1574 ROWE AND LEVIN STUDIES IN THE CLXXIII .-Xt udics in the Dihydmnaphthalene Se?*ies. Part I. The ar- Dih yd yo-a -nap h t h y lanzines and their Deqivatives . By FREDERICK. MAURICE ROWE and ESTHER LEVIN. THE investigation of the conditions governing the conversion of a-naphthylamine into ar-tetrahydro-a-naphthylamine by the action of sodium and an alcohol carried out by one of us (T. 1918 113, 955; J . SOC. Dyers and Col. 1919 35 128) culminated in the proof that the first stage in the reaction is the formation of 5 8-dihydrea-naphthylamine which undergoes isomeric change to the 5 6- or 7 8-compound and that the latter is then reduced to t'he tetrahydroiderivative ( J . SOC. Chem. I d . 1920 39 2 4 1 ~ ) , thus : H NH, /\/\ I l l \/A/ H H NH, H A / \ I l l \/\/ -+ B NH, \/\/ H Them appears to be little doubt that the reason why ar-tetra-hydro-a-naphthylamine has been obtained in the past only when sodium and amyl alcohol have been employed for the reduction, and not when other alcohols have been used is that the normal conditions of the reaction have been suitable for the isomerisation of the intermediate 5 8-dihydro-a-naphthylamine only in the former case.The isomerisation. which is effected by heating with sodium alkyloxide is influenced by both the factors of temperature and concentration of the alkali. There is an important difference in properties between 5 8- and 7 8-dihydro-a-naphthylamine for only the latter is reduced to ar-tetrahydro-a-naphthylamine by treatment with sodium and ethyl alcohol in the absence of an indifferent solvent of high boil-ing point.The present communication consists of a description of the means employed for the isolation of the pure dihydro-a-naphthylamines, the proof of their constitution and the preparation of certain of their derivatives. Owing to the close relationship betweeii a-naphthylanhe its two dihydro-derivatives and its tetrahydro-derivative the discovery of a suitable derivative of these bases which by possessing a dis-tinctive crystalline form in each case would afford a ready means of purification and characterisat.ion was highly desirable DIHYDRONAPHTHALENE SERIES. PART I. 1575 After a number of trials it was found that the most suitable compound to prepare was the benzylidene derivative which was readily obtained in a pure condition from each of the crude bas-, and moreover by hydrolysis of the benzylidene derivatives the bases were readily obtained in a pure state.The following table shows the difference in melting point and crystalline form exhibited by the four benzylidene derivatives : Benzylidene -a - naphthylamine. Small pearly plates. m. p. 70-71O Benzylidene - 5 8 -dihydro - a - Massive rhombic pyra-naphthylamine. mi& with brachy-domes and brachv-m. p. 69'. pinalioids. naphthyl amine. are a combination of a rhombic prism and pyramid with brachypinakoicis. thylamine. with brachypinakoids. Benzylidene - 7 8 - dihydro - a- Long crystals which m. p. 64'. Benzylidenetetrahydro-a - naph- Flat rhombic prisms m. p. 61.6'.The melting point of each of these compounds was depressed by admixture with any other. It should be noted that although ar-tetrahydro-a-naphthylamine has been frequently compared with o-2-xylidine in the past as far as the formation of a crystalline benzylidene derivative is concerned it is more strictly comparable with p-xylidine as the isomeric xylidines form non-crystalline benzylidene derivatives. The benzylidene derivatives of the three hydrogenated bases readily form large crystals and it is a simple matter to obtain well-formed crystals of these compounds weighing upwards of 1 gram each. Both 5 8- and 7 8-dihydro-a-naphthylamine condense with diazonium salts with the direct formation of aminoazo-compounds, and they may also be diazotised and combined with amines or phenols forming azo-dyes which differ in shade from similar azo-dyes derived from a-naphthylamine or ar-tetrahydro-a-naphthyl-amine.The relation of the shades of similar azo-dyes produced from the four amines by the two different methods is shown in the following table : Naphthaleneazo-p-naphthol ........................ 5 8-Dihydronaphthaleneazo-~-naphthol ......... 7 8-Dihydronaphthaleneazo-p-naphthol ......... Tetrahydronaphthaleneazo-p-naphthol.. .......... p-8ulphobenzeneazo-a-naphtlhylamine ......... p-Sulphohenzeneazo-5 8 - dihydro -a - naphthyl-p-Sulphobenzeneazo - 7 8 - dihydro -a - napht.hy1-p - Sulphobenzeneazotetrahydro -a -naph thylamine amine. amine. Clarot. Red rather bluer than Para-Red. Orange-red. Orange.Reddish-brown. Brownish-yellow Dull orange. Vivid orange 1576 ROWE AND LEVIN STUDIES IN THE As the four acid dyes are velry sensitive to acids the shades are those produced after the dyed material had been soaped. The shade produced by an azo-derivative of 5 8-dihydro-a-naphthylamine is more nearly related to that produced by a similar azo-derivative of a-naphthylamine whilst the shade produced by a 7 8-dihydro-a-naphthylamine derivative is more nearly related to that produced by a similar tetrahydro-a-naphthylamine derivative. The crude base was prepared from a-naphthylamine by the action of sodium and ethyl alcohol in the presence of an indifferent solvent of high boiling point (Farbenfabriken vorni. F. Bayer & Co., D.R.-P. 305347). A mixture of 400 C.C.of dry solvent naphtha (b. p. 139O) and 30 grams of sodium contained in a flask fitted with a reflux condenser was boiled and a solution of 34 grams of a-naphthylamine in rather more dry ethyl alcohol than is necessary to dissdve the sodium added drop by drop through the condenser. Boiling was continued until all the sodium had disappeared; an excess of alcohol is desirable in order to complete the reaction as quickly as possible. The mixture was poured into water the solvent naphtha layer separated acidifield with hydrochloric acid, and the solvent naphtha removed by distillation in a current of steam. The residue was filtered from a little tar and allowed to crystallise. The hydrochloride was basified the base allowed to crystallise and after pressing well it was melted with 10 per cent.of its weight of toluene cooled in a freezing mixture of ice and salt filtered quickly and dried. It was converted into the benzylidene derivative by mixing 31 grains of the base with 15 grams of benzaldehyde and allowing to remain until thel mixture solidified. The product was pressed well and crystallised twice from light petroleum (b. p. 70O). Benzylidene-5 g-dihydro-a-nczpht~~iylami,i e forms massive rhoiiibic pyramids with brachydomes and brachypinakoids inelting at 6 9 O (corr.) (Found C = 87-75 ; H = 6.51. C,;H,,N requires C = 87.55 ; H=6.44 per cent.). The benzylidene derivative was hydrolysesd by warming with hydrochloric acid and the benzaldehyde removed by distillation in a current of steam. The residue after filtration n-as basified and the base distilled DIHYDRONAPHTBALENE SERIES.PART I. 1677 5 8-Dihydro-a naphthylaminp forms large colourless rhombic plates or needles melting at 3'i.So (corr.) and boiling a t 2 4 7 O / 408 mm. and the hydrochloride forms sto'ut colourless needles. Both the base and the hydrochloride turn pink on exposure t o air (Found C = 82.59 ; €I = 7.65. C,,€I,,N requires C = 82.76 ; l-3 =7*58 per cent.). When the amine was diazotised and treated with an alkaline solution of sodium stannite Ag- or 1 4-dihydronaphthalene con-sisting of colourless plates melting at 24.5-25O was obtained, which formed a compound with mercuric acetate crystallising from benzene in colourless needles melting a t 121° and a dibromide, long glistening thin prisms melting at 71.5-72O.5 8-Dihydroaccto-a-?iap~~thalide crystallises from alcohol in colourless silky needles melting at 163O (corr.). It may be1 sub-limed unchanged (Found C = 77.15 ; H = 7.01. C,,HI30N requires C = 77.01 ; H = 6.95 per cent .). 2 4 -D ini trop h en y l-5 8-di hy d r o-a-72 np h t h ylamine was obtained by heating under reflux a mixture of 5 grams of the base 6.9 grams of 4-chloro-m-dinitrobenzene dissolved in 100 C.C. of alcohol and a solution of 4.6 grams of crystallised sodium acetate in a little water. The product crystallises from acetic acid or toluene in reddish-brown rhombic plates melting at 144O' (corr.) (Found : C=61*89; €€=4*27. C,,fI,,0,N3 requires C=61*74; H=4.18 per cent .). The sodium salt of p-sulphobenzeneazo-5 8-dihydro-a-naphthyl-mnine was obtained by the addition of diazotised sulphanilic acid to an aqueous solution of the hydrochloride of the base.The product which separated as a crystalline precipitate was dissolved in the minimum quantity of boiling dilute aqueous sodium carbonate and on cooling the salt separated in glistening brown plates. 6 S(0r 7 g ) - D ~ ~ . y d r o - a - n a p k t h y l ~ ~ ~ n e , a-Naphthylamine was reduced to 5 8-dihydro-a-naphthylamine, as already described. When all the sodium had disappeared the mixture was distilled until the internal temperature rose to 140°, and heating was continued a t that temperature for one hour, during which period ammonia was evolved o'wing to some decom-position of the amine. The mixture was poured into water the 3 M 1578 STUDIES IN THE DIHYDRONAPHTHALENE SERIES.PART I. oily layer separated acidified with hydrochloric acid and the remainder of the solvent naphtha removed by distillation in a current of steam. The rwidue was filtered from tar and allowed to crystallise. The hydrochloride separated in straw-coloured, feathery needles quite different in appearance from the less soluble hydrochloride of the isomeric base. The hydrochloride was basified the base extracted with ether and converted into the benzylidene derivative as described for the isomeric compound. Benzylidene-7 8-dihydro-a-naphthylamine separates from light petroleum in long crystals which are a combination of a rhombic prism and pyramid with brachypinakoids melting a t 64O (corr.) (Found C = 87.39 ; H = 6.48.C,,H,,N requires C = 87.55 ; H = 6.44 per cent .) . The benzylidene derivative was hydrolysed by warming with hydrochloric acid the benzaldehyde removed by extraction with ether the solution of the hydrochloride basified extracted with ether and the base distilled. 7 8-Dihydro-a-nuphthylamine is a colourless oil boiling a t 180-182°/30 mm. which rapidly darkens on exposure to air and is less stable than the isomeric base. It did not crystallise when maintained a t - 1 8 O for a considerable time (Found C=82.66; €1=7*71. C,,H,,N requires C=82*76; H=7.58 per cent.). When the amine was diazotised and treated with a solution of alkaline sodium stannite hl- or 1 2-dihydronaphthalene crystal-lising in coloarless plates melting a t -go was obtained which formed a compound with mercuric acetate of high melting point, insoluble in benzene and a dibromide stout prismatic crystals melting a t 70-71'.7 8-Dihyclroaceto-a-nuphthalide forms colourless silky needles melting a t 153O (corr.). The yield was not good olwing to the instability of the amine a t the temperature of acetylation (Found : C = 77-00 ; H = 7.01. C,,HI30N requires C = 77.01 ; H= 6.95 per cent.). 2 4-Dinitropheny 2-7 8-dihydro-a-nupht hylamine was obtained in a similar manner to that used for the isomeric compound. It crystallises from acetic acid or toluene in glistening reddish-brown leaflets or needlw melting at 136O (corr.) (Found C=61*78; H = 4.13. The sodium salt of p-sulpho benzeneazo-7 8-dihydro-a-naphthyl-amine was obtained in a similar manner to that used for the immeric compound. It crystallises in reddish-brown glistening plates. ar-Tetrahydro-a-naphthylamine was readily obtained from 7:8'-dihydro-a-naphthylamine by adding 15 grams of sodium to a C,,H130,N3 requires C = 61-74 ; H = 4.1 8 per cent .) THE FORMATION AND STABILITY OF SPIRO-COMPOUNDS. 1579 boiling solution of 10 grams of the base in 200 C.C. of dry ethyl alcohol. The mixture was worked up in the usual manner. For purposes of comparison benzyliclene-ar-tetrah.ydro-a-nuphth ylumine was prepared from ar-tetrahydro-a-naphthylamine. It crystallises from light petroleum in flat rhornbic prisms with brachypinakoids melting a t 6 1 . 5 O (corr.) (Found C= 86.70 ; H = 7.33. C,,H,,N requires C = 86.81 ; €I = 7-23 per cent.). DYESTUE'FS RESEARCH LABORATOBY, MUHICIPAL COLLEGE OB TECHNOLOGY, MANOHESTEB. [Received November loth 1920.