Grignard Reaction Lab

Ishaan Sangwan

Experiment 7: Grignard Reaction

Discussion

In this experiment, a Grignard reaction was performed to create a carbon-carbon bond, between a bromide and carbon dioxide. The product was then protonated to form a carboxylic acid, which was identified by obtaining its melting point, and by performing a titration with NaOH to obtain its molecular weight.

In organometallic chemistry, carbon is bound to a metal. Usually, carbons are bound to elements that are more electronegative than carbon, and have a partial positive charge, making them electrophilic. When a carbon is bound to a metal, it has a partial negative charge, since it is more electronegative than the metal, and is hence nucleophilic. A nucleophilic carbon can then attack

Had these pockets not been filled, they could have been filled by diethylether vapor, which would have frozen these joints. The Mg used in this experiment was crushed, and then reacted with iodide in order to bring fresh Mg to the surface to improve the reaction. The formation of MgI2 was also exothermic, which added heat to help start the reaction. A liquid solid extraction was performed in this experiment to remove impurities that had sank to the bottom on the flask, like unreacted bromide and the aforementioned side products. Then, a liquid liquid extraction was performed to pull the carboxylic acid into an aqueous sodium hydroxide layer from the organic ether layer.

The molecular weight of the unknown was calculated by figuring out how many moles of NaOH reacted with the unknown. Since there ratio of reactants reacting was 1:1, the moles of NaOH would be the same as the moles of carboxylic acid. The moles of NaOH were calculated by multiplying the concentration of NaOH by the volume used in the titration. The molecular weight of he carboxylic acid was then calculated by dividing the mass of the carboxylic acid sample by the number of moles of carboxylic