Laboratory preparative formats

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. 

Among compounds other than simple alkyl halides a halo ketones and a halo esters have been employed as substrates m the Gabriel synthesis Alkyl p toluenesul fonate esters have also been used Because phthalimide can undergo only a single alkyl ation the formation of secondary and tertiary amines does not occur and the Gabriel synthesis is a valuable procedure for the laboratory preparation of primary amines... 

Intermediate formation of formyl chloride is not necessary since the actual alkylating agent, HCO", can be produced by protonation of carbon monoxide or its complexes. However, it is difficult to obtain an equimolar mixture of anhydrous hydrogen chloride and carbon monoxide. Suitable laboratory preparations involve the reaction of chlorosulfonic acid with formic acid or the reaction of ben2oyl chloride with formic acid ... 

In laboratory preparations, sulfuric acid and hydrochloric acid have classically been used as esterification catalysts. However, formation of alkyl chlorides or dehydration, isomerization, or polymerization side reactions may result. Sulfonic acids, such as benzenesulfonic acid, toluenesulfonic acid, or methanesulfonic acid, are widely used in plant operations because of their less corrosive nature. Phosphoric acid is sometimes employed, but it leads to rather slow reactions. Soluble or supported metal salts minimize side reactions but usually require higher temperatures than strong acids. 

For the laboratory preparation of phosphine, only a few of the many methods of formation are suitable. Among these the hydrolyses of calcium phosphide 8o- 3) jnagnesium phosphide aluminium phosphide zinc phos-... 

Our experience has shown that the hydrolysis of aluminium phosphide with cold water is the most suitable method for the laboratory preparation of phosphine. Here it is important that the aluminium phosphide be as pure as possible in order to avoid the formation of spontaneously inflammable phosphine. The presence of small quantities of diphosphine and also higher phosphines are responsible for this spontaneous inflammability 96.276-278) jj. gp, pears, however, that these are only formed when P—P bonds are already present in the phosphide. Accordingly the hydrolysis of aluminium phosphide, prepared from the elements with phosphorus in slight excess, always leads to spontaneously inflammable phosphine. The formation of diphosphine and higher phosphines from aluminium or alkaline earth metal phosphides, which contain excess phosphorus, can be easily understood when the lattices of these compounds are considered. 

Prior to publication of the 1987 GLP revisions, many laboratories prepared combined reports, and the author knows of no instance in which the FDA rejected a study for failure to provide signed and dated reports from each of the scientists or other professionals involved in the study. For such laboratories it is probably advisable to reconsider prior pohcy on report preparation. The intent of the regulation (to provide accountability) can be met with the format of a combined report, but with an indication on the signature page of the portion of the report prepared by each signatory. 

Problem 30.4 In a convenient laboratory preparation ol dry hydrogen bromide, Br2 is dripped into boiling tetralin the vapors react to form naphthalene and four moles of hydrogen bromide Account, step by step, for the formation of these products. What familiar reactions are involved in this aromatization ... 

In contrast, triphenylchloromethane does not react in EtjO with Na sand . The Na surface is covered so tightly with impurities as it is prepared that the bulky triphenylchloromethane (unlike smaller 1-chloropentane) cannot penetrate. After addition of sharp particles of glass and shaking, even seed-sized (ca. 0.5 mm) particles of Na can be induced to react . Alternatively, the addition of benzophenone, tetraphenylethylene, chlorobenzene, bromobenzene, or n-butyl chloride can bring about reaction . These compounds may function as Na carriers (shown for benzophenone and tetraphenylethylene by formation of known Na complexes), or to clean the surface of the Na metal. For laboratory preparations of triphenylmethylsodium, triphenylchloromethane is reacted... 

An economical procedure for the formation of r-butyl esters is the reaction of a carboxylic acid with 2-methyl propene in the presence of an acid catalyst. For a laboratory-scale preparation, formation of the mixed anhydride using MsCl in the presence of r-BuOH gives the ester in good yield. ... 

The formation of alkanenitriles from alcohols and HCN is of no interest for laboratory preparations. However, a large number of publications, particularly patents, have appeared, which deal with technical applications of this procedure. A few review articles " serve very well as introductions to this field. Under particularly mild conditions allyl and propargyl alcohols can be transformed into the corresponding nitriles with hydrogen halides in the presence of Cu salts. - The possibility of generating nitriles from alcohols via the analogous halides needs no further treatment at this stage. 

The generation of 3-hydroxypropionitrile from ethylene oxide and HCN in a closed vessel was described in 1878. As the reactivity of epoxides exceeds that of acyclic ethers considerably, oxiranes do represent useful starting materials for hydroxynitriles and their derivatives. For laboratory preparations, the use of alkali metal cyanides (Scheme 13) - instead of HCN will be more convenient. The syntheses of (14) and (15) (Scheme 13) were accomplished in a buffered (MgS04) aqueous solution at about pH 9.5. The intermediate formation of epoxides on treatment of 2-halo alcohols with CN ions has already been mentioned in Section 1.8.1.2.1.ii. 

From a knowledge of the solubility rules (see Section 4.2) and the solubility products listed in Table 16.2, we can predict whether a precipitate will form when we mix two solutions or add a soluble compound to a solution. This ability often has practical value. In industrial and laboratory preparations, we can adjust the concentrations of ions until the ion product exceeds K p in order to obtain a given compound (in the form of a precipitate). The ability to predict precipitation reactions is also useful in medicine. For example, kidney stones, which can be extremely painful, consist largely of calcium oxalate, CaC204 (K p = 2.3 X 10 ). The normal physiological concentration of calcium ions in blood plasma is about 5 mM (1 mM = 1 X 10 M). Oxalate ions ( 204 ), derived from oxalic acid present in many vegetables such as rhubarb and spinach, react with the calcium ions to form insoluble calcium oxalate, which can gradually build up in the kidneys. Proper adjustment of a patient s diet can help to reduce precipitate formation. Example 16.10 illustrates the steps involved in precipitation reactions. 

Discussion The methods of preparing chlorine fall into four general classes, the electrolysis of a chloride, which is the chief industrial method, the oxidation of hydrochloric acid in which the oxygen from the oxidizing agent unites with the hydrogen of the acid and liberates the chlorine, the deeom-pO Sition of a hypochlorite, and the formation of a chloride which immediately breaks up into chlorine and another chloride containing less chlorine. The last of these methods is the one commonly used for the laboratory preparation of the element. 

Discussion Of the various methods for the formation of carbon dioxide, which will be taken up later in Experiment 40, the most convenient for laboratory preparation is the action of an acid on a carbonate. The progress of the reaction depends upon the instability of carbonic acid, which breaks up into water and carbon dioxide. Substances are chosen, therefore, which will react to form carbonic acid by double decomposition and these are, as just stated, a carbonate and an acid. If a slow steady stream of gas is desired, an insoluble carbonate, usually calcium carbonate, is selected, since a soluble carbonate reacts too rapidly. The acid employed must be one which will form a soluble compound with the metal of the carbonate, for if an insoluble compound were formed, it would coat over the solid carbonate and prevent further access of the acid. 

General reviews on cyclic acetals of carbohydrates have appeared. The cyclic acetals of the aldoses and aldosides have been treated in this Series by de Beider, but inclusion of cyclic acetals of ketoses was beyond the scope of his Chapter. Other articles, by Barker and Bourne, Mills, and Ferrier and Overend, have been concerned with the stereochemistry and conformation of cyclic acetals of the carbohydrate group. The purpose of the present article is to supplement de Beider s Chapter with a description of the pertinent original work, optimal laboratory preparations, properties, and applications of the cyclic acetals of ketoses, and to provide a summary of the known theoretical aspects of their formation, rearrangement, and hydrolysis. 

Alternative laboratory preparations include the reaction of ethyl formate with sulfuryl chloride at 170°C 272 reaction of chloro-... 

In laboratory prepared samples, if air is not excluded during the formation of the hydrate, then O2 and N2 can end up in the cages not occupied by the main guest. This shows up as extra electron density in x-ray diffraction single-crystal structural studies, and paramagnetic O2 molecules cause relaxation effects and line-shape distortions in NMR spectra. 

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