[AC Prabakar]

Hi all!
I am having a compound with 4amine functional groups and when i am trying to prepare salt with acids(like HCL,Methane sulphonic acid) is it possible to form with both the acids?
 
I know that according to the pKa of the amine and acids salts will form.
My doubt is, is a single moiety with more than one amine can form a salt with two acids?

I couldn't find any literature/references on above said snag.(although i searching on available sources)
It will be helpful i could get some idea from you people(especially references/case studies)


Thanks in advance!

[Honclbrif]

http://en.wikipedia.org/wiki/Double_salt?

[Dan]

Can you explain yourself a little more clearly?

Do you mean: Is the following type of reaction possible?

H₂NCH₂CH₂NH₂ + 2 HA A^- H₃N⁺CH₂CH₂N⁺H₃ A^-

The answer to which is yes, ethylenediamine dihydrochloride is commercially available.

[nox]

^I'm gonna go with the double salt interpretation as well.

[AC Prabakar]

First thanks to all of u!

http://en.wikipedia.org/wiki/Double_salt?

I want to know whether this double salt phenomenon is possible for organic compound.

Can you explain yourself a little more clearly?

Do you mean: Is the following type of reaction possible?

H₂NCH₂CH₂NH₂ + 2 HA A^- H₃N⁺CH₂CH₂N⁺H₃ A^-

The answer to which is yes, ethylenediamine dihydrochloride is commercially available.

Yeah it is my mistake only i should have explained bit more!
Here it is...
1)In your above example, instead of 2 molecules(or equivalence) of HA if i take 1 molecule of HA and 1 molecule of some other acid(for example say HX) what will happen?
2)In the above example the ethylenediamine is having 2 amine functional which are equivalent to each(in terms of pka,1°amine).If i take one compound which contains two amine functional which are different in terms of pka and 1°amine,2°amines what will happen?

I hope i explained my best..

[Dan]

Ah, ok I see. I guess if the pKa differences are enough you will form a double salt. The question is whether it is a mixed double salt or not. For example:

H₂NCH₂CH₂NH₂ + HCl + HBr Br^- H₃N⁺CH₂CH₂N⁺H₃ Cl^-

This I suspect will depend on the stability of the mixed salt versus the the non-mixed salt - ie. the packing in the lattice etc. There are two options in such a reaction, the first being the one above (mixed salt) the second being:

H₂NCH₂CH₂NH₂ + HCl + HBr 1/2[Br^- H₃N⁺CH₂CH₂N⁺H₃ Br^-] + 1/2[Cl^- H₃N⁺CH₂CH₂N⁺H₃ Cl^-]

So in that case you have two different salts forming. I'm not sure how easy it would be to predict which type you'd get in any given case. Rochelle's salt is an example of an organic mixed salt, off the top of my head I can't think of any others.

In a way this is similar to the crystallisation of a racemic mixture. Sometimes a mixture of enantiopure crystals will form, which can then be separated by hand (eg. Pasteur and tartatic acid). In other cases racemic crystals will form and there is no resolution. It depends on whether or not an RSRSRSRSRS lattice is more stable than an RRRRRRR (or SSSSSSSS) lattice.

Similarly, it would depend on the stability of [Br(EDA)Br]_n and [Cl(EDA)Cl]_n versus [Br(EDA)Cl]_n <- I mean crystal lattices here, not polymers - the representation is crude, but I hope you see what I mean.

[nox]

I want to know whether this double salt phenomenon is possible for organic compound.

Yep, Rochelle's salt is a pretty well known example

http://en.wikipedia.org/wiki/Rochelle_salt

[AC Prabakar]

Thanks to both of u for your explanations and sharing your views!!!!
Let me check the (characterise) the formed salt mixture and if it has been solved i will update u..

Parallely let me check for the reported literature/case studies!!!!

Thanks once again!!!

[AWK]

Though formation othis type salts cannot be excluded, its isolation may be very difficult.