Prepare an ice bath in a 100-mL beaker on a magnetic stir plate. To a clean, dry

Question

Prepare an ice bath in a 100-mL beaker on a magnetic stir plate. To a clean, dry 5-mL conical vial, pipet 0.20 mL of methyl benzoate. To the methyl benzoate, add 0.45 mL of concentrated (18 M) sulfuric acid and a spin vane. Attach an air condenser to the conical vial. Carefully clamp the apparatus so that the vial is immersed in the ice bath. Begin stirring. Into a clean, dry 3-mL conical vial, add 0.15 mL of concentrated (18 M) sulfuric acid and 0.15 mL of concentrated (16 M) nitric acid. Cool the mixture in a second ice bath. With a Pasteur pipet, slowly add the cooled sulfuric acid-nitric acid solution to the stirred solution of methyl benzoate through the air condenser. The addition should take approximately 15 minutes. Adding the nitrating agent more rapidly increases the amount of by-products and decreases the yield. When all the nitrating agent has been added, carefully remove the ice bath. Continue stirring until the reaction has come to room temperature. Then let the reaction flask stand undisturbed for 15 minutes. Place 2 g of ice in a 30-mL beaker. With a Pasteur pipet. transfer the reaction mixture to the beaker. Rinse the reaction vial with 1 mL of cold water. When the ice has melted, vacuum filter the crude crystals using 3 Hirsch funnel. Wash the crystals with two 1.0-mL portions of cold water and finally with two 0.3-mL portions of cold methanol. The crude product can be recrystallized from methanol. Record the mass of the dry product and calculate the yield.

Explanation / Answer

Methyl benzoate is a colorless liquid with chemical formula C8H8O2.

Its molar mass is 136.15g·mol1 and density is1.0837g/ml

Step-1 Calculate the mass of methyl benzoate –

Given – Volume of methyl benzoate = 0.20 ml

Mass of methyl benzoate = Volume of methyl benzoate x density of methyl benzoate

Mass of methyl benzoate = 0.20ml x 1.0837g/ml = 0.2167g

Step-2 Write the chemical equation of the reaction-

C6H5 COOCH3 + HNO3 --------> C6H4COOCH3NO2 + H2O

Step-3 calculate the moles of methyl benzoate-

Number of mole methyl benzoate = Mass of methyl benzoate/ Molar mass of methyl benzoate

Number of mole methyl benzoate = 0.21674g/136.15g·mol-1

                                                               = 0.00159 moles

Step-4 calculate the moles of methyl 3-nitrobenzoate

1 mol of methyl benzoate needed to produce 1 mol of Methyl 3-Nitrobenzoate

0.00159 Moles of methyl benzoate needed to produce 0.00159 moles of Methyl 3-Nitrobenzoate

Step -5 Calculate yield of Methyl 3-Nitrobenzoate-

Molar mass of Methyl 3-Nitrobenzoate (C6H4O2CH3NO2) = 181.1463 g/mol

The theoretical yield of Methyl 3-Nitrobenzoate = 0.00159 mol x 181.1463 g/mol = 0.288 g

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