Nitration of Toluene
Electrophilic Aromatic Substitution: The Nitration of Toluene
Abstract
This industrially important reaction of EAS: The Nitration of Toluene exhibits how the attack of a nitronium ion would give out major and minor products at different positions of toluene. This is an electrophilic substitution mechanism. Mixture of concentrated sulphuric and nitric acid will produce a nitronium ion, which will attack ortho-, meta- and para- positions at Toluene. (Mechanism at appendix).
Introduction/Procedure
Toluene is cooled down to almost 0’C because the overall reaction is quite exothermic. High temperatures can cause the experiment to explode and also possible formation of di and tri nitrotoluene compounds.
After nitration, this experiment goes through series of purification/cleaning procedures. This makes sense because we would not want inorganic ions floating around in our final product.
After the reaction is complete, steam bath is required to separate the two layers of mixture. Lower layer is extracted since it’s aqueous layer filled with H2SO4, HNO3 and H2O. Add Et2O, aq Na2CO3 and water to multiply the product so that it can be extracted again. Bottom aqueous layer loaded with Na+, HCO3-, Cl- is extracted using Pasteur pipet. Dry the product with CaSO4 thoroughly. This step is important because if there’s any water residue left, it will show when drying ether at rotary evaporator step. Also, water is incompatible to GC. After vacuum filtration, we can add ether and use rotarary evaporator to dry out the ether and then if the product is clean, it is ready of GC and further procedures.
qDiscussion of Results Under normal conditions (low temperature/low acid concentration), this reaction would give out three products of ortho-, meta- and para- nitrotoluene. But, in this experiment, traces of 2,4 – dinitrotoluene and 2,6 – dinitrotolune are observed which in turn can be concluded that experiment could be done at lower temperature and at lower acidity.
Abstract
This industrially important reaction of EAS: The Nitration of Toluene exhibits how the attack of a nitronium ion would give out major and minor products at different positions of toluene. This is an electrophilic substitution mechanism. Mixture of concentrated sulphuric and nitric acid will produce a nitronium ion, which will attack ortho-, meta- and para- positions at Toluene. (Mechanism at appendix).
Introduction/Procedure
Toluene is cooled down to almost 0’C because the overall reaction is quite exothermic. High temperatures can cause the experiment to explode and also possible formation of di and tri nitrotoluene compounds.
After nitration, this experiment goes through series of purification/cleaning procedures. This makes sense because we would not want inorganic ions floating around in our final product.
After the reaction is complete, steam bath is required to separate the two layers of mixture. Lower layer is extracted since it’s aqueous layer filled with H2SO4, HNO3 and H2O. Add Et2O, aq Na2CO3 and water to multiply the product so that it can be extracted again. Bottom aqueous layer loaded with Na+, HCO3-, Cl- is extracted using Pasteur pipet. Dry the product with CaSO4 thoroughly. This step is important because if there’s any water residue left, it will show when drying ether at rotary evaporator step. Also, water is incompatible to GC. After vacuum filtration, we can add ether and use rotarary evaporator to dry out the ether and then if the product is clean, it is ready of GC and further procedures.
qDiscussion of Results Under normal conditions (low temperature/low acid concentration), this reaction would give out three products of ortho-, meta- and para- nitrotoluene. But, in this experiment, traces of 2,4 – dinitrotoluene and 2,6 – dinitrotolune are observed which in turn can be concluded that experiment could be done at lower temperature and at lower acidity.