most recent 30 from http://lab.chempedia.com 2010-03-10T21:55:43Z http://lab.chempedia.com/feeds http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://lab.chempedia.com/questions/124/glovebox-best-practices verpa 2010-03-09T01:04:55Z 2010-03-10T19:42:37Z

<p>As some one who has spent too much time doing air sensitive chemistry, I've always wondered what is the best practice for bringing small quantities of liquid samples into the glovebox.</p> <p>Most books say 'use screw tap seals' but that's impractical when switching back and forth from Schlenk lines which are configured for penny stoppers and rotating taps.</p> <p>9/10 times, a parafilmed, greased, and kecked stopper will hold as you pump down the vacuum ... but it's always made me slightly nervous.</p> <p>To get the ball rolling, these were what I've known various groups to do:</p> <ol> <li>Very, very slowly (30 min for small port) increase vacuum on intake port ( and invoke the power of prayer ).</li> <li>Always bring liquid samples into glovebox under vacuum (sample under vacuum).</li> <li>Always bring liquid samples into glovebox frozen.</li> </ol> <p>Just looking to see what else people have done, and which you consider the best.</p>

http://lab.chempedia.com/questions/40/whats-your-favorite-preparative-organic-reaction Bill Town 2009-11-18T18:15:28Z 2010-03-10T18:07:41Z

<p>Please supply reaction scheme images for your favorite reactions. I need some good examples to illustrate (using Reaxys) how a given functionality is converted into another functionality and which protocol I need to use so that a third functionality remains stable during the reaction (the use of free sites and generic groups etc). The examples shouldn't be too basic or too complex. I don't have access to a modern organic chemistry textbook.</p>

http://lab.chempedia.com/questions/110/scale-up-parameters Chemjobber 2010-02-10T00:01:00Z 2010-03-10T18:05:39Z

<p>By what maximum factor is it safe to scale up a reaction? I've heard 4X and 10X -- what do you think? </p> <p>For example, let's say you're moving from bench-scale (max 12L RBF) to kilo-scale (72L RBF). </p>

http://lab.chempedia.com/questions/98/physical-organic-chemistry-textbook Mark 2010-01-12T15:30:18Z 2010-03-10T17:59:52Z

<p>Can anyone recommend a good Physical Organic Chemistry textbook ?? Tx.</p>

http://lab.chempedia.com/questions/120/whats-your-glassware-cleaning-procedure Egon Willighagen 2010-03-07T15:32:58Z 2010-03-10T17:51:04Z

<p>A long time ago, when I was still in organic chemistry, I practically found it better to not try to get the glassware as clean as possible, but do be fine with 99.9% clean (I never really quantified it :). Just make it look clean is good enough.</p> <p>My feeling was that reactions went more smoothly, and it sure saved me a lot of time. I figured it did not really matter anyway, as it was at least as clean was any analytical method could detect. That my reactions actually went a bit more smoothly might have just been perception, but I wondered if a bit of dirt might just get the things going.</p> <p>That said, it sounds all too homeopathic to me now, but since there was no other discussion going on here, I wonder what other people think about the amount of cleaning needed for organic synthesis:</p> <p>as clean as possible, or just the regular kitchen clean?</p>

http://lab.chempedia.com/questions/121/what-is-molecular-gastronomy Rich Apodaca 2010-03-08T15:37:26Z 2010-03-09T11:31:09Z

<p>The other day, the subject of "Molecular Gastronomy" came up. What is it and is this a real subfield in chemistry?</p>

http://lab.chempedia.com/questions/57/whats-special-about-microwave-heating Rich Apodaca 2009-11-27T16:34:28Z 2010-02-24T15:11:48Z

<p>Few of the papers I've seen on organic synthesis with microwaves as a heat source report a side-by-side comparison with the same reaction in a conventional heat bath. And most reactions run under microwave irradiation can also be run with conventional heating.</p> <p>Beyond acting as a controlled heat source, what can microwave irradiation do for a reaction that can't be done with a conventional heat bath? Where can I find an actual rate comparison between microwave heating and conventional heating?</p>

http://lab.chempedia.com/questions/103/most-compelling-reason-for-using-a-paper-lab-notebook-over-an-electronic-lab-note Rich Apodaca 2010-01-31T16:31:06Z 2010-02-17T18:53:24Z

<p>There's been a lot of time and money spent on selling the advantages of Electronic Laboratory Notebooks (ELNs). Yet many continue to use paper notebooks.</p> <p>So, what's the most compelling reason for using a Paper Lab Notebook rather than an Electronic Lab notebook for chemistry research?</p> <p><a href="http://electroniclabnotebook.com/" rel="nofollow">This company</a> does a pretty good job of explaining one pretty serious problem with ELNs. The US is a first to invent country and that means a lot in a patent dispute comes down to the believability of the record documenting the invention. Today, computer systems built 20 years ago look like toys. Many of today's ELNs will look like toys in 20 years. The vendor may have gone bankrupt and the tools to read the data may be obsolete.</p> <p>A paper notebook will remain readable and understandable by a jury of non-scientists for many decades.</p>

http://lab.chempedia.com/questions/101/how-are-you-managing-data-produced-in-your-lab avi 2010-01-24T07:42:35Z 2010-02-17T02:19:38Z

<p>Are lab books still in fashion? Has anyone evaluated lab management programs such as BioKM (www.biodata.com)?</p>

http://lab.chempedia.com/questions/113/solubility-of-alcohols-in-ammonia Egon Willighagen 2010-02-11T04:49:45Z 2010-02-15T22:55:10Z

<p>There was a question this week on the <a href="http://www.indiana.edu/~cheminfo/network.html" rel="nofollow">CHMINF-L mailing list</a> about the <a href="https://listserv.indiana.edu/cgi-bin/wa-iub.exe?A2=ind1002&amp;L=CHMINF-L&amp;P=R4575" rel="nofollow">solubility of alcohols in ammonia</a>. Now, <a href="http://lab.chempedia.com/users/27/andrew-lang" rel="nofollow">Andrew</a> has been posting solubilities for a number of solvents, but I do not believe the ONS Solubility project has yet started measuring ammonia solubility (which would be experimentally trickier than many less volatile solvents).</p> <p>There were two replies, but none about the solubility of alcohols... anyone here with pointers?</p>

http://lab.chempedia.com/questions/23/things-you-wont-work-with Rich Apodaca 2009-11-15T03:11:35Z 2010-02-12T16:01:12Z

<p>Derek Lowe has written an excellent series of posts on <a href="http://pipeline.corante.com/archives/things%5Fi%5Fwont%5Fwork%5Fwith/" rel="nofollow">things he won't work with</a>. Many of the things on his list can really mess you up. Other are just smelly. Neat dimethyl zinc is of the first kind:</p> <blockquote> <p>But neat dimethyl zinc. . .no, I don't think so. A colleague of mine made some in graduate school, and came down the hall to us looking rather pale. He'd disconnected a length of rubber tubing from his distillation apparatus and seen it go up in immediate, vigorous flames. "This stuff makes t-butyllithium look like dishwater" is the statement I remember from that evening. You can buy the pure stuff from Alfa, if you're inclined to run a head-to-head comparison. Do make sure to post the video on YouTube; that's as close as I want to get.</p> </blockquote> <p>And thioacetone is of the second kind, where Derek quotes a 1960s report:</p> <blockquote> <p>Recently we found ourselves with an odour problem beyond our worst expectations. During early experiments, a stopper jumped from a bottle of residues, and, although replaced at once, resulted in an immediate complaint of nausea and sickness from colleagues working in a building two hundred yards away. Two of our chemists who had done no more than investigate the cracking of minute amounts of trithioacetone found themselves the object of hostile stares in a restaurant and suffered the humiliation of having a waitress spray the area around them with a deodorant. The odours defied the expected effects of dilution since workers in the laboratory did not find the odours intolerable ... and genuinely denied responsibility since they were working in closed systems. To convince them otherwise, they were dispersed with other observers around the laboratory, at distances up to a quarter of a mile, and one drop of either acetone gem-dithiol or the mother liquors from crude trithioacetone crystallisations were placed on a watch glass in a fume cupboard. The odour was detected downwind in seconds.</p> </blockquote> <p>One item not on his list but on mine is lithium aluminum hydride. Actually, this falls more into the category of "things I will go to great lengths to avoid using, especially on a large scale" because I have used it. The workup is time-consuming and generates hydrogen gas, handling the material in its solid form should only be done in a glovebox, and for some reactions, safer alternatives have been developed over the years.</p> <p>What's the one thing you won't work with?</p>

http://lab.chempedia.com/questions/29/alcohol-benzylation-under-neutral-conditions Rich Apodaca 2009-11-17T18:13:31Z 2010-02-11T01:27:57Z

<p>What's a high-yielding alcohol benzylation procedure that works under neutral conditions?</p>

http://lab.chempedia.com/questions/72/benzoic-acid-solubility-thf Andrew Lang 2009-11-29T22:24:24Z 2010-02-09T12:39:37Z

<p>What is the solubility of benzoic acid in THF?</p>

http://lab.chempedia.com/questions/74/benzoic-acid-solubility-toluene Andrew Lang 2009-11-29T22:26:59Z 2010-02-08T00:27:23Z

<p>What is the solubility of benzoic acid in toluene?</p>

http://lab.chempedia.com/questions/68/benzoic-acid-solubility-ethanol Andrew Lang 2009-11-29T17:51:25Z 2010-02-07T21:47:16Z

<p>What is the solubility of benzoic acid in ethanol?</p>

http://lab.chempedia.com/questions/70/benzoic-acid-solubility-methanol Andrew Lang 2009-11-29T17:54:42Z 2010-02-07T21:47:16Z

<p>What is the solubility of benzoic acid in methanol?</p>

http://lab.chempedia.com/questions/64/benzoic-acid-solubility-benzene Andrew Lang 2009-11-29T16:29:32Z 2010-02-07T20:24:50Z

<p>What is the solubility of benzoic acid in benzene?</p>

http://lab.chempedia.com/questions/66/benzoic-acid-solubility-chloroform Andrew Lang 2009-11-29T16:34:01Z 2010-02-07T20:24:50Z

<p>What is the solubility of benzoic acid in chloroform?</p>

http://lab.chempedia.com/questions/95/gc-ms-lab-for-undergrads Amanda 2010-01-05T19:02:30Z 2010-02-06T23:39:59Z

<p>I am looking for a GC-MS lab that I could use for my Analytical Chemistry class. Any ideas?</p>

http://lab.chempedia.com/questions/25/nmr-shifts-of-common-solvent-impurities Rich Apodaca 2009-11-15T16:03:46Z 2010-01-30T02:50:22Z

<p>At some point I managed to lose my copy of a paper listing 1H and 13C NMR shifts of common solvents. Does anyone have the reference handy?</p>

http://lab.chempedia.com/questions/49/co-solute-effect jean-claude.bradley 2009-11-19T20:05:38Z 2010-01-29T23:24:55Z

<p>Anybody have links to papers covering theory or experiments on the effect of a co-solute on the solubility of a compound?</p>

http://lab.chempedia.com/questions/96/practical-experience-with-hydrogenation Chemjobber 2010-01-07T21:52:32Z 2010-01-08T17:15:48Z

<p>What are key practical tips for doing hydrogenations? What would you tell younger chemists about hydrogenation? Anything from safety to mechanistic insights (such as they are) to practical aspects would be greatly appreciated. </p>

http://lab.chempedia.com/questions/92/solubility-of-sodium-acetate-in-ethanol Chemjobber 2009-12-21T15:16:42Z 2010-01-06T19:24:56Z

<p>What is the solubility of sodium acetate in absolute ethanol at room temperature? Is it low, moderate or high? Where might I find information like this? </p>

http://lab.chempedia.com/questions/20/best-practices-for-solvent-stills Rich Apodaca 2009-11-15T02:23:00Z 2009-12-29T00:24:50Z

<p>Continuously-operated solvent stills have been the cause of many laboratory fires in the last several years. Although alternatives exist, not every lab is willing to upgrade.</p> <p>Does your lab currently use solvent stills? If so, what best practices do you follow when working with them?</p>

http://lab.chempedia.com/questions/37/most-widely-used-but-rarely-cited-papers Rich Apodaca 2009-11-18T15:53:32Z 2009-12-21T16:24:21Z

<p>What are the most widely-used, but rarely cited papers in experimental chemistry? My votes for organic synthesis would be:</p> <ul> <li><a href="http://dx.doi.org/10.1021/jo00408a041" rel="nofollow">Rapid chromatographic technique for preparative separations with moderate resolution</a> - "flash chromatography"</li> <li><a href="http://dx.doi.org/10.1021/jo971176v" rel="nofollow">NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities</a></li> </ul>

http://lab.chempedia.com/questions/24/whats-your-favorite-chemistry-cartoon Rich Apodaca 2009-11-15T15:36:18Z 2009-12-16T20:00:16Z

<p>I like this one from <a href="http://chemstickfig.blogspot.com/2009/10/45-not-future.html" rel="nofollow">Chemical Stick Figures</a>.</p> <p><img src="http://img17.yfrog.com/img17/4785/cartoonak.jpg" alt="alt text" /></p> <p>P.S. Links are fine if the cartoon isn't free to use; no <a href="http://en.wikipedia.org/wiki/Inline%5Flinking" rel="nofollow">hotlinking</a> w/o permission, please.</p>

http://lab.chempedia.com/questions/84/simple-experiments-using-green-chemistry Rich Apodaca 2009-12-02T18:43:22Z 2009-12-16T16:33:46Z

<p>Where can I find some simple experiments that demonstrate green chemistry? I'm looking for experiments that can be used either hands-on with students performing them or as a demonstration for beginning chemistry classes.</p>

http://lab.chempedia.com/questions/56/catalysis-with-silica-gel-for-organic-synthesis Rich Apodaca 2009-11-27T16:18:09Z 2009-12-07T22:02:28Z

<p><a href="http://kilomentor.chemicalblogs.com/55%5Fkilomentor/archive/1085%5Fthe%5Fpossibility%5Fof%5Fusing%5Fsolid%5Falumina%5For%5Fsilica%5Fgel%5Fcatalysis%5Fin%5Fdevelopment%5Fof%5Fan%5Forganic%5Fsynthetic%5Fstep.html" rel="nofollow">This Kilomentor post</a> got me thinking about silica gel as a catalyst for lab-scale synthetic reactions. I've found isolated papers on the subject, such as <a href="http://dx.doi.org/10.1021/jo062670e" rel="nofollow">this one from Rajca</a>.</p> <p>I have two questions:</p> <ul> <li>Have you used silica gel as a catalysts, and if so for which reaction?</li> <li>Where can I find a recent, comprehensive review of the literature on silica gel as a catalyst for lab-scale organic synthesis?</li> </ul> <p>I'm especially interested in something pointing to the solid surface itself, rather than acid catalysis in general, as contributing to the rate acceleration.</p>

http://lab.chempedia.com/questions/77/experimental-technique-video-tutorials Rich Apodaca 2009-11-30T17:47:53Z 2009-12-02T18:18:18Z

<p>Where can I find a good source of free videos demonstrating experimental techniques in chemistry?</p>

http://lab.chempedia.com/questions/62/benzoic-acid-solubility-acetonitrile Andrew Lang 2009-11-28T20:48:08Z 2009-11-28T20:50:38Z

<p>What is the solubility of benzoic acid in acetonitrile?</p>