Polymerization potassium hydride

ET-IR spectroscopy was employed to investigate the structures of the 1 1 complexes between Li" and the guanidine-substituted azo compounds pyiidine-2-azo-p-phenyltetramethylguanidine and 4,4 -bis(tetramethylguanidine)azoben-zene. Both Li" complexes exist as dimers in acetonitrile solution.The structural chemistry of potassium N,N -di(tolyl)formamidinate complexes has been investigated in detail. These compounds were prepared by deprotonation of the parent Af,N -di(tolyl)formamidines with potassium hydride (Scheme 13). The resulting adducts with either THE or DME display one-dimensional polymeric solid-state structures that exhibit /r-fj fj -coordinated formamidinates. 

Potassium enolates of aldehydes, Enolates of aldehydes are somewhat difficult to generate because of competing polymerization by base. They have been obtained recently in high yield by use of potassium hydride in THF at 0° and successfully alkylated, sulfenylated with diphenyl disulfide, and converted into o-iodo aldehydes by iodine. The last two reactions have not been observed previously. Sulfenylation of aldehydes has previously used indirectly generated lithium enolates and a reactive sulfenyl chloride. All three reactions are useful, however, for aldehydes with only one a-proton. Otherwise yields of monosubstituted aldehydes are low and largely by-products are obtained. 

It was observed that ammonolysis of B(C2H,Si(R)H2)3 (Scheme 2, route A) requires basic catalysts such as n-butyl lithium. The reaction is performed in analogy to the potassium hydride-catalyzed cross-linking of cyclic silazanes described by Seyferth et al. [8]. Most probably, n-BuLi initially deprotonates the weak nucleophile ammonia with the formation of lithiiun amide and evaporation of n-butane. The stronger nucleophilic amide then replaces a silicon-bonded hydride, which subsequently deprotonates ammonia, leading to the evolution of molecular hydrogen. The silylamines that arise are not stable under the reaction conditions applied (refluxing solvent), and by fast condensation of ammonia the polymeric precursors form [6]. 

The first PFS-fr/ock-polymethacrylate copolymer was reported in 2002 28 The procedure involved a two-step anionic polymerization (Scheme 3.7). Hydroxy terminated polyferrocenylsi-lane (PFS-OH) was initially synthesized using r-butyldimethylsilyloxy-1-propyllithium as an initiator bearing a protected alcohol functionality. Once isolated, PFS-OH was deprotonated using potassium hydride to afford the alkoxy chain end that initiates dimethylaminoethyl methacrylate (DMAEMA) for anionic polymerization. The PFS- -PDMAEMA block copolymer was obtained in a high yield (Mn = 11,000 PDI =1.3) and with a low polyferrocenylsilane content (PFS PDMAEM A = 1 5). 

OXOLANE (109-99-9) Forms explosive mixture with air (flash point 6°F/— 14°C also listed at 1.4°F/—17°C cc). Unless inhibited, forms 2-tetrahydrofuryl hydroperoxide and then forms unstable and explosive polyalkylidene peroxide. Polymerization can occur in the presence of acids, bases (e.g., potassium hydroxide, sodium hydroxide), and certain salts. Peroxides can be removed by treatment with a slightly acidic solution of strong ferrous sulfate treated with sodium bisulfate. Violent reaction with strong oxidizers, bromine, oxygen, magnesium tetrahydroaluminate, metal halides, peroxyacetic acid, potassium hydride. Storage tanks and other equipment should be absolutely dry and free from air, ammonia. 

When compared to SiC, less work has been reported on the production of Si3N4 by the polymer pyrolysis route. Most efforts have focused on polymer precursors based on polysilazanes, a class of polymers having Si-N bonds in the main chain (58-61). The reactions to produce the Si-N bond in the chain backbone are based on the ammonolysis of methylchlorosilanes. A preceramic polymer can be prepared by the ammonolyis of methyldichlorosilane, followed by the polymerization of the silazane product catalyzed by potassium hydride (69) ... 

The regiochemistry of the reaction proved solvent dependent for the hydrosilylation of diphenylethene, and while preparations in benzene gave products deriving from 2,1-insertion of the alkene into the M-H o-bond, preparations in THF gave the opposite regioisomer proposed to derive from a similar 2,1-insertion into a M-Si o-bond. Potassium hydride is also an active catalyst for the hydrosilylation of 1,1-diphenylethylene in hydrocarbon solvents with reactions proceeding with anti-Markoviukov addition of the silane to the alkene, but is inactive or shows polymerization of the alkene for other substrates [116]. 

Kroll et al reported on the synthesis of a supported version of a chiral Schrock catalyst prepared by ROMP. For precipitation polymerization, they prepared a bis(norborn-2-ene)-substituted chiral phenoxide, which could be polymerized without any protection/deprotection steps using Ru(CF3COO)2(IMesH2) (=CH-2-(2-PrO)-C6H4). Reaction of the polymeric support with potassium hydride followed by addition of... 

Sulfur dioxide Halogens, metal oxides, polymeric tubing, potassium chlorate, sodium hydride... 

A polymer containing side-chain benzylphosphonium residues has been prepared and used in olefin synthesis. A suspension in THF was treated with base and benzaldehyde overnight and the polymeric phosphine oxide was then removed by filtration. The yields of stilbenes, 40% with potassium t-butoxide and 60% with sodium hydride, were not improved by using an excess of base or of aldehyde. 

Sulfides Sulfur Sulfur dioxide Sulfuric acid Sulfuryl dichloride Acids, powerful oxidizers, moisture Oxidizing materials, halogens Halogens, metal oxides, polymeric tubing, potassium chlorate, sodium hydride Chlorates, metals, HC1, organic materials, perchlorates, permanganates, water Alkalis, diethyl ether, dimethylsulfoxide, dinitrogen tetroxide, lead dioxide, phosphorus... 

Some strategies used for the preparation of support-bound thiols are listed in Table 8.1. Oxidative thiolation of lithiated polystyrene has been used to prepare polymeric thiophenol (Entry 1, Table 8.1). Polystyrene functionalized with 2-mercaptoethyl groups has been prepared by radical addition of thioacetic acid to cross-linked vinyl-polystyrene followed by hydrolysis of the intermediate thiol ester (Entry 2, Table 8.1). A more controllable introduction of thiol groups, suitable also for the selective transformation of support-bound substrates, is based on nucleophilic substitution with thiourea or potassium thioacetate. The resulting isothiouronium salts and thiol acetates can be saponified, preferably under reductive conditions, to yield thiols (Table 8.1). Thiol acetates have been saponified on insoluble supports with mercaptoethanol [1], propylamine [2], lithium aluminum hydride [3], sodium or lithium borohydride, alcoholates, or hydrochloric acid (Table 8.1). 

Reduction (lithium aluminium hydride/tetrahydrofuran) of the tetraester 34 to the tetraol 35, followed by chlorination (thionyl chloride), afforded 36 in good yield. This tetrachloride was then subjected to base-promoted P-elimination (potassium rerf-butoxide) giving the desired bisdiene 37 in quantitative yield without purification. The sensitivity of 37 toward both thermal and photochemical degradation and its propensity to polymerize necessitated its immediate use following its preparation. 

Rb2C2, Na, Na2C2, SnO, diaminolithiumacetylene carbide. Will react with water or steam to produce toxic and corrosive fumes. Incompatible with halogens or interhalogens, lithium nitrate, metal acetyUdes, metal oxides, metals, polymeric tubing, potassium chlorate, sodium hydride. 

It follows from this discussion that all solvents and monomers used must be carefully purified. Hydrocarbons should be stirred over sulphuric acid for many days and ethers refluxed over sodium—potassium alloy or sodium fluorenone before fractionation. Traces of unsaturated materials in aliphatic hydrocarbons can be removed by silica gel. After fractionation, a preliminary drying over calcium hydride can be followed by storage over sodium—potassium alloy for ethers, or a treatment with butyllithium or similar non-volatile reactive organometallic reagent for hydrocarbons. Monomers cannot be treated quite so drastically, but fractionation followed by a pre-polymerization in vacuum over butyl-... 

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