# Homework Help: Predict the mechanism

1. Jun 30, 2007

### pardesi

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.
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

2. Jul 2, 2007

### pardesi

any clue anyone

3. Jul 2, 2007

### chemisttree

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. Jul 2, 2007

### pardesi

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

5. Jul 2, 2007

### chemisttree

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. Jul 2, 2007

### pardesi

tahnks
by that i meant 1-butene and 2-butene

7. Jul 2, 2007

### chemisttree

What mechanism do you propose?