Preparation of a Halogenoalkane Essay

Hence pure product can be obtained when we distillate the mixture at a temperature of 45oC-55oC. Discussion The reaction between HCl and the 2-methylpropan-2-ol will build up pressure in the conical flask. It is because the reaction is exothermic, it causes serious evaporation, giving out a large amount of water vapour. And the sudden build up of pressure may break the funnel hence HCl is added in 10 portions but not all together. The separating funnel is used to separate 2 immiscible layer of liquid. When the mixture is stable, the denser liquid will be at bottom and the other will be on top. When we open the tap, the bottom layer can be obtained, leaving the upper one left in the funnel. The liquid at the junction of the 2 layer should be removed as that is a mixture of the 2 layer which is impure. Although this can ensure a pure product obtained, but this will reduce the yield since some chemical is lost. Anhydrous sodium sulphate is added to make sure all water is removed. Because the presence of water may increase the difficulty of distillation. Since high temperature favor the dissolve of product into water. Also if water is presented in the distillation process, water may evaporate and contaminate the distillate. Hence all water must be removed. The reaction of sodium sulphate with water is as follow: Na2SO4+10H2O? Na2SO4†¢10H2O Filtration can remove insoluble substance from a mixture. With the use of filter paper, only liquid passes through, the solid is left as residue. A clean mixture can hence be obtained. Distillation is used to separate a miscible mixture with distinct boiling point. One liquid can be distillate when the solution reaches its boiling point. The other liquid will be left behind since the temperature is not high enough to vaporize that liquid. The water in of condenser should be at the lower end to make sure water can stay in the condenser for a longer time. In this synthesis SN1 reaction is favored for several reasons. Firstly, a tertiary alcohol is presented in the experiment. The alcohol we used have 3 alkyl group, the molecule is therefore sterically hindered, this will favor SN1. Cl- is the weak base used in the reaction, this will also favor SN1 reaction. Thirdly the carbocation formed, is stable, since the three attached alkyl groups do positive inductive effect on the carbocation, making it less positive. The stable carbocation will also favor the SN1 reaction. It should be noted that acidic medium is necessary for the reaction. It is because OH- is a poor living group, in normal situation it may attach back to the carbocation. In an acidic medium, the –OH group is protonated first. The breaking of C—O bond will give a H2O molecule which is a stable living group and prevent OH- to interfere the experiment. In the experiment NaHCO3 is used to remove HCl rather than NaOH or other strong base. It is because a reaction between HCl and a strong base will produce a large amount of heat. The increase in temperature combine with the acidic medium will favor elimination which is unwanted and may affect the yielding of the reaction. There are several errors in the experiment: the alcohol used in the reaction is volatile, this will lead to a loss of material during the process. We should perform the experiment faster in order to reduce the loss and to obtain a larger yield of product. When we separate the organic layer and the aqueous layer using the separating funnel, the liquid in the junction of 2 layers is removed. This will drain away some chemical. The loss in the chemical content will reduce the yield. We can improve the situation by removing the organic layer as less as possible. During the transfer of material, some material will be left behind. The loss of material will also reduce the yield. We should wait when we transfer the material, until all material adhere to the surface is transferred. While filtrating, some solution is left on the filter paper, which will lead to a loss of chemical. We should wait until no more liquid is drained from the filter paper to make sure all chemical is collected.