Annals of West University of Timisoara

Series Chemistry 21 (2) (2012) 67-76

MALACHITE GREEN WITH SNCL4

E.C.Belgiu, Dorina Modra

West University of Timişoara, Faculty of Chemistry-Biology-Geography, Department of Biology-Chemistry, Pestalozzi Street, 16, Timişoara, 300115 , ROMANIA

Received: 28 November 2012 Modified: 7 December 2012 Accepted: 10 December 2012

SUMMARY

In this work, we obtained a dye that is used mainly in the textile industry and as a therapeutic agent antifungal, antibacterial and antiparasitic in aquaculture. Were searched as better working conditions and simple to have a good yield. It was determined the best conditions for the catalyst. The work temperature is easy to obtain, and the reaction time is not very long. We have used SnCl4 and had better yields than other catalysts used before. The main parameters that guided the experiment were the catalysts, the molar ratio of reactants, reaction solvent and reaction time. The results led to the establishment of optimal synthesis conditions. Keywords: green; catalyst; solvent; temperature; time.

INTRODUCTION

Dyes industry remains a vibrant and challenging zone that requires a continuous flow of new research. Dyes can be classified according to their chemical structure and method of use or application. According to the classification by chemical structure, triarylmethane dyes are among the most important dyes. Both leuco forms, as well as triarylmethane dyes are compounds with various industrial applications, biological and analytical. They have a wide spectrum of technological applications. Malachite green (structure shown in Figure 1) is a triarylmethane cationic dye which is widely used in the textile industry as dye for wool, nylon, silk, cotton and polyacrylonitrile fibers. [1] It is used 67 B ELGIU E.C., M ODRA D. for dye plastics, lacquers, tanneries, food industry, paper and cellulose, as well as in dye printing works, cosmetics, pharmaceutical materials, etc. [2]. Malachite green dye is frequently used in the manufacture of inks. It is also used as a fungicide and antiseptic in aquaculture and fisheries due to its high efficacy against fish and roe parasites. [3-5]

Figure 1. Malachite green dye structure (as chloride) The study of literature presents different methods for making triarylmethane dyes including arenas nucleofile reaction with triethyl orthoformate also oxidative coupling of aniline N, N- disubstitute with a metallic catalyst (palladium catalysts, etc.) or are made with microwaves [6] etc. [7-9]. One of the most useful methods for the synthesis of triarylmethane dyes is the reaction of aryl aldehydes with N, N dimethylaniline. This reaction is usually performed in the presence of Brønsted acids: sulfuric acid, hydrochloric acid, methanesulfonic acid or para toluene sulfonic acid and Lewis acid, zinc chloride, zeolites, montmorillonite K-10, etc.. [10] The procedures presented has some disadvantages such as low yields, use of corrosive acids for installation, excess of solvent, severe reaction conditions, long reaction time and inconvenience in handling reagents. Recently they have been successfully used for the synthesis of triarylmethane dyes, catalysts of copper (II), zirconium nitrate (IV), SbCl3 [11-14]. Bi(NO3)3 was used as a catalyst in conditions that we do not use reaction solvent and allowed to obtain desired products with excellent yields. [11] Development of simple methods for efficient synthesis of dye malachite green, consequently, is an interesting challenge. In this work we describe a new route for getting the leucomalachite and dye malachite green by using SnCl4 as a catalyst. Our research showed that N, N-dimethylaniline reacts with benzaldehyde and in the presence of SnCl4 to produce adequate leucomalachite with good yields. We studied the reaction of benzaldehyde and N, N-dimethylaniline to establish different reaction conditions (with solvent, solvent-free, reaction time, etc.). Were tested as solvents dichloromethane, 68 SYNTHESIS OF TRIPHENYLMETHANE DYE MALACHITE GREEN ethanol and ethyl ether. The best results were obtained in the condition in which we worked with solvent. The reaction for the synthesis of the leucomalachite and malachite green dye is shown in Scheme 1. CHO N(CH ) 3 2 H

catalizator PbO2 2 (CH ) N N(CH ) + 3 2 C 3 2 -H2O

OH HCl + (CH3)2N C N(CH ) N(CH ) ]Cl 3 2 (CH3)2N C 3 2 -H2O

Scheme 1. Reaction of obtaining malachite green dye

MATERIALS AND METHODS

In this work we used: benzaldehyde, N, N-dimethylaniline, hydrochloric acid, para toluenesulfonic acid, SnCl4, as analytical purity reagents and are used as such, without being purified. Solvents and the other materials used are analytical pure and used without special treatment. Melting point determination is made using the device "Melting Point Meter" KRS- P1, from the company Krüss Optronic GmbH. The IR spectrum was performed using a Perkin Elmer FT-IR spectrophotometer - Spectrum 100.

RESULTS AND DISCUSSION

Syntheses performed were made in order to find optimal conditions for the reaction of benzaldehyde with N, N-dimethylaniline (various catalyst in concentration of 20% moles compared to benzaldehyde, varying molar ratios, different solvents, different reaction times) to obtain good yields of dye. 69 B ELGIU E.C., M ODRA D.

Influence of catalyst In this context were performed syntheses by condensation of benzaldehyde with N, N-dimethylaniline in the presence of: hydrochloric acid, p-toluenesulfonic acid and tin tetra chloride. Molar ratio of reactants benzaldehyde: N, N-dimethylaniline used is 1: 3. Temperature of work is 115-120 C. We aimed to obtain the leucomalachite which oxidizes to dye malachite green. The oxidation was performed with lead oxide. Reaction time to obtain the leucomalachite is 4 hours and the oxidation of the leucomalachite to malchite green was 2 hours, total time of reaction was 6 hours. Results and working conditions are presented in Table I. The amount of catalyst used is 20% moles compared to benzaldehyde used in the synthesis.

Table I. Results and working conditions

Current Catalyst Yield Issue [% moles] [% ] 1. HCl 37% 65.21 20 % 2. APTS 68.76 20 %

3. SnCl4 80.15 20 %

The abbreviations are: B = benzaldehyde; N,N , DMA = N, N-dimethylaniline; APTS = para toluenesulfonic acid. The graph in Figure 2 represents the variation of yield in dye depending on the reaction catalyst used.

70 SYNTHESIS OF TRIPHENYLMETHANE DYE MALACHITE GREEN

Figure 2. Variation of yield depending of the reaction catalyst It is found that tin chloride is an efficient catalyst, in the synthesis of the leucomalachite respectively malachite green dye, obtaining higher yields than when using various acid catalysts. Influence of molar ratio of reactants To study how the reaction occurs by condensation of benzaldehyde with N, N- dimethylaniline in the presence of SnCl 4 catalyst it was track the influence of molar ratio of reactants over the yield working with molar ratios benzaldehyde: N, N-dimethylaniline 1: 2, 1 : 3, 1: 5. We worked with a molar ratio of catalyst of 20% moles towards benzaldehyde. Working temperature was 115-120 C. We aimed to obtain the leucomalachite which is then oxidized to green malachite, the oxidation was performed with lead oxide. The reaction time to obtain leucomalachite is 4 hours and the oxidation of the leucoderived to malachite green dye was 2 hours. Results and working conditions are presented in Table II.

Table II. Results and working conditions

Current Molar report Yield [% ] Issue B : N,N DMA 1. 1 : 2 40.21

2. 1 : 3 80.15

3. 1 : 5 82.40

The abbreviations are: B = benzaldehyde; N,N DMA = N, N-dimethylaniline. 71 B ELGIU E.C., M ODRA D.

Based on data obtained it was drawn graph in Figure 3, which represents the variation of the yield in dye depending to the variation of ratio of reactants.

80 70 60 50 40 30 20 Conversion [%] Conversion 10 0 1:2 1:3 1:5

Molar ratio Benzaldehyde : N,N dimethylaniline

Figure 3. Variation of yield depending of ratio of reactants. From experimental data it is found that with increasing molar ratio of reactants benzaldehyde : N, N-dimethylaniline it increases the final yield in malachite green dye. The molar ratio use in the other synthesis is 1: 3. This is because when using a molar ratio of benzaldehyde: N, N-dimethylaniline of 1 : 4 color yield increase very low, only 2.5%. If you are working with the molar ratio of 1 : 5 problems appear to remove the unreacted dimethylaniline. Influence of reaction solvent to obtain the leucomalachite To follow the influence of reaction solvent to obtain the leucomalachite were used as solvents: dichloromethane, ethanol and ethyl ether. The reaction time is 4 hours and 2 hours leucomalachite synthesis of lead dioxide oxidation to obtain malachite green dye. The amount of solvent used is 30% (vol.) compared with the reaction mixture. The molar ratio of benzaldehyde: N, N-dimethylaniline used is 1: 3. The amount of catalyst SnCl 4 used in all syntheses is 20% moles towards benzaldehyde. The experimental data are shown in Table III.

Table III. Results and working conditions

Current Reaction solvent Yield Issue [% ] 1. Free solvent 80.15 2. dichloromethane 60.76 3. ethanol 50.80 4. ethyl ether 49.40 72 SYNTHESIS OF TRIPHENYLMETHANE DYE MALACHITE GREEN

In Figure 4 are graphically represented the values obtained in laboratory syntheses.

Figure 4. Yield variation depending on the solvent used in the synthesis reaction of the leucomalachite Seen from the graph that the best yields are obtained when we use solvent-free. When used as a solvent of dichloromethane yield is higher (60%) than in variants where we used ether or ethanol etilic were it lies around 50%. Influence of reaction time to obtain the leucomalachite During the reaction time it was tested in the case of synthesis to obtaining the leucomalachite to get optimal time of reaction. Reaction time tested were : 1 hour, 2 hours, 4 hours and 8 hours. Working conditions used in the synthesis options are: molar ratio of benzaldehyde: N, N-dimethylaniline of 1: 3. The reaction temperature of 115-120 C.

SnCl4 catalyst is used in the synthesis in a rate of 20% moles towards benzaldehyde. It works without reaction solvent and the oxidation time of leucomalachite in all cases was 2 hours. In Table IV are presented the working conditions and the results obtained.

Table IV. Results and working conditions

Current Reaction time Yield Issue [hours] [%] 1. 1 25.12

2. 2 55.45

3. 4 80.15 4. 8 81.81 73 B ELGIU E.C., M ODRA D.

The results are shown in the graph in Figure 5.

25.12

81.81

55.45

1 h 2 h 4 h 8 h

80.15 Figure 5. Yield variation depending on the reaction time of leucomalachite synthesis Seen from the graph that with increasing reaction time in the synthesis of the leucomalachite it increase also the yield. At a reaction time of 4 hours the yield is 80.15%. If reaction time increases twice the efficiency is low, leading to the idea that a reaction time of 4 hours at the of synthesis leucomalachite is enough for a good reaction yield. The reaction time refers to the time of refluxing in the leucoderived synthesis. Malachite green dye obtained after processing the raw product, following the experimental data it was analyzed. The dye shows a melting point of 138-139 C and the IR spectrum determined is shown in Figure 6. In Figure 7 is presented malachite green dye structural formula determined using HyperChem program. 98.5 95

90 2206.80 1943.52 2167.59 1878.17 85 2083.28 3066.07 2015.27 3329.68 80 3025.03 1991.74 2985.94 1973.46 2951.86 75 2877.34 2802.16 1649.04 913.11 70 870.71 858.90 65 1677.84 1256.98 1277.65 1073.98 1101.88 747.58 60 1029.75 %T 1057.39 55 1319.57 946.88 1166.22 831.06 50 1611.27 1205.19 1492.30 1153.46 762.21 1443.55 1190.29 718.27 45 1122.00 1221.67 800.90 40 1349.23 35 789.58

30 1517.29 697.50

20.0 4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 650.0 cm-1 Figure 6. IR spectrum of malachite green dye 74 SYNTHESIS OF TRIPHENYLMETHANE DYE MALACHITE GREEN

Figure 7. Molecular structural formula of malachite green dye The dye obtained was used in dyeing of textile fibers: cotton, nylon, polyester, wool. In a future article we will study how the dye binds with the fiber.

CONCLUSION

It was demonstrated that SnCl4 is a efficient catalyst for the reaction of N, N- dimethylaniline with benzaldehyde compared with acid catalysts. At the same time we determined the optimal reaction conditions for this catalyst. Using SnCl4 as a catalyst in the amount of 20% moles compared with benzaldehyde, good yields were obtained of malachite green dye working with molar ratios of benzaldehyde : N, N-dimethylaniline of 1: 3 at a total reaction time of 6 hours. The work temperature is 115-120 C without reaction solvent. Studies have led to the determination of the optimum conditions of synthesis of malachite green dye. Simple experimental procedure, without reaction solvent the conditions and good yields are the advantages of the present method.

REFERENCES

1. Muthyala R., Lan X., The Chemistry of Leuco Triarylmethanes, Chemistry and applications of leuco dyes, editor Plenum Press, New York, 1997 2. Malpert J.H., Grinevich O., Strehme B., Jarikov V., Mejiritskia A., Douglas C. Neckers D.C., “Color intensity control in polymers using triarylmethane leuconitriles as color formers”, Tetrahedron, 57 (2001) 967-974. 3. Khodabakhshi A., Amin M.M.A., “Determination of malachite green in trout tissue and effluent water from fish farms”, Int J Env Health Eng, 1 (2012) 10-14. 4. Hashimoto J.C., Paschoal J.A.R., Queiroz J.F., Reyes F.G., “Considerations on the Use of 75 B ELGIU E.C., M ODRA D.

Malachite Green in Aquaculture and Analytical Aspects of Determining the Residues in Fish: A Review”, Journal of Aquatic Food Product Technology, 20(3) (2011) 273-294. 5. Guo, Z.Y., Gai, P.P., Hao, T.T., Duan, J., Wang, S., “Determination of malachite green residues in fish using a highly sensitive electrochemiluminescence method combined with molecularly imprinted solid phase extraction”, J. Agric. Food Chem., 59 (2011) 5257–5262. 6. Guzman-Lucero D., Guzman J., Likhatchev D., Martinez-Palou R., “Microwave-assisted synthesis of 4,4′-diaminotriphenylmethanes”, Tetrahedron Lett., 46(7) (2005) 1119–1122. 7. Podder S., Choudhury J., Roy U K., Roy S., “Dual-Reagent Catalysis within Ir-Sn Domain: Highly Selective Alkylation of Arenes and Heteroarenes with Aromatic Aldehydes”, J Org Chem., 72 (2007) 3100-3103. 8. Nair V., Abhilash K. G., Vidya N., “Practical synthesis of triaryl- and triheteroarylmethanes by reaction of aldehydes and activated arenes promoted by gold(III) chloride”, Org Lett., 7(26) (2005) 5857-5859. 9. Esquivias J., Gómez Arrayas R., Carretero J C., “A Copper(II)-Catalyzed Aza-Friedel–Crafts Reaction of N-(2-Pyridyl)sulfonyl Aldimines: Synthesis of Unsymmetrical Diaryl Amines and Triaryl Methanes”, Angew Chem, Int Ed., 45(4) (2006) 629–633. 10. Zhang Z. H., Yang F., Li T. S., Fu C. G., “Synthesis of Triarylmethanes via Baeyer Condensation of Aromatic Aldehydes with N,N-Dimethylaniline Catalysed by Montmorillonite K-10”, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 27( 21) (1997) 3823-3828. 11. Bardajee G. R., Jafarpour F., “Bi(NO3)3·5H2O mediated synthesis of 4,4′-diaminotriarylmethane leuco malachite compounds under solvent-free conditions”, Cent Eur J Chem., 7(1) (2009) 138- 142. 12. Jafarpour F., Bardajee G. R., Pirelahi H., Oroojpour V., Dehnamaki H., Rahmdel S., “An Efficient Solvent-free Synthetic Technique of 4,4′-Diaminotriarylmethane Leuco Materials”, Chin J Chem. , 27(7) (2009) 1415-1419. 13. Bardajee G. R., “Solvent-free Cerium(IV) Ammonium Nitrate Catalyzed Synthesis of 4,4′- Diaminotriarylmethane Leuco Malachite Materials”, International Journal of ChemTech Research, 1(3) (2009) 452-456. 14. Hou J.T., Gao W.J, Zhang Z. H., “An efficient and convenient protocol for the synthesis of diaminotriarylmethanes”, Monatshefte für Chemie - Chemical Monthly, 142(5) (2011) 495-499.