Essay Chem Lab

769 Words Feb 18th, 2012 4 Pages
Chem 201 Lab
October 21, 2011

Lab #6: Preparation of 2-chloro-2-methylbutane – an Sn 1 Reaction
Purpose
The purpose of this experiment was to prepare an alkyl halide, 2-chloro-2-methylbutane by reacting 2-methyl -2-butanol (t-amyl alcohol) with hydrochloric acid. Alkyl halides are of wide interest because they are widespread and have diverse beneficial and detrimental impacts .The overall reaction is given below:

Procedure
1 ml of 2-methyl-2-butanol was measured using 1 ml syringe and transferred into a 5 ml conical vial. 2.5 ml of highly concentrated Hydrochloric acid was then slowly added while the vial was constantly swirled. After mixing alcohol with HCl the vial was capped with a screw cap and gently shaken for about 10
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For this particular reaction calculations were straight forward due to 1:1 stoichiometric ratio with an excess of acid. Using physical density constant, the volume of 2-methyl-2-butanol was first converted into grams of alcohol. The grams were then converted into moles of alcohol using its molecular weight. Using the reaction stoicheometry, the moles were then converted into moles of chloride (product). Finally knowing the molecular weight of the product allowed to convert grams into moles.
Calculating mass of 2-methyl-2-butanol:
Density = mass/volume mass = density x volume = 0.815 (g/ml) x 1 (ml) =0.815 g
Moles = grams/ MW = 0.815 (g) / 88.15 (g/mol) = 0.00925 moles
Using 1:1 stoichiometric ratio for product theoretical yield estimation:
0.00925 moles x MW of chloride (35.45) = 0.328 grams of product
Percent Yield = Actual yield / theoretical x 100% = 0.228 (g) / 0.328 (g) x 100% = 69.51 %
Discussion
It is not uncommon to have a percent yield less than 100% as was observed in our experiment. Imperfect percent yield can be interpreted that the condition were not optimal and could be improved. Despite careful measurements some component will still be lost during transferring between containers. One way to get a better percent yield is by minimizing transfers. A low percent yield could be a result of evaporation

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