Kinetics of an Sn1 Reaction
- Pages: 2
- Word count: 402
- Category: College Example
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An SN1 reaction of tert-butyl chloride takes place in two steps. First, the Alkyl Halide will leave the molecule. In this step the bond is breaking, which takes a longer amount of time, so it will determine the rate of the reaction. As a result, it forms a tertiary carbocation, since this is very stable, the nucleophile will quickly attack making the second step of this reaction proceed quickly. Process
(150 mL) of stock .04M NaOH was placed into an Erlenmyer flask and set aside to fill the burette as needed. A 50:50 mixture of acetone and water was put into a (100 mL) Erlenmyer flask and sealed with parafilm to prevent evaporation. (1g) of 2-chloro-2-methylpropane was weighed out and put into an Erlenmyer flask, the solvent was added and the flask was sealed. The solution was shaken and the stopwatch was started. Next, two infinity samples were created by adding (10 mL) of the reaction mixture to each of two Erlenmyer flasks containing (10 mL) of water. Both were sealed with parafilm and left to be tested later.
A clean dry pipette was then used to remove (10 mL) aliquots from the reaction mixture at 15 minute intervals up to 90 minutes and then a final aliquot was taken at 115 minutes. Each (10 mL) aliquot was placed in the Erlenmyer flask that contained (15 mL) of acetone. The exact time was recorded and 3 drops of phenolphthalein indicator was added to the flask and then titrated with the standard NaOH solution. Finally, the 2 infinity samples were titrated in the same way and the [HCl] was calculated. [HCl]t was calculated from each aliquot sampling. Lastly, Excel software was used to plot ([HCl] -[HCl]t) vs. time(t). The slope of the straight line through the points enabled the calculation for the rate of the reaction.
According to the data chart, the Rate constant for the hydrolysis of tertbutylchloride in 50/50 acetone/water (volume) is: k=4E-4/second
The rate constant for the hydrolysis of tertbutylchloride in 60/40 acetone/water is: K=7E-5/second
Discussion and Conclusion
The more polar the solvent the faster takes place the nucleophilic substitution. The rate of hydrolysis is faster in a solvent that has a higher percentage of water. Overall, this experiment was pretty useful in determining the rate of hydrolysis in acetone/water, however the human eye is not exact and the titration measurments could be a little off.