Preparation and Reactivity of Sn1 2-Bromobutane

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Preparation and SN1 Reactivity of 2-Bromobutane

Paul DeJong

Department of Chemistry, Illinois State University, Normal, IL 61790-4160

Submitted: April 4, 2013

Introduction

The purpose of part 1 of the lab is to prepare 2-Bromobutane using SN1 reactions. The purpose of part 2 of the lab is to determine the relative reactivity of alkyl halides under SN1 conditions. Results and Discussion

The Overall Reaction

The Proposed Mechanism

Experimental Procedure
To prepare 2-bromobutane in part one of the lab, you have to set up a flask apparatus with a thermowell and a Claisen adapter. Attached to the Claisen adapter is a thermometer measuring the temperature in the flask and a vertical condenser for reflux. Add in the reactants to the flask, sulfuric acid, 2-butanol, and ammonium bromide. Heat to 95OC and then maintain temperature for 30 minutes. Then, water was added and simple distillation began. The aqueous layer of the distillate was removed leaving the product, 2-bromobutane. For part 2, two drops of each of the following were placed in 3 different test tubes: 2-bromobutane, 1-bromoutane and 2-bromo-2-methylpropane. In each of the tubes an even amount of silver nitrate is added. Observations of the reactions precipitate are recorded. Same process is done with 2-chlorobutane, 2-iodobutane, and 2-bromobutane. Experimental Stoichiometry

Compound| Molecularweight| Quantity| Moles|
2-butanol| 74.12 g| 7.4 mL (6.0 g)| 0.081|
Sulfuric acid| 98.08 g| 20 mL (12M)| 0.24|
Ammonium bromide| 97.94 g| 8.0 g| 0.082|
The limiting reactant is 2-butanol.

Yield Data
2-bromobutane| |
Molecular Weight| 137.02 g|
Theoretical Yield (moles)| 0.081 mol|
Theoretical Yield (grams)| 11.10 g|
Actual Yield| 10.11 g|

NMR Table

Signal| Chemical Shift| Multiplicity| Integration|
A| 4.11| Multiplet| 1H|
B| 1.85| Pentet| 2H|
C| 1.60| Doublet| 3H|
D| 1.08|...
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