Chemistry: Post your doubts here!

[daredevil]

N 2011 q13 q24 q29 q30 q31 q34 q37 q38 q39

Can u plz solve these questions for me??

 

[A star]

N 2011 q13 q24 q29 q30 q31 q34 q37 q38 q39

Can u plz solve these questions for me??

link?

 

[daredevil]

link?

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_12.pdf

 

[A star]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_12.pdf

13c as they contain the common oxide of all three element hydrogen carbon and sulpher
24c as in first reaction is nuclophylic substitution in which C=O will be replaced with a c-cN and OH bond then H2SO4 oxidised the CN to CO2H and then it formed a ester of the formulae given

 

[A star]

29B as the dibromoalkane formed will form a diol as each bromine will be substituted by a OH ion

 

[daredevil]

13c as they contain the common oxide of all three element hydrogen carbon and sulpher
24c as in first reaction is nuclophylic substitution in which C=O will be replaced with a c-cN and OH bond then H2SO4 oxidised the CN to CO2H and then it formed a ester of the formulae given

in 13 i am confused y H2S or SO3 will not be formed?

 

[daredevil]

13c as they contain the common oxide of all three element hydrogen carbon and sulpher
24c as in first reaction is nuclophylic substitution in which C=O will be replaced with a c-cN and OH bond then H2SO4 oxidised the CN to CO2H and then it formed a ester of the formulae given

in the 24th question ... nitriles are oxidised to form acids right?? why is there a branching (OH) chain too?? that's wat confused me in this question...

 

[A star]

in 13 i am confused y H2S or SO3 will not be formed?

well you are burning the compound in air and they will break and oxidise them selves instead of reacting between themselves
and SO3 requires certain conditions or a very STRONG oxidising agent as SO2 will not oxidise easily

 

[daredevil]

29B as the dibromoalkane formed will form a diol as each bromine will be substituted by a OH ion

oo i just confirmed all three answers... only 13th is ryt...
24's answer is actually B
and 29's answer is D

 

[daredevil]

well you are burning the compound in air and they will break and oxidise them selves instead of reacting between themselves
and SO3 requires certain conditions or a very STRONG oxidising agent as SO2 will not oxidise easily

oh okaay thanks

 

[A star]

n

in the 24th question ... nitriles are oxidised to form acids right?? why is there a branching (OH) chain too?? that's wat confused me in this question...

not branching Br are attached to two different Cs hence OH will also do the same hence they look branched

 

[A star]

oo

oo i just confirmed all three answers... only 13th is ryt...
24's answer is actually B
and 29's answer is D

ps typo error thats what i meant

 

[daredevil]

n
not branching Br are attached to two different Cs hence OH will also do the same hence they look branched

ummm okay but now tell me about q24 too u explained Q29

 

[iKhaled]

ummm okay but now tell me about q24 too u explained Q29

Q24 the answer will be B because see..

CH3CHO + HCN -----> CH3H(OH)CN
CH3CH(OH)CN + dil. H2SO4 ----> CH3CHCOOH (hydrolysis of nitriles forms acid)

acid + alcohol will give u an ester so CH3CH(OH)COOH + CH3OH ----> CH3CH(OH)CO2CH3 so the answer is B

did u get it ?

 

[daredevil]

Q24 the answer will be B because see..

CH3CHO + HCN -----> CH3H(OH)CN
CH3CH(OH)CN + dil. H2SO4 ----> CH3CHCOOH (hydrolysis of nitriles forms acid)

acid + alcohol will give u an ester so CH3CH(OH)COOH + CH3OH ----> CH3CH(OH)CO2CH3 so the answer is B

did u get it ?

yeah I'm just confused by the (OH) in the ester... i mean there is an alcohol group on the ester?? how does that work out?!!

 

[iKhaled]

yeah I'm just confused by the (OH) in the ester... i mean there is an alcohol group on the ester?? how does that work out?!!

what's wrong with that? it doesn't matter and it can't react with the alcohol because they r both alcohols..compounds like these r called 'hyrdoxy' so this one will be called
2-hyrdoxy methyl propanoate (i guess thats the correct name) but alll what i want to tell u that it doesn't matter since there is a carboxylic acid group already reacting with an alcohol group then definitely we will have an ester..got me ?

 

[syed1995]

in the 24th question ... nitriles are oxidised to form acids right?? why is there a branching (OH) chain too?? that's wat confused me in this question...

CH3CH(OH)CN > CH3CH(OH)COOH > CH3CH(OH)COOCH3

Answer B

 

[daredevil]

what's wrong with that? it doesn't matter and it can't react with the alcohol because they r both alcohols..compounds like these r called 'hyrdoxy' so this one will be called
2-hyrdoxy methyl propanoate (i guess thats the correct name) but alll what i want to tell u that it doesn't matter since there is a carboxylic acid group already reacting with an alcohol group then definitely we will have an ester..got me ?

ohh okay -_- yeah i got u now.... gosh i cud just blow up organic chem if i got the chance!! every question seems to be an alien !! -_- x.x
Thankss btw for ur help... i'll b needing a lot of it especially in the organic section over the next couple of days ^_^

 

[daredevil]

CH3CH(OH)CN > CH3CH(OH)COOH > CH3CH(OH)COOCH3

Answer B

ohh thanks.... that means.... no matter wat is dangling from the rest of the chain most of the times our main focus will be on the funtional group only. ryt?

 

[syed1995]

ohh thanks.... that means.... no matter wat is dangling from the rest of the chain most of the times our main focus will be on the funtional group only. ryt?

YEA pretty much..