Secondary recrystallisation

Some developments in grain-oriented Si-Fe alloys have used grain-growth inhibitors to enhance preferential orientation during secondary recrystallisation (Taguchi et al, 1976). The features of domain structures in grain-oriented Si-Fe have been studied by Nozawa et al. (1988). 

One disadvantage of using acetic anhydride is that with primary amines, traces of the diacctyl compound, RN(COCH3)2, niay be formed the chances of this secondary acetylation are, however, usually remote, and recrystallisation from an aqueous solvent will generally hydrolyse the diacetyl derivative rapidly back to the mono-acetyl compound. 

The chloroplatinates prepared as above are sufficiently pure for direct analysis without recrystallisation. The chloroplatinates of the amines are usually freely soluble in hot water, but recrystallisation (when required) should not be attempted until the process has been found to be successful with a small test-portion of the chloroplatinate. The chloroplatinates of many primary and secondary amines decompose in hot water, the amine being oxidised, and the chloroplatinate reduced to the metal some amines furthermore co-ordinate readily with the metal when the chloroplatinate is boiled with water and a mixed product is obtained on cooling. 

Method 1. Treat 2 0 g. of the mixture of amines with 40 ml. of 10 per cent, sodium hydroxide solution and add 4 g. (3 ml.) of benzenesulphonyl chloi de (or 4 g. of p-toluenesulphonyl chloride) in small portions. Warm on a water bath to complete the reaction. Acidify the alkaline solution with dilute hydrochloric acid when the sulphonamides of the primary and secondary amines are precipitated. Filter off the solid and wash it with a little cold water the tertiary amine will be present in the filtrate. To convert any disulphOnamide that may have been formed from the primary amine into the sulphonamide, boil the solid under reflux with 2 0 g. of sodium dissolved in 40 ml. of absolute ethyl alcohol for 30 minutes. Dilute with a little water and distil off the alcohol filter off the precipitate of the sulphonamide of the secondary amine. Acidify the filtrate with dilute hydrochloric acid to precipitate the derivative of the primary amine. Recrystallise the respective derivatives from alcohol or from dilute alcohol, and identify them inter alia by a determination of the m.p. 

The most versatile derivative from which the free base can be readily recovered is the picrate. This is very satisfactory for primary and secondary aliphatic amines and aromatic amines and is particularly so for heterocyclic bases. The amine, dissolv in water or alcohol, is treated with excess of a saturated solution of picric acid in water or alcohol, respectively, until separation of the picrate is complete. If separation does not occur, the solution is stirred vigorously and warmed for a few minutes, or diluted with a solvent in which the picrate is insoluble. Thus, a solution of the amine and picric acid in ethanol can be treated with petroleum ether to precipitate the picrate. Alternatively, the amine can be dissolved in alcohol and aqueous picric acid added. The picrate is filtered off, washed with water or ethanol and recrystallised from boiling water, ethanol, methanol, aqueous ethanol, methanol or chloroform. The solubility of picric acid in water and ethanol is 1.4 and 6.23 % respectively at 20°. 

Purification as their N-acetyl derivatives is satisfactory for primary, and to a limited extent secondary, amines. The base is refluxed with slightly more than one equivalent of acetic anhydride for half to one hour, cooled and poured into ice-cold water. The insoluble derivative is filtered off, dried, and recrystallised from water, ethanol, aqueous ethanol or benzene (CAUTION toxic ). The derivative can be hydrolysed to the parent amine by refluxing with 70% sulfuric acid for a half to one hour. The solution is cooled, poured onto ice, and made alkaline. The amine is steam distilled or extracted as above. Alkaline hydrolysis is very slow. 

Place a mixtiu of 0 5 g. of finely powdered thioimea, 0-5 g. of the alkyl halide and 5 ml. of alcohol in a test-tube or small fiask equipped with a refiux condenser. Reflux the mixture for a i)eriod depending upon the nature of the halide primary alkyl bromides and iodides, 10-20 minutes (according to the molecular weight) secondary alkyl bromides or iodides, 2-3 hours alkyl chlorides, 3-6 hours polymethylene dibromides or di-iodides, 20-60 minutes. Then add 0 6 g. of picric acid, boil until a clear solution is obtained, and cool. If no precipitate is obtained, add a few drops of water. Recrystallise the resulting S-alkyl-iao-thiuronium picrate from alcohol. 

Method 2. Place a 3 0 g. sample of the mixture of amines in a flask, add 6 g. (4-5 ml.) of benzenesulphonyl chloride (or 6 g. of p-toluenesulphonyl chloride) and 100 ml. of a 5 per cent, solution of sodium hydroxide. Stopper the flask and shake vigorously until the odour of the acid chloride has disappeared open the flask occasionally to release the pressure developed by the heat of the reaction. Allow the mixture to cool, and dissolve any insoluble material in 60-75 ml. of ether. If a solid insoluble in both the aqueous and ether layer appears at this point (it is probably the sparingly soluble salt of a primary amine, e.g., a long chain compound of the type C,H5(CHj) NH2), add 25 ml. of water and shake if it does not dissolve, filter it off. Separate the ether and aqueous layers. The ether layer will contain the unchanged tertiary amine and the sulphonamide of the secondary amine. Acidify the alkaline aqueous layer with dilate hydrochloric acid, filter off the sulphonamide of the primary amine, and recrystaUise it from dilute alcohol. Extract the ether layer with sufficient 5 per cent, hydrochloric acid to remove all the tertiary amine present. Evaporate the ether to obtain the sulphonamide of the secondary amine recrystallise it from alcohol or dilute alcohol. Finally, render the hydrochloric acid extract alkaline by the addition of dilute sodium hydroxide solution, and isolate the tertiary amine. 

A copper-chromium oxide on pumice catalyst has particular value for the dehydrogenation of primary and secondary alcohols to the corresponding carbonyl compounds (see Section 5.6.1, p. 581). Dissolve 10.4g of barium nitrate (AnalaR) in 280 ml of water at about 80 °C and add to this hot solution 87 g of copper(n) nitrate trihydrate (AnalaR) stir the mixture and heat until a homogeneous solution results. Prepare a solution of 50.4 g of recrystallised ammonium dichromate in a mixture of 200 ml of water and 75 ml of concentrated ammonia solution (d 0.880). To the ammonium chromate solution at 25-30 °C add the hot (80 °C) nitrate solution in a thin stream with stirring. Allow the mixture to cool and filter off the yellowish-brown precipitate with suction press with a glass stopper and suck as dry as possbile. Transfer the... 

To an ice-cold mixture of 1.0 ml of concentrated sulphuric acid and 5 ml of saturated aqueous potassium dichromate solution, add 2 ml of the alcohol or its concentrated aqueous solution. If the alcohol is not miscible with the reagent, shake the reaction mixture vigorously. After 5 minutes, dilute with an equal volume of water, distil and collect the first few ml of the aqueous distillate in a test tube cooled in ice. (Aldehydes and ketones are volatile in steam.) Test a portion of the distillate for a carbonyl compound with 2,4-dinitrophenylhydrazine reagent (p. 1218). If a solid derivative is obtained, indicating that the compound was a primary or secondary alcohol, test a further portion with SchifFs reagent (p. 1291) to distinguish between the two possibilities. The derivative may be recrystallised the m.p. may give a preliminary indication of the identity of the alcohol. 

The Schotten-Baumann method of benzoylation with benzoyl chloride in the presence of aqueous sodium hydroxide may be used. Full details are given under Primary and secondary amines, Section 9.6.21, p. 1273. Alternatively, dissolve 1.0 g of the phenol in 3 ml of dry pyridine and add 0.5 g of benzoyl chloride. After the initial reaction has subsided, warm the mixture over a small flame for a minute or two and pour, with vigorous stirring, into 10-15 ml of water. Allow the precipitate to settle, decant the supernatant liquid, stir the residue thoroughly with 5-10 ml of m sodium carbonate solution, filter and recrystallise from ethanol or from light petroleum. 

Diaminodiphenylarsinic acid.— This acid is a by-product of the Bechamp reaction between aniline and arsenic add at 180° C. The crude aminophenylarsinic acid from the reaction is dissolved in hot sodium hydroxide solution, a little charcoal added, then 2 volumes of alcohol, and the whole filtered. From the filtrate the sodium salt of the primary acid separates out, which is removed and the filtrate evaporated. Alcohol is then added, the solid removed, and the alcohol evaporated off from the filtrate, which on neutralisation with hydrochloric acid gives the secondary acid as a resinous mass. This is dissolved in sodium hydroxide, filtered, and neutralised with dilute hydrochloric acid, when the product is precipitated as a powder. It is filtered off, washed, dried, and recrystallised from 50 per cent, acetic acid. The yield is 2 to 8 per cent. ... 

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