Hydroxamate test

Acidic Iron(III) Hydroxamate Test. With iron(III) chloride alone a number of substances give a color which can interfere with this test. Dissolve 2 drops (or about 30 mg) of the unknown in 1 mL of ethanol and add 1 mL of 1 N hydrochloric acid followed by 1 drop of 10% aqueous iron(III) chloride solution. If any color except yellow appears you will find it difficult to interpret the results from the following test. 

Alkaline Iron(III) Hydroxamate Test. First test the unknown with iron(III) chloride alone. (See under Group 1(e), Acidic Iron(III) Hydroxamate Test.)... 

The acid iron(III) hydroxamate test, Group 1(d), can be applied directly to the amine salt. 

Although esters, like aldehydes and ketones, are neutral compounds that have a carbonyl group, they do not usually give a positive 2,4-dinitrophenylhydrazine test result. The two most common tests for identifying esters are the basic hydrolysis and ferric hydroxamate tests. 

Before starting, you must determine whether the compound to be tested already has enough enolic character in acid solution to give a positive ferric chloride test. Dissolve 1 or 2 drops of the imknown liquid or a few crystals of the unknown solid in 1 mL of 95% ethanol, and add 1 mL of 1 M hydrochloric acid. Add 1 or 2 drops of 5% ferric chloride solution. If a burgundy, magenta, or reddish-brown color appears, the ferric hydroxamate test cannot be used. It contains enolic character (see Experiment 52F). 

Chemical Tests. Does this ester give a positive hydroxamate test (see Chapter 9) Check the solubility of ethyl laurate in water. Would you have predicted the result Is the ester soluble in 85% phosphoric acid or in concentrated sulfuric acid ... 

Check the solubility of acetanilide in water. Is the aqueous solution acidic, basic, or does it remain neutral as indicated by pH paper Does the ignition test indicate that an aromatic group is present Does the soda lime or sodium fusion test indicate the presence of nitrogen Does the hydroxamate test for amides give a positive result ... 

Chemical Tests. Chemical classification tests may also be performed on the amide product. The ignition and the Beilstein test (Chapter 9) are used to confirm the presence of the aromatic ring and the halogen group, respectively. Does the hydroxamate test for amides (Chapter 9) give a positive result ... 

Hydroxamate Test for Amides. Unsubstituted (on nitrogen) amides, and the majority of substituted amides, will give a positive hydroxamate test ... 

Hydroxamate Test. Carboxylic esters can be identified by conversion to hydroxamic acid salts. Acidification of this salt produces the corresponding hydroxamic acid (RCONHOH), which is identified by formation of a red-to-purple color in the presence of Fe " ion ... 

A colorless liquid, bp = 199-201 °C, bums with a yellow, sooty flame. The sodium fusion test proved negative for the presence of halogens, nitrogen, and sulfur. The compound was not soluble in water, 5% aqueous sodium hydroxide, or 5% hydrochloric acid. However, it dissolved in sulfuric acid with evolution of heat. It did not give a precipitate with 2,4-dinitrophenylhydrazine solution, and it did not decolorize bromine-methylene chloride solution. The unknown liquid did give a positive hydroxamate test and was found to have a saponification equivalent of 136. Identify the unknown liquid. 

Chemical Tests. Chemical classification tests (Chapter 9), such as the ignition test and the soda lime test (or sodium fusion test), may also be conducted to further establish the identity of the product. The hydroxamate test may be used to establish the presence of the amide functional group. 

E. Racker There is further evidence lactoyl glutathione gives a negative nitro-prusside test and a positive hydroxylamine test. The nitroprusside test becomes positive on alkaline hydrolysis of the ester and the hydroxamic test becomes negative. 

Alcohols can be converted with acetyl chloride to corresponding acetates, which can be detected by the hydroxamate test. Since tertiary alcohols with acetyl chloride predominantly give tertiary alkyl chlorides, the reaction is carried out in the presence of dimethylaniline, which binds the liberated hydrogen chloride. 

Procedure Acetyl chloride (0.05 ml), dimethylaniline (0.05 ml), and 0.1 ml of the tested alcohol are shaken occasionally in a micro test tube. After 3—4 min the mixture is diluted with 0.5 ml of ice-cold water, stirred thoroughly (decomposition of acetyl chloride), and the ester allowed to separate. One to two drops of the ester layer are transferred with a micropipette into another test tube, where the hydroxamate test is then carried out 0.5 ml of a saturated methanolic hydroxylamine hydrochloride solution is added, the mixture is shaken and then mixed with 0.5 ml of a saturated KOH solution in methanol. The mixture is shaken again and heated over a water bath or over a microflame just to the boiling point, and after cooling it is acidified with 2 n HCl and additioned with 1 —2 drops of a 1% ferric chloride solution. Pink, red, or violet color is proof of the presence of alcohol in the original sample. 

Complete hydrolysis of h3 uronic acid with mineral adds produces D-ghicosamine, acetic add, and carbon dioxide, the last named indicating the presence of a uronic acid. The latter compound was identified as d-g ucuronic acid by oxidation with nitric add, which led to the formation of D-glucaricacid. D-Glucuronic add was subsequently isolated after enzymic degradation. The carboxyl group of the uronic moiety is free, as shown by salt formation, titration, and the positive hydroxamic test after ester formation. 

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