97 XTV.-CONTRIBUTIONS FROM THE LABORATORY OF THE UNIVERSlTY OF ZURICH. 11. Piazine-deriva.tives. By ARTHUR T. MASON Ph.D. F.I.C. Senior Demonstrator of Practical Chemistry. IN a paper pnblkhed in the Berichte (20 267) entitled “Ueber Condensations-derivate des Aethylendiamins,” I described amongst others two substances belonging to a class of nitrogenous compounds to which at the suggestion of Professor Merz I gave the name “ pyrazines ; ” this has since been changed t o “ piazines.”” The * In a paper which has just appeared in t,he Journal fiir pmktische Chemie (38, 185)) Professor Widman discusses the defective nomenclature a t present adopted in the aromatic and more especially in the alkalo‘id series. I n many caws the names have been chosen so as to indicate as far a~ possible the methods of preparation first discovered and then subsequent investigators seeing the inappropriateness of the terms thus given have adopted new ones so that in not a few cases we have one and the same compound referred to by different investigators under totally different names.A good illustration of this is offered in the many changes which the important nitrogenous compound above mentioned under the name of “ piazine,” hm under-gone. Its tetramethyl-derivative was discovered in 1879 by G utknecht in V. Meyer’s laboratory (Ber. 12 2290) and several other derivatives were imme-diutely afterwards studied by Treadwell and by Treadwell and Steiger (Ber. 14, 1461 ; 15 1059) and named a t the suggestion of Victor Meyer “ ketines.” At the suggestion of Professor Merz I afterwards proposed the name “ pyrazines” (Ber.20, 267) and in the same Journal Wolff adopted independently the same terni (Ber., 20,425) in both instances with the object of bringing out the analogy with the “ pyridines.” Victor Meyer finding the term “ ketines ’) inappropriate afterwards, and objecting to ‘‘ pyrazines )’ on the ground that Knorr (Annalen 238 144) had already used that term for pyrazole tetrahydride now proposed “ aldines ” (Ber., 21 20) but most of the investigators who have worked on this group still adopt the name “ pyrazines.” This single instance shows that a state of chaos exists and that some systematic nomenclature is an abRolute necessity. I n accordance with this Widman has propounded a systematic nomenclature for all compounds containing nitrogen in the ring.Every compound is an “azine” which contains a ring consisting of six atoms of carbon and nitrogen. He calls them respectively monuzines diazines triazines &c. according as they contain one or more atoms of nitrogen. To the “monazines” we should strictly have to reckon pyridine and quinoline but to alter existing names in these cases is impracticable and unnecessary. The I‘ diazines ” are divided into three great classes according as they contain the nitrogen-atoms in para- meta- or ortho-position relatively to each other. The first member of the para-class would thus be styled “ paradiazine,” but as this is rather long “ piazine ” can be used. In the meta-class we should have “ metadiazine,” which when shortened give 9s MASON PIAZINE-DERIVATIVES.simplest compounds and types of this class are the hypothetical ‘‘ piazine” and its hexahydride the latter of which has long been known as “ diethylenediamine.” H /N\ HC I CH Piazine (Pgrazine). /N\ HtC CH, I 1 \N/ HtC CH, Piazine hexahydride or diethylenediamine. The derivn tives described in the above-mentioned paper were “ phenanthrapiazine (xenylene-pyrazine) dihydride ” and ‘‘ diphenyl-piazine dihydride,” and they were prepared by the action of ethylene-diamine on phenanthraquinone and berizil respectively ; but in spite of their apparently similar modes of formation I found them to possess very different degrees of stability towards acids ; for whereas the phenanthra-derivative was not altered by concentrated hydro-chloric acid even at a temperature of 200” except that a salt was formed the diphenyl-derivative was split up into its constituents even by the dilutest mineral acids.These differences coupled with the fact (see p. 99) that diphenylpiazine dihydride gives by the loss of two atoms of hydrogen a very stable base have led me to the con-clusions on the one hand that the so-called phenanthrapiazine dihydride is in reality only phenanthrapiazine and on the other hand that the distribution of affinities is a radically different one to that holding in diphenylpiazine dihydride. That the first supposition was correct was easily proved by a new series of analytical data. For analysis the substance was recrystallised from glacial acetic acid and dried at 100”.The following results were obtained :-0.1432 gram gave 0.0579 gram water and 0.4385 gram carbon di-0.1540 gram gave 0.0645 gram water and 0.4694 gram carbon di-oxide. . - oxide. oxide. 0.1500 gram gave 0.0620 gram water and 0.4605 gram carbon di-(‘ miazine,” and in the ortho-aeries we should have ‘‘ arthodiazine,” or better, “ oiazine.” From these three parent substances we can have derivativee containing, besides the nitrogen-ring a benzeiie-ring to denote which the syllable “ phen ” is prefixed As will be seen I have adopted Widman’s nomenclature in this paper, Anding it most decidedly the simplest and best MASON PIAZINE-DERIVATTVES. 99 Calculated for 7--- -7 Phenanthrapiazine Phenanthra- Found. 7 dihydride. piazine. r-&-C16H12N2- C16H10N2- I.11. 111. C 82-76 83.47 83.51 83.12 83.72 H 5.17 4.37 4.49 4.65 4.59 These results point most deci-dedly to the fact that the compound is simply phenanthrapiazine and this agrees with recent experiments made by Strache in this laboratory ; he found that in the condensa-tion of a-propylenediamine with phenanthraquinone two atoms of hydrogen also disappear phenanthramethylpiazine being formed. The difference in the distribution of affinities in the two compounds is I think well expressed by the following formula :-Phenanthrapiazine. Diphenylpiazine dihydride. In corroboration of this view I have been able to prepare from the unstable diplienylpiazine dihydride by elimination of two atoms of hydrogen a base which is eminently stable towards acids./N\ HC I C The above-mentioned dihydride melts at 181" to a yellow liquid, and if heated for some time about 20" above this temperature the viscous mass thus obtained does not become solid and crystalline again on cooling; not until it had stood for several days were any signs of crystallisation visible. I€ however the product after two or three hours' heating at 200" be treated with tolerably concentrated hydrochloric acid the greater part will dissolve on warming and on filtering from undissolved resinous matter a solution of the hydro-chloride is obtained; on adding water to this until a permanent turbidity appears and allowing it to stand the new base is deposited as a crystalline precipitate the hydrochloride being decomposed by water. On recrystallisation from 50 per cent.alcohol the substance ia obtained in large colourless plates having the melting point 118-119". It distils with sligbt decomposition at about 340" small quantities of benzene and ammonia being liberated and a car 100 MASON PIAZINE-DERIVATIVES. bonaceons residue being left. The benzene wag recognised by conversion into aniline and testing with calcium hypochlorite. On finding that the compound was capable of distillation I imme-diately tried this method of preparation and found it decidedly the best. The dihydride is quickly distilled from a fractionating flask into a porcelain dish. It parts with two atoms of hydrogen and the base distils as a pale-yellow oil accompanied by a small quantity of benzene; this however soon evaporates and the whole on cooling solidifies to a mass of prismatic needles which are recrystallised from aniyl alcohol and washed with cold light petroleum.The mother-liquor is freed from light petroleum and amyl alcohol by distillation, and the residue is then redistilled when a second though small portion of base is obt,ained ; thiP however does not crystallise until it has stood several days and even then only part,ially owing to the presence of another compound in appreciable quantity in the form of a thick light brown syrup. The latter on oxidation with chromic acid in glacial acetic acid solution gave small quantities of benzoic acid but probably no piazinecarboxylic acid; it was not further investigated. Working according to this method and starting from 85 grams of benzil I got $0 grams of dihgdride and from this 55 grams of crude distillate which on recry stallisation yielded 40 grams of almost pure diphenylpiazine.It is insoluble in water, easily soluble in alcohol ether and benzene. From light petroleum, in which it is only sparingly soluble in the cold more easily on heating it crystallises in beautiful prismatic needles. The subst'alice dried at 130' gave the following results :-0.1833 gram gave 0-0908 P a m water and 0.5595 gram carbon di-0.1620 pram gave 0.0790 gra4m water and 0.4929 gram carbon di-oxide. oxide. Calculated for Found. r-- 7 7--7 C16H12N2' C16H14Nfl. I. 11. C 82.75 82-05 83.24 82.97 H 5-17 5-98 5.50 5-41 Diphenylpiazine has only feeble basic properties being precipi-tated by water from its solution in concentrated acids.It dissolves in concentrated sulphnric acid with a golden-yellow colonr which on addition of water becomes green ; if the solution in concentrated acid is heated it graduallg assumes a reddish tinge. If a crystal of potassium nitrate be added to the golden-yellow solution in concen-trated acid it immediately assumes a pale-green colour ; with potassium dichromate the colour is dirty green MASON P1AZINE-I)ERlVATIVES. 101 The pZatinochZoride ( Cl6H,,N,),,H2PtC1~ was prepared by adding hydrochloric acid to an alcoholic solution of the base and then alcoholic platinic chloride. The salt soon separates in the form of long yellow prismatic needles which as the following analpes show, are pure. The salt was dried a t 100".0.1008 gram salt gave 0.0225 gram platinum. 0.1923 , , 0.0426 , Y 9 Found. r-'-7 (C16H12N2)2,H2PtC16. I. 11. Calculated for Pt 22.25 22.32 22.15 No methyl iodide addition product could be obtained even on heating at 150° the base behaving in this respect like the previously described phenanthrapiazine. Dinitrodipheny ~ i u z i n e C1BH10N400 is prepared by warming a solu-tion of the base in concentrated nitric acid for some time on the water-bath. On precipitation with water an amorphous yellow powder is obtained having a very low and inconstant melting point ; hitherto I hare not been able to obtain this substance i n a crystalline form. It is easily soluble in hot alcohol only sparingly in ether and benzene insoluble in water and light petroleum.On rubbing the compound i n an agate mortar it becomes strongly electrical and it is only with the greatest difficulty that it can be brought together afterwards. For analysis it was dried in a vacuum over sulyhuric acid. 0.2058 gram gave 32.6 C.C. moist nitrogen a t 21" and 730 mm. Calculated for C16H10N404. Found. IT. 17.39 17-30 Reduction of Diphenylpiazixe. The method followed was that of Wischnegradski-Ladenburg, improved by Bamberger (Ber. 20 2915) which has yielded such excellent results of late. 15 grams of sodium were added quickly to about 50 C.C. of almost. boiling amyl alcohol contained in a litre flask connected with a reflux condenser and to this was added in a con-tinuous stream a boiling solution of diphenylpiazin2 in about 200 C.C.of amyl alcohol. The solution of the base is best added by means of a long funnel hanging in the condenser tube. Immediately the first drop comes in contact with the sodium the whole assumes a rich yellow colour and a rather violent reaction commences. The contents of the flask were kept boiling until the last particle o 102 MASON PIAZINE-DERIVATIVES sodium had disappeared and then poured while still hot into about half a litre of cold water the whole transferred to a separating funnel and well shaken in order to decompose the amyl alcoholate. The water was then drawn off and the residue after washing twice was distilled from a fractionating flask till the temperature had risen to about 1.50" when most of the amyl alcohol had passed over. The bases which on cooling solidify to a crystalline mass were dissolved in dilute hydrochloric acid filtered and the filtrate boiled with animal charcoal till colourless.On precipitation with sodium hydmte, the bases fall as an almost white crystalline precipitate composed of slender needles. By repeated recrystallisation from light petroleum, the mixture can be separated into two portions from which two dis-tinct hydrides can be isolated having the constant melting points 122-123" and 108-log" the latter being the more easily soluble. These compounds are apparently accompanied by a third having a much lower melting point. The properties of the bases are so similar that it was only by working on considerable quantities of rather expensive material that I was able to prepare enough of the two compounds to compare their properties and those of some of their derivatives.In the following part of the paper I describe merely the experimental results hitherto obtained reserving theo-retical considerations for a future communication when I hope to have isolated the third base. The two hydrides are referred to as a and 6 respectively as on analysis they both gave numbers closely agreeing with those demanded by diphenylpiaeine hexahydride. The simplest nomenclature to adopt for the substitution products of the " piazines " is probably the one made use of in this pamper ; it was suggested by Knorr's nomenclature for the (' pyrazoles." The following scheme will illustrate its use (Annalen 238 137) :-a (2 3) Diphenylpianine Hexahydride C,6H,,N2.This base crystallises from light petroleum in long slender white It is a strong Analysis of the substance 0,1279 gram gave 0.089 gram water and 0.3767 gram carbon needles having the constant melting point 122-123". base dissolving readily in dilute acids. dried at 100" gave the following numbers :-dioxide MASON PIAZINE-DERIVATIVES. 103 0.1482 gram gave 0,1056 gram water and 0.4372 gram carbon dioxide. Found. Calculated for 7- 7 C16H18N2. I. 11. C 80.66 80.32 80.66 H 7-57 7.73 7-91 The base is easily soluble in alcohol and benzene less readily in ether and light petroleum and insoluble in water. Hydrochloride C,6HlaN,,2HC1.-The base dissolves readily in dilute hydrochloric acid and on evaporation and standing in the cold the salt separates in long glistening white needles.For analysis the salt was dried at loo" a previous experiment having shown that there was no water of crystallisation in the air-dried salt. Melting point about 310". 0.137 gram gave 0.126 gram silver chloride. Calculated for C16H,,N2,2HC1. Found. C1 22.82 22.79 PZatinochZoride CISH18N2,H2PtC1 + $H20.-The hydrochloride in aqueous solution is treated with platinic chloride ; on standing the salt separates as a yellow crystalline powder. It is recrystallised from dilute hydrochloric acid and as thus prepared forms golden-yellow prismatic needles. The analysis gave the following num-bers :-0.2499 gram of air-dried salt gave 0.0035 gram water at 100". 0.2499 7 9 9 0.0737 , platinum. Calculated for C16H18N2,H2PtC16 + aH20.Found. HzO . 1.37 1.40 Pt 29.61 29-49 Nitroso-derivative CleH16N604.-The base was dissolved in dilute hydrogen chloride and to the cold solution an aqueous solution of potassium nitrite was added as lung a3 any precipitation took place. The white crystalline powder was collected washed well with water, and recrystallised from dilute alcohol. It separates after a short time in white prismatic needles which after a second recrystallisation melt sharply at 142-143' to a pale-yellow liquid. It is insoluble in water and light petroleum easily soluble in alcohol and benzene but only sparingly in ether. For the nitrogen determination the substance was dried at 100" ; the following results were obtained :-0.160 gram gave 33.4 C.C. moist nitrogen at 16" and 723 mm 104 MASON PIXZINE-DERIVATIVES.Calculated for C16H16N604* Found. N 23-31 23-13 The compound has therefore in all probability the following con-stitution :-N-NO N OH*~cACH*c6& NOH*=(! (bHaC6H5 ‘LNO The further study of this interesting substance is reserved. Action of Methyl Iodide on the a-Hydride C,,HIsN,. The base dissolves in methyl iodide to a clear colourless liquid, which on warming on the water-bath to expel excess of iodide and allowing it to remain in the cold crystallises t o an almost colourless mass the mother-liquor reacting strongly acid. Recrystallised from hot water it forms long colourless needles. It was dried at 100’ for the iodine estimation :-0.1515 gram gave 0.0889 gram silver iodide; 0.1525 gram gave 0.03077 gram silver iodide.Found. Calculated for 7-CH3H23N21* I. 11. I . 32-06 31.69 32.14 It is thus seen that the substance is a hydriodide of the (1 4) dimethyl (2,3) diphenylpiazine tetrahydride. I t is singular that only a monacid salt’ is formed the other molecule of hydriodic acid re-maining in the aqueous solution. (I 4) Dimethyl (2 3) Diphenylpiazine Tetrahydride, CH2.N ( CH3) *C H*C,H, ~H,~N(cH,)~H.c~H,’ is a strong base and is precipitated in slender white needles from an aqueous solution df the above salt on treatment with sodium carbonate. The substance thus obtained however is mixed with small quantities of a compound of a very low melting point and it is best t.0 extract several times with ether after adding the sodium carbonate in order to free the mixture from this product.The aqueous solution is then evaporated t o a small volume and on standing deposits the new base in long colourless needles having the melting point 263-264”. I MASON PIAZINE-DERIVATIVES. 105 is easily soluble in alcohol and water on warming but only very Rparingly in ether and benzene. For analysis the substance was dried at loo" and the following numbers were obtained :-0-1538 gram gave 0.1183 gram water and 0.4560 gram carbon Calculated for dioxide. Clt?H22N2. Found. C . 81-20 80-86 H. 8.27 8.54 Platinum Doub-ie SaZ.t ( Cl,H2,N,),,'2HCl,( PtCI,) + 8H,O. The base was dissolved in absolute alcohol concentrated hydro-chloric acid added and then an alcoholic solution of platinic chloride. The salt separates as a yellowish-brown crystalline powder which can be recrystallised from dilute hydrochloric acid.Thus prepared the salt forms yellow prismatic needles which on analysis give the following numbers :-gram air-dried salt gave 0.0127 gram water at 120". 9 , 0.01343 , platinum. 7 , 0.0130 , water at 120". {KE ,, (0.1620 ? 7 3 0.0372 , platinum. 0.1620 ,, Found. Calculated for +-7 (CIBHZ2N2)3,2HCl,(PtC14)2 + 8HZO. I. 11. H,O 8.53 8.48 8.02 Pt 23.03 32.92 22.96 The salt for analyses I and I1 were from different preparations. /3 (2 3) Diphenylpiazine Hexahydride CI6Hl8N2. This base is more easily soluble in light petroleum than the a-com-pound and remains in the filtrates together with small quantities of the base of low melting point above mentioned from which however, it is difficult to completely separate it.The most suitable solvent is 50 per cent. alcohol from which it separates in long silky white needles. By repeated recrystallisation the melting point ultimately becomes constant at 108-109". When freshly prepared and still moist the needles present a glistening silky appearance but on drying they become drill white the change being in all probability due to the 1058 of water or alcohol of crystallisation ; the distinction between the OC-and /?-compounds being very marked. Like the a-base it is easily soluble in alcohol and benzene less so in ether and insoluble in water ; i t has strong basic properties dissolving easily in dilute mineral YOL. LV. 106 MASON PIAZINE-DERIVATIVES. acids. For analysis the substance was dried in a vacuum over sulphuric acid ; the following results were obtained :-0.1527 gram gave 0.1103 gram water and 0.449 gram carbon dioxide.0.1409 , 0.099 , Y7 0.4416 , 9 7 9 , @163 9 19 C.C. moist nitrogen at 25" C. and 720 mm. 0-1863 , 20.3 , 10" C. , 723 , 9 9 Found. Calculated for +-7 1 6H18N2* I. 11. C . 80.66 80.19 80.25 H 7-57 8.02 7-80 I)u' 11.76 12.31 12.03 BytlrochZode C,,HI,N2,2HC1.-The base is dissolved in alcohol, concentrated hydrochloric acid added and the whole allowed to stand when the salt separates in colourless prismatic needles. The melting point is about 295". As the air-dried substance contains no water of crystallisation it was dried at 120" for analysis :-0.1520 gram gave 0.1384 gram silver chloride.Calculated for C16H,,N2,2HCJ Found. C1 22.82 22.57 PZatinochZoride C,,~,,N,,H,Pt~~ + 2H20.-The base is dissolved in 95 per cent. alcohol concentrated hydrochloric acid added and then an alcoholic solution of platinic chloride. On standing the solution deposits long pale-yellow needles which as the following analyses show are pure:-0.1201 gram air-dried salt gave at 120" C. 0.0064 gram water. 0.1201 , 7 ) 7 7 7 9 7 0.0067 ,, 0.1210 , 7 7 1 . , 0.0339 gram platinum. Found. Calculated for r- 7 C ~ ~ H ~ N ~ H Z P ~ C & + 2HzO. I. 11. H20 5.26 5.32 5.54 Pt . 28.44 - 28.01 On oxidation with chromic acid in glacial acetic acid solution, (2 3) diphenylpiazine gives a phenylpiazinecarboxylic acid which yields well-characterised salts. The melting point is about 202". This as well as other products shall be described in a future paper. In conjunction with Mr. L. A. Dryfoos to whom I am indebted for several of the analyses in the above paper I am studying the action of ethylenediamine on the recently discovered a-diketones of th MASON ACETAMIDE AND PHENANTHRAQUINONE. 107 fatty series and have already obtained interesting results which we hope to communicate to the Society a t no distant date. I cannot close t,his paper without expressing my thanks to Professor Victor Merz for his kindness and valuable advice during the whole of my student life at Zurich