Question

Can I get help with this question please. I did the lab of 3-methylcyclohexanol mix with H3PO4+H2SO4 given the alkene. I obtained the alkene by Hickman stillhead.

Thank you!!!

4. Det egen te gaan Briefly explain the operation of a Hickman stillhead. Why was the product isolated by distillation instead of another method such as extraction or column chromatography? mann comentarios en poste a y nangan man

Answer 1

Answer :-

I] Operation of Hickman still head :

A Hickman still head distillation apparatus is a short path micro-scale purification apparatus that is used to distill small amounts of materials/liquids. This is similar to simple distillation and only one fraction is usually collected. The purity is related to difference in boiling points, and fractionating columns can be employed to increase separation and purity.

1) The Hickman distillation head/ Hickman still head is used as receiving device for the distilled liquid.

2) The complete apparatus consists of a flask or vial containing the liquid and a magnetic spine vane attached to the bottom of the Hickman still head. If desired a condenser is added to the top joint.

3) A thermometer can be suspended down the middle inorder to record the distilling temperature, with the bottom of the thermometer in the bottom part of the Hickman head just below the circular well.

4) The vapours of the heated liquid rise upward and are cooled and condensed either on the inside walls of the Hickman head or on the walls of the condenser.

5) As liquid drains downward, it collects in the circular well at the bottom of the still. The well can contain as much as 2 ml of liquid.

II] It is more convenient to use distillation process because -  

• it is obviously cheaper than other extraction techniques like column chromatography.
• it is obviously easy to handle and use.
• for using column chromatography we first need to carry out the reaction using a different apparatus and then pour the mixed liquid in column for it's separation and isolation. Also as this E1 elimination reaction involves using inflammable and corrosive liquids like alcohol and acid mixture respectively, it is better to carry out the reaction in distillation assembly as it will easily carry out the reaction and the isolation of the alkene.
• also, the alkene is not just isolated but also obtained in a purified form, because it initially gets collected in the form of vapours and then gets converted into a liquid form.
• high quantity of solvent is required in column chromatography, which is not the case with distillation apparatus.

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