Sodamide

It is an important intermediate in the indigo industry. When phenylglycine is fused with sodamide a good yield of indoxyl is obtained. The indoxyl is easily oxidized to indigo. 

The azides are salts which resemble the chlorides in solubility behaviour, for example silver azide, AgNj, is insoluble and sodium azide, NaN3, soluble in water. Sodium azide is prepared by passing dinitrogen oxide over molten sodamide ... 

Sodamide. This substance is prepared by the reaction between gaseous ammonia and molten sodium ... 

Sodamide should never be stored in a stoppered bottle from which samples are to be removed intermittently, since dangerous mixtures may result when the substance is exposed for 2-3 days to even limited amounts of air at the ordinary temperature. As a safe practice, sodamide should be used immediately after preparation, and should not be kept longer than 12-24 hours unless it be under an inert solvent. Even small amounts of unused sodamide should be removed from the apparatus in which it was made by washing with methyl or ethyl alcohol. In all cases where a yellowish or brownish colour develops, due to the formation of oxidation... 

Sodamide may be readily pulverised by grinding in a glass mortar under an inert hydrocarbon solvent (benzene, toluene, xylene, etc.). 

The formation of ethyl acetoacetate is an example of a general reaction knowu as the acetoacetlc ester condensation in which an ester having hydrogen on the a-carbon atom condenses with a second molecule of the same ester or with another ester (which may or may not have hydrogen on the a-carbon atom) in the presence of a basic catalyst (sodium, sodium ethoxide, sodamide, sodium triphenylmethide) to form a p-keto-ester. The mechanism of the reaction may be illustrated by the condensation of ethyl acetate with another molecule of ethyl acetate by means of sodium ethoxide. ... 

The acetoacetic ester condensation (involving the acylation of an ester by an ester) is a special case of a more general reaction term the Claisen condensation. The latter is the condensation between a carboxylic ester and an ester (or ketone or nitrile) containing an a-hydrogen atom in the presence of a base (sodium, sodium alkoxide, sodamide, sodium triphenylmethide, etc.). If R—H is the compound containing the a- or active hydrogen atom, the Claisen condensation may be written ... 

If much liquid ammonia is lost during the preparation of the sodamide, the volume should be m e up to 500-600 ml. before adding the y picoline. 

The acylation of ketones with esters an example of the Clalsen condensation is generally effected with a basic reagent, such as sodium ethoxide, sodium, sodamide or sodium hy dride. Thus acetone and ethyl acetate condense in the presence of sodium ethoxide to yield acetylacetone ... 

CONDENSATIONS WITH SODAMIDE IN LIQUID AMMONIA Acetylenic compounds are conveniently prepared with the aid of Uquid ammcx as a solvent. The preparation of a simple acetylenic hydrocarbon ( -butylacetylene or 1-hexyne) and also of phenylacetylene is described. Experimental details are also given for two acetylenic carbinols, viz., 1-ethynyl-eyciohoxanul and 4-pentyn-l-ol. It will be noted that the scale is somewhat laige smaller quantities can readily be prepared by obvious modifications of the directions. 

Sodamide is first prepared in situ by the reaction of sodium with Uquid ammonia in the presence of a catalyst ... 

A solution of mono-sodium acetylide in liquid ammonia is formed by passing excess of acetylene gas into the suspension of sodamide ... 

Phenylacetylene is readily prepared by the dehydrohalogenatlon of styrene dibromide with a solution of sodamide in liquid ammonia ... 

The acetylenic alcohol 4 pentyn-l-ol is conveniently prepared by treatment of tetrahydrofurfuryl chloride with sodamide iu liquid ammonia ... 

Some unreaeted sodium may be left 011 the walls of the flask in this method and this may partly reduee soino produet, siieh as an alkylaeetylene, derived from the sodium acetylide. The preparation of sodamide is not attended by mueh splashing and little (if any) unreaeted sodium remains on the walls of the flask. Although more manipulation and a somewhat longer time is required for the sodamide method, the latter is generally preferred as it is more adaptable and somewhat less troublesome. 

A solution of sodamide in liquid ammonia (essentially the amide NHj ion) is a very powerful alkylation catalyst, enabling condensations to be carried out with ease and in good yield which are otherwise either impossible or proceed with difficulty and are accompanied by considerable by-products. Thus 3-alkylpjTidines, otherwise inaccessible, are easily prepared from 3-picoline (see 3-n-amylpyridine in Section V,20). Also benzyl cyanide (I) and cyclohexyX bromide give a- r/ohexylphenylacetonitrile (II) ... 

Sodamide. Assemble the apparatus shown in Fig. VI, 16, 1, a. Fill the bath to a point about half-way up the side of the flask with methyl alcohol (or methylated spirit) and add solid carbon dioxide (Dry Ice or Drikold) in lump form until a white frost commences to form on the outside of the bath (2) the bath temperature should be about — 35 . 

Sodium acetyllde. Replace the ammonia - addition tube by a wide tube reaching almost to the bottom of the flask (or use the device depicted in Fig. II, 7, 12, b) and pass acetylene (Fig. VI, 16, 1, c) into the suspension of sodamide in liquid ammonia maintain the bath temperature at about — 35° so that little ammonia is lost. Continue the passage of acetylene until a uniformly black liquid is formed (usually 4r-5 hours) (7). Carefully watch the wide gas entry tube if much solid collects inside this tube, remove it before the tube is completely blocked. Add liquid ammonia, if necessary, to restore the original volume (ca. 3 5 litres). 

The absence of a colour can be readily ascertained by dipping a glass rod into the solution and withdrawing it rapidly when the solution is colourless, all the sodium has been converted into sodamide by the catalyst present. 

This procedure may be used for the preparation of finely-divided sodamide If the sodamide is to be used in any other solvent than liquid ammonia, the ammonia is allowed to evaporate whilst the new solvent is slowly added from a dropping funnel alternatively, the new solvent may be added before the ammonia evaporates. If dry sodamide is required, the product may be freed from the last traces of ammonia by evacuation at 100°. The sodamide prepared by this method must be used immediately if allowed to stand, it rapidly changes into explosive substances. 

Pentyn-l-ol. Prepare a solution of sodamide in liquid ammonia as detailed for n-Butylacetylene. Use a 3-htre three-necked flask, equipped with a Dewar type of reflux condenser (Fig. II, 1, 4, h) cooled with Dry Ice... 

This reaction involves the condensation of an aldehyde or ketone with an a-halo ester in the presence of a basic condensing agent (sodium ethoxlde, sodamide, finely divided sodium or potassium iert.-butoxide) to give a glycldio (or ap-epoxy) ester. Thus acetophenone and ethyl chloroacetate yield phenyl-methylglycidic ester (I) ... 

The 2-aminopyridliie is prepared by adding pure, dry pyridine to sodamide in dry toluene at 110° ... 

Aminopyridine. In a 1 litre three-neoked flask, equipped with a sealed mechanical stirrer, reflux condenser, thermometer and inlet tube for nitrogen, place 300 ml. of dry toluene (1) aud 75 g. of fine granular sodamide (2) bubble a steady stream of nitrogen thi ough the toluene. Stir the mixtiue vigorously and heat the flask in an oil bath until the internal temperatime is 110° (the bath temperatime required is approximately 130°). Add 100 g. of pure dry pyridine (compare Section 11,47,22)... 

It is important to use recently-prepared pure sodamide, which must be of fine granular form. Old material of irregular lumpy form, even if ground gives poor results, and should not be employed. The sodamide may be prepared as detailed in Section 11,50,j. A satisfactory grade is marketed by May and Baker Ltd. 

A suspension of 2.3 mol of sodamide in about 1.5 1 of liquid amnonia was prepared as described in Chapter II, Exp. 11. To this suspension was added 1 g of triphenylmethane. Acetylene (4-5 1/min) was introduced until the red colour of the triphenylmethane anion had disappeared. The flask was then placed in a cooling bath with dry-ice and acetone (-50°C) and the introduction of acetylene (1-1/min) was continued for an additional 10 min. Dry DMSO (200 ml) was then poured into... 

To a suspension of 7.5 mol of sodamide (see Chapter 11, Exp. 11) in 4.5-5 1 of liquid ammonia were added 2.0 mol of the chloro acetal in 30 equal portions with intervals of 2 min. Twenty minutes after this addition the stirrer was removed,... 

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