved, including that of methane, as can the co-condensation of alkanes and alkenes. 

Nippon Shokubai and U.K. Seung are producing a fluorescent polymer claimed to be made from a co-condensation of ben2oguanamine and formaldehyde. Fine highly thermoset particles are manufactured in solution and later dried. It is useful in a wide range of appHcations, specifically plastics, and markets where bleed is a problem. 

In this case the Ar and/or Ar group(s) will contain an ether oxygen. As before if Ar = A then basically identical products may be made by the two polysulphonylation routes (see e.g. Figure 21.4). Where a diether and a disulphonyl chloride are co-condensed there may be some reaction at o- and m-positions in addition to the desired reaction at the para-position. It has been found that o- and m-linked polymers are more brittle, at least in the above example. It is of interest to note that self-condensation of the monosulphonyl chloride of diphenyl ether, on the other hand, can proceed so as to give a virtually all-para and hence tough material. Whilst the self-condensation polysulphonylation route has been used commercially it is understood not to be in current commercial use. 

By the mid-1990s world production of aminoplastics was estimated at about 6 000 000 t.p.a. of which more than 5 000 000 t.p.a. were urea-formaldehyde resins. The bulk of the rest were melamine-formaldehyde. Such bald statistics, however, disguise the fact that a considerable amount of aminoplastics used are actually co-condensates of urea, melamine and formaldehyde. 

Modification of urea-formaldehyde resins with other reagents gives rise to a number of useful materials. For example, co-condensation of urea-formaldehyde and a monohydric alcohol in the presence of small quantities of an acidic catalyst will involve simultaneous etherification and resinification. n-Propanol, n-butanol and isobutanol are commonly used for this purpose. As an example n-butanol will react with the methylol urea as shown in Figure 24.4. 

Co-condensation of melamine, urea and formaldehyde in a multistep reaction [36-40]. A comprehensive study of various reaction types has been done by Mercer and Pizzi [41]. They especially compare the sequence of the additions of melamine and urea, respectively. 

PMF-resins usually contain little or no urea. The analysis of the molecular structure of these resins has shown that there is no co-condensation between the phenol and the melamine, but that there are two distinct networks [52-55]. The... 

During the hardening of PMF-resins no co-condensation occurs in the hardened state two independent interpenetrating networks exist [58]. Indications for a co-condensation via methylene bridges between the phenolic nucleus and the amido group of the melamine had been found by H-NMR only in model reactions between phenolmethylols and melamine. 

The urea usually is added to the finished PF-resin and causes a distinct decrease of the viscosity due to disruption of hydrogen bonds [95] and due to dilution effects. There is obviously no co-condensation of this post-added urea with the phenolic resin. Urea only reacts with the free formaldehyde of the resin forming methylols, which, however, do not react further due to the high pH [19]. Only at the higher temperatures of the hot-press does some phenol-urea co-condensation occur [93,94,96]. 

A real co-condensation between phenol and urea can be performed by two ways (I) reaction of methylol phenols with urea [98-101] (2) acidic reaction of UFC (urea-formaldehyde concentrate) with phenol followed by an alkaline reaction [102,103]. 

Alkaline co-condensation to yield commercial resins and the products of reaction obtained thereof [93,94] as well as the kinetics of the co-condensation of mono methylol phenols and urea [104,105] have also been reported [17]. Model reactions in order to prove an urea-phenol-formaldehyde co-condensation (reaction of urea with methylolphenols) are described by Tomita and Hse [98,102, 106] and by Pizzi et al. [93,104] (Fig. 1). 

Organic substances react vigorously, often enflaming. Co-condensation of FBr02 with the Lewis acid AsFs produced [Br02] [AsF6] . Vibrational spectra establish the expected nonlinear structure of the cation (3 bands active in both Raman and infrared). FBr02 can also react as a fluoride ion acceptor (from KF). 

A model similar to that of the iron complex 31 was proposed for the cobalt species synthesized as a result of co-condensation of cobalt vapors with pyrrole in vacuum. A frozen matrix formed is subsequently warmed to room temperature (89JA3881). An oligomer or a polymer results, in which a- and ir-donor functions are realized simultaneously. The model proposed differs from that for the iron pyrrolyl complex by inclusion of the Co—Co bonds to attain the 18-electron configuration. 

Co-condensation reaction of the vapors of l,3-di-rcrt-butylimidazol-2-ylidene and nickel, palladium, or platinum gives the coordinatively unsaturated 14-electron sandwiches [L M] (M=Ni, Pd, Pt) of the carbene type (990M3228). Palladium(O) carbene complexes can also be prepared by the direct interaction of l,3-R2-imidazol-2-ylidenes (R=/-Pr, r-Bu, Cy, Mes) (L) with the palladium(O) compound [Pd(P(o-Tol)3)2] (OOJOM(595)186), and the product at the first stage is [(L)PdP(o-Tol)3l, and then in excess free carbene [PdL ]. 

The metal-vapor synthesis, involving co-condensation of nickel vapors, r-BuC = P, and 1,2,4-triphospholyl system leads to the mixed-ligand species 178 (94AGE2330). 

Co-condensation of Hf and Zr atoms from an electron-gun evaporation device, with P(Me)3 and arenes at 77K gave good yields of the species [M(arene)2P(Me3)]. Metal vapor synthesis led to Fe(i7 -arene)L2 and Fe(i7 -arene)-(i7 -diene), where L is a phosphorus ligand. In addition, complexes of stoichiometry Fe(T) -diene)L3 (where L is again a... 

Jacob s group reported a protocol that used mild H2O2 oxidations and MPTMS for three approaches, namely, grafted, coated, and co-condensed MCM-41 and HMS materials [58] (Figure 6.1a). The propyl spacer was stable to the oxidation conditions while sulfonic groups were generated as evidenced by NMR spectra. These materials... 

Finally, it should be mentioned that the unstable species may be generated in a matrix by co-condensation of metal atoms evaporated from the effusion cells and stable molecules diluted with an excess of inert gas. Equation (3) represents an example. 

The co-condensation at low temperature of a metal vapor (commonly produced by resistance or electron-beam heating of metals) with a vapor of weakly stabilizing organic ligands (such as -pentane, toluene, tetrahydrofu-ran, acetone, or acetonitrile), using commercially available reactors, affords solid matrices, where reactions between the ligand molecules and metal atoms can take place (Scheme 1(A) Figure 1) [5]. 

Figure 1. Condensation of solvent vapor (A) and co-condensation of metal vapor with solvent vapor (B).

The chemo- and regioselectivities of hydroformylation reactions of open chain, conjugated dienes using the usual catalyst are, in most cases, rather low [36]. The rhodium/ mesitylene co-condensate (catalyst A), in the presence of bis(diphenylphosphino)ethane, DPPE, catalyses the hydroformylation of 1,3-butadiene, isoprene, and E,Z)-, 3-pentadiene to the corresponding p,y-unsaturated monoaldehydes, with unusually high chemo- and regioselectivities (Scheme 17). 

Table 5. Hydroformylation of open-chain conjugated dienes by rhodium/mesitylene co-condensate, catalyst A . Substrate...

In a typical run, bis(l,2-diphenylphosphino)ethane (DPPE) (0.022 g, 0.05 mmol) and 1,3 diene (32.5 mmol) are added to a portion of the co-condensate, containing 5.2 mg of rhodium (0.05 mg. atom) in 10 ml of mesitylene. The solution is introduced by suction into an evacuated, 80 ml stainless steel autoclave. Carbon monoxide is introduced to the desired pressure and the autoclave is rocked and heated at 80 °C. Hydrogen is rapidly charged to give 1 1 gas composition. When the pressure reaches the theoretical value corresponding to the desired conversion, the autoclave is cooled, depressurised, and the reaction mixture analyzed by GLC. The crude product is distilled. The aldehydes are obtained as pure samples by preparative GLC and characterized by H NMR spectroscopy and GC-MS analysis. 

Anchored amine materials can be prepared through a number of synthetic methodologies. Because of the potential importance of these materials to organic synthesis, a ninhydrin assay was developed as a rapid laboratory determination of available surface amines. The assay agreed well with expected values for aminopropyltriethoxysilane grafted onto commercial silica. The assay also distinguished between reactive amines and protonated or poisoned surface amines on co-condensed SBA-15 materials. 

Other alkylgold(III) compounds are [Au2(/r-X)2(CF3)4] (X = Br, I) synthesized by co-condensation of gold with CF3Br and CF3I, respectively, and may be sublimed at room temperature.1654 Trifluoromethylated compounds are potentially useful precursors for CVD studies as they are expected to show enhanced volatility.1655 m-[Au(CF3)2I(PMc3)] is formed in quantitative yield by oxidative addition of trifluoromethyl iodide to [Au(CF3)(PMe3)], the reaction is proposed to proceed via radical intermediates.1524,1656... 

Interest in the interaction of water and nitric acid has arisen from several considerations involving such widely diverse problems as determining nitric acid uptake by water droplets and ice particles, to questions concerning the co-condensation of water and nitric acid to form polar stratospheric clouds146 and related ones about nitric acid incorporation in protonated water clusters existing in the upper atmosphere. Crutzen and Arnold suggested147 that,... 

The aluminium-solvent slurry produced by metal atom/solvent co-condensation at — 196°C is so reactive that oxygen is abstracted from the solvent ether as the mixture is allowed to melt. Hydrocarbon solvents are more suitable (but halocarbon solvents would react explosively). 

A polyether-alcohol, prepared by co-condensation of ethylene oxide and propylene oxide with a polyhydric alcohol, was stored at above 100°C and exposed to air via a vent line. After 10-15 h, violent decomposition occurred, rupturing the vessel. It was subsequently found that exothermic oxidation of the product occurred above 100°C, and that at 300°C a rapid exothermic reaction set in, accompanied by vigorous gas evolution. 

The compound, prepared by by co-condensation of diethyl sulfite (3.5 mmol) and chlorine fluoride (10 mmol) at —196°C, followed by slow warming to —78, then —20°, is unstable. Trap-to-trap distillation must be effected with great care, as violent explosions occurred (even on this small scale) when cryogenic cooling was removed from the traps. Scaling up is not recommended. 

During the preparation of the hexamethoxides of rhenium, molybdenum and tungsten by co-condensation with excess tetramethoxysilane on a cold surface, simultaneous co-condensation is necessary to avoid the danger of explosion present when sequential condensation of the reactants is employed. In the latter case, the high concentrations of hexafluoride at the interface leads to violent reaction with the silane. 

Some of the carbonyls with a high degree of coordinative unsaturation were produced by co-condensation of metal atoms and CO rather than photolytically (13). 

The general technique of the metal vapor experiments described below was to co-condense the vapors of the transition metal with those of the chosen hydrocarbon or hydrocarbon mixtures. In this paper we briefly outline the technique of metal atom synthesis and then show how it can be applied to alkane activation reactions. 

Introduction. In a typical experiment, the metal vapor is co-condensed at a liquid nitrogen-cooled surface with the ligand substrate vapor. Upon... 

Skell (.17.) found that co-condensation of zirconium atoms with neopentane gave a residue which upon... 

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