Tetrahydroborate reaction with alcohols

GLYCYL ALCOHOL (56-81-5) Combustible liquid (flash point 390°F/199°C). Violent reaction with strong oxidizers, acetic anhydride, calcium hypochloride, chlorine, chromic anhydride, chromium oxide, ethylene oxide, hydrogen peroxide, phosphorus triiodide, potassium permanganate, potassium peroxide, silver perchlorate, sodium hydride, sodium peroxide, sodium triiodide, sodium tetrahydroborate. Incompatible with strong acids, caustics, aliphatic amines, isocyanates, uranium fluoride. Able to polymerize above 293°F/145°C. 

SODIUM TETRAHYDROBORATE(l-) (16940-66-2) Combustible solid. Dust or powder forms explosive mixture with air autoignition above 550°F/288°C. Reacts with water, steam, moist air, alcohols, glycols, phenols, cresols, palladium dust, producing flammable hydrogen gas. Violent reaction with acids, forming diborane gas, with the possibility of explosion. Violent reaction with oxidizers, dimethyl formamide, aldehydes, ketones, metal powders, metal salts, sodium hydroxide. Polymerization may be caused by contact with bases, acrylonitrile, sodium borohydride. Forms explosive material that is ultra-sensitive to friction or shock, and moisture-sensitive with salts of ruthenium. Attacks metals. Corrodes glass slowly. 

WHITE PHOSPHORIC ACID (7664-38-2) A medium-strong acid. Violent reaction with strong bases. Violent reaction if water is added to concentrated acid. To dilute, always add acid to water heat will be generated. Reacts violently with solutions containing ammonia or bleach, azo compounds, epoxides, and other polymerizable compounds. Reacts, possibly violently, with amines, aldehydes, alkanolamines, alcohols, alkylene oxides, amides, ammonia, ammonium hydrox-ide, calcium oxide, cyanides, epichlorohydrin, esters, halogenated organics, isocyanates, ketones, oleum, organic anhydrides, sodium tetrahydroborate, sulfides. 

One of the reactions discussed in Volume 1, namely the reaction of sodium tetrahydroborate with alcohols (other than methanol), was suggested to involve the intermediate BH2 on the basis of the epr spectrum of an adduct with the spin trap nitrosodurene. The epr spectrum has been reassigned and attributed to the species DurN(0 )BHJNa, which is suggested to be formed from reaction of the spin trap with BHJ (or possibly from DurNO" + BH3). Thus the radical ion must be considered as an intermediate, although the previously suggested pathway may still be present as a minor component. 

Reaction of trialkoxyboranes with metal alcoholates, alcoholysis or hydride transfer reactions of tetrahydroborates with aldehydes or ketones all result in the formation of tetraalkoxobor-ates. Steric factors play an important role in these reactions. As a consequence, sec-alcohols react very slowly and tetra-r-alkoxoborates in general cannot be obtained by any of the reactions above. At elevated temperatures the tetraalkoxoborates revert to the trialkoxyborane and metal alkoxide.75 Thioalcoholysis of tetrahydroborates can also be effected but, in contrast to the situation in alcoholysis, the last hydrogen atom is more difficult to substitute, probably for steric reasons.119 Tetraalkoxoborates and tetramercaptoborates are readily hydrolyzed by water or moist air. 

Allylic alcohols have also been obtained in excellent (90%) yields by reduction of enones with diisopropoxytitanium(III) tetrahydroborate (equation 55)206. The reaction... 

Calcium bis[tetrahydroborate(l-)] may be prepared from sodium tetra-hydroborate( 1 -) and calcium dichloride by cation exchange11 in a suitable solvent such as dimethylformamide,12 an amine13,14 or an alcohol.13,14 A particularly good preparation of very pure Ca[BH4]2 involves the reaction of calcium dihydride with the triethylamine-borane adduct.15,16 This method may also be used for the preparation of other tetrahydroborates of alkali and alkaline earth metals. The triethylamine-borane adduct17 may be synthesized in a variety of ways, e.g., from triethylamine, sodium tetrahydro-borate(l —), and trichloroborane 18 from a trialkoxyborane, aluminum metal, and hydrogen in the presence of triethylamine 19 or by hydrogenation under pressure of a mixture of triethylborane and triethylamine.20 The triethylamine-borane adduct is a colorless liquid (mp — 2°). It is stable to air and moisture at room temperature and it is easily purified by vacuum distillation (bp 95-96°/12 torr). 

Caution. Calcium dihydride and calcium bis[tetrahydroborate( 1 —)] react vigorously with water, alcohols, and other compounds which contain acidic hydrogen atoms, sometimes with spontaneous ignition. The reaction should be carried out in an efficient hood and the reagents and products should be handled under an inert gas. 

The catalytic effect of several alcohols in the preparation of dichlorotetrakis(pyridine)rhodium(III) cation has long been known.1 In recent years, a variety of reducing agents, present in catalytic quantities, have been used in the preparation, of several rhodium(III) complexes.2 In the absence of catalysts, these reactions are often laborious, and/or incomplete, by comparison with the catalyzed reaction, for example, the preparation of pentaamminechlororhodium(III) chloride (Claus salt) by the method of Lebedinsky.3 Conversion of [Rh(NII3)[,CI]Cl2 to the pentaamminehydridorhodium(III) salt [Rh(NII3) I 1JW()4 by treatment with zinc and ammonia is rapid, and the reaction is relatively clean.4 The formation of hydrido species by tetrahydroborate treatment6 is not a satisfactory preparative procedure. 

Asymmetric reduction of ketones. This chiral surfactant catalyzes the reduction of ketones by NaBH in H20-l,2-dichloroethane. More interestingly, the reaction is stereoselective ( + )-alcohols are formed in excess, the optical yield depending on the concentration of the catalyst. L-N-Methyl-N-hexadecylephedrinium bromide was also used, but optical yields of alcohols were lower with this reagent. Presumably the alkylephedrinium tetrahydroborate is formed in the aqueous phase and passes into the organic phase, where reduction occurs with stereoselectivity. ... 

Properties Colorless liq. or rhombic crystals, odorless sol. in water, alcohol misc. with many org. soivs. m.w. 97.99 dens. 1.70 (20/4 C) vapor pressure 0.0285 mm (20 C) m.p. 42.4 C b.p. 158 C starts to dec. above 200 C forming polyphosphoric acids Toxicology ACGIH TLV/TWA1 mg/m STEL 3 mg/m LD50 (oral, rat) 1530 mg/kg, (skin, rabbit) 2740 mg/kg mod. toxic by skin contact human poison by ing. corrosive irritant to eyes, skin, mucous membranes systemic irritant by inh. common air contaminant TSCA listed Environmental Environmentally hazardous Precaution DOT Corrosive material strong acid mixts. with nitromethane are explosive incompat. with alkalis corrosive to many metals violent reaction possible with sodium tetrahydroborate Hazardous Decomp. Prods. Heated to decomp., emits toxic fumes of PO,... 

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