Grignard reaction
Experiment C.
Aim:
To protect one of two carbonyl groups (C1) in order to allow the other to react twice with a Grignard followed by removal of the protecting group by acid hydrolysis to give final product (C2).
Method:
Ethyl acetoacetate (30.03g), ethylene glycol (15.01g) and toluene-p-sulphonic acid (0.13g) were added to a 250 cm3 round bottomed flask, containing a stirrer bar and toluene (100 cm3), fitted with a condenser and dean-stark head. Solution was heated strongly under reflux using a heater stirrer block for approximately one hour. During heating 4.5 cm3 of water was collected.
Solution was cooled, placed in a separating funnel and washed with NaOH (2M, 35 cm3) and water (2 x 50 cm3), organic layers were collected and dried over potassium carbonate and Buchner filtered. Excess toluene was removed by rotary evaporation ensuring bath temp was around 40 °C.
Vacuum distillation apparatus was set up and residue placed in a round bottomed flask. Residue was distilled under reduced pressure by way of vacuum for approximately one hour. Residual toluene was collected in one vial between 24–28 °C then a slight temperature drop was observed indicating all toluene had been removed. Pig was turned to allow collection of pure product into a separate flask from 78 °C. a clear liquid was collected as the product (C1) weighing 21.94g. Percentage yield was calculated and IR spectrum was run.
Next, apparatus for Grignard reaction was placed in an oven for an hour to ensure no moisture was present then set up for reflux with a dropping funnel to equalise pressure and a jack to allow easy removal of apparatus from heat.
Magnesium turnings (2.68g), anhydrous diethyl ether (15 cm3), a crystal of iodine and a stirrer bar were added to the round bottomed flask (250 cm3) and anhydrous diethyl ether (25 cm3) and dry bromobenzene (15.7g) were added to the dropping funnel, ensuring tap was closed. Dropping funnel was opened slightly allowing a small amount of bromobenzene
Aim:
To protect one of two carbonyl groups (C1) in order to allow the other to react twice with a Grignard followed by removal of the protecting group by acid hydrolysis to give final product (C2).
Method:
Ethyl acetoacetate (30.03g), ethylene glycol (15.01g) and toluene-p-sulphonic acid (0.13g) were added to a 250 cm3 round bottomed flask, containing a stirrer bar and toluene (100 cm3), fitted with a condenser and dean-stark head. Solution was heated strongly under reflux using a heater stirrer block for approximately one hour. During heating 4.5 cm3 of water was collected.
Solution was cooled, placed in a separating funnel and washed with NaOH (2M, 35 cm3) and water (2 x 50 cm3), organic layers were collected and dried over potassium carbonate and Buchner filtered. Excess toluene was removed by rotary evaporation ensuring bath temp was around 40 °C.
Vacuum distillation apparatus was set up and residue placed in a round bottomed flask. Residue was distilled under reduced pressure by way of vacuum for approximately one hour. Residual toluene was collected in one vial between 24–28 °C then a slight temperature drop was observed indicating all toluene had been removed. Pig was turned to allow collection of pure product into a separate flask from 78 °C. a clear liquid was collected as the product (C1) weighing 21.94g. Percentage yield was calculated and IR spectrum was run.
Next, apparatus for Grignard reaction was placed in an oven for an hour to ensure no moisture was present then set up for reflux with a dropping funnel to equalise pressure and a jack to allow easy removal of apparatus from heat.
Magnesium turnings (2.68g), anhydrous diethyl ether (15 cm3), a crystal of iodine and a stirrer bar were added to the round bottomed flask (250 cm3) and anhydrous diethyl ether (25 cm3) and dry bromobenzene (15.7g) were added to the dropping funnel, ensuring tap was closed. Dropping funnel was opened slightly allowing a small amount of bromobenzene