Nucleophilic Substitution

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  • Topic: Solvent, Ethanol, Nucleophilic substitution
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  • Published : November 1, 2010
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Nucleophilic Substitution
Samantha Gutierrez

Nucleophilic Substitution
Introduction:
The purpose of this lab is to investigate how different factors affect the rate of SN1 and SN2 reactions. SN2 reactions proceed via a one step mechanism in which the incoming nucleophile attacks the electrophilic carbon center from the opposite side of the leaving group. This reaction mechanism implies that the stereochemistry of a chiral center will be inverted. SN1 reactions proceed via two steps, slow dissociation of the C-X bonds to form an intermediate carbocation and a fast second step in which the C-Nucleophile bond is formed. Since the intermediate carbocation is trigonal planar, the nucleophile can attack with equal probability from above or below. This will result in racemization, partial conversion of one enantiomer, of a chiral center, since equal amounts of each enantiomer will result. Substitution reactions are an important class of reactions because of their synthetic utility and importance in understanding the mechanism of a variety of organic reactions. Materials & Methods:

(Effect of Structure of the Alkyl Halide)
2mL of 15% of NaI in acetone was put into three test tubes. Two drops of 1-bromobutane were added to the first test tube. Two drops of 2-bromobutane were added to the second test tube. Two drops of 2-methyl-2-bromobutane were added to the third test tube. The test tubes were stopper and were shaken to mix the chemicals. The test tubes were observed for cloudiness or precipitation. Observations were recorded. 2mL of 0.1 M AgNO3 in absolute ethanol was added into three test tubes. One drop of 1-bromobutane was added to the first test tube. One drop of 2-bromobutane was added to the second test tube. One drop of 2-bromo-2-methylpropane was added to the third test tube. The test tubes were then stopper and were shaken to mix the chemicals. The test tubes were watched for cloudiness or precipitants. Observations were recorded. (Steric Effect)

1mL of 15% NaI in acetone was added to two test tubes. Two drops of 1-bromobutane were added to the first test tube. Two drops of 1-bromo-2-methylpropane were added to the second test tube. The test tubes were then stopper and were shaken to mix the chemical. The test tubes were observes and observations were recorded. (Effects of Leaving Group)

1mL of 15% NaI in acetone was added to two test tubes. Two drops of 1-bromobutane were added to the first test tube. Two drops of 1-chlorobutane were added to the second test tube. The test tubes were then stopper and were shaken to mix the chemicals. The test tubes were observed and observations were recorded. 2mL of 0.1 M AgNO3 in absolute ethanol was added to two test tubes. At the same time, one drop of 2-bromo-2-methylpropane was added to the first test tube and one drop of 2-chloro-2-methylpropane was added to the second test tube. The test tubes were then stopper and were shaken to mix the chemical. The test tubes were observed and observations were recorded. (Effect of Solvent Polarity)

2mL of 0.1 AgNO3 in absolute ethanol was added to the first test tube. 2mL of 0.1 M AgNO3 in 5% ethanol/ 95% acetone was added to the second test tube. At the same time, one drop of 2-chloro-2-methylpropane was added to each test tube. The test tubes were then stopper and were shaken to mix the chemicals. The test tubes were then observed and observations were then recorded. (Determination of the Rate Law)

1mL of 15% NaI in acetone was added to two test tubes. At the same time, two drops of 1.0 M 1-bromobutane were added to one test tube and two drops of 2.0 M 1-bromobutane were added to the other test tube. Observations were recorded and rates of the two reactions were compared. 1ml of 1.0 M 1-bromobutane was added into two test tubes. At the same time, two drops of 7.5% NaI solution were added to one test tube and two drops of 15% NaI solution were added to the other test tube. Observations were...
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