Sciencemadness Discussion Board

Substrates conc. and different products

biomechem - 4-1-2017 at 12:37

I wonder if there is a difference beetween concentration of substrates and obtained product.

For example using lower or higher concentration of nitric acid but the same amount of moles, and adding more or less H2SO4 to maintain the same water/ sulphuric acid ratio when nitrating substituted benzene like phenol or toluene will provide products in the same ratio with the same yield?
Or maybe is it possible to change o-, m-, p- and multi-substituted byproduct ratio?

Finally is it possible to increase concentration of nitric acid in situ by adding more H2SO4 and e.g. KNO3 salt?

aga - 4-1-2017 at 13:34

Merely Wondering is not an Amateur Chemist pursuit, and this is a forum for Amateur Chemists.

Quite often the Real members of this forum wonder, then try these things and sometimes (not often) report amazing results.

Wondering is mostly for somewhere else where people just Talk all the time and never Do anything to find out for themselves.

Not sure there is a suitable forum out there for that kind of Wondering, but this one is certainly not.

Perhaps there is. Google is your friend.

[Edited on 4-1-2017 by aga]

biomechem - 4-1-2017 at 14:40

I've been searching for an answer for a really long time and finally I got nothing. I would love to check it in practise but unfortunately I do not have favorable conditions for it I mean even if I somehow get pure reagents I will not be able to monitor the product.
What is wrong with asking interesting questions to people that have a way greater knowledge that I have, and what is more tools needed to find the answer?
At last I must say I've read a lot of stuff including handbooks, articles etc. but I have never seen answer for my problem.

[Edited on 4-1-2017 by biomechem]

Okay, I missed one important thing. A HNO3 acquired in situ is used for multiple nitration of compounds as toluene so I have answer for one of my questions.

[Edited on 4-1-2017 by biomechem]

PHILOU Zrealone - 4-1-2017 at 15:05

Quote: Originally posted by biomechem  
I wonder if there is a difference beetween concentration of substrates and obtained product.

For example using lower or higher concentration of nitric acid but the same amount of moles, and adding more or less H2SO4 to maintain the same water/ sulphuric acid ratio when nitrating substituted benzene like phenol or toluene will provide products in the same ratio with the same yield?
Or maybe is it possible to change o-, m-, p- and multi-substituted byproduct ratio?

Finally is it possible to increase concentration of nitric acid in situ by adding more H2SO4 and e.g. KNO3 salt?

Maybe there is a book about nitration into the Library of the forum.

There you will read that:
1°) the type of substituant onto the benzen ring dictates the easiness, readyness and statistical favored orientation of introduction of the nitro group and of subsequent nitro groups into the aromatic ring.
2°) the type of nitrating agent plays a role onto the easiness, readyness and statistical % of favored orientation of introduction of the nitro group and of subsequent nitro groups into the aromatic ring...and sometimes onto the products...
--> HNO3 conc (red or white), HNO3 dil, HNO3/H2SO4, HNO3/H3PO4, HNO3/P2O5, HNO3/As2O5, N2O5, Na/K/Li/NH4 nitrate and H2SO4, HNO2, HNO3/Ac2O,... behaves sometimes almost the same or totally differently.

biomechem - 4-1-2017 at 15:34

Quote: Originally posted by PHILOU Zrealone  

There you will read that:
1°) the type of substituant onto the benzen ring dictates the easiness, readyness and statistical favored orientation of introduction of the nitro group and of subsequent nitro groups into the aromatic ring.
2°) the type of nitrating agent plays a role onto the easiness, readyness and statistical % of favored orientation of introduction of the nitro group and of subsequent nitro groups into the aromatic ring...and sometimes onto the products...
--> HNO3 conc (red or white), HNO3 dil, HNO3/H2SO4, HNO3/H3PO4, HNO3/P2O5, HNO3/As2O5, N2O5, Na/K/Li/NH4 nitrate and H2SO4, HNO2, HNO3/Ac2O,... behaves sometimes almost the same or totally differently.


Thank you for answer, and please do not get me wrong, but I already know that. I've also heard about inductive and mesomeric effects.

I am rather curious what role plays amount of sulfuric acid and concentration.
The more H2O will be present = the more diluted will be mixture the less efective will be H2SO4 in creating NO2+ so the yield will be lower. Moreover the less conc. the collision of molecules are less probable, but I think it is possible to overcome this problem by extra rxn time.

But what about using less concentrated HNO3 and more H2SO4 in order to "compensate" more water in mixture as it is hygroscopic?
Will its excess disturb the reaction or it will just "consume"additional water present because of the fact that less conc. nitric acid was used?
One of my ideas is the this additional sulfuric acid may react with substituted benzene in sulfonation reaction, but on the other hand sulfonyl groups are easily substituted by NO2 groups.
So what will really happen?

[Edited on 4-1-2017 by biomechem]

unionised - 5-1-2017 at 03:32

Quote: Originally posted by aga  
Merely Wondering is not an Amateur Chemist pursuit, and this is a forum for Amateur Chemists.
[Edited on 4-1-2017 by aga]

Actually, wondering, and even asking, are part of the process of amateur chemistry.
Without wondering "could I do so and so?" you don't get round to trying it.
Without asking if others have tried it you risk not only reinventing the wheel, but repeating the mistakes of other-perhaps dangerous mistakes.

Obviously, it's nice when people report that actual outcomes of their experiments, but a brief survey of the forum's posts shows that's not the bulk of what's done here. (A lot of thread titles end in question marks- that strongly suggests they are questions rather than lab write-ups.)

PHILOU Zrealone - 5-1-2017 at 13:09

Quote: Originally posted by biomechem  
Quote: Originally posted by PHILOU Zrealone  

There you will read that:
1°) the type of substituant onto the benzen ring dictates the easiness, readyness and statistical favored orientation of introduction of the nitro group and of subsequent nitro groups into the aromatic ring.
2°) the type of nitrating agent plays a role onto the easiness, readyness and statistical % of favored orientation of introduction of the nitro group and of subsequent nitro groups into the aromatic ring...and sometimes onto the products...
--> HNO3 conc (red or white), HNO3 dil, HNO3/H2SO4, HNO3/H3PO4, HNO3/P2O5, HNO3/As2O5, N2O5, Na/K/Li/NH4 nitrate and H2SO4, HNO2, HNO3/Ac2O,... behaves sometimes almost the same or totally differently.


Thank you for answer, and please do not get me wrong, but I already know that. I've also heard about inductive and mesomeric effects.

I am rather curious what role plays amount of sulfuric acid and concentration.
The more H2O will be present = the more diluted will be mixture the less efective will be H2SO4 in creating NO2+ so the yield will be lower. Moreover the less conc. the collision of molecules are less probable, but I think it is possible to overcome this problem by extra rxn time.

But what about using less concentrated HNO3 and more H2SO4 in order to "compensate" more water in mixture as it is hygroscopic?
Will its excess disturb the reaction or it will just "consume"additional water present because of the fact that less conc. nitric acid was used?
One of my ideas is the this additional sulfuric acid may react with substituted benzene in sulfonation reaction, but on the other hand sulfonyl groups are easily substituted by NO2 groups.
So what will really happen?

[Edited on 4-1-2017 by biomechem]

Sulfonation only happen with H2SO4 (70-100%) depending onto the activation of the aromatic ring, and for some very resistant aromatic, if it contains SO3 --> over 100% H2SO4.
The reaction is into equilibrium with water and if too much water yield will be low.

It is written into organic chem books that you need concentrated HNO3 or H2SO4 to allow formation of NO2(+) and succeed to form nitro-aromatics...this is wrong
see nitration of naphtalene tread
and
see nitration of toluen tread
But the products may be different than expected because dillution of HNO3 favors side oxydation products...into the toluen case, nitrobenzoic acid.

Sometimes dillution is required to temper the reaction and avoid overnitration or oxydation like into the case of highly activated phenol...yielding brown tars with conc HNO3 alone at ambiant T°, but when using conc H2SO4 first you get TNP; and when using dilluted HNO3 alone, you get mono or dinitrophenols.

biomechem - 5-1-2017 at 19:47

Quote: Originally posted by PHILOU Zrealone  

It is written into organic chem books that you need concentrated HNO3 or H2SO4 to allow formation of NO2(+) and succeed to form nitro-aromatics...this is wrong
see nitration of naphtalene tread
and
see nitration of toluen tread
But the products may be different than expected because dillution of HNO3 favors side oxydation products...into the toluen case, nitrobenzoic acid.

Sometimes dillution is required to temper the reaction and avoid overnitration or oxydation like into the case of highly activated phenol...yielding brown tars with conc HNO3 alone at ambiant T°, but when using conc H2SO4 first you get TNP; and when using dilluted HNO3 alone, you get mono or dinitrophenols.


I couldn't be more grateful for your as comprehensive answer as it only could be.