be distinguished by their isomerization to hydroxamic acids (32) or by the benzoylation of the alkali salt folRCHsNOz --+ RCH=NOOH +RCONHOH
ment with hydrogen peroxide in the presence of ferric chloride. ArCONHz + HI% --+ ArCONHOH + H,O
lowed b y hydrolysis of the resulting hydroxamic acid benzoate (33). CdI&OCl -+RCONHOCOC& NaCl RCH=NOONa
Procedure.-Suspend a few milligrams of an aromatic amide in 5 cc. of water. Add a drop of ten per cent. ferric chloride and a few drops of three per cent. hydrogen peroxide. The color develops slowly in the cold or may be hastened by heating. The product is not stable in the presence of the oxidizing agent. Organic solvents interfere with the test.
+
+
AMIDES
C. Hofmann (34) found that aliphatic amides are rapidly converted to hydroxamic acids by means of hydroxylamine or its hydrochloride. Caprolactam was found by the writer to respond to this test also. RCONHZ NHsOR.HCl--+ RCONHOH + NHCI RCONH + NHrOH.HCI -+ RCONHOH u LNHvHCI
+
Procedure.-Boil 0.1 g. of an amide with 0.5 cc. of normal hydroxylamine hydrochloride solution (in methanol) for a few minutes. Cool. Add a drop of ten per cent. ferric chloride. An alternative test which may be successful when that just given fails, as, for example, in the case of acetanilide, depends.on the conversion of the amide to an ester by means of an alcohol (n-amyl is useful) and concentrated sulfuric acid. CHsCONHCdIs CJLOH -+CH~~OOCSHI~ GHaNHs Procedure.--Gently reflux a mixture of 0.5 g. of acetanilide, 2.0 cc. of n-amyl alcohol, and 0 . 5 ~ of ~ .concentrated sulfuric acid for five minutes. Cool and add about 10 cc. of ice water. Test the alcohol layer for ester in the usual way. Olivieri-Mandala (29) reported that aromatic amides are converted directly to femc hydroxamates by treat-
+
+
CYANATES
Just as ammonium chloride reacts with potassium cyanate to form urea so hydroxylamine hydrochloride reacts with this salt to form hydroxynreaa hydroxamic acid. The latter gives a distinctive purplishblue complex with femc ion (35, 36). KNCO + NH,OH.HCl--+ KC1 NHK!ONHOH
+
Procedure.-To an aqueous solution of hydroxylamine hydrochloride add a few milligrams of potassium cyanate and after a moment a drop of ten per cent. ferric chloride. Note: Werner (36) testsfor urea by heating it in a testtube and examining the sublimate formed for ammonium cyanate by the procedure given above. An alternative procedure involves heating urea with phosphorus pentoxide and passing the gases containing cyanic acid (HN=CO) into a solution of free hydroxylamine. Since alkyl isocyanates react with hydroxylamine to form alkyl hydroxynreas. (21) they may also be detected as hydroxamic .acids. RNCO + NHSOH--+ RNHCONHOH
LITERATITRE CITED
LOSSEN, Ann.,
150,314 (1869).
T m m m AND KRUGER.Ber.. 18.740 (1885).
HANTZS&
AND
DBSCH, Ann.; 323.23 (
JENKINS, I. Am. Chem. Soc.. 57,2733 (1933). Hum, aid., 45, 1475 (1923). Nea. Ann.. 298, 255 (1897): FENTON AND GOSTLING, J. C h . SOC.,73, 554 (1898). Worn, Ber., 43,2177 (1910). FEIGL,ANGER.AND FREDEN,Mikrochemie. 15, 18 (1934); Cf,, Reference 12, p. 266. FEroL AND ANGER. Mikrochcmie. 15, 23 (1934); Cf., Reference 12. p. 294. M~LIKEN "IdentEication , of pure organic compounds," John Wiley & Sons, New York City, 1916, Vol. 11, p. 2n
AND SCHENZ, Bet'., 34,2030 (1901). OLMERI-MANDALA, Gaza. chim. itel., 52, I, 107 (1922). BhawERGER, Ber., 52, 1116 (1919). SrmrN~nN D FUSON,"Identification of organic compounds, John Wiley & Sons Inc.. New York City.
B&ERGER
-..,, . ... ,=. -. ..
KAMM."Qualitative organic analvsis." 2nd ed.. John Wilev &Sons. Inc., New York C
1935, p. 40.
BAMBERGER nm, RUST,Ber., 35, 49 (1902). Am. Chnn. J., 20, 1 (1898); (b) JONES nm, (a) JONES,
,'""Y,.
PILOTY. Ber.. 29. 1559 (1896). O n w nm, DELEO, ibid., 69, 294 69,2027 (1936).
(1936); Cf., CAWI. ibid.,
BALBIANO, Atfi reale a c d . Lincei. (5) 20, 11, 245 (1911); ibid., 21, I, 389 (1912); ANGELI, ibid., ZO,II, 445 (1911); ibid., 21, I, 622 (1912); ibid., 22, I, 851 (1913).
OESPER.ibid., 42, 515 (1909).
HOFMANN. Ber.. 22, 2854 (1889). DnEsLEn AND STEIN,Ann., 150, 242 (1869). WERNER, "The chemistry of urea," Longmans, Green & Co.. London. 1923, p. 175.
