Prelab 4.1- Free Radical Chlorination PDF

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prelab for E1 reactions and alcohol dehydration (free radical chlorination in part 1) important in including the introduction for free radical chlorination...

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Expt#4 2/15/18

Anisha Reddy

Pre-lab: Free Radical Chlorination

Introduction: The goal of the experiment is to ree r chain using free radical chlorination. 1-chlorobutane is used as the carbon source to be chlorinated by sulfuryl chloride and AIBN as an initiator to produce the chlorine radicals. Sulfuryl chloride is used instead of chlorine gas because it is a liquid and easy to measure out, also a safer alterative. AIBN is a great initiator because it is a compound that spontaneously produces free radicals. 1-chlorobutane and sulfuryl chloride will produce four dichlorobutane isomers. The ratios of the different isomers produced depend on the transition states for the various C-H abstractions. The transition rate of primary C-H is higher than the secondary CH abstraction, which leads to the relative reactivity of secondary to primary hydrogen atoms towards chlorine 3.3: 1.0. This is the reason because secondary bonds are weaker than primary bonds, making it easier to abstract an H and replace with chlorine at the 2o position. The electronwithdrawing of the primary chlorine increases the strength of C-H bonds nearby and lowers their hydrogen relative reactivities. However, the secondary carbons are further away from the chlorine and reduce this withdrawing affect; 2o also has a more stable radical with two carbons inducing the position, creating more isomers at the 20 positions. The isomers and reactivity will be analyzed using gas chromatography to determine relative amounts/percents of each isomer in the product. Mechanism: See attached, last page Table of Reagents: Reactants: Compound

Amounts Used

1-chlorobutane

5.0-mL

Sulfuryl Chloride

2.0-mL

Molecular Weight (amu) 92.57

134.97

Used Grams

Moles Used Required 0.0479 mol

0.0247

Propertie s

Boiling Point (0C): 78.4 Melting Point (0C): -123.1 Density (g/mL): 0.886 Boiling

Azobisisobutyronitrile

0.1 g

--

mol

Point (0C): 69.1 Melting Point: -55.1 Density (g/mL): 1.667

--

Boiling Point (0C): Melting Point (0C): 104.5 Density (g/mL): 1.1

164. 21

**Limiting reagent is Sulfuryl Chloride less moles than 1-chlorobutane Table of Products: Compound

Theoretical Yield (grams)

Yield Moles

1,1-dichlorobutane

3.137 g total for all 4 isomers

0.0247 mol total

Theoretical Molecular Weight (amu) 127.01

Theoretical Boiling Point (0C)

Theoretical Density (g/mL)

112

1.086

127.01

124

1.112

For all 4 isomers

1,2-dichlorobutane

1,3-dichlorobutane

127.01

134

1.115

1,4-dichlorobutane

127.01

153.9

1.141

SO2

1.582

0.0247 mol

64.07

-10°C

1.25

HCl

0.9006

0.0247 mol

36.46

Conc. Dependent

Conc. dependent

References: All structures from Sigma-Aldrich, Inc. Site, all table information from Wikipedia...