question related to free radical mechanism

[ashwinkandel]

25 When heated with chlorine, the hydrocarbon 2,2-dimethylbutane undergoes free radical
substitution.
In a propagation step the free radical X• is formed.
CH3CH2C(CH3)2CH3 + Cl? ? X? + HCl

How many different forms of X• are possible?
A 1
B 2
C 3
D 4

can someone tell me the answers with reason and reacction plz.

[ashwinkandel]

another question too..
27 Which isomer of C4H10O forms three alkenes on dehydration?
A butan-1-ol
B butan-2-ol
C 2-methylpropan-1-ol
D 2-methylpropan-2-ol

[Deadly_king]

another question too..
27 Which isomer of C4H10O forms three alkenes on dehydration?
A butan-1-ol
B butan-2-ol
C 2-methylpropan-1-ol
D 2-methylpropan-2-ol

Butan-1-ol will form only one alkene since the OH group is found on the first carbon atom. Hence upon dehydration the OH group and an adjacent H atom will condense to form one mole of water to form an alkene.

Butan-2-ol will form 2 alkenes since it has equal chance of producing an alkene with the hydrogen atom from adjacent H atoms from both sides(Either the first carbon atom or the third one). Its OH group is situated on the second carbon atom.

2-methylpropan-1-ol has one OH group on the first carbon atom and two methyl groups on the neighbouring carbon atom. However, since it is a primary alcohol, dehydration will result in the formation of only one alkene since the carbon atom containing the OH group is attached to only one other carbon atom.

2-methyl-propan-2-ol is a secondary alcohol. If you draw its structural formula, you'll realize that any alkene formed will be the same one due to different possible orientations. Hence it will form only one type of alkene.

For me, all the four answers given are inappropriate. But if I had to choose one, it will be butan-2-ol since it can form the most alkenes possible (2).

NOTE : All primary alcohols are first eliminated since they can form only one type of alkene upon dehydration.

Though I can't find any other worth explanation  

[Deadly_king]

25 When heated with chlorine, the hydrocarbon 2,2-dimethylbutane undergoes free radical
substitution.
In a propagation step the free radical X• is formed.
CH3CH2C(CH3)2CH3 + Cl? ? X? + HCl

How many different forms of X• are possible?
A 1
B 2
C 3
D 4

can someone tell me the answers with reason and reacction plz.

I believe it is 4

Free radical substitution reaction may occur on each carbon atoms of the butane group. This makes a total of 3 types.

Then one type for the methyl groups, in both cases it will be the same radical. Hence it is taken as only one type.

Try draw its displayed formula. It might help you to understand better and don't forget about the different orientations 

[ashwinkandel]

this is the question from 2010 paper no 12. according to marking scheme the answer of question one which i asked is B and question two is C.

[Deadly_king]

this is the question from 2010 paper no 12. according to marking scheme the answer of question one which i asked is B and question two is C.

Yeah.........the first question is C indeed.

Sorry for the mistake. I misunderstood the question.

When you draw the displayed formula you'll notice that the compound has 4 methyl groups(CH₃) and one CH₂ part. Free radical substitution mechanism involves the substitution of one H atom by a halogen atom.

So when one H atom is removed from the first CH₃, one type of radical is formed and when one H atom is removed from the CH₂ part, another type of radical is formed. Then another type is formed when one H atom from any 3 methyl groups on the third carbon atom. Due to orientations any radical formed with the methyl groups will be the same. This makes a total of 3 types.

Reactions :
1. CH₃CH₂C(CH₃)₂CH₃ + Cl* ---> CH₂*CH₂C(CH₃)₂CH₃ + HCl

2. CH₃CH₂C(CH₃)₂CH₃ + Cl* ----> CH₃CH*C(CH₃)₂CH₃ + HCl

3. CH₃CH₂C(CH₃)₂CH₃ + Cl* ---> CH₃CH₂C(CH₃)₂CH₂* + HCl


By the way I modified my post for the second number  

[ashwinkandel]

THANKS DEADLY_KING. U HAVE BECOME BY TEACHER. I UNDERSTOOD IT CLEARLY.

[Deadly_king]

THANKS DEADLY_KING. U HAVE BECOME BY TEACHER. I UNDERSTOOD IT CLEARLY.

OMG

Me.......teacher

You must be joking dude

Anyway it's a great pleasure to help you

[Vin]

OMG

Me.......teacher

You must be joking dude

Anyway it's a great pleasure to help you

Believe me man, you should seriously opt for the option, as a career. You'll earn gigabucks! :@ At least teachers here do.

[Deadly_king]

Believe me man, you should seriously opt for the option, as a career. You'll earn gigabucks! :@ At least teachers here do.

But what makes you think i'll be successful as a teacher I am only sharing the knowledge that I acquired throughout my studies.

Yeah......I know teachers especially those giving tuitions earn a lot. But really, am not so interested in earning money.

Since i've been a kid I wanted to help those in need.........that's why I badly want to be a medical practitioner. In this way i'll be able to help the poor and even save lives.
I know this may be an ancient reason but I believe in that

Anyway thanks for the compliment