Isobutylene Reacting w Cl2: Mechanism, Structure, Radioactive Carbon

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In summary, it was found that when isobutylene reacts with Cl_{2} under 0^{o}C in the absence of light it gives more methallyl chloride(3-chloro,2-methyl propene) than the addition product. Bubbling oxygen through the reaction mixture doesn't affect the product formation.
  • #1
pardesi
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it was found that when isobutylene reacts with [tex]Cl_{2}[/tex] under [tex]0^{o}C[/tex] in the absence of light it gives more methallyl chloride(3-chloro,2-methyl propene) than the addition product.bubbling oxygen through the reaction mixture doesn't affect the product formation.
thsi reaction is carried with labelled iso-butylene with the C-1 labelled as 14C.now the reaction product was made to go through ozonolysis and it was found that the majority of radioactive carbon was present in chloroacetone(about 97%) and very few in formaldehyde.

a)give the structure of methallyl chloride obtained and mention the position of the radioactive carbon.

b)is the reaction ionic or free radical?

c)outline a mechanism

d)suggest a reason why isobutylene is more prone than 1-2-butene?

e)under similar conditions in the presence of oxygen 3,3-dimethyl-1-butene yeilds more addition product but also a small yield of 4-chloro-2,3-dimethyl-1-butene.how do you fit this fact with the mechanism u proposed and also account for the minor product
 
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any clue anyone
 
  • #3
What do you think will happen when chlorine reacts with isobutene? Which functionality is reactive with chlorine? The mechanism is either an ionic one or a free radical one. What effect would oxygen have on an ionic reaction? A free radical one? The question states that no change is observed when it is conducted in the presence of oxygen...

For part d), it is helpful to recognize that there is a vinylic t-butyl group in the starting material.
 
  • #4
yes i got the first two and yes it is an ionic one since oxygen has no effect
about the third i think first the chlorine attacks the double bond and forms the cation and then cation forms the alkene by elimantion...but i can't satisfy myself with the ans of d and e

sorry for not having posted this before:cry:
 
  • #5
pardesi said:
yes i got the first two and yes it is an ionic one since oxygen has no effect
about the third i think first the chlorine attacks the double bond and forms the cation and then cation forms the alkene by elimantion...but i can't satisfy myself with the ans of d and e

sorry for not having posted this before:cry:

I don't know what 1-2-butene is so I can't help with that one. Correct the nomenclature and you will probably see the answer.

For e), is direct elimination of the addition product's 2-chloro group possible from the adjacent t-butyl group?
 
  • #6
tahnks
by that i meant 1-butene and 2-butene
 
  • #7
What mechanism do you propose?
 

1. What is the mechanism of the reaction between isobutylene and Cl2?

The mechanism of the reaction between isobutylene and Cl2 involves a free radical chain reaction. Initially, Cl2 undergoes homolytic cleavage to form two chlorine radicals. These radicals then react with isobutylene to form a carbon-centered radical and a chlorine-substituted isobutylene molecule. The carbon-centered radical then reacts with another Cl2 molecule, forming a new chlorine radical and a molecule of isobutylene with two chlorine substituents. This process continues until all of the Cl2 is consumed.

2. What is the structure of the product formed from the reaction between isobutylene and Cl2?

The product formed from the reaction between isobutylene and Cl2 is isobutyl chloride. It has the chemical formula C4H9Cl and a structure with a chlorine atom attached to the second carbon atom in the isobutylene chain.

3. How does radioactive carbon play a role in this reaction?

Radioactive carbon, specifically carbon-14, can be used as a tracer in this reaction to track the movement of carbon atoms. When a molecule of isobutylene containing a radioactive carbon atom reacts with Cl2, the resulting product will also contain the radioactive carbon atom. By analyzing the radioactivity of the product, scientists can determine which carbon atoms in the reactant molecule were involved in the reaction.

4. Why is isobutylene often used in reactions with chlorine compounds?

Isobutylene is often used in reactions with chlorine compounds because it has a double bond between two of its carbon atoms. This double bond makes it more reactive and susceptible to undergoing addition reactions with chlorine. Additionally, the resulting product, isobutyl chloride, is a useful intermediate in the production of other chemicals such as isobutyl alcohol and isobutylamine.

5. What are some potential hazards of working with isobutylene and Cl2?

Both isobutylene and Cl2 are highly flammable and can pose a fire or explosion hazard if not handled properly. In addition, Cl2 is a toxic gas that can cause severe respiratory irritation and damage if inhaled. Proper safety precautions, such as wearing appropriate protective equipment and working in a well-ventilated area, should always be taken when working with these substances.

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