Alkali metals Group hydroxides

Alkali metal (Group IA or Group 1) hydroxides (LiOH, NaOH, and so on)... 

Alkali metal (Group IA) hydroxides (LiOH, NaOH, KOH, RbOH, CsOH), Calcium hydroxide, Ca(OH)2, strontium hydroxide, Sr(OH)2, and barium hydroxide, Ba(OH)2... 

Like a strong acid, a strong base dissociates completely into ions in water. All oxides and hydroxides of the alkali metals—Group 1 (IA)—are strong bases. The oxides and hydroxides of the alkaline earth metals—Group 2 (IIA)—below beryllium are also strong bases. 

Their hydroxides are not as thermally stable as those of the alkali metals. Group 2 hydroxides decompose on heating ... 

Classically, a base is a substance capable of liberating hydroxide ions, OH , in water solution. Hydroxides of the alkali metals (Group lA) and alkaline earth metals (Group 2A),suchasLiOH, NaOH, KOH, Ca(OH)2,and Ba(OH)2,are the most common inorganic bases. Water solutions of bases are cdlled alkaline solutions or basic solutions. Some of the characteristic properties commonly associated with bases include the following ... 

Table 4.2 T lists the common strong acids and bases. You should commit these to memory. As you examine this table, notice first that some of tire most common adds, such as HCl, HNO3, and H2SO4, are strong. Second, three of the strong adds result from combining a hydrogen atom and a halogen atom. (HF, however, is a weak acid.) Third, tire list of strong adds is very short. Most adds are weak. Fourfli, tile onfy common strong bases are the hydroxides of Li , Na, IC, Rb, and Cs (tire alkali metals, group lA) and the hydroxides of Ca, Sr, and Ba ...

There are relahvely few common strong bases. The most common soluble strong bases are the ionic hydroxides of the alkali metals (group lA) and the heavier alkaline earth metals (group 2A), such as NaOH, KOH, and C a(OH)2. These compounds completely dissociate into ions in aqueous solution. Thus, a solution labeled 030 M NaOH consists of 0.30 M Na iaq) and 0.30 M OH aq) there is essentially no undisstKiated NaOH. 

Although all the hydroxides of the alkali metals (group lA) are strong electrolytes, LiOH, RbOH, and CsOH are not commonly encountered in the laboratory. The hydroxides of Ihe heavier alkaline earih metals, Ca(OH)2, Sr(OH)2, and Ba(OH)2, are also strong electrolytes. They have limited solubilities, however, so tiiey are used only when high solubility is not critical. 

The list of strong bases is also fairly short. It consists of the hydroxides of alkali metals (Group lA) and the hydroxides of the heaviest alkaline earth metals (Group 2A). The dissociation of a strong base is, for practical purposes, complete. Equations representing dissociations of die strong bases are as follows ... 

As with the hydroxides, we find that whilst the carbonates of most metals are insoluble, those of alkali metals are soluble, so that they provide a good source of the carbonate ion COf in solution the alkali metal carbonates, except that of lithium, are stable to heat. Group II carbonates are generally insoluble in water and less stable to heat, losing carbon dioxide reversibly at high temperatures. 

Hydrogen can be prepared by the reaction of water or dilute acids on electropositive metals such as the alkali metals, alkaline earth metals, the metals of Groups 3, 4 and the lanthanoids. The reaction can be explosively violent. Convenient laboratory methods employ sodium amalgam or calcium with water, or zinc with hydrochloric acid. The reaction of aluminium or ferrosilicon with aqueous sodium hydroxide has also been used. For small-scale preparations the hydrolysis of metal hydrides is convenient, and this generates twice the amount of hydrogen as contained in the hydride, e.g. ... 

I) Refluxing said benzyl ester with an aqueous alcoholic alkali metal hydroxide solution to saponify the benzyl ester group, neutralizing the saponification mixture by the addition of hydrochloric acid, extracting the neutralized mixture with chloroform, and separating the resulting (S,N-ditrityl-L-cysteinyl)-L-proline. 

When a carbonyl group is bonded to a substituent group that can potentially depart as a Lewis base, addition of a nucleophile to the carbonyl carbon leads to elimination and the regeneration of a carbon-oxygen double bond. Esters undergo hydrolysis with alkali hydroxides to form alkali metal salts of carboxylic acids and alcohols. Amides undergo hydrolysis with mineral acids to form carboxylic acids and amine salts. Carbamates undergo alkaline hydrolysis to form amines, carbon dioxide, and alcohols. 

Another salt-like group of compounds that have acid-base properties is the hydrides of the alkali metals and calcium, strontium, and barium. These hydrides will react with water to form the hydroxide ion and hydrogen gas ... 

As far as propargyl thioethers are concerned, the substrates in this section follow all the principles discussed for propargyl ethers and propargylamines in the two preceding sections. For alkyl propargyl thioethers typical bases used are sodium amide in liquid ammonia, alcoholate or alkali metal hydroxide [178, 186-189, 191, 287-291], and again some derivatives of carbohydrates have been used successfully [292, 293], If an ester group is also present in the molecule, the reaction can be accompanied by a hydrolysis to the carboxylate [294]. 

Similarly, the cations that form strong bases (the alkali metals and the metals below beryllium in Group 2 (IIA)) do not tend to react with hydroxide ions. These cations are weaker acids than water. Therefore, when a salt contains one of these ions (for example, Na ) the cation has no effect on the pH of an aqueous solution. 

Strong bases include the oxides and hydroxides of the alkali metals and also the soluble oxides and hydroxides of the Group 2 metals, such as barium oxide and barium hydroxide. 

The presence of three nitro groups on the aromatic ring of picryl chloride makes the chloro group extremely reactive towards nucleophiles. Picryl chloride (87) is hydrolyzed to picric acid (4) in the presence of hot water or aqueous sodium hydroxide. Aminolysis of picryl chloride in the presence of primary and secondary amines is complete in minutes at room temperature. Picryl chloride is therefore a very useful starting material for the synthesis of a range of other picryl derivatives. The reaction of picryl chloride (87) with ammonia can be used to synthesize 2,4,6-trinitroaniline (53) (picramide). Treatment of picryl chloride with alcohols under reflux forms picric acid and the alkyl chloride of the corresponding alcohol, whereas the same reaction in the presence of alkali metal hydroxides, or the alkoxide anion of... 

Nitroalkanols are intermediate compounds that are used extensively in many important syntheses 142). They can be converted by hydrogenation into / -aminoalcohols, which are intermediates for pharmacologically important chemicals such as chloroamphenicol and ephedrine. They are obtained by Henry s reaction by the condensation of nitroalkanes with aldehydes. The classical method for this transformation involves the use of bases such as alkali metal hydroxides, alkoxides, Ba(OH)2, amines, etc. 142-144). However, these catalysts give predominantly dehydrated products—nitroalkenes— which are susceptible to polymerization (Scheme 16). The reaction proceeds by the nucleophilic addition of the carbanion formed by the abstraction of a proton from the nitro compound to the carbon atom of the carbonyl group, finally forming the nitroaldol by abstraction of a proton from the catalyst. 

This type of alkoxylation chemistry cannot be performed with conventional alkali metal hydroxide catalysts because the hydroxide will saponify the triglyceride ester groups under typical alkoxylation reaction conditions. Similar competitive hydrolysis occurs with alternative catalysts such as triflic acid or other Brpnsted acid/base catalysis. Efficient alkoxylation in the absence of significant side reactions requires a coordination catalyst such as the DMC catalyst zinc hexacyano-cobaltate. DMC catalysts have been under development for years [147-150], but have recently begun to gain more commercial implementation. The use of the DMC catalyst in combination with castor oil as an initiator has led to at least two lines of commercial products for the flexible foam market. Lupranol Balance 50 (BASF) and Multranol R-3524 and R-3525 (Bayer) are used for flexible slabstock foams and are produced by the direct alkoxylation of castor oil. 

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