Hi does anyone have a step by step lab synthesis for Dimethyl Carbonate, which does not involve phosgeneBromicAcid - 15-1-2008 at 16:24
When I wanted some of the organic carbonates and looked into it, there weren't too many methods I found by which to make them without phosgene. Sure,
you could use a chloroformate and react it with an alcohol, but how to get there without phosgene?
The best method I found was to first produce ethylene carbonate and then react that with methanol. I managed the first of these two steps with what I
thought was decent success however never actually succeeded in the overall plan.
Anyway, whether it is feasible or not is up for debate but the overall plan was something like this:
Heat urea with ethylene glycol under reduced pressure to strip off ammonia-
OHCH<sub>2</sub>CH<sub>2</sub>OH + NH<sub>2</sub>CONH<sub>2</sub> --->
(-OCOCH<sub>2</sub>CH<sub>2</sub>O-) + NH3
The ethylene carbonate is a cyclic organic molecule, one of the oxygens in the structure above is not a part of the ring and makes up the carbonate
functional.
Then by heating the ethylene carbonate with the alcohol of your choice, in this case methanol (under pressure) you end up with a mixture of
carbonates-
Ethylene Carbonate + Methanol ---> (CH<sub>3</sub>CO<sub>3</sub> + CH<sub>3</sub>CO<sub>3</sub>CH<sub>2</sub>CH<sub>2</sub>OH + Ethylene
Carbonate + Ethylene Glycol + Methanol
Anyway, I thought it was a pretty neat method to get to these compounds. If you want to skip the first step supposedly ethylene carbonate is
purchasable, but if you're looking at that route there is nothing to prevent you from buying your dimethyl carbonate directly.
There is more information on this in the carbonate thread if you are interested.
[Edited on 1/15/2008 by BromicAcid]solo - 15-1-2008 at 16:27
Synthesis of dimethyl carbonate using CO2 and methanol: enhancing the conversion by controlling the phase behavior Zhenshan Hou, Buxing Han, Zhimin Liu, Tao Jiang and Guanying Yang Green Chem. 2002, 4, 467 - 471
Abstract
The critical parameters and phase behavior of the multi-component system CO2-CH3OH–CH3I–H2O–CH3OC(O)OCH3 (dimethyl carbonate, DMC) were
determined. The concentrations of the components were selected in such a way that they simulated the compositions of the reaction system at different
conversions for synthesizing DMC using CO2 and methanol in a batch reactor. The critical density of the reaction system decreases with the conversion
of methanol. The critical temperature and critical pressure of the reaction system increase with the conversion. Based on the determined critical
parameters and phase behavior, DMC synthesis using CO2 and methanol was run at various pressures that corresponded to conditions in the two-phase
region, the critical region as well as the single-phase supercritical region. The original ratios of the reactants CO2CH3OH were 82 and 73, and the
corresponding reaction temperatures were 353.2 and 393.2 K, respectively, which were slightly higher than the critical temperatures of the reaction
systems. The results indicate that the phase behavior affects the equilibrium conversion of methanol significantly and the conversion reaches a
maximum in the critical regions of the reaction system. At 353.2 K, the equilibrium conversion in the critical region is about 7%, and can be about
three times as large as those in other phase regions. At 393.15 K, the equilibrium conversion in the critical region is also much higher and can be
twice as large as those in other phase regions.
Thanks Bromic acid and Solo, so on the face of it, its not an easy compound to prepare. I did read a something about passing CO2 into methanol, whilst
being irradiated by microwaves. I can't find the details of this reaction as I read about it a few years ago. If anyone has details of this microwave
reaction, it could be useful, as supposed to be high yielding.Nicodem - 17-1-2008 at 12:27
Dimethyl carbonate is cheap and unregulated, so just about anybody can just buy it from the nearest chemical supplier. Unfortunately, any amateur
preparation would cost at least ten times its commercial price.
The industrial method of preparation consists in the oxidation of carbon monoxide in methanol with oxygen. The reaction is catalyzed by a copper salt.
See: US4318862 and EP425197.mechem - 19-1-2008 at 11:34
Thanks LSD25, looks very interesting, the heated autoclave with stirring under pressure might be a bit of a challenge, but when I get a bit of time I
will give it a shot. Just to clarify from the text, is it 14 molar quantity of methanol to 1 molar quantity urea and the same weight of PPA as urea
used.
Also you mention heating mono ammonium phosphate in a microwave in order to obtain PPA. Once the ammonia has been driven off is PPA the only
substance left and what sort off time frame does it take and yield expected. PPA has quite a high boiling point of about 550-C so if you put the MW on
to high, this might be why you are breaking your glassware, does the reaction work on lower settings (prob. need the extra heat
Methanol is used extensively for the production of biodiesel and by drag racers. If not then you could mail order some R/C fuel. Order the one with
the lowest nitromethane content (cheaper) and distill it collecting the methanol at 65-C, the remaining castor oil having a much higher boiling point.BromicAcid - 19-1-2008 at 12:20
One idea that I've been rolling around for awhile in my head is to just mix methanol and chloroform and keep it in contact with oxygen and hit it with
some UV light. It's pretty well known that chloroform decomposes in contact with oxygen to phosgene and that methanol or ethanol is added to
chloroform to 'stabilize it' whereby phosgene produced is converted to the carbonate and HCl. So maybe this could be parlayed into an effective
synthesis for dimethyl carbonate with the phosgene being consumed as it is produced. Followed by a bicarb wash and fractional distillation at the end
or something.
Another method that I didn't look into much is the reaction between methanol and concentrated NaOH solutions with carbon dioxide. I read this can
produce 1-2% dimethyl carbonate leaving me to wonder if you could use a concentrated NaOH solution with some sodium carbonate mixed in since IIRC the
method did not require excess pressure. If that is the case perhaps methanol could be dripped into a hot
NaOH/Na<sub>2</sub>CO<sub>3</sub> solution and the dimethyl carbonate continuilly distilled off (ala diethyl ether synthesis).
Anyway, just some more ideas.mechem - 19-1-2008 at 13:08
Hi Bromic acid
well the first one might take years and would be low yielding. In the second one as soon as CO2 mets the NaOH solution you would get instant Na2CO3.
Not sure what would happen if NaOH was mixed with methanol under anhydrous conditions to form a methoxide, then this be reacted with CO2.BromicAcid - 19-1-2008 at 13:12
Not sure about the exact rate of the first reaction but chloroform can decompose a few percent in a six month time frame just from occasional use with
subsequent flushing with nitrogen afterward. Hence it's classification as an air sensitive chemical from some suppliers, I was just thinking that if
you took it out of its protective amber bottle and shone some UV into the mix along with a constant supply of oxygen you might be able to get decent
results out of the thing. However this is just conjecture.mechem - 19-1-2008 at 14:42
Probably if you get a large clear glass flask add some chloroform methanol and a bit of conc. NaOH sol in it, leave it for some months in the
sunlight.BromicAcid - 20-1-2008 at 10:11
LSD25, the method to produce ethylene carbonate is exactly what I was talking about at the beginning of this thread and also in the other thread.
Also in the other thread patent number 4390708 was also mentioned which is likely the one you are talking about with respect to oxalyl chloride
Quote:
A process is provided for producing oxalyl chloride by first photochemically chlorinating ethylene carbonate to form tetrachloroethylene carbonate and
hydrogen chloride and then decomposing the tetrachloroethylene carbonate to oxalyl chloride and phosgene.
Though that doesn't have much to do with making organic carbonates unless you were looking at using the phosgene generated though there are much
easier ways to make the chemical.S.C. Wack - 26-4-2008 at 01:54
This is a (less-than-preparative) laboratory process for making dimethyl carbonate as asked for. It does not involve a COCl2, CO, or methyl
chlorocarbonate via formate route. I pulled up this ref while looking at alternative methods of producing acid chlorides from carboxylic acids. With
the long process necessary to make benzoyl chloride by this method, it would be foolish to not chlorinate benzaldehyde instead. There is however a
bonus in making the benzoyl chloride: methyl chlorocarbonate byproduct.
And so of course it does suck in its own way, mostly in the use of CS2 to produce the reagent (CH3)(CCl3)O, [CAS 20524-84-9] modest yields, and of
course all the chlorine.
Highlights:
The Preparation of Bis-(methoxythiocarbonyl) Disulfide.
To a stirred solution of 160 g. of sodium hydroxide, 600 ml. of water and 800 ml. of methanol, cooled by means of an ice-bath, was added dropwise over
a 1-hour period 240 ml. of carbon disulfide.
After the addition was complete, 0.1 g. of potassium iodide was added and chlorine was bubbled through the mixture until the color of free iodine
indicated that the end-point had been reached. The iodine color was discharged with 10% sodium bisulfite and the xanthate disulfide was separated,
washed repeatedly with water, and dried over calcium chloride. The crude disulfide was used for later experiments because it cannot be distilled, even
at reduced pressure, without decomposition.
The Preparation of Methyl Trichloromethyl Ether (I).
In a chlorination flask fitted with a mechanical stirrer was placed 212 g. of crude bis-(methoxythiocarbonyl) disulfide. While the flask and its
contents were cooled in an ice-salt bath a stream of anhydrous chlorine was passed in at such a rate that the temperature did not rise above 10°
except at night when chlorination was discontinued. Chlorination was continued until the weight had increased 420 g., and required 58 hours including
two overnight periods. The reaction mixture was distilled using a 12-in. column packed with glass beads. The first fraction boiling 57-60° (760 mm.)
consisted chiefly of sulfur dichloride. The second, a pale yellow liquid, boiled 48-51° (100 mm.) and contained the major part of the I. The residue
consisted chiefly of sulfur monochloride and intermediate chlorination products from the reaction.
The second crude fraction was cooled in an ice-salt-bath while anhydrous cyclohexene was added dropwise with stirring until the yellow color had been
discharged. The resulting mixture was then distilled through a 12-in. packed column and yielded 110 g. of nearly colorless I. Sometimes the last
traces of yellow color were hard to eliminate but careful redistillation usually gave a colorless, pure product in 30% yield or better with the
properties: b.p. 109.5-110° (760 mm.).
Reaction of I with Methanol.
In a flask fitted with sealed stirrer, dropping funnel and reflux condenser attached to a Dry Ice-trap was placed 200 ml. of absolute methanol.
Compound I, 15 g., was then added dropwise to the stirred methanol and when all had been added the reaction mixture was heated on a steam-bath and
maintained at reflux temperature for one hour. After cooling and pouring the mixture into water, the reaction product was recovered by extracting with
ether, washing with sodium bicarbonate, drying and distilling. The product was a colorless liquid (3.9 g.) boiling 90-93°.
The yield of dimethyl carbonate was 44% of the theoretical based on the methyl trichloromethyl ether used.
Reaction of I with Benzoic Acid.
A mixture of 12.2 g. of benzoic acid and 15 g. of I was maintained at reflux temperature until the evolution of hydrogen chloride had ceased.
Two fractions were obtained on distilling the black reaction mixture. The first, boiling 72-76° (760 mm.), was identified as methyl chloroformate by
density and refractive index and by forming methyl p-nitrophenyl carbonate. This derivative melted 108-109° after recrystallization from alcohol and
melted unchanged when mixed with an authentic sample. The yield of methyl chlorocarbonate was 37.6%.
The second fraction, consisting of 6.5 g. of liquid with the characteristic odor of benzoyl chloride, was identified by boiling point, refractive
index, density and the formation of benzanilide. The melting point of the latter derivative was unchanged when mixed with an authentic sample. The
yield of benzoyl chloride was 46%.
CO<sub>3</sub> + CH<sub>3</sub>CO<sub>3</sub>CH<sub>2</sub>CH<sub>2</sub>OH + Ethylene
Carbonate + Ethylene Glycol + Methanol