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Antoncho
(Official Hive Translator)
01-05-02 08:06
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COBr2 generation[crazy...] Some questions....
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A disclaimer first: Antoncho knows that SWIA is insane, don’t bother to tell him that<img src="../forum/images/icons_lightgrey/crazy.gif" alt="crazy" title="Crazy" heigth="15" width="15"><br><br>Now, here’s SWIA’s plan: <br>1st – chill some HCOOH , H2SO4 and bromine in a freezer (well, Br2 would freeze, so…)<br>2nd – add 3-4 drops of H2SO4 to the HCOOH (supposedly generating some CO in situ)<br>3rd – add several drops of Br2 and allow to decolorize.<br>4th – repeat steps 2 & 3 several times.<br>5th – xtract the mixtr w/DCM or CCl4 and use the (supposedly) COBr2 soln as is for forming Vilsmeier complex w/DMF<br><br>The residual formic acid hopefully won’t interfere w/the rxn (??) as well as bromomethyleniminium salt should precipitate and can bee washed w/ some DCM to purify, no?<br><br>And here come the questions – at least twenty of them, I think…<img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15"><br><br>1) what are the ordinary conditions of making CO from HCOOH? Namely, how much H2SO4 is required for HCOOH to start giving off CO, or does it happen immediately on their contact? At lower temps.?<br>2) Does Br2 react w/HCOOH? If so, what happens? Maybee better 1st add bromine, not sulfuric? Can smth like this occur: HCOOH + Br2 à 2 HBr + CO2 ?? <br>3) What side rxns can occur, you think? I mean, what else (possibly hazardous) can happen to a mixtr of HCOOH, H2SO4 & Br2? (gawd, just to pronounce these three words in one sentence makes SWIA shiver)<br><br><br>Oh my dear comrade bees, please do not let SWIA, this mentally unstable, yet charming in his naiveness fellow, end his life as a result of some stupid mistake<img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15"><img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15"><img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15"><br><br>He just built from scratch a fume cupboard, which turned out to bee pretty effective. He thinks he can try to pull this rxn without taking too much chances – but he’s never seen a prep’n of this disgusting comp’d, COBr2, even can’t find its bp on ChemFinder – it does exist though, & it should bee a liquid at RT, which is also nice.<br><br>His chemical intuition tells him it’s possible this way, but his chem. intuition usually misinforms him<img src="../forum/images/icons_lightgrey/laugh.gif" alt="laugh" title="Laugh" heigth="15" width="15"><img src="../forum/images/icons_lightgrey/laugh.gif" alt="laugh" title="Laugh" heigth="15" width="15"><img src="../forum/images/icons_lightgrey/crazy.gif" alt="crazy" title="Crazy" heigth="15" width="15"><br><br>Help.<br><br>Antoncho<br>
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<font color="#FF0033">Rhodium</font><br>
<i>(<span title="The user's title at the time of posting">Chief Bee</span>)</i><br>
<span title="Posting date">01-05-02 09:28</span><br>
<span title="Link to this post by using the markup [252948]">No 252948</span><br>
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<title>Re: COBr2 generation[crazy...] Some questions....
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<font color="red">ATTENTION!</font color="red"> Nobody without a proper lab and adequate ventilation should try this out! Carbonyl bromide (COBr2) is a close analog of the WWI war gas phosgene (COCl2)!
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Antoncho<br>
<i>(<span title="The user's title at the time of posting">Official Hive Translator</span>)</i><br>
<span title="Posting date">01-05-02 10:07</span><br>
<span title="Link to this post by using the markup [252952]">No 252952</span><br>
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<title>Re: COBr2 generation[crazy...] Some questions....
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.....<img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15"><img src="../forum/images/icons_lightgrey/laugh.gif" alt="laugh" title="Laugh" heigth="15" width="15"><img src="../forum/images/icons_lightgrey/wink.gif" alt="wink" title="Wink" heigth="15" width="15"> thanks a lot!<img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15"><br><br>I figured you read my disclaimer, and just wanted to inform the others who might not know this, right?<br><br>Well - still, does anyone have a clue at if this might work?<br><br>Antoncho
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<font color="#ff0000">lugh</font><br>
<i>(<span title="The user's title at the time of posting">Hive Bee</span>)</i><br>
<span title="Posting date">01-05-02 12:17</span><br>
<span title="Link to this post by using the markup [252977]">No 252977</span><br>
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<b title="The subject of this post">Re: COBr2 generation[crazy...] Some questions....</b>
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No comment on the proposed route except for "Good Luck" <img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15"> Carbon monoxide is formed when air free formic acid is dropped into concentrated sulfuric acid at 120°-130°C, in an evacuated flask. Impurities are carbon dioxide and acid spray. The general method of preparation for carbonyl halides is to react a metallic halide with carbon monoxide under high pressure, first done by Hieber. Another method that may prove fruitful is to react carbon tetrabromide with sulfuric acid. Another name for this compound is bromophosgene, a military poison gas <img src="../forum/images/icons_lightgrey/frown.gif" alt="frown" title="Frown" heigth="15" width="15"><br><br>
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halfapint<br>
<i>(<span title="The user's title at the time of posting">Ubiquitous Precursor Medal Winner</span>)</i><br>
<span title="Posting date">01-05-02 12:49</span><br>
<span title="Link to this post by using the markup [252983]">No 252983</span><br>
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<b title="The subject of this post">Re: COBr2 generation[crazy...] Some questions....</b>
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Yo, Antoncho, making CO from formic acid with sulfuric acid is a dehydration. That means the sulfuric acid must bee concentrated, namely in excess. So to get that part working, I think you'd need to add the formic to excess sulfuric, sorry. I'd keep the bromine out of that. It sounds like the ingredients for a VERY TOXIC CAUSTIC MESS. If you were lucky (??) enough to get some carbonyl bromide generated, you get all the leftover bromine with it, plus all the goodies formic acid can make, in your chlorinated organic solvent, and that's not what you want.<br><br>How about the Gattermann reaction? Its main drawback seems to be that it uses overpressure, in an industrial setting, to give yields. CO and HCl gases are reacted with the aromatic in the presence of AlCl3, (and the ref I'm looking at says also CuCl). I imagine yields of the aldehyde would bee pitiful just bubbling the gases through, at atmospheric pressure. But I don't know that for sure. Heat (and perhaps UV excitation) will work wonders on the reactivity of gases passing through solutions. That's just a shot in the dark. But I don't think your proposal is that much better.<br><br>Why not first generate your CO, and then bubble it through a Br2 solution in DCM or ether? That seems a more controllable approach. Don't know the bp of carbonyl bromide, but there must be some good way to separate it from bromine. Got to bee far easier than getting it out of the soup you were trying to make.<br><hr>turning <b>science fact</b> into <b><i><font color="red"><<science fiction>></font color="red"></i></b>
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Antoncho<br>
<i>(<span title="The user's title at the time of posting">Official Hive Translator</span>)</i><br>
<span title="Posting date">01-08-02 20:12</span><br>
<span title="Link to this post by using the markup [254260]">No 254260</span><br>
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<b title="The subject of this post">Re: COBr2 generation[crazy...] Some questions....</b>
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Well, after a little literature research, looks like it's not so simple...<br><br>CO & Cl2 react quite slowly in presence of sunlight (Sunlight, ?) and in darkness only at 500 C. The substitute for light can bee various catalysts such as sulfur or charcoal (they say, "animal charcoal" - anyone knows WTF is this?).<br>The book made no mention of COBr2 - and it lists even very rare compds, so it makes me wonder... Bromine would bee obviously pretty hard to get to react...<br><br>Halfapint, you've definitely got a point ('soup', huh?<img src="../forum/images/icons_lightgrey/wink.gif" alt="wink" title="Wink" heigth="15" width="15"> - i definitely disagree w/your term 'caustic', though<img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15">) - but now i think the only way would bee to saturate a CCl4 soln of chlorine w/CO and some catalyst - alas, there is no way to know how much COCl2 would bee actually made - maybee if one knew how much Cl2 DCM or CCl4 dissolve, but....<br><br>Too bad - looks like this whole idea isn't practical<img src="../forum/images/icons_lightgrey/frown.gif" alt="frown" title="Frown" heigth="15" width="15"><br><br>Dangerous, too<img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15"><br><br>Antoncho
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<font color="#FF0033">Rhodium</font><br>
<i>(<span title="The user's title at the time of posting">Chief Bee</span>)</i><br>
<span title="Posting date">01-09-02 01:13</span><br>
<span title="Link to this post by using the markup [254342]">No 254342</span><br>
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<b title="The subject of this post">Re: COBr2 generation[crazy...] Some questions....</b>
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Animal charcoal is an old term for activated carbon.
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halfapint<br>
<i>(<span title="The user's title at the time of posting">Ubiquitous Precursor Medal Winner</span>)</i><br>
<span title="Posting date">01-09-02 10:07</span><br>
<span title="Link to this post by using the markup [254432]">No 254432</span><br>
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<b title="The subject of this post">Re: COBr2 generation[crazy...] Some questions....</b>
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Yeah, activated carbon, but animal charcoal is specifically made outa burned bones. It's said to bee wonderfully effective in decolorizing solutions, better than regular activated charcoal made from wood. Didn't know about its catalytic activity.<br><br>Antoncho, a few months back you were willing to use sulfur to produce sulfur monochloride. You must still have some sulfur lying around. Not that I'm encouraging carbonyl bromide production. A whiff of phosgene, inadvertantly created, was quite enough for me! And using sulfur, I suspect that even more nasties could be produced.<br><br>Phosgene can result from thermal degradation of chloroform, etc., so there must be more routes we don't see. What I don't see, is a safe way to work with carbonyl bromide or chloride. Congrats on your new fume hood.<br><br>Lugh knows how this stuff is made: carbon tetrabromide in sulfuric acid. Bromoform, though, is easier to make. Perhaps there is a route from that. Too bad, but these exceedingly dangerous irritants might bee just too nasty for us to mess with.<br><br>"Caustic" has two overtones. In a limited sense, it applies to alkaline corrosiveness, but the wider sense of generally corrosive, whether alkaline or acidic, is often used, for example in the transportation industry.<br><br>When I mentioned the Gattermann formylation, it was to bring out that the hypothetical "formyl chloride" was produced in situ in that case. There should bee a direct variation, with HBr in the reaction mix, so just the CO would have to be introduced as a gas. That's as far as my ignorance will stretch.<br><hr>turning <b>science fact</b> into <b><i><font color="red"><<science fiction>></font color="red"></i></b>
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<font color="#ff0000">lugh</font><br>
<i>(<span title="The user's title at the time of posting">Hive Bee</span>)</i><br>
<span title="Posting date">01-09-02 12:23</span><br>
<span title="Link to this post by using the markup [254469]">No 254469</span><br>
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<b title="The subject of this post">Re: COBr2 generation[crazy...] Some questions....</b>
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<blockquote title="Quoted text"><hr><p>Lugh knows how this stuff is made<p><hr></blockquote><p><br><br>Not really, but another known route to these very dangerous compounds is to bubble the halogen gas through prussic(hydrocyanic) acid, which can be obtained by hydrolysis of <i>amygdalin</i> a component of bitter almonds and cherry kernels. Needless to say, a powerful fume hood is a necessity in dealing with such deadly gases <img src="../forum/images/icons_lightgrey/frown.gif" alt="frown" title="Frown" heigth="15" width="15"><br><br>As far as procedures for bromination of methane, these references may bee helpful: <i>Ber</i> <b>18</b> 2017 & <b>24</b> 4249 and <i>Ann</i> <b>231</b> 195 <img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15"> <br><br>The most convenient preparation of carbon tetrabromide is the exhaustive bromination of acetone; 4 g of acetone in 5 L of water are mixed with a solution of 224 grams of sodium hydroxide dissolved in 250 ml of water, 84.6 ml of bromine in successive .5 ml quantities, and the mixture shaken vigourously after each additon. After 24 hours, the supernatant liquid is siphoned off, the solid tetrabromide is dried on porous earthenware, and purified by sublimation. It forms lustrous, white crystals of a pungent odor, mp 94 C, insoluble in water, soluble in alcohol, ether and chloroform. Alternatively, it can be prepared by by the action of bromine on carbon disulphide in the presence of iodine <i>JCS</i> <b>8</b> 161 (1870) & <b>9</b> 773 (1871) <img src="../forum/images/icons_lightgrey/smile.gif" alt="smile" title="Smile" heigth="15" width="15"><br><br>It will keep well when pure, but polymerizes into cyanuric bromide in the presence of bromine or hydrobromic acid <img src="../forum/images/icons_lightgrey/frown.gif" alt="frown" title="Frown" heigth="15" width="15">
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