08-27-04 00:56
No 527604
As we know urea is the amide of carbonic acid.
Can urea be diazotized w/HCl NaNO2 to convert it to carbonic acid which in turn can be esterified w/MeOH in acidic media to afford dimethyl carbonate? Does anyone have references for the mentioned conversions?
(Hive Addict)
08-27-04 01:32
No 527615
urea is the amide of carbamic acid H2N-COOH
The easiest way to get carbonic acid H2CO3 would be to bubble CO2 into water. It cannot be esterified with MeOH however, as H2CO3 solutions heavily release carbon dioxide, especially on heating. And that's only one reason I can think of, while I believe there is other hurdles.
You would need COCl2 (phosgene, the acid chloride of carbonic acid) or one of its derivatives for a DMC synthesis from MeOH and you better avoid using chemical warfare agents in a synthesis.
I am not aware of any feasible DMC synth, but it looks like an interesting research target.
--psyloxy--
(Hive Addict)
08-27-04 02:47
No 527627
A relatively promising way could be this one:
formic acid methyl ester is chlorinated in the dark w/dibenzoylperoxide as radical starter to get methyl chlorocarbonate (CAS# 79-22-1) :
Yura; KGKZA7; Kogyo Kagaku Zasshi; 51; 1948; 157; Chem.Abstr.; 1951; 5476
Works with sunlight as well, see: Patent DE297933 Example 4,
J.Mol.Struct.; EN; 213; 1989; 97-116
Hentschel, J.Prakt.Chem.; <2>36; 1887; 214,309 (211-212 at gallica.bnf.fr)
Delepine; BSCFAS; Bull.Soc.Chim.Fr.; <4>27; 1920; 39
This is distilled over lead oxide to get dimethylcarbonate:
Ber. 13,1880;1697-1698
Various attempts at the synthesis of dimethylcarbonate were fruitless. It was however easy to reach that goal if raw, water containing methyl chlorocarbonate was heated to reflux over lead oxide (which one not specified) for a longer time, followed by distillation and purification by fractionation and washing with water.
--psyloxy--
(Newbee)
08-27-04 03:20
No 527635
A Remarkable Effect of Alkali Addition in the Oxidative Carbonylation of Methanol to Dimethyl Carbonate
Wei-Liang Feng1), Yong Cao1), Nan Yi1), Wei-Lin Dai1) and Kang-Nian Fan1)
1) Department of Chemistry & Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University
(Received May 17, 2004)
The presence of a small amount of alkali additive in the polymer-complexed copper catalysts can lead to a remarkable increase in the reaction efficiency for the oxidative carbonylation of methanol to dimethyl carbonate.
Chemistry Letters
Vol. 33 (2004) , No. 8 p.958
A Remarkable Effect of Alkali Addition in the Oxidative Carbonylation of Methanol to Dimethyl Carbonate Catalyzed by a Polymer-complexed Cu(II) Catalyst System
Wei-Liang Feng, Yong Cao, Nan Yi, Wei-Lin Dai and Kang-Nian Fan
(Hive Addict)
08-27-04 03:43
No 527640
...a teflon lined stainless steel autoclave filled with MeOH/CO/O2 at 120°C. Hmmmm....
There's a bunch of working methods for the preparation of other methylating agents, trimethylphosphate, dimethylsulfate / sodium methyl sulfate, methyl tosylate, methyl iodide. If you have to make your own you better stick to them. I don't see a useful kitchen procedure to DMC, unless maybe someone can get that Kogyo Kagaku Zasshi article...
--psyloxy--
(Newbee)
08-27-04 07:06
No 527705
that is the standard industrial way to make it. DMC is a "favored child" for the role of environmentally freindly methylating/carbonylmethylating agent. However, it needs a pressure vessel or gas-solid PTC setup to be used. What do you want to use it for?
It's good to bee back! Don't trust your computer!!
(Hive Addict)
08-27-04 13:02
No 527764
Lutesium: when posting an article, please include the reference for the article itself in the message. The references included in the article are less important than that.
fear fear hate hate
(Newbee)
08-27-04 15:50
No 527776
Correct me if Im wrong but I dont think methyl iodide is a a good ally in methylations. For grignards, quarnitery amine preperations (for PTC or Mannich reactions) it has no substitute. But the Mw and expense make it impossible for experimental use (waste waste waste
) I am also convinced that it is too weak for the methylation of deactivated oxygens on the phenyl ring (can syringaldehyde be methylated w/meI ?) therefore you have to run the rxn longer and if you are not working under inert atmosphere longer times in alkalis with an access to O2 means oxidation of the phenol therefore yield will drop. No need to mention that its highly volatile, poisonous (not carcinogenic) and it decomposes over time upon exposure to light and heat. Too many negatives...
No need to mention the evil REAL CARCINOGEN DMS (Dna Methylating Snag
) I dont want to use trimethyl phosphate cuz it never seemed appealing to me (due to the vaccum pyrollysis stage of preperation - its methlyating capacitiy is not worth the hassle)
My books mention diazomethane as the most "cute" methylating agent which has only N2 as the byproduct and its as powerful as DMS. But get ready - This is a new door for another disease: CHEMICALLY CAUSED ASHTMA when breathed
And it may decide to explode whenever it wants if the storage conditions (esp. the storage bottle which has to be smooth surfaced - projecting glass + diazomethane + movement = EXPLOSION)What more? DMC is impossible to make. It needs explosive setups CO gas or psoghene - ARE WE GETTING ARMED FOR WORLD WAR 3?
Ohhhhh.. What left?
Yeah the alkyl tosylates. Many say its harmless and easy to prepare + work with. But it wont suprise me if chemists start dying one by one from a newly evoked TOSYLOALOSIS disease.
I would better begin practicing the alkylating journey by making TNT and Nitroglycerine first
Sure they wont be so cruelGod help us to replace that H with a CH3 on phenols. Why is this so DANGEROUS? WHY??
(Hive Addict)
08-28-04 18:36
No 527971
Correct me if Im wrong but I dont think methyl iodide is a a good ally in methylations.
How do you get that impression ?
Methylation of syringaldehyde with MeI :Phytochemistry; 25; 9; 1986; 2093-2102
I am also convinced that it is too weak for the methylation of deactivated oxygens on the phenyl ring (can syringaldehyde be methylated w/meI ?) therefore you have to run the rxn longer and if you are not working under inert atmosphere longer times in alkalis with an access to O2 means oxidation of the phenol therefore yield will drop.
Don't be convinced before you've tried and found out.
No need to mention the evil REAL CARCINOGEN DMS (Dna Methylating Snag )
It is up to you to take the appropriate precautions when preparing or handling DMS or any other toxic/carcinogen/whatever substance. There's fume hoods, goggles, gloves and gas masks - use them together with knowing what you do and how to respond to a leakage or whatever.
Stop whining, take measures.
I dont want to use trimethyl phosphate cuz it never seemed appealing to me (due to the vaccum pyrollysis stage of preperation
What's so damn hard about that preparation ? You mix two compounds, stir, heat, apply vacuum, and distill your product. Standard things to do in an org. chem. lab. The yield could be higher, but given the cheapness of P2O5 and the ease of preparation I rate it among my favorite methylating agents.
its methlyating capacitiy is not worth the hassle
Patent US4453004
Example 1
In a three-neck flask (capacity 100 mL) equipped with a mechanical stirrer and reflux condenser...
Example 4
In an apparatus similar to Example 1, 15.2 g (0.083 mol) of syringaldehyde and 15.0 g (0.11 mol) of potassium carbonate were heated to 105°C under nitrogen and 15 mL (0.12 mol) of trimethyl phosphate were added over 10 minutes. The mixture was maintained at about 80°C for 3 hours then cooled to 45°C and quenched with 50 mL of H2O. The tan solid which precipitated was collected, washed with 3 x 50 mL of water and dried to give 15 g (92%) of 3,4,5-trimethoxybenzaldehyde.
My books mention diazomethane as the most "cute" methylating agent which has only N2 as the byproduct and its as powerful as DMS. But get ready - This is a new door for another disease: CHEMICALLY CAUSED ASHTMA when breathed And it may decide to explode whenever it wants if the storage conditions (esp. the storage bottle which has to be smooth surfaced - projecting glass + diazomethane + movement = EXPLOSION)
You label it cute and give all the reasons why it isn't. It is however a really interesting methylating agent. I never looked into it much.
Concerning the asthma: 1)don't breath it, it's that simple - but yeah, you'll have to invest in a bit of equipment. 2) Is it acute or chronic ?
What more? DMC is impossible to make. It needs explosive setups CO gas or psoghene
I wouldn't say it's impossible to make, just needs some research. It might not be worth the hassle, but that can only be told, if the research (loads of visits to the library) is done.
ARE WE GETTING ARMED FOR WORLD WAR 3?
We better should. Spiritually :)
Yeah the alkyl tosylates. Many say its harmless and easy to prepare + work with.
My personal favorites. Synthesis is straight forward. Methylation results are comparable to DMS.
But it wont suprise me if chemists start dying one by one from a newly evoked TOSYLOALOSIS disease.
The general opinion of alkyl tosylates being safer than DMS must have some reason. If you don't want to believe that, treat it like DMS to make free from any doubt.
--psyloxy-
(Moderator)
09-01-04 02:07
No 528617
(Rated as: good read)
The article of most interest to kitchen chemists
formic acid methyl ester is chlorinated in the dark w/dibenzoylperoxide as radical starter to get methyl chlorocarbonate (CAS# 79-22-1) :
Yura; KGKZA7; Kogyo Kagaku Zasshi; 51; 1948; 157
Chemistry is our Covalent Bond
(Hive Bee)
09-01-04 09:03
No 528798
what about deriving DMC from polycarbonate+methanol?
for instance reacting sodium methoxide with lexan.
(Newbee)
09-08-04 23:19
No 530349
A little more chlorination might yield trichloromethyl chloroformate:
http://www.orgsyn.org/orgsyn/orgsyn/prep
An excellent phosgene substitute. Something the acid people might bee vaguely interested in.
Only problem is...how to deal with the nasty methyl formate. Isn't that a gas?
It's good to bee back! Don't trust your computer!!