Can someone help me make sense of GCMS? I performed radical chlorination of alka

Question

Can someone help me make sense of GCMS? I performed radical chlorination of alkanes. 2 different reactions. The first was of 1-chlorobutane, and the other was 2,2,4-trimethylpentane. My question is why are my relative reactivity of hydrogen in my reactions so different from approximate relative reaction rates? How do I interpret my relative reactivity of hydrogens? Thank you.

Peak #1

Peak #2

Peak #3

Peak #4

Name of product responsible for that peak

1,1-dichlorobutane

1,2-dichlorobutane

1,3-dichlorobutane

1,4-dichlorobutane

Number of hydrogen that can react to give this product

2

2

2

3

Product yield based on percent yield

6%

23%

51%

20%

Yield per hydrogen

3

11.5

25.5

7

Relative reactivity of hydrogens

1

3.8

8.5

2.3

Peak #1

Peak #2

Peak #3

Peak #4

Name of product responsible for that peak

2-chloro-2,4,4-trimethylpentane

3-chloro-2,2,4-trimethylpentane

1-chloro-2,4,4-trimethylpentane

1-chloro-2,2,4-trimethylpentane

Number of hydrogen that can react to give this product

1

2

3

3

Product yield based on percent yield

4

27

28

41

Yield per hydrogen

4

14

9

14

Relative reactivity of hydrogens

1

3.5

2.3

3.5

Peak #1

Peak #2

Peak #3

Peak #4

Name of product responsible for that peak

1,1-dichlorobutane

1,2-dichlorobutane

1,3-dichlorobutane

1,4-dichlorobutane

Number of hydrogen that can react to give this product

2

2

2

3

Product yield based on percent yield

6%

23%

51%

20%

Yield per hydrogen

3

11.5

25.5

7

Relative reactivity of hydrogens

1

3.8

8.5

2.3

Explanation / Answer

Free radical halogenation

First Table is showing data for the free-radical chlorination of 1-chlorobutane

Chlorination occurs best at the center which is least hindered, that is the second chloride would preferentially add at the terminal carbon. This is unlike free radical bromination which occurs at most substitted carbon center. Therefore as can be seen the product percent yield is maximum for 1.4-dichlorobutane and least for 11,-dichlorobutane. Also the relative reactivity of addition of second chloride is highest among all.

Second table shows free radical halogneation of 2,2,4-trimethylpentane

Once again as can be seen the yield for terminal hydrogen substitution by chloride is maximum giving highest yield for the 1-chloro-2,2,4-trimethylpentane. The substitution at least sterically hindered center gave highest yield as expected in the free radical chlorination reaction. The relative reactivity of hydrogen shows what type of carbon center it is. For primary carbon it is same on both ends as 3.5. For secondary center it is lower and is 2.3. For tertiary the probability if lowest with vaue 1.

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