Lab: Dehydration of cyclohexanol to cyclohexene What is the role of anhydrous so

Question

Lab: Dehydration of cyclohexanol to cyclohexene

What is the role of anhydrous sodium sulfate in this experiment?

Procedure: Place 1.0 mL of cyclohexanol (MW = 100.2 g/mol) from a graduated cylinder in a 3 mL reaction vial. Weigh the vial to determine the exact weight of the cyclohexanol used. With the help of separate Pasteur pipets, add ten drops of 85% phosphoric acid and four drops of concentrated sulfuric acid to the vial. Put a spinvane magnetic stirring bar in the vial, attach a Hickman distillation head, and a water-cooled reflux condenser as shown at the end. Do not use the optional drying tube. Circulate water through the outer jacket of the condenser. Heat the vial gently in a heat transfer block while stirring with the help of a magnetic stirrer. The distillate will collect in the Hickman well. Continue distillation until about 0.3 mL of liquid is left behind in the vial. Remove the heat source and allow the vial to come to room temperature and then remove the condenser Remove as much distillate as possible from the Hickman wel using a Pasteur pipet and transfer it to a 5 mL reaction vial. Wash the sides of the Hickman head with 1.0 mL of saturated sodium chloride so that as much liquid as possible is washed down into the well of the Hickman head. Transfer this liquid into the 5 mL vial containing the distillate Cap the vial and shake the mixture. Allow the mixture to stand for a short while so that the aqueous layer (bottom layer) and the organic layer (upper layer) are separated. Carefully remove the lower aqueous layer using a Pasteur pipet and place it in a test tube. Make sure that all the aqueous layer is removed. This aqueous layer is discarded. Transfer the organic layer into a new reaction vial. Add about 0.25 g (one microspatula-full) of granular anhydrous sodium sulfate. Cap the tube with a stopper and gently shake it and set it aside for about ten minutes to remove the last traces of water. Transfer as much of the dry liquid from 5 mL vial into a small tared vial with a screw cap lined with aluminum foil or Teflon septum Make sure that you leave the solid sodium sulfate behind. Weigh the product (Mw = 821 g/mol) and calculate the percentage yield.

Explanation / Answer

Anhydrous sodium sulfate is drying agent

A organic solvent is in contact with aquous solvent (water) during the phase speration the small trap of water (aq phase) is present in the organic solvent layer, due to this the synthsized final product ( cyclohexane) is may be observe as stkiy mass due to less solublity of final organic product ( cyclohexane)

hence it is important to use a drying agent to absorb the water molecules from organic solvent layer

here sodium sulfate act as drying agent which have more affinity towards the water molecule and absorbe the water from upper organic layer

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