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The dehydration of Cyclohexanol to form Cyclohexene.

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The dehydration of Cyclohexanol to form Cyclohexene. In order to dehydrate Cyclohexanol it is required that a dehydration agent, in this case phosphoric acid, be added and for the mixture to be distilled with the Cyclohexene being taken off between 343K and 363K. This reaction gives the formula: In order to keep the experiment at a manageable size 0.1 mole of Cyclohexanol was used along with 4cm3 of concentrated Phosphoric acid. 0.1 mole of Cyclohexanol x 100.2 = 10.2 100.2 0.962 = 10.4 cm3 However because the measuring cylinder only measured to the nearest 1cm3 ,10cm3 had to be used instead. This volume was placed into a 50cm3 pear shaped and the 4cm3 of phosphoric acid was added slowly while shaking the flask. The flask was then attached to the rest of the apparatus as shown below; Because the boiling point of Cyclohexene is 356K and for water it is373K it was decide best to reflux the mixture between the 343K and 368K or 70oC and 90oC as read off the thermometer. ...read more.


The first stage of the purification was completed with a separating funnel such as the one in the diagram on the right. To the mixture, an equal amount of sodium chloride solution was added, in order to increase the density of the water and ease the separation of the water and Cyclohexene. The funnel was then shaken, with a stopper in the opening and the two layers allowed to separate. Because Cyclohexene has a density of 0.81g cm-3 and the water's density has been increased by the sodium chloride solution the two layers separated easily and most of the unwanted products were removed by running the lower aqueous layer into a sink. The bottom layer also included the residual phosphoric acid as it was kept to the bottom by the salt. After the majority of the unwanted products had been removed, anhydrous calcium chloride was added to dry the top layer and the mixture was decanted and then filtered ...read more.


Some of this can be accounted by the fact that only 0.096 moles of Cyclohexanol were used and therefore the yield should really be taken on 0.096 moles instead, giving a yield of 72.5% The measuring cylinder used to measure out the 0.096 moles of Cyclohexanol was only accurate to the nearest 1cm3 therefore it is quite possible that 9.5cm3 of Cyclohexanol was measured out which is 0.091 moles, giving a yield of 76% or based on 10.5 cm3, a yield of 69.0%. The balance was only accurate to the nearest 0.01g and therefore the weight of Cyclohexene produced could instead have been 5.655g which, working on 0.091 moles of reactant, gives a yield of 76.7%. On the other hand the weight might have been 5.645 which, working on 1.008 moles of reactant, gives a yield of 68.9%. From this we can se that the maximum yield for the experiment is around 77% which is reasonable for an experiment of this nature. ...read more.

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