Author Topic: Sulfate salt  (Read 6326 times)

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  • Guest
Sulfate salt
« on: October 25, 2004, 12:07:00 AM »
I think in the hydrochloride salt, the hydrogen in the HCl forms a hydrogen bond with the nitrogen in the MDMA molecule, correct ?

Now, I am not sure what kind of bond it is formed in the sulfate salt. BTW, is it written 2(MDMA).SO4, is this correct ? Is it a normal covalent bond ? ( I don't think so )


  • Guest
complex salt, not ionic
« Reply #1 on: October 25, 2004, 04:42:00 AM »
Both HCl and sulfate salt are complex salts, meaning their ions aren't held together by the usual ionic forces but rather just by weak forces like dipole/dipole or van-der-waals or (in this case) H-bridge bonds. This kind of intermolecular force can be seen with molecules containing N or O bearing one ore more hydrogens (like NH2 for example).

Therefore, the correct formula are:

MDMA*HCl   or   (MDMA)2*H2SO4

(each hydrogen from the acid attracts one amine nitrogen, which becomes partially positive, depicted through "delta+" at the nitrogen and "delta-" at the hydrogen bearing counterpart, i.e. Cl or SO4)

Because the hydrogen bond is rather weak compared to electron sharing bonds, complex salts are usually not very stable, compared to ionic bonds (like with NaCl) or electron sharing bonds (which are called covalent bonds).



  • Guest
« Reply #2 on: October 25, 2004, 05:12:00 AM »
> Both HCl and sulfate salt are complex salts, meaning their ions aren't
> held together by the usual ionic forces but rather just by weak forces
> like dipole/dipole or van-der-waals or (in this case) H-bridge bonds.

wtf? i have never heard of this.
of course it's ionic forces between MDMAH+ and Cl- resp. MDMAH+ and HSO4- or SO4--.

could you please provide a pointer detailing the "complex salt"-thingy? textbook
or otherwise? i think you are confusing this with hydro-complexes as in CaSO4.2H2O.
(those aren't H-bridges either, but dative bonds)

ps: for a great book about bonds, complexes and all that stuff, check out
"Inorganic Chemistry: Principles of Structure and Reactivity" by Huheey.
very recommended.


  • Guest
intramolecular forces..
« Reply #3 on: October 25, 2004, 05:59:00 AM »
"Hydrogen Bonding
A hydrogen bond is not a covalent bond but a particularly strong transient dipole-dipole interaction. A hydrogen atom can participate in hydrogen bonding if it is linked covalently to an electronegative atom such as oxygen, nitrogen or fluorine. Hydrogen bonding is a strong intermolecular interaction, requiring ~5kcal mol-1 to break (c.f. ~100kcal mol-1 required to break a C–H or N–H covalent bond). Hydrogen bonding is replete in nature (i.e. DNA base pairing) and has a large effect upon the physical properties of organic compounds."


(utf google..)

Also good:



  • Guest
example for H bonding in complex salt
« Reply #4 on: October 25, 2004, 06:14:00 AM »
"An Intriguing Hydrogen Bond Pattern in a Maleate Salt. Connie G. Chidester, Michael S. Bergren and Richard F. Heier, Pharmacia & Upjohn, Kalamazoo, MI

PNU-95666E is a dopamine D 2 agonist currently in Phase II Clinical trials for acute treatment of Parkinson’s disease. Although during several years of preclinical testing it was widely perceived in the research community as an important and interesting compound, it was unusually difficult to crystallize and the crystal structure was done only recently. PNU-95666E is the (R) isomer of a methylamino-imidazoquinolinone, (5-(methylamino)-5,6-dihydro-4H-imidazo {4,5,1-ij} quinolin-2(1H)-one). The (R)-dipropylamino analog PNU-86170 crystallizes readily as either the free base or a salt and a crystal structure had been done of the hydrobromide. However, suitable crystals of the free base of PNU-95666 could not be obtained, and of the many salts tried, including hydrochloride, hydrobromide, fumarate, maleate and various hydrates of these, only the maleate salts seemed at all amenable to crystallization. After considerable effort, diffraction quality crystals were eventually obtained of the maleate.

The crystal structure is triclinic, spacegroup P1, with two molecules in the asymmetric unit and an equal number of maleic acid molecules. The hydrogen bonding pattern is complex and beautiful and offers many clues toward understanding why the compound was so difficult to crystallize and why the maleic acid salt was the key to crystallization. Hydrogen bonding patterns involving maleates in other crystal structures are compared."





  • Guest
« Reply #5 on: October 25, 2004, 06:48:00 AM »
very cute, but:
i didn't ask you for the definition of H-bridges (which i know well), but for
the definition of "complex salts" and why you think that MDMA.HCl is such a beast.


  • Guest
« Reply #6 on: October 25, 2004, 08:10:00 AM »
Firstly, I didn't answer any question about which type of bonds do keep complex salts together (it differs with different salts), but rather responded to your statement "of course it's ionic forces between MDMAH+ and Cl- resp. MDMAH+ and HSO4- or SO4--.". Because it is not ionic but H-bond forces.

Secondly, complex salts are those carrying a "*" in their name. This little sign depicts that the part on the left is complexed with the part on the right. Like with MDMA*HCl (ever saw Na*Cl?? Nope. Amine*HCl? D'oh - very common..)
Look it up for yourself whereever you like.



  • Guest
you're mistaken
« Reply #7 on: October 25, 2004, 08:27:00 AM »
when people write MDMA.HCl, they don't mean that it's a complex. it's
just a lazy notation.
think about it: MDMA is a (broensted) base, HCl is a strong broensted
acid. do you really believe that in MDMA.HCl the proton stays with the HCl?
that's completely illogical.

complexes are what you get when you react a lewis acid with a lewis base.
(due to the lone pair amines are lewis bases too, but i don't see how HCl
would be a lewis acid.)

> Look it up for yourself whereever you like.

did you invent this expression? if not, then just tell me from where you got it.


  • Guest
Let's take an example: methylamine forms a...
« Reply #8 on: October 25, 2004, 09:20:00 AM »
Let's take an example: methylamine forms a salt which is often called methylamine hydrochloride (MeNH2*HCl), which in fact means the same thing as methylammonium chloride (MeNH3Cl, can also be expressed as an ion pair MeNH3+Cl-). I guess you could even call ammonium chloride with the name ammonia hydrochloride and mark it as NH3*HCl. Why would MDMA be any different?

I assume that complex salt means an ion pair of a charged complex and some counter ion. A few randomly picked inorganic examples:
3Zn2+(aq) + 2[Fe(CN)6]3-(aq) --> Zn3[Fe(CN)6]2(s)
Al(OH)3(s) + KOH(aq) --> [Al(OH)4]-(aq) + K+(aq)

Maybe one could call any of the above amine salts a complex salt. An amine and a proton complex with each other to form an ammonium ion (lewis base + lewis acid), our complex ion. When this is done with HCl, we have the Cl- ion as the counter ion for the complex ion. When this ion pair, a salt, crystallizes, the crystal lattice includes both the ammonium ions and the chloride ions, in 1:1 ratio. So maybe you can call it a complex salt. It is just a word, it doesn't rule out ionic bonds in the crystal lattice in any way. Similarly writing MDMA*HCl is just a way to describe a salt, MDMAH+Cl-.


  • Guest
Salts are salts whether organic or inorganic
« Reply #9 on: October 25, 2004, 09:53:00 AM »
I don't want to anger anybody but hypo and moo are right. MDMA or other amine salts are ionic salts just like NaCl or other inorganic salts. Actually, you could even call the quarternary nitrogen cation  R3NH+ that result from their protonation a "Lewis complex". That's because a proton is a Lewis acid (it accepts electron pairs) and R3N: is a Lewis base (it donates the electron pair). It all depends on whether you prefer the Lewis or Bronstead acid-base definitions and concepts.
The resulting salts like amine hydrochlorides, sulphates and even acetates are all bonded by ionic interactions between the cations and anions, hence they are usually crystalline solids. H-bonds or dipol-dipol interactions are something else and their energy of interaction is several magnitudes lower when compared to the ionic 'bond'.


  • Guest
hm yeah...
« Reply #10 on: October 25, 2004, 09:56:00 AM »
> An amine and a proton complex with each other to form an ammonium ion
> (lewis base + lewis acid), our complex ion.

you've got a point there.

but while technically H+ is a lewis acid, it's an exception in that
you wouldn't call an ammonium compound a complex. all Hs on the nitrogen
are equivalent, so it's just a covalent bond. (ok, you could say that N---
is a quadruple lewis base, but this would be quite a stretch, wouldn't it?)
for this type of compound the lewis acid/base theory just doesn't fly as
well as the broensted one (yeah, i know - lewis is a superset of broensted).

and even if you call it a complex, the correct way to write it would be
[MDMA*H]Cl or something like that. or Na[CH3COO*H]. i don't think i could
get used to this.  ;)

so imho MDMA*HCl or MeNH2*HCl is slightly wrong. from a formal point of
view it describes what happens (MDMA gives an electron pair to HCl), but
it gives an incorrect picture of the actual electron configuration. (as
shown by indole_amine's confusion)


  • Guest
It was merely a thought play to illustrate how
« Reply #11 on: October 25, 2004, 10:21:00 AM »
It was merely a thought play to illustrate how the language and semantics are only there for communication. You can name a molecule in numerous ways for example, maybe detailing different aspects and points of view, but the actual molecule stays the same.

I see your point regarding the hydrogens on the amine though.


  • Guest
From my point of view, main problem is that I...
« Reply #12 on: October 25, 2004, 01:53:00 PM »
From my point of view, main problem is that I was missing the two H's in the H2SO4. So it is very similar to the HCl salt case.

Thanks to indole_amine for explaining that the two H's are there also.

Just in case, other projects etc. apparently going well, again busy with work, will keep you informed.