650 MORGAN: INF~UENCE OF SUBSTITUTION ON THE

LXVII.-InJuencc o f Substitution on the Reactivity of the Aromatic m-Diamines.

By GILBERT THOMAS MORGAN, D.Sc.

IT has already been shown in a recent communication (this vol., p. 86) that the reactivity of the aromatic m-diamines towards diazonium salts may be very considerably modified by the introduction of substituent radicles into certain positions in the aromatic nucleus. It was found that the symmetrically disubstituted rn-diamines furnished only small quantities of azo-compounds, whereas their isomerides containing a free para-position with respect to an amino-group gave rise to azo- derivatives in theoretical quantities.

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REACTIVITY OF THE AROMATIC METADIAMINES. 651

The behaviour of the homologues of m-phenylenediamine on methyl- ation has now been investigated, and the results indicate that the diminution in reactivity, brought about by the introduction of radicles into the para-ortho-positions with respect to the nitrogen atoms, is equally noticeable when the diamines are subjected to the action of alkylating agents.

The influence of substitution on the methylation of primary aromatic amines has already been studied by Pinnow (Bey. , 1897, 30, 3110; 1899, 32, 1401 ; 1901, 34, 1129), who treated the hydrochlorides or hydrobromides of these bases with methyl alcohol a t 145-190'. Under these conditions, a monoamine in which the two ortho-positions adjacent to the nitrogen atom are both unoccupied yields a mixture of tertiary base and quaternary salt, If, however, the amine contains a substituent radicle in one of these posit,ions, it gives rise to a dialkyl derivative only. It remained uncertain as to whether this rule holds for the diamines, for although the methylation of benzidine and the three phenylenediamines had been investigated (Pinnow, Zoc. cit.), the research was not extended to the homologues of these diamines.

A n examination of m-tolylenediamine (2 : 4-diaminotoluene) and 4 : 6-diamino-m-xylene from this standpoint shows that Pinnow's generalisation may be extended to the m-diamines, the former of these bases furnishing a mixture of 2 : 4-tetramethyldiaminotoluene and the quaternary hydrochloride or hydrobromide, the latter yielding 4 : 6- tetramethyZEiamirzo-m-xylene as the sole product.

A comparative experiment made with m-phenylenediamine led to the production of the tertiary base and the quaternary salt together with fluorescent, tarry impurities, the alkylation taking place more energetically, but less smoothly, than with the homologous diamines. Diaminomesitylene, when treated in this manner, remains practically unchanged.

These results indicate that the successive introduction of methyl groups into the three positions (X, Y, Z ) adjacent to the two nitrogen atoms of m-phenylenediamine,

NH, Y -- x< -- >H2,

Z is attended by a well-marked diminution in the reactivity of the diamine towards methyl chloride or bromide, the interaction being prevented when the substitution of the three contiguous hydrogen atoms is complete (compare E. Fischer and Windaus, Ber., 1900, 33, 345 and 1967).

The tertiary diamines obtained in this investigation exhibit a gradation in properties similar to that observed in the case of the

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652 MORGAN: INFLUENCE OF SUBSTITUTION ON THE

corresponding primary bases ; their reactivity diminishes as the homologous series is ascended. When distilled under diminished pressure, these tertiary bases are obtained as almost colourless, oily liquids ; tetramethyl-m-phenylenediamine, however, rapidly darkens on exposure to light and air, whilst tetramethyl-4 : 6-diamino-m-xylene remains unchanged even after a year. The intermediate homologue, tetramethyl-2 : 4-diaminotoluene, becomes darker on keeping, but much less rapidly than the first member of the series.

The two lower homologues readily react with diazo-compounds, and the azo-colours obtained by the action of diazotised primulin closely resemble those produced from the corresponding primary diamines. 2 : 4-Te tramethyldiaminotoluene readily condenses with p-nitrobenzene- diazonium chloride, giving rise to p-nitrobenzene-5-azo-2 : 4-tetramethyl- diaminotoluene,

NMe,

N02*C,H,*N2<->Me, , Me

in theoretical yield, and similar results are obtained with other diazonium salts. 4 : 6-Tetramethyldiamino-rn-xylene does not combine with diazotised primulin, and when treated with a solution of p-nitro- benzenediazonium chloride containing sodium acetate, it remains entirely unchanged.

This inactivity of the symmetrically disubstituted tertiary diamine should be contrasted with the behaviour of 4 : 6-diamino-m-xylene under similar conditions (this vol., p. SS), for it furnishes additional evidence in support of the view that the readily decomposable initial product of the action of a diazonium salt on the primary base is an unstable diazoamine which subsequently undergoes transformation into tarry products and a small amount of azo-compound,

Me NH*N:NX Me NH, /--'\ \--/

Me NH,

I n the present instance, however, where the initial attachment of the diazo-residue to one of the nitrogen atoms is rendered impossible by the complete alkylation of the amino-radicles,

Me NMe,

<I> Me NMe, '

the production of This hindrance

an o-azo-derivative is altogether prevented. to the formation of azo-derivatives, due to alkglation ,

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REACTIVITY OF THE AROMATIC METADIAMINES. 653

although so strikingly manifested in the case of the preceding tertiary diamine, does co t obtain among the tertiary amines containing a free para-position with respect to nitrogen. As already indicated, 2 : 4- tetramethyldiaminotoluene yields azo-compounds quite as readily as 2 : 4-tolylenediamine itself, in this respect resembling dimcthylaniline, which is employed in the production of several well-known azo- d o u r i n g matters.

The difference in reactivity between 2 : 4-tetramethyldiaminotoluene and 4 : 6-tetramethyldiamino-m-xylene is also demonstrated by their bebaviour towards formaldehyde. The lower homologue readily interacts with this reagent, yielding 2 : 4 : 2' : 4'-octamethyZtetraminodi- tolyl-5 : 5'-methane,

Me Me

The disubstituted tertiary diamine, on the contrary, is not affected by formaldehyde, even when the experiment is carried out under pressure a t high temperatures in the presence of excess of acetic anhydride.

EX P E R I M E N TAL.

Nethy Zu tion of m-Tot ylenediumi fie.

m-Tolylenediamine hydro bromide and an excess of alcohol (6-7 mols.) were heated in sealed tubes a t 180° until the product on cooling no longer deposited a crystalline hydrobromide, this result being usually obtained in 8 to 10 hours. The pressure was released after 4 hours' heating in order to prevent the tubes from bursting. The product, after being heated on the water-bath to remove t,he unaltered methyl alcohol, was treated with excess of potassium hydroxide solution, the oil which separated being extracted with ether. The liquid of high boiling point remaining after the removal of the ether distilled at 254-259' under 757 mm. pressure, the greater portion boiling between 255' and 256O.

2 : 4-Z"etramethyldiaminotoZuene, thus obtained as a pale brownish- yellow oil, was further purified by repeated distillation under reduced pressure and finally boiled at 148-150' under 24-26 mm. pressure ; it has a sp. gr. 0.9661 at 24' and does not solidify at - 10'.

The pkatinichloride, C,,H,8N,,H,PtCl,, separates from aqueous ~ 0 1 ~ - tions in stellar aggregates of slender, transparent, yellow prisms ; it rapidly darkens when left in contact with the mother liquor, and is decomposed by boiling water, evolving formaldehyde and yielding a dark red solution. The salt when dried at 80-90' gave the following numbers on analysis :

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654 MORGAN: INFLUENCE OF SUBSTITUTION ON THE

0.2542 gave 0.0840 Pt. C,,H20N,C16Pt requires Pt = 33 -1 6 per cent.

The picrate crystallises from ethyl acetate in hard, transparent, yellow prisms, and melts a t 162-163' ; it is formed by the union of picric acid and the diamine in molecular proportion :

Pt = 33.04.

0.1479 gave 22.4 C.C. moist nitrogen at 16' and 760 mm. N = 17.66. C17H2107N5 requires N = 17.20 per cent.

The methobromide, NMe, C6H3Me NMe3Br. -The solution of po tass- ium hydroxide employed in liberating the tertiary base assumed a dark brown colour, and when saturated with the solid reagent yielded a heavy brown oil which rapidly solidified to a mass of brown, acioular crystals. This substance, which contained bromine, was identified a s the quaternary bromide by conversion into the corresponding chloride and subsequent formation of the plntinichloride. A solution of the bromide was triturated with moist silver oxide and filtered, the filtrate being then treated with hydrochloric acid and platinic chloride.

The platiniddoride, NMe2*C6H3Me*NMe,,HPtC16, which separates out may be crystallised from hot water without decomposition ; it is deposited on cooling in transparent, brownish-yellow prisms and is far more stable than the corresponding salt of the tertiary base :

0,2269 gave 0.0736 Pt. Pt = 32.43. 0.1861 ,, 0.0603 Pt. Pt = 32.40.

C12H2,N,Cl,Pt requires Pt = 32-39 per cent,

The remainder of the methobromide was converted into the tertiary diamine either by heating with ammonia under pressure (Pinnow, Zoc. cit.), or by treating the quaternary salt with moist silver oxide and evaporating down the filtered solution of the quaternary ammonium hydroxide.

The methylation follows the same course when m-tolylenediamine hydrochloride is employed, the product in this case being a mixture of the tertiary base with the methochloride.

Methylation of 4 : 6-Diamino-m-xybne, A mixture of 4 : 6-diamino-m-xylene hydrochloride and excess of

methyl alcohol was heated in sealed tubes at 180° until it remained viscid on cooling; the product, after being heated on the water-bath to remove excess of methyl alcohol, was rendered alkaline with strong potassium hydroxide solution and extracted with ether. The ethereal extract, when dried over potassium hydroxide, and subsequently dis- tilled, yields an oily base boiling at 243-245' under 757 mm. pressure. 4 : 6-Tetramethyldiamiwo-m-xyler~e, a pale brownish-yellow oil boiling

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REACTIVITY OF THE AROMATIC METADIAMINES. 6 5 5

at 124-125" under 12 mm. pressure, remains liquid a t - 10' and has a sp. gr. 0.9434 a t 18'; it does not darken perceptibly when kept for 12 months in diffused light,

The pkc~tinicl~loride, C,H2Me,(NMe2),,H,PtCJ6, separates from an aqueous solution of its generators in transparent, orange-yellow, acicular prisms ; i t is moderately soluble in water, melts indefinitely above 200°, and is fa r more stable than the corresponding salt of 2 : $-tetramethyl- cliaminotoluene ; i t may be crystallised from hot water without decom- position, and separates in reddish-orange needles often more than an inch in length :

0.2682 gave 0*0861 Pt. Pt = 32-10,

The picrate, C,H,Me,(NMe,)2,C,H,(N02)3*OH, obtained by mixing together alcoholic solutions of its generators, crystallises from ethyl acetate in hard, transparent, yellow, rhombic prisms, sparingly soluble in the alcohols, but dissolving more readily in acetone; when rapidly heated, i t melts at 202-203O, but slowly decomposes when maintained a t 193-195" :

C,,H,,N,CI,Pt requires Pt = 32.39 per cent.

0.22 gave 30.5 C.C. moist nitrogen at 1 4 O and 756 mm. N = 16.22. C,,H,,O,N, requires K = 16-62 per cent.

4 : 6-Tetramethyldiamino-1 : 3-xylene is produced with equal readi- ness from 4 : 6-diamino-nz-xylene hydrobromide and methyl alcohol, the tertiary base being the sole product whether the hydrochloride or tbe hydrobromide is employed.

Diaminomesitylenc hydrochloride, when heated with methyl alcohol, does not undergo methylation, the greater part of the primary diamine being recovered on working up the product.

I n preparing this diamine from dinitromesitylene (m. p. 56') by the action of iron filings and water acidified with hydrochloric acid, it was found that only one of the nitro-groups became involved in the reduction, so that nitromesidine crystallised out from the filtered solution in golden-yellow needles melting a t 70". The complete reduc- tion was accomplished by means of excess of t in and hot hydrochloric acid, but even with this reagent the action was very slow.

Comparative experiments made on the methylation of m-phenylene- diamine showed that the action is less under control than i n the case of the homologous diamines, the production of the tertiary base and quaternary salt being attended by the formation of fluorescent, tarry impurities.

The tertiary base, tetrame thyl-m-phenylenediamine, after treatment with acetic anhydride to remove any secondary amines, was purified by repeated rectification under reduced pressure, and finally ob-

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656 MORGAN: INFLUENCE OF SUBSTITUTION ON THE

tained as a brownish-yellow oil rapidly darkening on exposure, boiling a t 151-157O under 26 mm. pressure, and having a sp. gr. 0.9934 at 27' (compare Romburgh, Rev. Trccv. Chim., 1888, 7, 3 ; Wurster and Morley, Bey., 1879, 12, 1814).

Tertiary m-Diamines and Diaxonium Salts.

When a piece of cotton cloth impregnated with diazotised primulin is introduced into an aqueous solution of tetramethyl-m-phenylene- diamine or its tolylene homologue, a brownish-red azo-colouring matter is developed on the fibre, the colour of which closely resembles tha t obtained by the use of the corresponding unalkylated m-diamine. 4 : 6-Tetramethyldiamino-m-xylene, on the other hand, does not com- bine with this diazo-compound.

p-Nitro6enzene-5-ccx0-2 : 4-tetramethyZdiarninotoluene.- A solution of p-nitrobenzenediazonium chloride, when added to 2 : 4-tetramethyl- diaminotoluene dissolved in cold dilute hydrochloric acid, produced a dark-red precipitate the formation of which was completed by the addition of excess of sodium acetate. This insoluble product was crystallised from alcohol, separating from its solutions in dark-green leaflets with a bronze lustre; the yield was quantitative.

p-Nitrobenzene-5-azo-2 : 4-tetramethyldiaminotoluene is sparingly soluble in cold alcohol, dissolving more readily in ethyl acetate and crystallising from this solvent in leaflets melting a t 126-127'. Its solutions in the organic solvents have a deep purple colour and the azo-compound dissolves in cold concentrated sulphuric acid to an intense brownish-red solution :

0.1808 gave 33.4 C.C. moist nitrogen at 15' and 756 mm. N = 21.52. C17Hz10,N, requires N = 21.41 per cent.

The hydrochloride and platinichloride are red precipitates, the nitrate crystallises from alcohol in deep red leaflets, the picrate separates from the same solvent in red needles.

When the preceding experiment was repeated with 4 : 6-tetramethyl- diamino-m-xylene, the introduction of the p-nitrobenzenediazonium chloride produced no effect on the solution of the tertiary diamine. After remaining for 24 hours, the mixture deposited a tarry pro- duct, due t o the gradual decomposition of the diazonium base set free by the sodium acetate, but the filtered solution still contained the un- altered diamine. This base was completely recovered by treating the solution with excess of potassium hydroxide and extracting with ether, being precipitated in the form of its picrate by the addition of an alcoholic solution of picric acid to the ethereal extract. The yield of

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R E A C T I V I T Y O F THE AROMA'I'IC M E T A D I A M I N E S . 657

recrystallised picrate obtained in this operation was 90 per cent. of the theoretical.

Teel.ticwy rn- Diamines and Formddelqde.

Six grams OF 2 : 4-tetramethyldiaminotoluene dissolved in 20 grams of acetic anhydride were treated with 2 C.C. of 40 per cent. formalde- hyde solution and allowed to remain for 20 hour s ; the mixture was then heated to boiling, subsequently cooled, and rendered alkaline with excess of ammonia. The oily product which first separated rapidly solidified, and, after drying on a porous tile, was crystallised from ethyl acetate or alcohol.

2 : 4 : 2' : 4'-0ctc~metT~~ZtetraminoditoZ~Z-5 : 5'-nxethane separates in well- defined, transparent, colourless prisms, either obliquely truncated or terminated by pyramids ; the crystals often exhibit external twinning and melt a t 86' :

0.1473 gave O*4037*CO2 and 0.1322 H,O. 0.1833 ,, 24.6 C.C. moist nitrogen at 18' and 764 mm. N = 15.58.

C = 74.74 ; H = 9.97.

C23H36X4 requires C = 75-00 ; H = 9.78 ; N = 15.21 per cent.

The tetrnmine is readiIy soluble in most organic solvents with the exception of light petroleum ; it dissolves in dilute aqueous solutions of the mineral acids, and yields a colouring matter of the acridine series when heated with hydrochloric acid a t 150". It is not an analogue of the leuco-base of malachite-green, for it does not give rise to a colouring matter of this type when oxidised with lead peroxide and acetic acid.

The picrate separates from ethyl acetate in spherical aggregates of hard, transparent, yellow crystals and melts a t 147-148'.

4 : 6-Tetramethyldiarnino-m-xylene7 when dissolved in acetic anhy- dride and treated with formaldehyde solution, remains unaltered even when an excess of the reagents is employed in sealed tubes a t 150-170" ; the unchanged base recovered from the mixture boils at 243-248O (corr. 245O), and yields the characteristic picrate (m. p. 202-203').

ROYAL COLLEGE OF SCIESCE, LONDON. SOUTH KENSINGTOX, S. W.

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