PREPARATION OF BASES

Bases can be prepared in several ways. Many bases contain metals, and some metals react directly with water to produce a solution of base. Lithium, sodium, and potassium react very vigorously with water to produce their hydroxides  

Many metal oxides form bases when they are dissolved in water. When waste liquor (a concentrated solution of salts and materials extracted from wood) from the sulfite paper-making process is burned to produce energy and reclaim magnesium hydroxide, die magnesium in die ash is recovered as MgO. This is added to water 

Many important bases carmot be isolated as the hydroxides, but produce OH ion in water. A very good example is ammonia, NH3. Ammonium hydroxide, Nlf OH, carmot be obtained in a pure form. Even when ammonia is dissolved in water, very litde NHjOH is present in the solution. However, ammonia does react with water to give an ammonium ion and a hydroxide ion  

Since only a small percentage of the ammonia molecules react this way, ammonia is a weak base. 

Many salts that do not themselves contain hydroxide ion act as bases by reacting with water to produce OH Sodium carbonate, Na2C03, is the most widely used of these salts. When sodium carbonate is placed in water, tiie carbonate ion reacts with water to form a hydroxide ion and a bicarbonate ion, HC03  

---

Based on the kinetic studies, a mechanism for this oxidation was proposed45 which involves a nucleophilic attack by the sulphide on a cyclic hydrogen-bonded form of the peracid (equation 9). Since oxidation using peracids occurs under very mild conditions, it can be successfully applied to the preparation of base sensitive sulphoxides. Thus, di(a-bromobenzyl) sulphoxide 25, which is very labile in the presence of a base, was obtained by careful oxidation of a-di(a-bromobenzyl) sulphide by means of m-chloroperbenzoic acid (MCPBA)46 (equation 10). 

Preparation of base metals by coupled reduction with platinum group metals. Very pure metals of the alkaline- earth, lanthanide and actinide series can be prepared from their oxides (or fluorides) through coupled reduction by pure hydrogen in presence of platinum group metals. According to a precursory paper on this subject (Berndt et al. 1974), the preparation scheme of Li, Ca, Sr, Ba, Am and Cf was described. As an example, Ca can be obtained by synthesis of a Pt compound, followed by its vacuum decomposition and recovery by distillation of the more volatile base metal ... 

Besides the produciion of syntJietic fuels from synthesis gas, the selective preparation of base materials for the chemical industry is an important goal. Especially, the selective formation of short-chain olefins and alcohols has been tlie subject of recent research. Some illustrative examples have been chosen to point out recent development. However, it should be kept in mind that these new catalysts have so far not been proved under industrial conditions where they could lose part of their exceptional properties. 

Incorporation of the catalyst into the monolith during manufacture. This method always leads to poor utilization of the catalytic material some is buried within the crystalline matrix and is not accessible to reactants. As the catalytic material modifies the monolith s physical properties, either a limit has to be placed on the amount of catalytic material incorporated or some deterioration in monolith performance has to be accepted. This method of manufacture is reserved for the preparation of base-metal catalysts, particularly nickel and manganese catalysts. Care has to be taken to avoid the formation of spinels, etc., although in some cases the formation of a complex oxide structure is actively sought. 

In the laboratory, other metals, like iron, zinc, etc., in connection with an add, are only rarely used in the place of tin or stannous chloride, for the. reduction of nitro-compounds. On the large scale, iron, owing to its cheapness, is used in the preparation of bases like aniline, toluidine, a-naphthyl amine, etc., from the corresponding nitrocompounds. By the use of iron and hydrochloric acid, the reduction should theoretically take place in accordance with the following equation ... 

UNIDO Project - Implementation of Stockholm POPs convention in the Czech Republic Project objective is preparation of bases for ratification of Stockholm Convention ... 

There are a number of possible methods of deposition of the metals onto support materials these include impregnation, absorption or ion exchange, coprecipitation with the support and vapour deposition. Vapour deposition is not practical on economic grounds and co-precipitation, often used for the preparation of base metal catalysts, cannot be used because of the problems of recycling and recovery. Thus precious metal catalysts are usually prepared by the impregnation or ion exchange of metal salts onto the support materials. A schematic representation of the ion exchange process is shown below. 

A large number of papers continue to appear on the preparation of base or sugar modified oligonucleotides by more or less standard phosphoramidite methods. Among base modified monomers prepared this year are the phosphoramidites of 2-amino-2 -deoxyadenosine (111), ... 

Step 1. Preparation of Base Fluid Bulk base fluid samples were prepwed by mixing water, viscosifiers, and barite. Immediately after mixing all water-based fluids were covered and left undisturbed for a minimum of 24 hours to ensure full hydration of... 

Step 1. Preparation of Base Fluid The fluid samples were initially mixed with tap water in bulk using a stand mixer to begin hydration of the polymer. Hot water was used to accelerate the hydration time. The polymeric fluids were then placed in a blender and mixed for 30 minutes, and left to sit for 24 hours to ensure complete hydration. 

HaralambidiS) J, Chai, M., and Tregear, G W, (1987) Preparation of base-modified nucleosides suitable for nonradioactive label attachment and their incorporation into synthetic oligodeoxyribonucleotides. Nucl. Acids Res, 15, 4857 876. 

This form of limited-conversion hydrocracking is a process that selectively prepares high quality residues for the special manufacture of base oils of high viscosity index or treating residues having low BMCl for the conversion of heavy fractions to ethylene, propylene, butadiene and aromatics. 

Osazone formation. The preparation of glucosazone has already been given (p. 137). It may be carried out on a small scale by either of the following methods, according as (a) the phenyl hydrazine base, or (Z>) one of its salts, is used. 

The low reactivity of aliphatic ethers renders the problem of the preparation of suitable crystalline derivatives a somewhat difficult one. Increased importance is therefore attached to the physical properties (boding point, density and refractive index) as a means for providing preliminary information. There are, however, two reactions based upon the cleavage of the ethers which are useful for characterisation. 

Note on the laboratory preparation of monoethylaniline. Although the laboratory preparation of monomethyl- or monoethyl-aniline is hardly worth whUe, the following experimental details may be useful to those who wish to prepare pure monoethylaniline directly from amline. In a flask, fitted with a double surface reflux condenser, place 50 g. (49 ml.) of aniline and 65 g. of ethyl bromide, and boU gently for 2 hours or until the mixture has almost entirely sohdified. Dissolve it in water and boil off the small quantity of unreacted ethyl bromide. Render the mixture alkaUne with concentrated sodium hydroxide solution, extract the precipitated bases with three 50 ml. portions of ether, and distil off the ether. The residual oil contains anihne, mono- and di-ethylaniline. Dissolve it in excess of dilute hydrochloric acid (say, 100 ml. of concentrated acid and 400 ml. of water), cool in ice, and add with stirring a solution of 37 g. of sodium nitrite in 100 ml. of water do not allow the temperature to rise above 10°. Tnis leads to the formation of a solution of phenyl diazonium chloride, of N-nitrosoethylaniline and of p-nitrosodiethylaniline. The nitrosoethylaniline separates as a dark coloured oil. Extract the oil with ether, distil off the ether, and reduce the nitrosoamine with tin and hydrochloric acid (see above). The yield of ethylaniline is 20 g. 

---