Atomic hydrogen, polymerization with

Structural characterisation of 58 and 59 have demonstrated that the PF, anion is located in the cleft between the two dialkylammonium cations forming hydrogen-bonds with the benzylic hydrogen atoms of one of the cations and with one of the hydrogen atoms of a hydroquinone ring. In contrast, a polymeric as-... 

A stable aluminum hydride, AlHj, has been known to exist since some time. It has been prepared by various techniques including the direct reaction of metallic A1 with atomic hydrogen by Siegel [105], AIH3 is soluble in ether when freshly synthesized but polymerizes while aged and forms insoluble precipitate whose structure depends on the degree of polymerization of -(AIH3)- monomer. 

Alkenes are known to form d - complexes with low valent transition metal ions (or atoms), thus stabilizing their low valent complexes (152). Complexes of this type are key intermediates in a variety of catalytic processes, e.g., hydrogenations, polymerizations,... 

Thallium(I) hydride has been identified spectroscopically in the products of an electric discharge in hydrogen at a thallium cathode, or from thallium and atomic hydrogen.343 An unstable polymeric solid has also been reported.344 The borohydride TIBH4 can be obtained by reacting Tl1 compounds with LiBHU, and T1A1H4 is formed similarly 344 the borohydride, which has an ionic lattice, can also be prepared from KBH4 and aqueous TlNOs-345... 

EtC=CSiMe3, MeC = CSiMe2-i-Pr, and MeC = CSiMe2-/-Bu all fail to polymerize with any of the Nb and Ta catalysts62. It will be reasonable to attribute this finding to the steric effect. MeC = CSiHMe2 does not polymerize with Nb or Ta catalysts, either 64). In this case it is presumed that the active hydrogen bonded to the silicon atom in the monomer reacts with the active species of polymerization to decompose it. 

In related findings, Jackson et al. (ref. 5), obtained similar IR spectra and a mass spectrum consistent with a linear hydrogenated polymer with a chain length of 20-30 carbon atoms. These authors analyzed the polymeric material extracted from a Ni/AhO catalysts, after they had been coked at 475°C by different aliphatic and aromaric hydrocarbons,... 

Abstraction of a hydrogen atom on the a-carbon or in the a.a. side chain of a protein leads to the formation of protein radicals. These may polymerize with other... 

The polymerization induces also a distortion of the Cl-octahedra packing. The deviation from an ideal chessboard-like arrangement can be approximated by a rotation of 30 about the layer normal. This rotation is much less important in the monomer form as can be observed on Figure 6. The displacement of the Cl-octahedra also affects the environment of the two ammonium groups (Figure 8). N(1) has four Cl-atoms within a radius of 3.4 A, whereas N(2) has five Cl-atoms within the same radius. N(1) is hydrogen bonded with two axial... 

One method we have developed for avoiding polymerization with the adsorbed water layer is to use a base catalyzed reaction in supercritical CO2 (SCF CO2). We have shown that SCF CO2 has the unique property of removing all adsorbed water from the silica surface. Once removed the amine base catalyses the reaction of the silane with the surface. As shown in Figure 1, the preadsorbed amine hydrogen bonds to the surface silanol and renders the Si-0 group of the silanol more nucleophilic for reaction with the silicon atom of the incoming chloro or alkoxysilane. Triethylamine is the preferred amine as it binds to all isolated silanols from SCF CO2 and is not removed with subsequent exposure to flowing SCF CO2 solvent. Furthermore a tertiary amine should be used as primary and secondary amines such as ammonia are known to react with CO2 to produce carbamates. " ... 

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