Metal hydroxides, reaction with acids

A base is any material that produces hydroxide ions when it is dissolved in water. The words alkaline, basic, and caustic are often used synonymously. Common bases include sodium hydroxide (lye), potassium hydroxide (potash lye), and calcium hydroxide (slaked lime). The concepts of strong versus weak bases, and concentrated versus dilute bases are exactly analogous to those for acids. Strong bases such as sodium hydroxide dissociate completely while weak bases such as the amines dissociate only partially. As with acids, bases can be either inorganic or organic. Typical reactions of bases include neutralization of acids, reaction with metals, and reaction with salts ... 

Although organosilanes appear to react slowly (if at all) with water alone, in the presence of acids or bases (e.g., alkali metal hydroxides), reactions to give a silanol and H2 are rapid, with bases being particularly powerful catalysts. The evolution of H2 in this type of reaction may be used as both a qualitative and a quantitative test for Si-H bonds, and the mechanism of the acid and the base hydrolysis has been discussed in detail (30,31). This hydrolytic method is not very common for the preparation of silanols that are to be isolated, because both acids and bases catalyze the condensation of silanols to siloxanes, and therefore, only compounds containing large substituents are conveniently made in this way. If an anhydrous alkali metal salt is used, a metal siloxide may be isolated and subsequently hydrolyzed to give the silanol [Eq. (10)] (32). 

The phase-transfer catalysed reaction of nickel tetracarbonyl with sodium hydroxide under carbon monoxide produces the nickel carbonyl dianions, Ni,(CO) 2- and Ni6(CO)162, which convert allyl chloride into a mixture of but-3-enoic and but-2-enoic acids [18]. However, in view of the high toxicity of the volatile nickel tetracarbonyl, the use of the nickel cyanide as a precursor for the carbonyl complexes is preferred. Pretreatment of the cyanide with carbon monoxide under basic conditions is thought to produce the tricarbonylnickel cyanide anion [19], as the active metal catalyst. Reaction with allyl halides, in a manner analogous to that outlined for the preparation of the arylacetic acids, produces the butenoic acids (Table 8.7). 

Barium hydroxide decomposes to barium oxide when heated to 800°C. Reaction with carbon dioxide gives barium carbonate. Its aqueous solution, being highly alkahne, undergoes neutrahzation reactions with acids. Thus, it forms barium sulfate and barium phosphate with sulfuric and phosphoric acids, respectively. Reaction with hydrogen sulfide produces barium sulfide. Precipitation of many insoluble, or less soluble barium salts, may result from double decomposition reaction when Ba(OH)2 aqueous solution is mixed with many solutions of other metal salts. 

Phenols can be converted into esters by reaction with acid chlorides or acid anhydrides and into ethers by reaction with alkyl halides in the presence of base (Following fig.). These reactions can be done under milder conditions than those used for alcohols due to the greater acidity of phenols. Thus phenols can be converted to phenoxide ions with sodium hydroxide rather than metallic sodium. 

If the metal hydroxide is precipitated first, the reactions with acid and base can be shown as... 

BORIC ACID (10043-35-3) BH3O3 Aqueous boric acid is a weak acid incompatible with alkali carbonates hydroxides strong reducing agents, including metal hydrides, nitrides, sulfides, and alkali metals. Violent reaction with potassium metal. Contact with acetic anhydride forms a heat-sensitive explosive. On small fires, use water fog. 

RUBIDIUM HYDROXIDE (1310-82-3) RbOH Extremely basic substance more basic than potassium hydroxide. Extremely hygroscopic. Violent, exothermic reaction with water. Violent reaction with acids, acrylonitrile, glycidol, nitrobenzene, TNT. Exothermic decomposition with maleic anhydride. Hydrolyzes angiotonin. Incompatible with organic anhydrides, acrylates, alcohols, aldehydes, alkylene oxides, substituted allyls, cellulose nitrate, cresols, caprolactam solution, epichlorohydrin, ethylene dichloride, isocyanates, ketones, glycols, nitrates, phenols, vinyl acetate. Increases the explosive sensitivity of nitromethane. Reacts with nitroalkanes, forming explosive products. Attacks glass, metals, plastics, and mbbers. 

ALLILE (CLORURO di) (Italian) (107-05-1) Forms explosive mixture with air (flash point -20°F/-29°C). Violent polymerization and explosion may occur from elevated temperatures, light, acid catalysts, ferric chloride, aluminum chloride, Lewis acids, or Ziegler catalysts, finely divided metals. Violent reaction with oxidizers, alkyl aluminum chlorides. Incompatible with strong acids, oleum, amines, aluminum chloride, boron trifluoride, chloro-sulfonic acid, ethylene diamine, ethyleneimine, ferric chloride, sodium hydroxide. Slow decomposition with moisture. Attacks some coatings, plastics, and rubber. Corrosive to steel. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

BOROHIDRURO SODICO (Spanish) (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. 

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