• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Chemistry: Post your doubts here!

daredevil

daredevil

Messages
1,394
Reaction score
1,377
Points
173
chocolate_girl

chocolate_girl

Messages
140
Reaction score
134
Points
38
daredevil said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_42.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_ms_42.pdf

In Q5, is it wrong to write just reduction instead of redox in the type of reaction G will hav with Na metal? Also how it is redox? the way i see it G is getting reduced and that is it.... ?? is it bcz it is losing H and also becoming negative (ox. state) that it is called redox?[/q
Sodium metal is oxidising from 0 to +1
Click to expand...
 
Amber

Amber

Messages
153
Reaction score
1,433
Points
153
daredevil

daredevil

Messages
1,394
Reaction score
1,377
Points
173
Amber said:
It has to be branched otherwise when the double bond is broken by hot conc H+ KMnO4 you willnot get compound E...Try working this question out from down to up
Click to expand...
then we can have a straight carboxylic acid too instead of the branched one (E) .......??
 
daredevil

daredevil

Messages
1,394
Reaction score
1,377
Points
173
Amber said:
no prob
hope u got it =)
Click to expand...
yeah i did... but who's to say what the next question will hold in store :') :p

and hey wud u happen to be some sort of an expert in nmr? nmr and organic are kinda not my strong suits in chem and shout out PROBLEM the loudest for me... if u cud help.... :))
 
Amber

Amber

Messages
153
Reaction score
1,433
Points
153
daredevil said:
yeah i did... but who's to say what the next question will hold in store :') :p

and hey wud u happen to be some sort of an expert in nmr? nmr and organic are kinda not my strong suits in chem and shout out PROBLEM the loudest for me... if u cud help.... :))
Click to expand...

ive got problems with nmr questions too but i could try helping =)
 
chocolate_girl

chocolate_girl

Messages
140
Reaction score
134
Points
38
daredevil said:
RNH2 + R'COCl --> R'CONH2 + HCl

There are two types of hyddrolysis of amides...
i) Acidic Hydrolysis:

RCONH2 + H2O --(H+ and heat)--> RCOOH + NH3

ii) Basic Hydrolysis:

RCONH2 + NaOH --(heat)--> RCOONa + NH3
Click to expand...

Thanks once again and another thing what is the compound R'CONH2 called and that the R in it is the carbon chain of acyl chloride only and wont v use the carbon chain of amide?
 
syed1995

syed1995

Messages
1,824
Reaction score
949
Points
123
daredevil said:
actually i was going to ask u the same question too...


A star syed1995 MustafaMotani u guys have any idea how to do this?? it's Q7 of May/June 2013 Paper 42
Click to expand...

NMR are Nasty.. anyway I'll give it a shot.

part (ai) M:M+1 is used for number of carbon atoms.. 100/1.1 * 3.35/43.3
= 7 Carbon Atoms



(aii) The ratio between M and M+2 peak is 3:1 meaning it's Chlorine.
PS: If it were 1:1 it would have been Bromine.



(aiii) NMR Spectrum shows 3 lines at different ppm so it has 3 different types of hydrogen environments.

NOTE THAT: Compound L reacts with sodium metal. MEANING THAT IT HAS -OH Group in it. Now we continue forward with the questions
(aiv)
Let's find the formula of the compound first.. The mass of the compound is 142. There is 7C present 1Cl present 1OH present.. and the rest are going to be H.

so 142= 7C+1Cl+1OH+XH
142=(7*12)+(1*35)+(1*17)+(X*1)
X=6
So Formula is C7(Cl)H6(OH)

Notice we have 7 Carbon atoms.. Our teacher has said whenever you have no. C>6 It's 90% a Benzene ring..
Now let's look at the Chemical shifts..
starting with the one on the very left. It has 4 written over it meaning it has 4 H attached in this environment. The chemical shift is 7-7.5

7-7.5 has Benzene ring with an H attached with it. It has 4H in this environment meaning our structure is now a benzene right with 4H.

89r4A.png


Cl cuz we were given a M+2 Peak given at the start.

Now let's look at the middle peak. It has 2H over it so it's probably a -CH2- group. we'll come to it later.

now the peak at the very right is 1H peak.. 99% of the time 1H peak represents -OH as far as our course is concerned.

So final structure will be something like
89rtk.png


Now we have to confirm whether this structure is correct or not.

The formula we derived was (Cl)C7H6OH
We know that there is a halogen present (Cl) from the M+2 Peak. We know that there are 7C atoms present from M+1 Peak. We know that there is a benzene right present with 4H.

Now compare that with what we have made.
  • There are 4H present in the Benzene Ring - Check
  • There is a environment present with 2H. CH2 present - Check
  • There is an alcohol present which is not a phenol - Check
  • There is a Halogen present - Check
 
chocolate_girl

chocolate_girl

Messages
140
Reaction score
134
Points
38
Please give me the reaction of one of the group 2 elements with each of the following
element+dilute ac
Element oxides, hydroxides and carbonates with water and with dilute acids
 
You must log in or register to reply here.
Top