Preparing NAOT

[Chromic]

A few trials:

1) 7ml o-toluidine, 14ml acetic acid (prep from NaOAc). Reflux 3hrs. Pour into 125ml water. 3g NAOT. 31% yield.
2) 32ml 2-aminotoluene, 64ml acetic acid (prep from NaOAc). Reflux (2-5p). Pour into 575ml water. 18.1g. 41%
3) 27.5ml OT, 55ml glacial AcOH. Reflux. (3-8p). Pour into 500ml water. 15.3g. 35%
4) 50ml OT, 100ml glacial AcOH. Reflux (1-4p). Pour into 900ml water. 24.6g. 35%

What the fuck is going wrong here? With Ac₂O, everyone speaks of a minimum 80% yield.

Would adding some sulfuric acid up the yields, or would it just end up making o-toluidine sulfate instead of catalyzing the condensation to make N-acetyl-orthotoluidine?

[Antoncho]

IIRC, Cheapskate mentioned adding MgSO4 to bind water...

i'll try to dig up some data on cryst. temps of some crystallohydrates..... lemmesee....




CaSO4*2H20 : -1,5H2O/128 C; -0,5H2O/163 Ñ
(permanently loses its ability to bind water upon total dehydration)

CaCl2*6H2O : -4H2O/45 C; -2H2O/>250 Ñ

MgBr2*6H2O: mp 172 C (obviously, w/out losing water)

MgSO4*7H2O: -6H2O/150 C; -H2O/200 C

CuSO4*5H2O: -2H2O/100 C; -2H2O/150 C; -H2O/250 Ñ

ZnSO4*7H2O: -7H2O/280 Ñ

ZnCl2 also completely loses water at circa 320 C.




Would that suffice for your needs, amigo?  Seems like MgSO4 or CuSO4 would bee your best bet.




Yours,

Antoncho

[moo]

According to

https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/dryingagent.html

zinc chloride is not suitable for drying amines. This is due to complex formation, so the same should apply to zinc sulfate. The document says nothing about incompatibilities of copper sulfate but I recall it was also unsuitable for drying amines, and as it also forms complexes with them it sounds reasonable as well.

[Antoncho]

I didn't think of this at 1st, but of course, zinc or aluminium cpds are too acidic for using w/amines, and copper also forms complexes w/both aliphatic and aromatic amines (this rxn can bee used as a test, see, e.g.,

http://www.chemistry.ccsu.edu/glagovich/teaching/472/qualanal/tests/copper.html

)


So, we're back to what we started at: good ol' dehydrated Epsom salt


Antoncho

[Chromic]

Perhaps three hours time wasn't long enough (and that 30 minutes extra you went made the difference) or maybe it was not using ice-cold water... I'm really at a loss. These reagents are supposed to be lab grade.

I'll try some dried MgSO4 if this latest run doesn't work, but I fear it's not going to bind the water at the reflux temperature of the mixture.