Chemistry: Post your doubts here!

[daredevil]

wow i donot get half the things being said here . so not reading from the start :3

yeah well u can catch up on the later posts (Y)

 

[♣♠ Magnanimous ♣♠]

namehere has some explanation...
let's see... ok..
thanks for your help.

see the deal is that if we are considering the PERCENTAGE of elements in the compound it is just like if we are taking 100g of the substance and then saying that e.g. 33.4g of it is C.
but the thing here is that if u add all the percentages we get 99.97% which means that a 0.03% part of the whole compound is unknown... it is prob something other than these three elements....
now if it is not an authentic source of cie papers (or even if it is) my guess wud be that they misprinted the question so dont fret over it all too much bcz ur method is definitely correct if u did it like u said u did...
other than that we can still be open for suggestions from other fellows and see if anyone has an explanation.

 

[♣♠ Magnanimous ♣♠]

please someone explain this quesiton...View attachment 38932

is this in AS level..
jaha tak muje pata hai , esa kuch maine padha hi nahi.

 

[Asad rehman]

View attachment 37866How do we do this?

D

 

[daredevil]

is this in AS level..
jaha tak muje pata hai , esa kuch maine padha hi nahi.

no it's in A2

 

[♣♠ Magnanimous ♣♠]

no it's in A2

phew....

 

[daredevil]

can anyone show me the reaction between phenylamine and propanoyl chloride??

 

[daredevil]

how many moles of H2 will be produced when 1 mol of this acid reacts with an excess of Na metal ??

the ms says 3 mol .... how??

also .... how many moles of NaOH will react with this acid
a) in the cold
b) on heating ??

 

[daredevil]

what does the OH in the middle of the bond between 2 C in the benzene ring mean??

 

[Amber]

3 mol of H2 are produced because Na will react with the 2 OH on the phenol and the 3 OH on the other ring and also with the OH of the acid group..so u have 6mol of H -----> 3 mol of H2

a) in the cold - 3 mol of NaOH (reacts with the 2 OH on the phenol and the acid group )
b) when heated - 4 mol of NaOH (breaks the ester bond in addition to reacting with the ones above)

 

[snowbrood]

daredevil 6Astarstudent can anyone help me understand that highlighted text in 3rd file from right well i think it contradicts with the data booklet in 4th file

 

[snowbrood]

View attachment 38934

how many moles of H2 will be produced when 1 mol of this acid reacts with an excess of Na metal ??

the ms says 3 mol .... how??

also .... how many moles of NaOH will react with this acid
a) in the cold
b) on heating ??

well Na reacts with alcohol phenol and carboxylic acid right so given this fact there are 6 hydrogen available to be replaced with Na metal 6 hydrogen atoms. 2 atoms in one molecule so 3 moles .
for (a) alcohols dont react with NaOH so 3 will react
for (b) again 2 OH of phenols and 1 OH of carboxylic acid will react but this time there would also be base hydrolysis so total 4 moles of NaOh required

 

[salvatore]

seondary structure consist of hydrogen bondings being formed between -CO and -NH group
they form either alpha helix of beta plated structures

the tertiary structure consist of 4 types of bondings
1. Hydrogen bonging
2. ionic bond between opositely charged groups
3. van der waals forces between hydrophobic R groups
4. disulphide covalent bridges (-S-S-), it's only formed between cystine molecules, as they are the only ones that have S in them

Primary structure only consist of arengements of aminoacids

Thanks man.. much appreciated

 

[daredevil]

daredevil 6Astarstudent can anyone help me understand that highlighted text in 3rd file from right well i think it contradicts with the data booklet in 4th file View attachment 38936 View attachment 38937 View attachment 38938 View attachment 38939

this has me beat.... it is contradictory.
at first i thought maybe bcz of OH or benzene ring the value shifted but even OH cant change the value this much...
i really succk big time at nmr..... and i request againn... IF anyone HAS any notes on NMR PLEAAASSEEE post them up and tag me.... thankss.... anything that cud help!!

 

[daredevil]

well Na reacts with alcohol phenol and carboxylic acid right so given this fact there are 6 hydrogen available to be replaced with Na metal 6 hydrogen atoms. 2 atoms in one molecule so 3 moles .
for (a) alcohols dont react with NaOH so 3 will react
for (b) again 2 OH of phenols and 1 OH of carboxylic acid will react but this time there would also be base hydrolysis so total 4 moles of NaOh required

okaayy i got the one with H but not the a and b parts..
if alcohols dont react then with which parts of the compound will 3 NaOH react?
same with the b part....

ummm are u saying that the phenols and carboxylic acid will react in a and b parts but alcohols won't ?

 

[daredevil]

daredevil 6Astarstudent can anyone help me understand that highlighted text in 3rd file from right well i think it contradicts with the data booklet in 4th file View attachment 38936 View attachment 38937 View attachment 38938 View attachment 38939

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

 

[A star]

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

am on it wait snowbrood

 

[sitooon]

3 mol of H2 are produced because Na will react with the 2 OH on the phenol and the 3 OH on the other ring and also with the OH of the acid group..so u have 6mol of H -----> 3 mol of H2

a) in the cold - 3 mol of NaOH (reacts with the 2 OH on the phenol and the acid group )
b) when heated - 4 mol of NaOH (breaks the ester bond in addition to reacting with the ones above)

daredevil

 

[A star]

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

ok guys here is my train of thought hope you follow(p.s I may be wrong so correct me if I am)
the compound has a total of 7 hydrogens and 7 carbons.
Now the peak at7.something confirms that it has a benzene ring. Now there must also be an OH that reacts with the Na metal but if we forma phenol with a chlorine attached it would leave a carbn short in our structure. so there must be an alcohol which is left which reacts with sodium metal as carboxylic acid would once again not fullfill the structure. now by attaching a chlorine and a methyl alcohol we remove 2 hydrogen and add three satisfying the no of Cs,Cls,Hs

 

[snowbrood]

okaayy i got the one with H but not the a and b parts..
if alcohols dont react then with which parts of the compound will 3 NaOH react?
same with the b part....

ummm are u saying that the phenols and carboxylic acid will react in a and b parts but alcohols won't ?

yea ofcourse thats the way it is