Study of the effect of changed ratio of catalyst sulphuric acid in the traditional way of nitration of arenes Sanjeeb Pandey, Anthony Schultz and Dr. David J. Oostendorp Division of Molecular and Life Science Loras College, Dubuque, IA Work Cited: Stock M., Leon. "The Competitive Nitration of Toluene and t-Butylbenzene." (1961): n.pag. Web. 26 Apr Lehman, J.W. (1998). Operational organic chemistry: A problem-solving approach to the laboratory course (3 rd ed.). Upper Saddle River, NJ: Prentice Hall. Smith, Janice G. Organic Chemistry. Boston: McGraw- Hill, Print. CONCLUSION The effect of changed ratio of sulphuric acid (catalyst) in percentage yield of nitrated arenes can be studied by using this method. Also, the effect on the isomeric distribution of nitrated product due to different ratio of sulphuric acid and due to the presence alkyl group in the benzene ring can be studied by using this method. DISCUSSION The data obtained from gas chromatography of the product was excluded because it showed a peak of impurities. The percentage yield of the nitrated product is lower than expected which might due to loss of product during multiple washings and separation of product. A decreased ratio of H2SO4 decreased the percentage yield of the nitrated product which showed the relation of sulphuric acid in nitrated product formation. A impurity peak was seen in the 13 C NMR and 1 H NMR of tert-butyl nitrobenzene which was found to be dichloromethane (CH 2 Cl 2 ). The isomeric distribution was as predicted. The product of 2:1 ratio of t-butyl benzene could not be obtained because the reactant was not nitrated. However, the relation between the isomeric distribution and ratio of sulphuric acid could not be studied because of the single run. It can be done by running multiple trials of same samples. I would like to thank Loras College for letting us conduct our research and mentor Dr. Oostendorp for his guidance in our research project. The percentage yield was calculated and Gas chromatography, Infrared spectrum and NMR was performed on the end product. RESULTS The percentage yield of nitro toluene using 1:1 ratio of H 2 SO 4 and HNO 3 was found to be 48.52% and that from 2:1 ratio was found to be 23.72%. 1 H NMR of 1:1 ratio nitro toluene gave a peak at ppm which indicates p-nitrotoluene and peak at 7.9-8ppm indicates formation of o-nitrotoluene. A small peak at 8ppm shows an insignificant amount of m-nitrotolene. The two isomeric distribution ratio (para:ortho) was found to 5:4. In 1 H NMR of 2:1 ratio nitro toluene, peaks of o- and p- are seen at same position in Fig 2: but with different isomeric distribution of 1:1. PURPOSE The purpose of this research is to study the effect of changed ratio of catalyst sulphuric acid (H 2 SO 4 ) in the percentage yield of nitrated arenes. Also, to study the effect of bulky alkyl group in nitration and their effect in isomeric distribution. INTRODUCTION Aromatic compounds undergo two different kinds of substitution reaction i.e. nucleophilic aromatic substitution and electrophilic aromatic substitution reaction. Presence of electron withdrawing substituents as a substituent in benzene ring favors electrophilic substitution reaction. Nitration of is an example of electrophilic substitution reaction. Nitration of toluene can be done by reacting toluene with equi-molar mixture of sulphuric acid and nitric acid at around 50 0 C. Nitric acid is the source of nitronium ion which is formed when it is catalyzed by sulphuric acid. The formation of o-, m- and p-isomers are determined by the presence of substituent in the benzene ring. Nitration of benzene gives high percentage of o-isomer than p-isomer but presence of bulky alkyl group such as t-butyl group in the benzene ring should favor the formation of p-isomers over o-isomers because of its steric effect. METHODS i) Preparations of nitro-toluene: In a 100 ml RB flask 5ml of conc. HNO 3 was mixed with 5ml of conc. H 2 SO 4 and 25ml of dichloromethane was added with 5ml of toluene. The mixture was refluxed for one hour. The same procedure was followed with 2:1 ratio of HNO 3 and H 2 SO 4. ii) Preparation of t-butyl nitrobenzene: In a 100 ml RB flask 5ml of conc. HNO 3 was mixed with 5ml of conc. H 2 SO 4 and 25ml of dichloromethane was added with 5ml of t-butyl benzene. The mixture was refluxed for one hour. The same procedure was followed with 2:1 ratio of HNO 3 and H 2 SO 4. Figure 1: 1 H NMR of nitro toluene(1:1). Figure 1: 1 H NMR of nitro toluene(1:1). Figure 3: 1 H NMR of t-butyl nitrobenzene (1:1) Figure 2: 1 H NMR of nitro toluene(2:1). Figure 2: 1 H NMR of nitro toluene(2:1). Figure 4: 13 C NMR of t-butyl nitrobenzene (1:1). Figure 4: 13 C NMR of t-butyl nitrobenzene (1:1). The percentage yield of t-butyl nitrobenzene was using 1:1 ratio of H 2 SO 4 and HNO 3 was found to be 68.85%. 1 H NMR of 1:1 ratio t- butyl nitrobenzene gave a doublet at ppm which indicates 1- tert-butyl-4-nitro benzene (Fig3). No peak for m-isomer at 8ppm was seen. An insignificant peak at around 7.8ppm which might be due to o-isomer was seen. An unusual peak at around 5ppm in 1 H NMR was seen. A 13 C NMR of the product showed three singlet at around ppm (Fig. 4). The isomeric distribution in nitration of tert- butyl benzene showed almost all p-isomer as a product. LORAS.EDU