Amine monomeric

Diborane [19287-45-7] the first hydroborating agent studied, reacts sluggishly with olefins in the gas phase (14,15). In the presence of weak Lewis bases, eg, ethers and sulfides, it undergoes rapid reaction at room temperature or even below 0°C (16—18). The catalytic effect of these compounds on the hydroboration reaction is attributed to the formation of monomeric borane complexes from the borane dimer, eg, borane-tetrahydrofuran [14044-65-6] (1) or borane—dimethyl sulfide [13292-87-0] (2) (19—21). Stronger complexes formed by amines react with olefins at elevated temperatures (22—24). 

Polycarbonates are prepared commercially by two processes Schotten-Baumaim reaction of phosgene (qv) and an aromatic diol in an amine-cataly2ed interfacial condensation reaction or via base-cataly2ed transesterification of a bisphenol with a monomeric carbonate. Important products are also based on polycarbonate in blends with other materials, copolymers, branched resins, flame-retardant compositions, foams (qv), and other materials (see Flame retardants). Polycarbonate is produced globally by several companies. Total manufacture is over 1 million tons aimuaHy. Polycarbonate is also the object of academic research studies, owing to its widespread utiUty and unusual properties. Interest in polycarbonates has steadily increased since 1984. Over 4500 pubflcations and over 9000 patents have appeared on polycarbonate. Japan has issued 5654 polycarbonate patents since 1984 Europe, 1348 United States, 777 Germany, 623 France, 30 and other countries, 231. 

It melts at 39°C and may be purified by vacuum sublimation. The Hquid boils at 233°C to give a monomeric vapor in which the Ti—Br distance is 231 pm. Titanium tetrabromide is soluble in dry chloroform, carbon tetrachloride, ether, and alcohol. Like titanium tetrachloride, TiBr forms a range of adducts with molecules such as ammonia, amines, nitrogen heterocycles, esters, and ethers. 

Similar interchange processes may occur in other condensation polymers under suitable conditions. There is ample evidence in the literature on polyamides, and on monomeric amides as well, for the occurrence of the amine-amide interchange reaction (II)... 

The commercial evolution of hindered amine stabilisers is best illustrated by the sequence of the monomeric Tinuvin 770, oligomeric Tinuvin 622, Chimassorb 944 and Chimassorb 119, and most recently Chimassorb 2020 (Figure 3.25) with increased control on volatility, migration, extractability and co-additive interactions [597]. The hindered amine thermal stabilisers Chimassorb 944 and Chimassorb 119, outperform Cyasorb UV3346 as to extraction resistance [565]. 

Zinc carbamate complexes are well known, and the structural types and stabilities can be compared with thiocarbamates and dithiocarbamates which are discussed in Sections 6.8.11.1.3 and 6.8.7.1.4482 Carbamates of zinc can be formed from the reaction of carbon dioxide with alkylzinc alkyl amides and further reaction with alkylzinc can give a distorted cubane structure.483 The tetrameric diethylcarbamate species initially formed can also be used to produce monomeric or dimeric carbamate structures in reaction with amines tetramethylethylenediamine forms a monomer [(Me2NCH2)2Zn(02CN(C2H5)2)2] with an octahedral zinc center and pyridine forms a dimer[CsH5NZn2Me(02CN(C2H5)2)3] with tetrahedral zinc centers.484... 

Polymeric or monomeric complexes are formed in the reaction between zinc halides and dimethyl(aminomethyl)phosphine oxide dependent on the ratio of reactants. The ligand can bind as bidentate to one metal center or bridge two metal centers through the amine N and phosphine oxide O atoms.851... 

The extent to which 151 phosphorylates the aromatic amine in the phenyl ring is highly dependent upon the solvent. For instance, aromatic substitution of N-methylaniline is largely suppressed in the presence of dioxane or acetonitrile while pho.sphoramidate formation shows a pronounced concomitant increase. The presence of a fourfold excess (v/v) or pyridine, acetonitrile, dioxane, or 1,2-di-methoxyethane likewise suppresses aromatic substitution of N,N-diethylaniline below the detection limit. It appears reasonable to assume that 151 forms complexes of type 173 and 174 with these solvents — resembling the stable dioxane-S03 adduct 175 — which in turn represent phosphorylating reagents. They are, however, weaker than monomeric metaphosphate 151 and can only react with strong nucleophiles. 

Full details on the phosphorylation of water and alcohols by 4-nitrophenyl dihydrogen phosphate and the NfC H ) - and N(CH3) -salts of its mono- and dianion have been published 146>. Phosphoryl group transfer from the monoanion and dianion is thought to proceed via the monomeric POf ion. Addition of the sterically unhindered amine quinuclidine to an acetonitrile solution containing the phosphate monoanion and tert-butanol produces t-butyl phosphate at a faster rate than does the addition of the more hindered diisopropylethylamine. This nucleophilic catalysis of the phosphorylation reaction is also explained by the intermediacy of the POf ion. 

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