Robert Shapiro, Gerald Sugerman, Howard Rachbach, and Harry Wagreich
The City College of New York New York
I
I
New Vat-DV~SSuitable for Student ~ x p k n e n t s
In chemistry courses which deal, in part, with the process of vat-dyeing, students generally use commercially prepared dyes to perform the appropriate operations on cloth. An important aim of this study unit should he an appreciation of the role of organic chemistry in dye-synthesis; therefore, the teaching of vat-dyeing should he enriched by giving students the opportunity of preparing a vat-dye prior to its use. Synthesis of vat-dyes is difficult in a student laboratory situation, since it often involves time-consuming and laborious operations. For example, one of the methods of preparing indigo involves bromination of c-nitro cinnamic acid, followed by dehydrohalogenation to form c-nitrophenyl propiolic acid which is finally reduced to indigo. All of these operations involve considerable time, elevated temperatures, hazardous conditions, and elaborate stepwise separations. These conditions of time and difficulty are paralleled in the synthesis of many other vat dyes. In this paper we wish to report the preparation of new vat-dye mixtures which can be made rapidly a t room temperature using relatively simple equipment. Hence, they are appropriate to student laboratory experiments.' Vat-dyes are distinguished by their insolubility in water. They must he converted to a soluble form before being applied to cloth. I n all cases, this form is obtained by reduction with suitable reagents, such as sodium hyposulfite in alkaline solution. The reduction product (leuco base) has a high affinity for textile fibers and is generally almost colorless. By means of air oxidation (or other suitable oxidizing agents), the original, highly colored compound is regenerated on the cloth and remains firmly affixed. Vat dyes are noted for their excellent fastness, i.e., retention of color on exposure to light, in laundering (washmg, bleaching, rubbing) and on contact with perspiration and industrial waste gases in the air (1). They are effective on a wide variety of fibers including cellulose fibers, wool, nylon, LcOrlon,"and acrylic fibers. The required reversible oxidation-reduction system in most vat-dyestuffs is present as carhonyl hydroxyl conversion. A classical example of vat-dye behavior is shown by indigo, which on reduction yields the soluble, Acknowledgments of Grantsin-Aid: ( 1 ) Frederick Gardner Cottrell Grant from the Research Corporation, and (2) The City College Research Committee. Organic analyses were done by the Schwarzkopf Microanalyticel Laboratory of Woodside, N. Y. This report is the result of joint research carried out in these Iabboratmies by a teacher (A.W.) and a group of under graduate "honors" and research students. We believe the work will be of interest to the readers of THIS JOURNAL for it8 pedagogical value (i.e., in the teaching of vat-dyeing) and as an example of directed undergraduate research.
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Journal of Chemical Education
indigo white. Other substances capable of undergoing typical vatdye behavior are derivatives of anthraquinone, naphthequinones, para and ortho henzoquinones. Preparation and Properties of N e w Dyes
It is well known that p-henzoquinone reacts with aromatic amines to yield stable, deeply colored compounds called aryl-amino-p-quinones, which have vatdye properties (3, 4, 5). According to Perkins (6), they have been used extensively in Europe for vat-dyeing of wool. He states further that, "No derivatives of the isomeric o-quinone have been found to he of interest as dyes." In a private communication, Dr. Perkins stated: "In dye research, only 2,5-dianilino p-quinone and derivatives thereof have come to our attention as having commercial possibilities. We assume from the paucity of literature and the absence of such products from the dye market, that corresponding ortho-quinones either do not exist or are not of interest as dyes." The apparent lack of interest in the preparation of aryl-amino-o-benzoquinones may be due to the presence of tarry byproducts which are difficult to remove. In addition, o-benzoquinone itself is unstable in media containing even traces of moisture, polymerizing to form tars of unknown composition (7, 8). Relatively few aryl-amino-ehenzoquinones have been prepared (8-11). In 1918, Kehrmann and Cordone (9) treated c-benzoquinone with aniline in dry chloroform. They identified the principal product as 4,5-diauilino o-benzoquinone by elemental analysis and preparation of the corresponding 2,3-dianilino-phenazinederivative. Another method of preparing this compound might he mentioned. It was shown that aqueous catecholaniline mixtures can be aerobically oxidized in the presence of the enzyme tyrosinase to yield 4,5-dianilino c-benzoquinone (10). Wagreich and Selson (12) measured the oxygen uptake in this enzymatic oxidation and found that three atoms of oxygen are absorbed in the formation of 4,5-dianilino o-benzoquinone per molecule of catechol. Catechol alone absorbed two atoms of oxygen. The mechanism for the formation of t.he 4,5-dianilino o-henzoquinone is presently unknown, hut must incorporate this information. The formation of 4,5-dianilino o-benzoquinone may be represented as follows:
k Catechol
4,5-dianilino o-benzoquinone
The only attempt to use mixtures believed to contain aryl-amino-o-benzoquinones in the dyeing of wool was reported by Bernardi in 1938 (8). He prepared vatdye mixtures resulting from the separate reactions between o-benzoquinoue (prepared by the oxidation of catechol with lead dioxide in anhydrous benzene) and the following amines a t room temperature: aniline, p-chloro-aniline, 0-, m-, and p-toluidme. He stated that the mixtures probably contained the corresponding mono and diaryl-amino 0-henzoquinones, although no separations or structural analyses were effected. We have extended Bernardi's work by preparing additional mixtures resulting from the oxidation of catechol in the presence of aromatic amines, and by using partially aqueous solutions to reduce fume and fire hazards and increase the ease of manipulation. The properties of these dyes have been evaluated. One dye mixture was analyzed completely. The reaction was carried out using 43 different aromatic amines which were systematically classified as follows: Class A: Class B: Class C: Class D: Claas E: Class F:
Anilines with no other reactive groups. Anilines with electronegative substituents. Polvnuclear and heterocvclic . -~ r i m a r vamines ~ecbndaryamines. Tertiary amines. Miscellaneous.
Despite the instability of o-benzoquinone in water, it reacts preferentially with aniline in aqueous solution to form stable products (9). The products in each case are described in Table 1. Primary and secondary aromatic amines generally gave good yields of brown or red products, not contaminated by tars. Some secondary amines (e.g., diphenylamine) and all tertiary amines yielded tarry substances. The absence of a replaceable hydrogen prevents tertiary amines from reacting in the usual manner. Aromatic amines containing two or more electronegative ring suhstituents (e.g., 2,4-dinitroaniline and 2,6dichloro-4-nitroaniline) did not react a t all and were recovered unchanged. By analogy of the reaction between p-benzoquinone and aniline proposed by Suida and Suida (4), these results are not unexpected. Thirty-one dye mixtures were found suitable for student laboratory exercises. They are labelled "fair," "good," or "fair to good" in the column titled "Dye Quality" in Table 1. Of these, seven exhibited typical vat-dye behavior (pale yellow on reduction and colored upon subsequent exposure to air). This is indicated in the same column as above. The colors are fast to washing and rubbing and have retained light fastness for over four years. The vat-dye behavior of 4,5-dianilmo o-henzoquinone may he shown as follows: H
dkaline reduction
19.7 g of potassium ferricyanide, dissolved in 80 ml of water, were added slowly with stirring at room temperature. The reaotion mixture was diluted with 50 ml of water, filtered, and washed with water until free of inorganic compounds and catecbol (as shown hy the absence of s blue color when a. few drops of 0.5 M ferric chloride solution were added to 5.0 ml of filtrate). It was then washed with 500 ml of 3 M HCI to dissolve any excess amine. The product was airdried for 15 min. The various mixtures may be used to dye wool according to the following procedure (13): A "stock wt" is prepared: 0.2 g of product is made into a. paste with 1.0 ml methyl alcohol. 1.0 ml of water is added followed by 2.0 ml. of 5.0 M sodium hydroxide solution. 0.2 g of sodium hyposulfite (Na&On) is sprinkled in with stirring. The "vat" is allowed to stand for 30 min. Additional small portions of sodium hyposulfite are added if necessary. A dye bath is prepared: 110 ml of water a t 50'C and 0.3 ml of 18 M ammonia water are mixed. A piece of white woolen cloth is added to the dyebath. Before adding the stock vat, 0.05 g of freshly dissolved glue is added to protect the wool from alkali. The cloth is dlowed to soak for a half hour or longer. After dyeing, the wool is airdried. This is followed by washing with 3.0 M hydrochloric acid and warm water to remove the alkali. The dyed cloth is then redried.
Analysis of a Dye Mixture
The reactions between o-benzoquinone and aromatic amines are not completely understood. Only one product from such a reaction mixture has been characterized. Separation and identification of the components of the mixture should clarify the origin of their dyeing properties and aid mechanism studies of these reactions. I n this report, one mixture was separated and analyzed, as follows: A mixture resulting from catechol-ferricyanide-aniline interaction was chromatographically separated using a column (length 60 cm; bore 107 em) with an alumina adsorbent. 1.0 g of crude product, dissolved in 9 : 1 benzene-acetone, was adsorbed on the column and developed with the same solvent. Three hands, in descending order, were observed: greenishgray (negligible quantity), light violet, and orange. Orange Band: This band was eluted with 9 : 1, benzene-acetone solution. Evaporation of the solvent, followed by several recryst,allizations from 1 : 4, methanol-benzene and 1 : 3, chloroform-heptane, yielded deep purple crystals, melting sharply a t 204'C. They were reduced in alkaline hyposulfite and gave a violet color in concentrated sulfuric acid which turned red on the addition of water. This compound was subjected to a complete elemental analysis; calculated for CzaHI9N30: C, 78.88; H, 5.24; N, 11.50; 0, 4.38. The values determined were: C, 78.90; H, 5.25; N, 11.50; 0, 4.38 (direct). Infrared analysis identified this compound as 2,s-dianilino p-benzoquinone anil, previously prepared by other methods (14, 15). The infrared spectrogram indicated the absence of a C=O group in this compound. I t is therefore better written as a tautomer of 2,5-dianilino p-benzoquinone anil. I t may he either (I) or (11) below. H
H
I
N.CaHr
N.C6H,
I N.CsH5 I
I1 N.CsH, I1
I1
I
CsH,-&-&-
C,H,N+=O
I
H
c~H,-N-(&I7 -
oxidation
I
H
Procedure 10.0 millimoles of catechol (1.1 g) and 20.0 millimoles of aromatic amine were dissolved in 50 ml of acetone in a beaker.
Violet Band: This hand was very tenacious and was, therefore, mechanically extruded and separated from the Volume 37, Number 70, October 7 9 6 0
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Table 1.
Dyeing Properties of Products of the Oxidation of Catechol in the Presence of Various Amines
Amine
Dve color
Nature of product
Dve aualitv
CLASS"A" Aniline o-Toluidine rn-Toluidine p-Toluidine
Red-brown powder Red-brown powder Red powder Red-brown powder
Bright brown Light buff Orange Khaki
2,4-Dimethyl aniline o-Anisidine
Pink Medium tan
o-Amino phenol o-Amino beneoic mid
Dtlrk brown powder Brown-violet crystals Dark red flakes Brown powder Red-brown powder CUSS "B" Dark brown powder Dark brown crystals
Pale violet Olive-green
m-Amino benzoic acid
Dark brown powder
Light tan
p-Amino benzoio acid
Dark brown powder
Sulfanilamide Sulfanilie acid o-Chloro aniline m-Chloroaniline o-Bromo aniline
Brick-red powder Dark blue powder Dull, orange-red powder Pale orange powder Pale orange powder with black powder impurity Pale orange flakes Pale oranse powder Red powder and gray powder Red-orange powder No react,ion-mine recovered No reaction-amine recovered Brick-red powder
m-Bromo aniline p-Bromo aniline, 2,6Dichloro amhne p-Nitro anilin! , 2,CDinitro amhne 2,B-Dichloro, 4-nitro aniline 2,4-Dimethyl, 5-nitro aniline
Tan Pale yellow-green Light pink Dark brown Red-orange
ideal v a t h v e behavior Good: Shows ideal vat-dve behavior Poor toefair Poor Poor to fair Good Good
Orange Bright red Light yellow-brown
Good Good Fair Good
Light buff
Poor
Almost none Dull brown Pele violet Doll red-brown Light brown Light brown
None Good Good Good Fair Fair Fair Fair
Fair: Shows ideal vaedye behavior Goad: Shows ideal vat-dye behavior Good: S h a m ideal vat-dye behavior Fair to good: Shows ideal vat-dye behaviar Very poor
2-Amino, Cmethyl pyridine %Amino, 6-methyl pyridine %Amino pyridine
CLASS'C" Brown powder; black tar Brown powder Black powder Red-brown oowder Light brown powder Light brown powder Gray-brown powder Light brown powder
N-methyl aniline
Black powder
Light brown
N-methyl, p-taluidine
Dark brown powder
Yellow-brown
N-ethyl aniline
Black crystals
Yellon.-brown
N-n-propyl aniline
Dark brown powder
Medium broxvn
Diphenyl %mine
Shiny black powder CLASS"Em Black tar Blsek powder Black tar CUSS T" Blsck tar Brown oowder
Pale gray
2- mini, 3-methyl pyridine
Good Poor Good Good: Shows ideal viledye behavior Fair to mod Poor torair Good Fair Good
CLASS"D"
N-N-dimethyl aniline N-N-diethyl aniline N-N-dimethyl p-toluidine p-Phenylene diamine 1-Amino evclohexane
adsorbent in a Soxhlet Extractor with methanol. A voluminous red precipitate appeared after addition of water and 2.0 ml of 3% hydrochloric acid (to prevent colloidal dispersion). After recrystallizing from methanol (three times) and acetone (twice), and drying for one hour in a drying pistol (in uaeuo), the red solid was identified as 4,5-dianilino o-henzoquinone by the following methods: (1) Nitrogen analysis; calculated for per cent nitrogen C18HmNa02: N, 9.65. The value found was 9.39; (2) unchanged mixed melting point with a pure sample prepared by another method (9) ; (3) preparation 528
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Journal o f Chemical Education
Light tan' .
Poor
Medium brown I h l l brown
Fair to good Fair
'
of the 2,3-dianilino-phenazine derivative; (4) positive comparative infrared spectra with the known compound. Both compounds were used to dye wool separately. 4,5dianilino o-benzoquinone dyed wool rose pink, while the dianilino p-benzoquinone-anil tautomer dyed wool tan. I t should he noted that the colors imparted by t,he crude mixture appear to be a combination of those imparted by its components. 4,5dianilino obenzoquinone appeared to be superior in color and fastness to the dianilino p-benzoquinone-anil tautomer.
Analyses of Other Mixtures
Mixtures resulting from separate reactions between o-toluidine and catechol and p-toluidiie and catechol in the presence of potassium ferricyanide were chromatographed. The lowest of the three hands in each case was eluted, recrystallized, dried, and subjected to elemental analyses. Toble 2.
Anolyticol Results
Calculated for CWH,~NSO:
%C
%H
%N
% O Mol.
79.44
6.00
9.27
5.29
302
Found: o-toluidine cornpound ,-toluidine corn-
79.51
6.09
9.29
5.01 (direct)
298
nounrl
79.07
wt.
(hv dif
The melting point of the o-toluidine compound is 143.5-145.5"C. The p-toluidine compound melts at 17&179"C. Infrared spectrograms indicate three possible structures in each case:
formation of tarry side products in most cases. At least seven dyes are ideally suited for strident laboratory preparations in enriching the teachmg of vabdyeing. They may be prepared readily and safely at room temperature in one laboratory period, utilizing commonly available apparatus. Each student may prepare a different mixture, thereby permitting a comparison of the different colors on cloth. 4,bdianilino a-henzoquinone and a tautomer of the known 2,5-dianilmo p-benzoquiuone anil were found to be the major products of the oxidation of catechol in the presence of aniline under the conditions cited here. The latter product had not been previously identified in this reaction. Work is continuing in the separation and identification of the other mixtures to determine whether any similarity exists in the pattern of these reactions. Literature Cited (1) Fox, M. R., "Vat Dyestuffs and Vat Dyeing," Chapman and Hall, London, England, 1946, p. 52-56. (2) BERNARDI,A,, Atti Xo eonm. intern. ehim., 4, 832 (1938). M., A N D TSATSAS,G., Bull., m e . ehim. France, (3) MART~NOFF, 14, 52-7 (1947). (4) SU~DA, H., A N D SUIDA,W., Ann., 416, 113 (1918). M., Rend. a c e d . sci. Napoli, (4),35, 158-63 (5) COVELLO, 11979) .- - ,. (6) Luss, H. A., "The Chemistry of Synthetic Dyes and Pigments," Reinhold Publishing Corp., N. Y., 1955, p. 433. (Chapter mitten by PERKINS,M. A.) (7) DOSKOGIL,J., Collection Creehslov. Chem. Cummuns., 15, 780-96 (1950). (8) W I L L S T ~ ~R., ~ RA N, D MULLER,F., Be7. ehem. ges., 41, \
28.50 ... 11908). ~
The dyeing properties of both compounds were examined. The violet o-toluidine compound dyes wool beige; the dark violet p-toluidine qompound imparts a pale yellow color t,o wool. Summary
In this work, 43 aromatic amines were treated with catechol in the presence of an oxidizing agent. The products were tested for dyeing properties. The use of acetone-water solutions effectively prevents the
(9) K E ~ R ~ ~ F., N NA N, D CORDONE,M., Bey. ehem. ges., 46, 3009 (1913). (10) PUGH,G. E., AND RAPER,H. S., Biochem. J., 21, 1370 (1927). R. D., Ber. ehern. ges., (11) JACKSON, C. L., A N D MACLAURIN, 38,4103 (1905). (12) WAGREICE, H., A N D NELSON, J. M., J. Am. Chem. Soc., 62, 154 (1938). (13) WHITTAKER,C. M., AND WILCOCK,C. C., "Dyeing with C a d Tar Dyestuffs," D. Van Nostrand Co., Inc., New Yark, 5th ed., London, 1949, p. 166-7. (14) ZINCKE,TH., AND HAQEN,D. V., Ber. ehem. ges., 18, 787 (1885). (15) HACKMAN, R. H., A N D TODD,A. R., Biochem. J., 55, 631-37 (1953).
Volume 37, Number 10, October 1960
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