I need to dissolve T4 and the accompanying notes advise to dissolve it in 4M NH4OH in methanol. Perhaps NH4OH is a common reagent or maybe not but either way, I don't have any in the lab. Can NaOH be used as a substitute or is NH4OH simply not a base in the same sense as NaOH?
Thank you in advance.
NH4OH 4M in methanol is a commercial solution (for exemple http://www.sigmaaldrich.com/catalog/product/aldrich/779423?lang=fr®ion=FR). You will probably need to buy it (replacing it with NaOH which is a strong bas is probably not a solution -and preparing NaOH/methanol solution might be dangerous-)
NaOH is a far stronger base than ammonia, so you will need to adjust the concentration. It will probably work, but you have to keep in mind that a) your ionic strength will be different, if that is important at all; b) somebody might complain that you didn't stick to protocol and hence may challenge parts of or the entire experiment. NaOH by the way is soluble in methanol to about 6M, and there are no great dangers in preparing the solution, except that it gets hot as you dissolve the solid NaOH.
I would certainly not say that preparing NaOH methanol solution is of no great danger. It depends on your expertise and to what equipment you have access. Moreover, thyroxine is not a cheap chemical, if you can afford it, you can afford the right solvent to disolve it.
In dry (anhydrous) methanolic ammonia we expect the following equilibrium of the solute (NH3(g)) with the solvent, methanol (MeOH):
MeOH + NH3 ⇌ MeO- + NH4+
That can also be named as ammonium methoxide solution in methanol.
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