Metal carbonates, reaction with acids

Metal carbonates react with acids in exchange reactions ... 

Although Pd-catalyzed intramolecular hydroamination reactions of alkynes have been known for ten years, analogous transformations of unactivated alkenes have only recently been developed [33]. Key to the success of these studies was the use of a cationic palladium complex bearing a pyridine-derived P-N-P pincer ligand (29). For example, treatment of 26 with catalytic amounts of 29, AgB F4, and Cu(OTf)2 led to the formation of pyrrolidine 27 in 88% yield with 4 1 dr (Eq. (1.13)). Detailed mechamstic studies have indicated these transformations proceed via alkene coordination to the metal complex followed by outer-sphere aminopaUadation to provide 28. Protonolysis ofthe metal-carbon bond with acid generated in situ leads to formation of the product with regeneration of the active catalyst. 

Chemical ingenuity in using the properties of the elements and their compounds has allowed analyses to be carried out by processes analogous to the generation of hydrides. Osmium tetroxide is very volatile and can be formed easily by oxidation of osmium compounds. Some metals form volatile acetylacetonates (acac), such as iron, zinc, cobalt, chromium, and manganese (Figure 15.4). Iodides can be oxidized easily to iodine (another volatile element in itself), and carbonates or bicarbonates can be examined as COj after reaction with acid. 

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). 

Ammonium carbonate slowly decomposes on exposure to air, or rapidly breaks down on heating to ammonia, CO2, and water bberates CO2 on treatment with dilute mineral acids. It reacts with metals forming their carbonates. Reaction with hydriodic acid produces ammonium iodide and forms ammonium oxalate with oxabc acid. 

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. 

The chemical reactivities of such titanium homoenolates are similar to those of ordinary titanium alkyls (Scheme 2). Oxidation of the metal-carbon bond with bromine or oxygen occurs readily. Transmetalations with other metal halides such as SnCl4, SbClj, TeCl4, and NbCls proceed cleanly. Reaction with benzaldehyde gives a 4-chloroester as the result of carbon-carbon bond formation followed by chlorination [9]. Acetone forms an addition complex. No reaction takes place with acid chloride and tm-alkyl chlorides. 

Most coordination catalysts have been reported to be formed in binary or ternary component systems consisting of an alkylmetal compound and a protic compound. Catalysts formed in such systems contain associated multinuclear species with a metal (Mt)-heteroatom (X) active bond ( >Mt X Mt—X > or — Mt—X—Mt—X— Mt = Al, Zn, Cd and X = 0, S, N most frequently) or non-associated mononuclear species with an Mt X active bond (Mt = Al, Zn and X = C1, O, S most frequently). Metal alkyls, such as triethylaluminium, diethylzinc and diethylcadmium, without pretreatment with protic compounds, have also been reported as coordination polymerisation catalysts. In such a case, the metal heteroatom bond active in the propagation step is formed by the reaction of the metal-carbon bond with the coordinating monomer. Some coordination catalysts, such as those with metal alkoxide or phenoxide moieties, can be prepared in other ways, without using metal alkyls. There are also catalysts consisting of a metal alkoxide or related compound and a Lewis acid [1]. 

Metal oxide species with acid or basic properties as efficient catalysts for alkylation and related reactions have been discussed in Section 5.2. An alternative approach is based on reactions of covalent metal-to-carbon (M-C) bonds. Transition metals are well-suited for this task, as they form directional bonds using hybrid orbitals, and undergo low-energy electron promotion and transfer processes. There are now many industrial processes involving transition metal-catalyzed carbon-carbon bond formation (for example, carbonylation, metathesis, and polymerization reactions, see Chapters 4, 6 and 7, respectively). In sections 5.3-5.4 we deal with other C-C bond forming reactions that can lead to fine chemicals (see Chapter 1). 

Bulk aluminum may undergo the following dangerous interactions exothermic reaction with butanol, methanol, 2-propanol, or other alcohols, sodium hydroxide to release explosive hydrogen gas. Reaction with diborane forms pyrophoric product. Ignition on contact with niobium oxide + sulfur. Explosive reaction with molten metal oxides, oxosalts (nitrates, sulfates), sulfides, and sodium carbonate. Reaction with arsenic trioxide + sodium arsenate + sodium hydroxide produces the toxic arsine gas. Violent reaction with chlorine trifluoride, Incandescent reaction with formic acid. Potentially violent alloy formation with palladium, platinum at mp of Al, 600°C. Vigorous dissolution reaction in... 

Monoethanolamine contains both a hydroxy group and a primary amine group and will thus rmdergo reactions characteristic of both alcohols and amines. Ethanolamines will react with acids to form salts and esters. Discoloration and precipitation will take place in the presence of salts of heavy metals. Monoethanolamine reacts with acids, acid anhydtides, acid chlorides, and esters to form amide derivatives, and with propylene carbonate or other cyclic carbonates to give the corresponding carbonates. 

The indium-mediated Barbier reaction has certainly become one of the most popular reactions for creating a carbon-carbon bond under aqueous conditions and has led to spectacular developments in recent years. Compared to other metals, indium is resistant to oxidation, hydrolysis, and has a very low first ionization potential (5.79 eV, in contrast to the second one which is quite normal) which confers on it a remarkable reactivity in Barbier-type reactions. In 1991, Li and co-workers reported the first allylation of aldehydes and ketones mediated by indium in water without any additives or special activation [133]. In particular, the use of indium allowed reactions with acid-sensitive compounds [134] or the preparation of complex carbohydrates such as deaminated... 

Metal chlorides can be prepared in a number of ways (a) direct combination of metal and molecular chlorine, (b) reaction between metal and hydrochloric acid, (c) acid-base neutralization, (d) metal carbonate treated with hydrochloric acid, (e) precipitation reaction. Give an example for each type of preparation. 

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. 

SODIUM BICARBONATE (497-19-8) CHNaOj Noncombustible solid. Aqueous solution is a strong base. Violent reaction with acids evolving carbon dioxide. Violent reaction with finely divided aluminum, fluorine, lithium. Incompatible with organic anhydrides, acrylates, alcohols, aldehydes, alkylene oxides, substituted allyls, cellulose nitrate, cresols, caprolactam solution, epichlorohydrin, ethylene dichloride, isocyanates, ketones, glycols, nitrates, phenols, phosphorus pentoxide, 2,4,6-trinitrotoluene. Forms explosive material with 2,4,5-trinitrotoluene and increases the thermal sensitivity of 2,4,6-trinitrotoluene (TNT) by decreasing the tenqjerature of explosion from 566°F/297°C to 424°F/218°C. Attacks metals. Thermal decomposition at 228°F/109°C, releasing oxides of carbon. 

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