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Chemistry 2211(PRIVATE) LABORATORY PRACTICUM - 4 DO NOT CONSULT WITH OTHER LABORATORY STUDENTS, THE LABORATORY INSTRUCTOR OR GRADUATE ASSISTANT UNLESS AN ISSUE OF SAFETY, EQUIPMENT NEEDS, OR EQUIPMENT FAILURE OCCURS. You may consult your laboratory notebook or the reference books in the laboratory You may take up to 150 minutes to carry out the procedure, complete your notebook writeup on the experiment, and submit to the instructor the notebook and clearly labeled product. THE MATERIALS THAT YOU WILL USE MAY BE HAZARDOUS. BE SURE TO FOLLOW PRUDENT LABORATORY PROCEDURES TO AVOID ANY PERSONAL RISK. CONSULT YOUR INSTRUCTOR IN CASE OF SAFETY QUESTIONS OR ANY ACCIDENT To a 125 mL erlenmeyer flask add 12 mL of concentrated sulfuric acid. Cool the acid to about 0°C, then add 6.1 g of methyl benzoate (FW 136 g/mol; density 1.09 g/mL). Keep the mixture near 0°C as you VERY SLOWLY add 8 ml of a cold mixture of 1:1 concentrated sulfuric and concentrated nitric acids. Add this acid mixture, while carefully swirling the flask, at a rate so as to maintain the temperature of the reaction below 15°C. After addition of the acid, allow the reaction mixture to warm to room temperature over 20 minutes, then pour the mixture over 50 g of crushed ice in a 250 ml beaker. After most of the ice has melted, recover the solids using a Buchner funnel. Wash the recovered solids with two 25 mL portions of ice cold water, then two times with 10 ml portions of ice cold methanol. Pull air through the crystals for several minutes to dry them. Recrystallize the product from a minimum quantity of methanol and recover the product using a Buchner funnel. Continue to pull air through the crystals for several minutes to partially dry them, then transfer the solids to a flask and further remove the solvent using the house vacuum system. Recover your reaction product, calculate its yield, and determine its melting point range. (The expected melting point of the product is somewhere between 60-90°C)

Answer 1

Q.1

The type of reaction in the flask is electrophilic substitution or nitration reaction.Nitonium ion formed from reaction of conc.nitric acid and conc.sulfuric acid

The carbonyl group withdraws electron density from the ring deactivating it towards electrophilic substitution. However the 3-position is less deactivated towards nitration than the other positions owing to the relative stability of the different intermediates. Therefore the reaction is regioselective for nitration at the 3-position

Q.2

As the product formed is methyl 3-nitro- benzoate which have higher solubility in methanol so minimum methanol is used to avoid yield loss and remove unwanted impurities.for recrystalizatiom mixture of methanol and water is prefered due to insolubility in water.

Q.3

The mixture of sulphuric acid and nitric acid is a concentrated acid solution and when it had into the reaction mass enormous heat is generated so cooling is necessary to control the exothermicity of the reaction.NOTE: The nitrating mixture is very corrosive.

Q.4

To remove excess of Sulphuric and nitric acid from the solid product (that is acidity) it is necessary to wash the product with several times cold water, if some dresses of acids are present then it will cause hydrolysis of Ester to form meta nitro benzoic acid.

Q.5

During suction filtration under vacuum the traces of solvents and acids will be removed and the product become dry it on buchner funnel the year pass through solid product carry traces of solvents and of acids from the solid product into vacuum