Question

A reaction product mixture containing hydrocarbons in diethyl ether is washed with saturated aqueous sodium chloride (brine) solution in a separatory funnel. Select the most likely reason for this step.
a. This step is to remove water from the ether layer.
b. This step is to extract the ether into the aqueous layer.
c. This step is to extract the hydrocarbons into the aqueous layer.
d. This step is to extract sodium chloride into the ether layer.

Answer 1

Answer:

Option A. This step is to remove water from the ether layer.

Explanation:

When the goal of an experiment is to conduct a reaction and isolate the product, it is referred to as work-up. The work-up refers to method aimed at purifying the material and most commonly occur in a separatory funnel. Solutions are added to the funnel to either extract or wash the mixture with the goal of isolating the product from excess reagents, catalysts, solvent, side product that may arise from side reactions.

Common washes include: Water, Sodium Bicarbonate, Sodium Carbonate, saturated sodium chloride (brine).

When an organic layer ( e.g. diethyl ether, ethyl acetate) is washed with brine, the purpose of the wash is to REMOVE LARGE AMOUNT OF WATER that may be dissolved in the organic layer.

Brine works to remove water from an organic layer because it is highly concentrated (since Sodium Chloride is highly water soluble. Therefore, the most likely reason for washing a reaction product mixture containing hydrocarbons in diethyl ether with with brine solution in a separatory funnel is to remove the water from the ether layer.