Question

In lab we performed a dehyrdation of methylcyclohexanol to methylcyclohexene using a phosphoric acid catalyst through fractional distillation. Then we were to extract the methylcyclohexene product through liquid liquid extraction in a separatory funnel. We added ether to suspend the cycloalkene. Then we washed this organic layer with water, NaHCO3 and NaCl. I was wondering what exact effects the water, NaHCO3 and NaCl have and why we specifically use them for this liquid liquid extraction.

Answer 1

After completion of the reaction, if any traces amount of unreacted methylcyclohexanol (starting materail) present in the reaction mixture can be removed by liquid liquid extraction with sat. NaHCO3. Methylcyclohexanol will form its Sodium salt and it can be soluble in water. the water soluble sodium salt of methylcyclohexanol can be separated from organic solvent (only product will be soluble in organic solvent).

After separation of organic product (present in organic layer), it is extracted with sat.NaCl (brine solution). Since, due to heavier density of brine water (NaCl water), it can easily separate the entire aqueous solution present in the organic solvent, to give exclusive organic layer.

Still, if any traces of queous solution present in the organic solution , that can be dried with drying agent of Na2SO4.