Chemistry: Post your doubts here!

[iKhaled]

what in the worls fajans rule?is itin As? few A2 friends saying it is in As

farjans law? excuse meeeeeee??? what is dat? :O

 

[A star]

google it i also did and another thing lucas test -_- i dont know what to believe

 

[iKhaled]

google it i also did and another thing lucas test -_- i dont know what to believe

i checked fajans law..not even a single sentence about it in my chemistry textbook (endorsed by Cambridge) so i don't think we will need to know that

 

[Beaconite007]

Do all halogenoalkane reactions(barring the reaction with ammonia) require heating under reflux?
And what are the conditions for the reaction of KCN with an aldehyde?

 

[A star]

Do all halogenoalkane reactions(barring the reaction with ammonia) require heating under reflux?
And what are the conditions for the reaction of KCN with an aldehyde?

thats all i can gather

 

[syed1995]

Do all halogenoalkane reactions(barring the reaction with ammonia) require heating under reflux?
And what are the conditions for the reaction of KCN with an aldehyde?

Well I think so.. not sure whether all require reflux or not.. Atleast the elimination reaction doesn't require reflux.. or does it?

It's HCN with a KCN catalyst .. to convert Aldehyde to hydroxy nitrile ..that's what my teacher told me...

HCHO + HCN --> CH2(OH)CN

 

[syed1995]

google it i also did and another thing lucas test -_- i dont know what to believe

You can say that this is in course.. in a sense that it's used to detect presence of a alcohol.. but then again we have tons of other things to test for a OH group..

Reaction with a oxidizing agent.. Reaction with Na .. Reaction with PCl5 so you don't really need to know about lucas' test you have tons of alternatives.

what in the worls fajans rule?is itin As? few A2 friends saying it is in As

But Fajan's rule .. Well that's not in AS level syllabus. I am quite confident on that..

littlecloud11 PhyZac

You guys know anything about this Fajan's rule and whether it's in AS level course or not.

Thanks in Advance.

 

[knowitall10]

what in the worls fajans rule?is itin As? few A2 friends saying it is in As

I don't think there's anything called the Fajan's Rule in our syllabus... i mean, hey, i typed it and there's a red line underneath the word Fajan's
Yeah, there're probably many tests for alcohol, so why even consider this Fajan's rule? i don't remeber looking it up in AS last year.. and for my fellow A2 candidates, have you ever crossed this when you revised the AS Organic? I don't think so...

 

[knowitall10]

Do all halogenoalkane reactions(barring the reaction with ammonia) require heating under reflux?
And what are the conditions for the reaction of KCN with an aldehyde?

Nucleophilic Substitution with alkali: heat under reflux
Nucleophilic Substitution with Cyanide ions (in ethanol): heat under reflux
Elimination Reactions: nope
I think that's about it... ironically, I had the same question all the time, but look, i just looked it up in my Chemistry textbook and figured it out by myself
But my tutor (not a very good one) used to put "H.U.R" * under everything.. so this didn't really erase my doubt.. just made me a bit confident about what i always thought. I hope i was helpful.
*Heat Under Reflux
Btw, if you have the orange textbook, i suggest u look this up in the old black textbook. you know what i'm talking about? because according to my school teacher, she found some useful things regarding organic reactions in that textbook. and if i'm not wrong, then one of the pages of the AS topic also has most of the reactions summarised in a single diagram Go ahead, look it up...Hopefully, it'll clear your doubts.

 

[littlecloud11]

You can say that this is in course.. in a sense that it's used to detect presence of a alcohol.. but then again we have tons of other things to test for a OH group..

Reaction with a oxidizing agent.. Reaction with Na .. Reaction with PCl5 so you don't really need to know about lucas' test you have tons of alternatives.



But Fajan's rule .. Well that's not in AS level syllabus. I am quite confident on that..

littlecloud11 PhyZac

You guys know anything about this Fajan's rule and whether it's in AS level course or not.

Thanks in Advance.

Oh, the things you guys come up with...
There's no Fajan rule whatsoever in either AS or A2. Relax.

 

[iKhaled]

I don't think there's anything called the Fajan's Rule in our syllabus... i mean, hey, i typed it and there's a red line underneath the word Fajan's
Yeah, there're probably many tests for alcohol, so why even consider this Fajan's rule? i don't remeber looking it up in AS last year.. and for my fellow A2 candidates, have you ever crossed this when you revised the AS Organic? I don't think so...

fajan's rule is not in A2 too..never heard of it

 

[A star]

Oh, the things you guys come up with...
There's no Fajan rule whatsoever in either AS or A2. Relax.

nethier did i some people of A2 said they did it. o well since its not there alls well

 

[A star]

o and do we have to learn the table of cations and anions for paper 2

 

[iKhaled]

o and do we have to learn the table of cations and anions for paper 2

their tests u mean ?

 

[Manobilly]

Can I get the link to the page or can any1 upload the organic chemistry reactions summarised in a single diagram

 

[A star]

their tests u mean ?

yes

 

[iKhaled]

yes

you need to know the common ones like copper, iron, sulphate carbonate and that stuff but not all of them

 

[PANDA-]

Yes. For paper two you need to know the tests for cations and anions, as it comes occasionally where they show you a reaction and you have to write an observation. Specially the anions like Cl, F, Br, I.

 

[Sapphires]

can someone please tell me the difference between potassium manganate and potassium dichromate? In which reactions do we use them because in some mark schemes they NOT K2Cr2O7 in a reaction which is oxidation. TY

 

[A star]

basically in those reaction which require mild oxidation
use dichromate else use magnate