Sciencemadness Discussion Board

methyl acetate from AgOOCH3

platedish29 - 19-6-2013 at 20:04

Hello everybody I was chewing here the idea that it might work out to react CH3I with AgOOCH3 to produce methyl acetate under acidified conditions.
The reaction overral would be a concerted reaction wherein AgI precipitates leaving methyl acetate as product.
I'm not sure about the purpose of acidification but it seems there might happen some kind of catalytic effect,
dunno, it might work!

12AX7 - 20-6-2013 at 15:32

Sounds like a rather expensive way to do it (what's wrong with GAA, methanol and some sulfuric acid?), but I don't see why it wouldn't work.

Tim

platedish29 - 20-6-2013 at 18:14

Production of methyl acetate entailed industrially from the eastman kodak process for methyl acetate, which functioned in the basis of column counter flows and flash distillations, and I don't have time for that!
A similar reaction of the silver type is for producing methyl nitrite from MeI and AgNO2, silver acts as a stabilizing agent whereas the nitrite attakcs as not to form methyl nitrate. For that reason the acetate might be somehow changed to give weird products.

CH3I + AgONO --> AgI + 1/y CH3ONO + 1/x CH3NO2

P.S.: seemingly this works out without the need for acidic enviroment as the nitrite ion is very reactive as people know it, but would the acetate act alike?

Addition of the sulfuric would be overkill as it would just precipitate out silver as the sulfate.
The solubility of silver acetate in aqueous solutions varies little even with the addition of other salts. However, aqueous nitric has an enchancing property on its solubility varying from 8.5g per 100mL at 3% HNO3 concentration to 79g per 100mL at 33% nitric at 25°C.
But as nitric is involved oxidation of the methyl iodide might occur, unless temperature is well regulated (copper nitrate has strong oxydsing properties on ethanol at RT so why should silver act alike? However, the nitrite example is straight forward and presumes no oxydation occurs even with the nitrite ion group hanging around).

Conclusion: the only advantage would be the 100% yield, so doing the maths here we see an aqueous solution of methylacetate in the given proportions (data given for 33% nitric, and d = 1.67 for the solution containg AgAcOO):
0.47AgCH3COO + 0.87HNO3 + 1.82H2O + 0.47CH3I comprises a solution containing 79g AgAcOO, 55g nitric, and only 32g water. As the methyl iodide is just poorly soluble in the beggining and as it would have no time to stay in solution, the final products in the container would be 66.7g MeAc, 55g nitric and 32g water. So, aside from suppsedly concentrating the nitric acid the media seems to be far to harsh to methyl acetate to survive, unless the 2nd order reversibility of such reaction is unfavorable at low temperatures.

from Wiki:
"In the presence of strong bases such as sodium hydroxide or strong acids such as hydrochloric acid or sulfuric acid it is hydrolyzed back into methanol and acetic acid, especially at elevated temperature."

So, now, we can support the need for neutralising the reaction medium. Further research revealed the calcium salt of nitric acid at conc. around 650g per liter can dissolve up to 45g AgAcOO, being d = 1.37 the density of the solution, this one comprising then 600g water to lately hold about just 20g MeAc. The drawback is that although product formation is ought to be 100% certain the concentration of the product in the final liquor demonstrated to be very low, as for some precipitative method must be implemented.
That fatally worn us to anticipate the countercurrent alike method again. Silver acetate can be dissolved back into the reaction liquor once no Ag+ or I- ions would be present at any decent levels anymore.

Poppy - 25-6-2013 at 11:15

Won't the calcium nitrate just competitively react with the CH3I to form insoluble calcium iodide and/ or nitromethane/ formaldehyde/ acid in a messep up reaction overrun?

EDIT: woohops, I thought CaI was the way insoluble but proved out to bear a similar solubility curve as the chloride!!



[Edited on 6-25-2013 by Poppy]

platedish29 - 25-6-2013 at 11:34

Thankfully not!! It seems a trend on ionic volumes plains a substantial role here, so calcium nitrate wouldn't mess up the thing unless higher temperatures are employed, even then, silver iodide should not apparently become very solubility sensitive in this case.

Poppy - 27-6-2013 at 18:41


No, this is not worth it, unfortunately this process works in these conditions for the much more soluble lead acetate.
The calculations can be demonstrated for the solubility increase in terms of ionic strenght:
u for 3,96 molar Ca(NO3)2 = 1/2 / (3.96x2^2 + 7,92x(-1)^2) which gives 11,88
The activity for AgAcOO then is: 0,178
which gives for the total solubility S^2 = 6.144x10^(-3)x0,178

being S = 0.18g/100

Which showed that only 0.18g of silver acetate will be solubilized taking into account the participation of the other ions. It was been much to accept this material is synthesized the way it is industrially because the silver route, even if it works, gives low yields.
I got some silver here and do not pretend to waste it!
An experiment with Pb(AcOO)2 showed that although the solubility is much higher the good old runaway occurs which is the formation of lots of stinky formaldehyde/ formic acid vapours loss of lead as no PbI formed immedatly, but things had to be neutralized before I could take out the lead so yeah. If anyone knows a way to stop this perhaps lead could be used which is much easier task than the destillative method applied industrially.
Maybe changing the calcium nitrate to calcium chloride might work as no oxidant would be present but the chloride ions causes lead to precipitate, so what ever...

platedish29 - 27-6-2013 at 18:45

Does anyone know an organic solvent suitable for the dissolution of silver acetate that does work for cooking methyl acetate?
The acetate is inorganic so some solvent might help dissolve it any ideas?

Nicodem - 28-6-2013 at 06:02

Quote: Originally posted by platedish29  
Does anyone know an organic solvent suitable for the dissolution of silver acetate that does work for cooking methyl acetate?
The acetate is inorganic so some solvent might help dissolve it any ideas?

Well, you don't need to be clever to realize that the most obvious choice for the solvent would be acetic acid. But then again, if you use acetic acid, why would you want to use silver acetate and methyl iodide? You can just use methanol instead.

Do you mind explaining the purpose of this thread? It is obviously not about studying the reaction of alkyl halides with silver carboxylates, because methyl acetate is the least suitable product for such a study (it is liquid, highly volatile, highly water soluble, requires fractionation, difficult to properly characterize without GC or NMR...). I wish it would be about that, as it would be an interesting topic for an amateur chemist, but it is obviously not.
Quote:
Conclusion: the only advantage would be the 100% yield, so doing the maths here we see an aqueous solution of methylacetate in the given proportions (data given for 33% nitric, and d = 1.67 for the solution containg AgAcOO):0.47AgCH3COO + 0.87HNO3 + 1.82H2O + 0.47CH3I comprises a solution containing 79g AgAcOO, 55g nitric, and only 32g water. As the methyl iodide is just poorly soluble in the beggining and as it would have no time to stay in solution, the final products in the container would be 66.7g MeAc, 55g nitric and 32g water. So, aside from suppsedly concentrating the nitric acid the media seems to be far to harsh to methyl acetate to survive, unless the 2nd order reversibility of such reaction is unfavorable at low temperatures.

I must admit I understood nothing of this. What would the purpose of nitric acid be? Where does that weird stoichiometry comes from? Why would acetone be the product? And what is the reference for all this?