Sciencemadness Discussion Board

NH3O-- Does this exist?

DDTea - 1-5-2004 at 13:49

I was thinking idly the other day about comparing Nitrogen and Phosphorus... And one of the things that came to my mind was the compound NH3O--basically, Ammonia with an Oxygen bound to the free electron pair on the Nitrogen atom. I did a google search for the formula "NH3O" and I did find some references, but I could not find a name. So I woul like to know: does this compound exist (and is not just made up for homework problems), and what is its name?? This is something that is bugging me.

My Guess

Turel - 1-5-2004 at 13:53

I've never heard of it, and I would think no it could not exist stably. It would be very prone to decomposition and rearrangement.

It could extrude water to give a nitrene, but I would think it would be very likely to rearrange instantly to hydroxylamine.

Such a compound would place a positive polar character on the nitrogen, and inductively onto the protons. The protons would exhibit attraction to the negatively polar oxygen, promoting the rearrangement to hydroxlamine.

This is my opinion of course, and not absolute fact.

fritz - 1-5-2004 at 14:02

according to the rule that the elements in the first periode are not allowed to have more than eight valence-electrons I doubt that such a substance exists.

Coordinate Valence

Turel - 1-5-2004 at 14:04

The compound would not violate this (very loose) rule. Coordinate valency would be responsible for it's formation.

unionised - 8-5-2004 at 07:57

Trimethylamine oxide does exist so the valency argument isn't valid. I guess the compound would isomerise to hydroxylamine (and/ or decompose to water, NH3, N2 H2 or whatever).

chemoleo - 8-5-2004 at 08:31

Do you think there is such a thing as N(CH3)5?
Or the +V state only exist with oxygen/sulphur and halogens?

Unfortunately.....

Turel - 8-5-2004 at 22:23

....no.

The closest you could get would be a tetramethylammonium halide. If you tried reacting this with something like methyl sodium, you would get elimination instead of substitution, giving sodium halide and ethane evolution. This is by the same mechanism as a name reaction I cannot recall at the present time. I *think* it may be known as hoffman elimination; not to be confused with hoffman hypohalite degradation.

Tetraalkylammonium ions are very stable in most conditions, but attempting to add a fifth alkyl function disrupts the ionic stability and always gives elimination.

What I am curious about is the potential for C-C coupling by this mechanism. Say phenyllithium and tetrabutylammonium bromide (known as TBAB) perhaps giving butylbenzene upon elimination? Interesting possibilities, both aromatic and aliphatic.

If_6_was_9 - 9-5-2004 at 06:56

Some amines can form oxides.

Proteios - 9-5-2004 at 09:48

NH3O exists as hydroxyl amine (and can be purchased from main stream chem suppliers)

But topologically its different to PH3O in that in the latter all the H are bonded to the P, while in the former 2 H are bonded to the N and the third to the O.


'5 valent N'....not with N.... no d electrons.

[Edited on 9-5-2004 by Proteios]

unionised - 9-5-2004 at 11:17

NH2OH exists but is unstable; you can buy salts of this base from the usual suppliers. That's not what he was asking about.
I think that you can get positive oxidation states of any of the elements; some of the products are rather reactive. OTOH
N(CH3)5 is tricky. I really don't think you could make it.

Pyrovus - 10-5-2004 at 03:26

The only structure for N(CH3)5 that seems reasonable would be the methyl salt of the tetramethyl ammonium ion; N(CH3)4[+] CH3[-]. I'm not sure how stable this would be, my guess is not very - as far as I know CH3[-] ions are quite reactive and would probably immediately react with the N(CH3)4[+] ion.

Turel - 10-5-2004 at 17:20

Have you not read my above posts?

axehandle - 10-5-2004 at 17:53

The skill of reading is too much to ask of people in this world.

chemoleo - 11-5-2004 at 10:30

Hmm, so what is the synthesis route to trimethylamine N-oxide? Surely it must be possible to methylate it further? As to the argument of elimination - why does it not happen with this compound, i.e. ethane evolution and production of monomethylamine N-oxide H3C-N=O?
I just dont follow this - N(CH3)3 (+III)exists, [N(CH3)4]+ (+IV) and (CH3)3NO (+V), so why not (CH3)3N(CH3)2 (+V)? Well I guess steric problems might make it unstable - but that wasn't the argument so far anyway.

I have 50 g of (CH3)3NO standing right next to me ;)

Ill Comparisons

Turel - 11-5-2004 at 14:39

Get a copy of March's Advanced Organic Chemistry, 5th Edition.

chemoleo - 11-5-2004 at 16:32

Ill comparison - how so? Surely helps more than referring to a book that I don't have.
Again - why does organic chemistry allow the making of (CH3)3NO, but not (CH3)3N(CH3)2?
In fact, I don't want to get into how it is made, the issue is more whether this compound can theoretically exist. So far I have seen no evidence to disprove this?!?

S.C. Wack - 11-5-2004 at 23:32

N can have eight electrons in its outer shell, and this shell is divided in two - the 2s shell can have one pair of electrons in it and does. The 2p shell can have six electrons and only has three. So it has three unpaired electrons, and usually shares these three orbitals with something else, giving normal covalent bonding. So, there are four orbitals available for pairing, and one is already paired. There are no other options, and this is so with all on this row of the periodic table.

In the coordinate pairing, as with trimethylamine oxide, the nitrogen is donating both electrons of its 2s pair, and so you see things like
_+
ON(CH3)3

In the case of NH4 cpds, the N loses an electron, allowing four pairs of bonds. This is a very simplistic explanation and Turel is of course correct, including the part about books. Physical chemistry just is not a simple subject, and cannot be discussed simply.

Proteios - 12-5-2004 at 13:46

As has been mentioned before, you only have an s and 3 p orbitals to play with.

The best hydbidisation u can get is sp3... tetrahedral. The d orbitals are too high in energy to hydridise ok for N. In P they are not.

to me its pretty simple why NMe5 dont exist. Why bromic acid dont exist is a far more subtle question!

BromicAcid - 12-5-2004 at 13:51

Quote:

Why bromic acid dont exist is a far more subtle question!


BUT I'M RIGHT HERE!

Seriously, bromic acid does exist, just not as a pure substance it would be incredibly unstable, increase the concentration to greater then 55% and autocatalyzed decomposition can occur (Same with chloric acid), however it has been detected in the vapor phase from a boiling solution of bromic acid and in the spectra from solutions of it indicating that it is indeed it's own existant molecule. Perhaps you ment perbromic acid, which was isolated only relatively recently in 1968.

[Edited on 5/12/2004 by BromicAcid]

Proteios - 12-5-2004 at 14:39

Quote:


Perhaps you ment perbromic acid, which was isolated only relatively recently in 1968.


Yeah, that one :)
by some mind blowingly obscure route too, like..... nuclear bombardmaent of the selenate!

[Edited on 12-5-2004 by Proteios]

BromicAcid - 12-5-2004 at 15:05

Considerably simpler then that actually. The first method to perbromic acid was:

XeF2 + BrO3-(aq) +H2O(l) ---> Xe(g) + 2HF(aq) + BrO4-

But more recent routes use F2 as the oxidizing agent. Although it is not commmerically availible to my knowledge it is somewhat easily manufactured and stable in concentrations to 50% (and its salts are compratively stable to perchlorate salts) Also it has the highest reduction potential of any of the peracids, very interesting.

For the longest time I thought perbromates were impossible to synthesize because of the earlier conjectures that the trends leading up to bromine rendered it incredibly unstable and it supported those theories. Recent studies conclude that the reason for the incredibly strong oxidizing agents necessary to form it stems from the almost rediculous instability of the +6 oxidation state that it must go though to end up at the +7 of the prebromate anion.

Tying this back to the topic at hand is the quote at the end of an entry on perbromic acid
Quote:

Thus, before dismissing any conjectured compound as impossible to synthesize, we must always be sure to explore all the possible preparative routes and conditions.


[Edited on 5/12/2004 by BromicAcid]

chemoleo - 12-5-2004 at 16:11

Thanks for the more detailed reply. I am always striving to learn :) - I have this reluctance to accept things because 'they are' - hence me asking for details :)

Unfortunately this seems to be the case here (i.e. 'it is';). The ominous N(CH3)5 (which it was to me ;)). I see now that the sp3 hybridisation (tetrahedral) would sterically and electronically not allow the existence of it.

But how about something like this - to extend the principle:

O=C=N(CH3)3 <--> O=(C-)-[N(CH3)3+]

or variations thereof (other atoms, i.e. N, S, etc)? I realise that the carboanion C- is not a happy entity - but I am more after the principle, rather than the specific example.

Oh, and what is N2O5 then?

(O=N=O)-O-(O=N=O) <--> (-O-(N+)=O)-O-(-O=(N+)=O) , whereby the former can't really exist? What are the angles of this thing? all tetrahedral angles?
How about [(CH3)2(N+)=CR2] [Cl-] This is basically the quaternary ammonium compound, but with a doublebond instead. Now this one is interesting - I am wondering as to the symmetry/angles, and whether it can exist.

At last I have argued myself into confusion again :D

Proteios - 12-5-2004 at 17:30

The guanidinium cation (H2N)3C is flat planar and sp2 hydridised on all the C and N atoms (flat trigonal). The remaining p orbital of the C and all the N atoms do interact to give a delocalised structure.... The practical upshot of which is the N-C bond doesnt rotate much. This structure is a motif in one of the DNA monomers... i forget which, and in the amino acid argenine

N2O5.... from memory is an unstable covelent structure. Essentially two nitrates sharing an oxygen. It dissassociates at really quite modest temperatures (RT i think) into NO3- and NO2+... the latter i think is interesting as an electrophile in organic chem. and physical chem as a fairly stable radical cation.