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PYRROL, C4H5N

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Originally appearing in Volume V22, Page 698 of the 1911 Encyclopedia Britannica.
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PYRROL, C4H5N or C41;T4•NH, an organic See also:base found in See also:coal-See also:tar and See also:Dippel's oil. It may be synthetically prepared by the dry See also:distillation of ammonium mucate, or, better, by See also:heating it with See also:glycerin to 180-200° C. (H. Schwanert, See also:Ann., 186o, 116, p. 257); by passing the vapour of diethylamine through a red-hot See also:tube; by distilling succinimide with See also:zinc dust (C. A. See also:Bell, Ber., 188o, 13, p. 877); by distilling See also:calcium pyroglutaminate: H02C' CH(See also:NH2)'See also:CH2'CH2 See also:CO2H = C4H4NH+See also:CO2+2H20 (L. Haitinger, Monats., 1882, 3, p. 228); and by boiling succinic dialdehyde.with See also:ammonia and glacial acetic See also:acid (C. Harries, Ber., 1901, 34, p. 1497).

It is a feebly basic, colourless liquid which boils at 13o° C., and possesses a See also:

smell resembling that of See also:chloroform. It is slightly soluble in See also:water, and turns See also:brown on exposure to See also:air. It has to some extent the See also:character of a secondary amine; the See also:hydrogen of the imino See also:group can he replaced by See also:potassium. It is resinified by the See also:action of concentrated See also:mineral acids. On warming solutions of pyrrol in dilute acid, ammonia is evolved, and an amorphous See also:powder of variable See also:composition, known as pyrrol-red, separates out. The pyrrol See also:ring is easily broken, e.g. See also:hydroxylamine gives the dioxime of succinic aldehyde. Pyrrol is readily converted into See also:pyridine derivatives by acting with bromoform, chloroform, or methylene iodide on its potassium See also:salt, /3-brom-and /3-chlorpyridine being obtained with the first two compounds, and pyridine itself with the last. See also:Iodine in alkaline See also:solution converts pyrrol into iodol (tetra-iodopyrrol), crystallizing in yellowish-brown needles, which decompose on heating. It may also be prepared by heating tetra-brom- or tetra-chlorpyrrol with potassium iodide in alcoholic solution (See also:German patent, 384231 1886). It is used as an antiseptic. Zinc dust and hydrochloric acid reduce pyrrol to pyrrolin (dihydropyrrol), C4H6•NH, a liquid which boils at 9o° C. (748 mm.); it is soluble in water and has strongly basic properties and an alkaline reaction.

Hydriodic acid at high temperature reduces pyrrol to pyrrolidine (tetra-hydropyrrol), C4HSNH. Pyrrolidine has also been prepared by A. Thiele (Ber., 1905, 38, p. 4Ip4) from ,B-chlorpropionic aldehyde diethyl acetal. The See also:

chlorine See also:atom in this See also:compound is replaced by the cyano-group, which is then reduced to. the CH2NH2. group and coupled up with See also:benzene sulphochloride to See also:form the compound C6H5S02NH(CH2)2.CH(OC2H6)2• This substance easily splits out See also:alcohol, and the ring compound then formed yields pyrrolidine on reduction by See also:sodium in amyl alcohol solution. An a-pyrrolidine carboxylic acid and its hydroxy derivatives have been detected by E. See also:Fischer among the products of See also:hydrolysis of proteids. R. Willstatter (Ber., 1900, 33, p. 1164) obtained this acid by the action of a methyl alcoholic solution of ammonia on dibrompropylmalonic ester at 140° C., the diamide formed being then hydrolysed either by hydrochloric acid or baryta water : CH2•CBr(CO2H)2 CH2• (CONH2) CH2• CH(CO2H) I —s I )NH—a >NH. CH2•CH2Br CH2 CH2 CH2 CH2 Numerous substitution derivatives of pyrrol are known. The N-derivatives are prepared by the action of alkyl halides and acid chlorides on potassium pyrrol.

The C-derivatives have been prepared in various ways. L. Knorr, by the action of ammonia on aceto-acetic ester, obtained 19-imidobutyric ester, which with nitrous acid yields a-isonitroso-$-imidobutyric ester, See also:

CH3.C(:NH)•C(:N•OH)•CO2C2H6. Reduction of this ester leads to the formation of ammonia, hydroxylamine, and dimethyl pyrrol dicarboxylic ester, HN/C(CH3) : C44 •CO2R \C(CO2R) :C•CH3• He also found that diaceto succinic ester reacts with compounds of the type NH2R(R=H, CH2, OH, NHC6H6, &c.) to form pyrrol derivatives :propionic acid with 'hydroxylamine. It is monobasic and yields salts which only crystallize with See also:great difficulty; when liberated from these salts by a mineral acid it forms a syrupy non-volatile See also:mass. In aqueous solution it gives a red See also:colour with ferric chloride. It shows characteristic ketone reactions, yielding a bisulphite compound and combining with hydro-cyanic acid to form the nitrile of a-oxyisosuccinic acid. When warmed with baryta water it gives uvitic acid. Pyruvic nitrile, or acetyl See also:cyanide, See also:CH3CO•CN, may be prepared by the action of See also:silver cyanide on acetyl chloride ; or of acetyl chloride on nitrosoacetone (L. Claisen and O. Manasse, Ber., .1887, 2o, p. 2196).

It is a liquid which boils at 93° C. and with See also:

caustic alkalis polymerizes to diacetyldicyanide.

End of Article: PYRROL, C4H5N

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