IGCSE CHEMISTRY DOUBTS

[Vin]

One more q

do we have cyclic hydrocarbons i guess one q had come abt properties

can somebody give info abt topics related to this..........

They are not in our syllabus, from what I know they are just another method of representing hydrocarbons in a circular way < I am NOT sure!

[Ivo]

~VIN1094~, for w08, Q7) b) iii), I do not get it at all.  The mark scheme says either 1 or 2-chloropropane is the product of the reaction, and that HCl is not a product.

Please explain, many thanks in advance.

[gaurav95]

Depends on the q, here its vitamin C. Usually all vitamins contain -OH groups. Only for the structural formula you need to specify -OH and not the molecular formula.


For Q.7 b)iii) There are 'n' number of types of chlorination. This depends on how much chlorine you use and which hydrocarbon you use.

When chlorination occurs it replaces one hydrogen atom from the hydrocarbon and forms HCl

E.g. Chlorination of methane::

    H                                                  H
    |                                                   |  
H- C - H   +    Cl₂ ------>  H- C - Cl  +  HCl
    |                                                   |
    H                                                  H

CH₄  + Cl₂  ----> CH₃Cl  +  HCl
Product:: Chloromethane (methyl chloride)
 

Similarly,
CH₃Cl + Cl₂  ----> CH₂Cl₂ + HCl

Product:: Dichloro methane (methylene chloride)


CH₂Cl2 + Cl₂ ----> CHCl₃  +  HCl

Product:: Trichloro methane (Chloroform)


CH₃Cl₃ +  Cl₂ ----> CCl₄  +  HCl

Product:: Tetrachloro methane (Carbon tetrachloride/Pylene)


I think you only need to know the names in bold. For your question, choose any of the following reaction BUT using butane and chlorine
Eg. C₄H₁₁Cl  + Cl₂ ----> C₄H₁₀Cl  +  HCl

OR to be safe give acc. to the ques

CH3-CH2-CH2-CH2-Cl  +  Cl2 ----> CH3-CH2-CH2-CHCL2  +  HCl
  
   H H H  H                             H  H  H Cl
   | |  |   |                             |  |  |  |
H-C-C-C-C-Cl   + Cl-Cl---->  H-C- C-C-C-Cl       +  H-Cl
   |  |  |  |                             |  |  |  |
   H  H H  H                            H  H  H H

Don't understand anything.. pls. ask.. Just under the concept of chlorination they may ask any other alkane next time
Draw the structures yourself you'll understand better

I am sorry VIn

but the q says that

Write a diff eqn for a  substitutuin reaction between butane and chlorine

[Vin]

~VIN1094~, for w08, Q7) b) iii), I do not get it at all.  The mark scheme says either 1 or 2-chloropropane is the product of the reaction, and that HCl is not a product.

Please explain, many thanks in advance.

that is for c) iii) not b) iii)

[Vin]

I am soryy VIn
but the q says that
Write a diff eqn for a  substitutuin reaction between butane and chlorine

I just gave you an example of methane... and how to name ...

I think you only need to know the names in bold. For your question, choose any of the following reaction BUT using butane and chlorine


Eg. C₄H₁₁Cl  + Cl₂ ----> C₄H₁₀Cl  +  HCl

OR to be safe give acc. to the ques

CH3-CH2-CH2-CH2-Cl  +  Cl2 ----> CH3-CH2-CH2-CHCL2  +  HCl
 
   H H H  H                             H  H  H Cl
   | |  |   |                             |  |  |  |
H-C-C-C-C-Cl   + Cl-Cl---->  H-C- C-C-C-Cl       +  H-Cl
   |  |  |  |                             |  |  |  |
   H  H H  H                            H  H  H H

Don't understand anything.. pls. ask.. Just under the concept of chlorination they may ask any other alkane next time
Draw the structures yourself you'll understand better

Got it?

[gaurav95]

I just gave you an example of methane... and how to name ...

Got it?

i m again sry but where is butane in these reactions i can see is butyl chloride or whatever

sry for irritating but i m not getting the concept.............sry

[Ivo]

I am sorry VIn

but the q says that

Write a diff eqn for a  substitutuin reaction between butane and chlorine

I was looking at the wrong part of the question, oops!

Anyway here is the answer to your question:

CH₃-CH₂-CH₂-CH₃ + Cl₂ -> CH₃–CH₂–CH(Cl)–CH₃ + HCl

That's right, isn't it?

[Vin]

I was looking at the wrong part of the question, oops!

Anyway here is the answer to your question:

CH₃-CH₂-CH₂-CH₃ + Cl₂ -> CH₃–CH₂–CH(Cl)–CH₃ + HCl.

That's right, isn't it?

Yes it is, but this reaction is given in the question itself! They are asking for different reaction...

[Ivo]

Yes it is, but this reaction is given in the question itself! They are asking for different reaction...

~VIN1094~, apparantly that's the trap CIE wanted people to make.  In the question, it does say a different equation for a substitution reaction between butane and chlorine, and not an additional chlorination of 1-chlorobutane.

So the product formed in my example is 2-chlorobutane as supposed to the 1-chlorobutane in the example.

[Vin]

~VIN1094~, apparantly that's the trap CIE wanted people to make.  In the question, it does say a different equation for a substitution reaction between butane and chlorine, and not an additional chlorination of 1-chlorobutane.

So the product formed in my example is 2-chlorobutane as supposed to the 1-chlorobutane in the example.

YES! You are right, I am a fool. Thanks

now i get it

[The Golden Girl =D]

YES! You are right, I am a fool. Thanks

now i get it

ur not a fool , u've been helpin everyone in physics and math ...etc

[Ivo]

YES! You are right, I am a fool. Thanks

now i get it

Hey, don't be so harsh on yourself!  The notes you did on substitution reactions were really good anyway, so it wasn't all a waste!!!

[gaurav95]

I was looking at the wrong part of the question, oops!

Anyway here is the answer to your question:

CH₃-CH₂-CH₂-CH₃ + Cl₂ -> CH₃–CH₂–CH(Cl)–CH₃ + HCl

That's right, isn't it?

r u sure???/

[Ivo]

r u sure???/

Tell me why it's not then   It's been 'approved' by ~VIN1094~, so I don't see why it's wrong.

[gaurav95]

some more doubts coming up...............

q4aii),iii)thensame q bii

q6bi its saying ammoniuum ion and ms is giving test abt nitrate ion............

q7b whole

thx in advance........