4.58 THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 11, No. 5

the residual oil distilled at zoo mm. pressure. Un- We therefore undertook a systematic study of the changed aniline remaining in the distillate is removed synthesis of the quaternary iodides with a view to by diazotizing' in hydrochloric acid and heating establishing the simplest conditions which would the solution. The acid solution is then rendered give satisfactory yields of the pure compounds. Our alkaline, the supernatant quinoline extracted with many experiments need not be described in detail. ether, the ether solution dried, the ether removed, After carrying out the addition reaction under varying and the residual oil distilled at atmospheric pressure. conditions-in pressure flasks, in flasks under reflux Quinoline thus obtained boils at 238' (uncorrected). condensers, with and without the use of various The yield is 65 per cent of the calculated amount, solvents, and with varying amounts of the components based upon the weight of aniline taken. -we find that it is best to use equimolecular amounts Calculated for COHIN:N = 10.86 per cent Found: N = 10.73 of the alkyl iodide and the base and to carry out per cent, 10.69 per cent the reaction in a round bottom flask surmounted by a worm condenser. The flask should never be filled 0CT33 beyond one-third1 of its capacity. 2,4-DIMETHYLQUINOLINE, 1 - A mix- Depending on the nature of the base used, the re- O-C& v action may proceed spontaneously and violently N (as in the case of quinoline methiodide) or it may ture of 120 g. of paraldehyde and 200 g. of acetone require external heating (as in the case of quinaldine is saturated with dry hydrochloric acid and allowed ethiodide). The presence of an a-methyl group in to stand for 24 hrs., care being taken to exclude moisture. the molecule appears to decrease the rate of reaction. The mixture is then slowly added to 200 g. of aniline The product is usually obtained in the form of a dissolved in 400 g. of hydrochloric acid, and the syrup solid cake, which may be gradually dissolved by treat- finally heated during I hr. (in a water bath) under a ment with hot alcohol. The iodide crystallizes from return condenser. On rendering alkaline, a yellow the alcoholic solution on cooling. In general, the separates from the solution. The oil is extracted oil yields of the quaternary halide are satisfactory, with ether, and the ether evaporated. The residue, varying from 60 to 80 per cent of the theoretical. without further purification, is dissolved in an equal We have found, however, that small amounts of im- weight of hydrochloric acid and diazotized. Here purities in the reagents may decrease these yields very again precautions are taken to remove nitroso com- materially. pounds by extraction of the cold acid solution with All the quaternary halides are crystalline compounds ether. The aqueous solution is rendered alkaline of a more or less pronounced yellow color. Many and the yellow oil extracted with ether. The usual of them melt with decomposition. All of them are procedure is followed in the final purification of the water-soluble and ionize in solution. The iodine 2,4-dimethylquinoline. The compound, which is ob- content of any quaternary base may be rapidly and tained in 25 to 30 per cent yield, based upon the weight accurately determined by a slight modification of of aniline taken, boils at 260-264 (uncorrected) the Volhard method. This method served a useful under ordinary pressure. purpose in permitting us to judge the purity of our Calculated for CiiHnN: N = 8.92 per cent. Found. N 8.78 per cent, 8.73 per cent.2 products. The above procedure is very much simpler and far From the standpoint of the producer of photo- more rapid than that outlined by v. Be~er.~ sensitizing dyes the following quaternary halides are perhaps the most important : quinoline methiodide COLORLABORATORY BUREAUOB CHEMISTRY and ethiodide, quinaldine ethiodide, toluquinaldine WASHINOTON,D. C. methiodide, and ~,4-dimethylquinolineethiodide. We have prepared relatively large amounts of these com- INTERMEDIATES USED IN THE PFtEPARATION OF pounds and small amounts of a few other analogous PHOTOSENSITIZING DYES. 11-QUATERNARY iodides, all of which are described in the experimental HALIDES part. By CARL H. LVNDAND LOUISE. WISE EXPERIMENTAL Received February 24, 1919 The second step in the synthesis of photosensitizing QUINOLINE METHIODIDE--.When small amounts of dyes is the formation of quaternary iodides from the this product-less than IOO g.-are required, the follow- bases described in the preceding paper. These com- ing procedure is convenient: Equimolecular amounts pounds result from the direct addition of methyl, of methyl iodide and quinoline are mixed in a round ethyl or other alkyl iodide to the quinoline base. bottom flask, and allowed to stand at room temperature Many of these addition products have been described under a reflux condenser. The mixture gradually in the literature, but there is too little available in- becomes warm and crystals begin to appear in the formation on the best conditions for the preparation flask. Since the reaction is exothermic, the mixture of these compounds. finally reaches a temperature at which the methyl- iodide boils vigorously. When this point is reached 1 No special precautions are necessary. Tetrahydroquinoline is not present. the flask must be cooled in an ice bath to keep the * Our thanks are due to Messrs. Jenkins and Ellis, of the Nitrogen reaction from proceeding too violently. After a Laboratory of the Bureau of Chemistry, for the analytical data given in this paper. 1 This simple precaution is necessary. Well-annealed flasks filled * Loc. cit. half full frequently cracked during the course of the reaction. May, 1919 THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY 459 yellow cake of the methiodide has formed, the flask from 95 per cent alcohol is obtained in the form of is immersed in a hot water bath and heated for several lemon-colored needles which melt at I 90 O (uncorrected). hours to insure a complete reaction. The solid cake Dbbner and Miller' give a melting point of 195'. in the flask is then covered with 95 per cent alcohol Calculated for CloHeN.CHs1. I = 44.53 per cent. Found: I = 4440 and the heating continued until the methiodide has per cent. dissolved, On cooling and stirring, a crop of small, QUINALDINE ETHIODIDE-EqUimOkCUlar amounts Of bright yellow crystals is obtained which are shown to quinaldine and ethyl iodide are mixed in a flask which be quinoline methiodide, monohydrate, CsH?.CHJ. is then connected with a reflux condenser. The H20. In the recrystallization of the crude methiodide mixture is heated on a steam bath for 18 to 20 hrs. it is necessary to use enough 95 per cent alcohol to The crude cake thus obtained is then heated under insure the presence of sufficient water to form this a reflux condenser with just enough 95 per cent alcohol monohydp-ate, otherwise a mixture of the monohy- to cause complete solution. (This requires about drate and anhydrous methiodide (melting 90' to 8 parts by weight of alcohol to I part of the crude I 20 ") is obtained and recrystallization is required. ethiodide.) On cooling, the alcoholic solution deposits The monohydrate melts at 70' to 71 ' (uncorrected). quinaldine ethiodide in the form of coarse, straw-colored The melting point recorded by Marckwald and Meyer' or brown needles, decomposing at 23 I O to 234' (uncor- is 72'. The yield varies from 70 to 80 per cent of rected). Miethe and Book2 who previously prepared the theoretical. this compound give the melting point as z34"-z35O. Calculated for CsH7.CHaI.HzO: I = 43.91 per cent. Found: Calculated for ClaHsN CZHII I = 42 44 per cent. Found: I = 42.30 I = 43 93 per cent. per cent, 42.20 per cent. By allowing the monohydrate to stand for several The yield of ethiodide was 70 to 80 per cent of the days over sulfuric acid in vacuo, complete dehydra- theoretical. When the alcoholic mother liquors from tion takes place. The melting point of the dehydrated the first crop of crystals are concentrated to one- tenth of their initial volume, a second crop of the ethio- compound is 131 ' to 133 O (uncorrected). Marckwald and Meyer2 give 133" as the melting point of the dide is obtained. This represents only about 5 per anhydrous compound. cent of the theoretical yield, and the crystals are so Calculated for CPHIN.CH~I:I = 46.82 per cent. Found: I = 46 66 impure that they require further purification. per cent. The procedure outlined above proved very satis- In the preparation of larger amounts of quinoline factory, and we found no difficulty in preparing several methiodide, it is expedient to modify the above method kilograms of the ethiodide by this method. since it, becomes almost impossible to control the re- Attempts to shorten the procedure met with little action by cooling with an ice bath (as described). success. When the initial time of heating on the The following modification is used: Methyl iodide steam bath was decreased to IO hrs., the reaction did is heated to boiling in a flask connected by means not go to completion, and yield of ethiodide was ma- of a two-hole stopper, with a reflux worm condenser terially decreased. Similarly no advantage was gained and with a dropping funnel. The source of heat by carrying out the reaction at a higher temperature is then removed and the quinoline added through (150"). In this case we also obtained a 70 to 80 per the dropping funnel at such a rate that moderate cent yield. refluxing of methyl iodide is maintained. After p-TOLUQUINALDINEMETHIODIDE - Equimolecular all the quinoline has been added, the mixture is allowed amounts of p-toluquinaldine and methyl iodide are to cool. From this point on the procedure is identical heated together under a reflux condenser for several with that outlined above. hours. The crude cake is recrystallized from 95 QUINOLINE ETHIODIDE-The procedure iS very similar per cent alcohol. The ethiodide is obtained in the to that used in the formation of the methiodide. form of fine, pale yellow, fluffy needles, decomposing In this case initial heating on the steam bath is re- at 246 '-247 O (uncorrected). Mbller3 gives the melting quired to start the reaction after the components point as ~36"-237~.The compound was dried at have been mixed. The reaction then proceeds with I 20' before it was analyzed. such violence that the flask must be removed from Calculated for CnHnN.MeI. I = 42.44 per cent. Found I = 42.14 the bath and rapidly cooled. The crude cake is re- per cent, 41.94 per cent crystallized from 95 per cent alcohol, and anhydrous The yield obtained varies from 65 to 75 per cent of quinoline ethiodide is obtained in the form of bright the calculated amount. yellow crystals melting at 155' to 157' (uncorrected), ~-TOLUQUINALDINEETHIODIDE-Equimolecular quan- tities of p-toluquinaldine and ethyl iodide are heated Miethe and Book3 give a melting point of I 56 ' to I 57 O. The yield varies from 75 to 85 per cent of the theoretical. together on the steam bath under a reflux condenser Calculated for CaH7N.CzHd: I = 44.53 per cent. Found: I = 44.35 for about 18 hrs. The resulting solid cake is recrystal- per cent. lized from alcohol in the usual manner. The ethiodide QUINALDINE METwoDmE-Only small quantities forms granular, yellow crystals decomposing at 213 O- of this compound were prepared and we have made 216' (uncorrected). The yield varies from 65 to no systematic study of the conditions for obtaining 70 per cent of the theoretical. Bing14who previously the best yields. The methiodide on recrystallization 1 Ber., 16 (1883), 2468. ' LOC. cit. 1 Ber., 83 (1900), 1884. *Ann,342 (1887),311. p LOG. cir. 4 "Ueber einige neue Isocyanine u. deren Einwirkung auf Bromsil- * Ber., 97 (1904), 2009. bergelatine." Techn. Stndien, 2 (1914), 12. 460 THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 11, No. 5 prepared this compound, obtained a 34 per cent shown the identity with the above-named German yield of the ethiodide, which melted at 217’. and British products of two of our dyes, which we Calculated for C1iH1iN.EtI. I = 40.54 per cent. Fbund: I = 40.08 have termed, respectively, “Pv. I” and “Pc. IX.” per cent. Pinaverdol is prepared from a mixture of the meth- 2,4-DIMETHYLQUINOLINE ETHIODIDE---Amixture Of iodides’ of toluquinaldine and quinoline by the action equimolecular parts of 2,4-dirnethylquinoline and of alkali and air. The probable constitution2 is best ethyl iodide is permitted to stand at room temperature represented by the formula: over night and then heated under reflux condenser on steam bath for 5 to 6 hrs. The product, when recrystallized from alcohol, yields granular, yellow crystals, m. p. 223-225’ (uncorrected). Beyerl gives the melting point as 214’. The yield is about 50 AW per cent of the theoretical. CHa I Calculated for CiiHnN.EtI: I = 40.54 per cent Found: I = 40.17 Pinacyanol is prepared from a mixture of the ethiodidesl per cent. of quinaldine and quinoline, by the action of formal- DETERMINATlON OF IODINE-The analytiCa1 pro- dehyde and alkali. The constitution of this dye is cedure for the determination of iodine in quaternary still in doubt, but from present indications it is prob- bases is as follows: A weighed sample (about 0.3 lematical whether the quinoline ethiodide actually g.) of the iodide is transferred to a 500 cc. heavy enters into the reaction. If it does not, the formula2 walled bottle (provided with a ground-in glass stopper). of the dye becomes The halide is dissolved in 200 cc. of water, and 5 cc. of 50 per cent nitric acid (free from halogens and oxides of nitrogen) are added to the mixture. A standardized 0.05 N silver nitrate solution is then gradually run into the mixture, which is vigorously shaken after the addition of each 5 cc. of the solution. When an When pinacyanol is treated with an excess of silver excess of silver nitrate is present 3 cc. of a saturated chloride under proper conditions, it is quantitatively ferric-ammonium alum solution (indicator) are added converted into the corresponding chloride (Pc. XII). and the mixture is again thoroughly shaken. The The greater solubility of this chloride renders it more pEecipitated silver halide need not be removed by suitable than pinacyanol (iodide) for use in bathing filtration. The excess of silver nitrate is then titrated plates. with 0.07 N ammonium thiocyanate solution. The In the synthesis of these dyes we have been guided fir;t permanent (salmon) pink coloration in the solu- largely by the German patents3 which give good tion marks the end-point of the titration. The per- descriptions of the methods of preparation, but which centage of iodine is calculated by the usual method. fail to emphasize a few necessary precautions. The COLORLABORATORY details of our own procedure for the preparation of BUREAUOF CHEMISTRY Pv. I and Pc. IX and XI1 and absorption curves WASHINGTON,D. C. of the dyes are given in the following experimental part: SYNTHESIS OF PHOTOSENSITIZING DYES2 EXPERIWENTAL PINAVERDOL AND PINACYANOL PV. I (PINAVERDOL OR SENSITOL GREEN)-Fourteen By LOUISE. WISE,ELLIOT Q. ADAMS,J. K. STEWART AND CARL H. LUND grams of $-toluquinaldine methiodide and 2 j.8 g. Received February 24, 1919 of anhydrous quinoline methiodide are dissolved in The photosensitizing dyes that have gained the 400 cc. 95 per cent alcohol. The solution is heated ascendancy in panchromatic plate manufacture are to boiling and 77 cc. of 0.7 N alcoholic potassium hy- two derivatives of quinoline, termed, “pinaverdol” droxide (= 3.0 g. of potassium hydroxide) are gradually and “pinacyanol” by the German dye manufacturers. added from a burette. The mixture is maintained Since 1916, these dyes have also been produced by at its boiling point for j min. after the addition of British manufacturing chemists under the names the alkali is complete. Fifty cubic centimeters of “sensitol green” and “sensitol red,” respectively. alcohol are then added, and the crimson-colored We have made more than fifteen dyes of this general solution is permitted to cool slowly. A blue-black, type.3 A study of their absorption spectra, together granular, crystalline mass is deposited. The crystals with the results of photosensitizing experiments are filtered and dried. The weight of the crude dye carried out under the direction of Drs. Merrill and is about 5.5 g. (about 25 per cent of the theoretical). Burns, of the Bureau of Standards, and by Mr. H. A. The product is pulverized, the powder introduced Piper, of the Chemical Section of the Science and into an extraction thimble and extracted with ether’ Research Department of Aircraft Production, has in a Soxhlet apparatus, until the extract is no longer

1 J. prakt. Chem., [2] 88 (1886), 406. J Cf. preceding article. a The work on photography formerly carried on in connection with 9 The mechanism of the formation of these dyes has been discussed in the Chemical Section of the Science and Research Department of the an earlier communication from this Laboratory (Wise and Adams, LOG. Bureau of Aircraft Production is now being completed by the Color Labora- cit.) . tory, Bureau of Chemistry, Washington, D. C. 8 Pinaverdol, D. R. P. No. 167,159, Example 1 (1903), Pinacyanol, *Wise and Adams, THISJOURNAL, 10 (1918), 801. D. R. P. No. 172,118, Example 1 (1905).