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Chromic
(Hive Addict)
12-06-01 01:53
No 244678
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Fully buffered peracetic
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Vibrating Lights has touched on this topic before in <span title="Jump to this post"><a href="../methods/000240562.html#Post240562">Post 240562</a> <i>(Vibrating_Lights: "Fully Buffered Peracetic", Methods Discourse)</i></span>, but I wanted to run it over again. I can't find a ref for a fully buffered peracetic, so here's the question, would this make sense:<br><br>Make peracetic acid:<br>8.7g 35% H2O2 (90mmol)<br>10.0g acetic acid (167mmol)<br>0.19g H2SO4 (2mmol)<br><br>Let stir 16h. Add 1.0g NaOAc to remove H2SO4 (just to be safe).<br><br>Add 14.2g NaHCO3 (169mmol) to 90ml of DCM containing 60mmol alkene (in an ice bath), drip in peracetic.
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Chromic<br>
<i>(<span title="The user's title at the time of posting">Hive Addict</span>)</i><br>
<span title="Posting date">12-06-01 02:47</span><br>
<span title="Link to this post by using the markup [244705]">No 244705</span><br>
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<title>Re: Fully buffered peracetic
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In trying to figure out what could have happened with my reaction, I went back and carefully measured the density of my hydrogen peroxide. The MSDS says it's 35%. However, when I measured its density at 20C, it came back as apx 1.098g/mL. This would seem to indicate that it's ~27%. Should I trust the MSDS or my density measurement (measured out exactly 98ml in a grad cylinder, and took the weight, then did the math)? This certainly is good quality peroxide as it turns my skin white in no time. :)
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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">12-06-01 02:53</span><br>
<span title="Link to this post by using the markup [244710]">No 244710</span><br>
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<b title="The subject of this post">Re: Fully buffered peracetic</b>
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Is the density difference large enough so that the cumulative errors in the volume and weight measurements you performed cannot cause this deviation in concentration?<br><br>If that is the case, then assume it is 27% and do the molar calculations from that. If you use too little peroxide, then you may get lower yields by some alkene not effected by it, but if you use too much, then the lower yields are from overoxidation of the alkene, and it cannot be revovered by collecting the forerun in a fractional vacuum distillation.
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Chromic<br>
<i>(<span title="The user's title at the time of posting">Hive Addict</span>)</i><br>
<span title="Posting date">12-06-01 03:09</span><br>
<span title="Link to this post by using the markup [244717]">No 244717</span><br>
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<b title="The subject of this post">Re: Fully buffered peracetic</b>
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The volume was 98.0 +-1%, the weight was 107.6 +-0.1g, it must have fallen b/w these two ranges:<br><br>99.0ml, 107.5g = 1.086... 24% (min mass / max vol)<br>97.0ml, 107.7g = 1.110... 30% (max mass / min vol)<br><br>This is according to data posted on the density of H2O2 at 18C, these values were measured at 20C. It should have a density of 1.1327<br><br>That is significant is a significant difference, no?<br><br>Ahah, yet another piece of information that doesn't make sense... the MSDS lists the density as 1.10g/mL. So maybe it's right after all? Other sites list it as 1.11g/mL, yet others list other values... now I'm totally confused!<br><br>Can someone give me accurate information on the density of 35% H2O2? I suppose I could check Perry's or the CRC or what not... but if anyone has the data handy, please share!
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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">12-06-01 03:18</span><br>
<span title="Link to this post by using the markup [244720]">No 244720</span><br>
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<b title="The subject of this post">Re: Fully buffered peracetic</b>
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I believe that is significant enough to assume that your H2O2 is not 35%, but rather 27%-ish. I cannot imagine that the H2O2 would expand that much within just 2°C to make such a difference.
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goiterjoe<br>
<i>(<span title="The user's title at the time of posting">Hive Addict</span>)</i><br>
<span title="Posting date">12-07-01 02:02</span><br>
<span title="Link to this post by using the markup [245133]">No 245133</span><br>
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<b title="The subject of this post">Re: Fully buffered peracetic</b>
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Rhodium, I think you meant to say to do the calculations based on it being 35% H2O2. If he considers it to be 27% and it is really 35%, he will be adding excess hydrogen peroxide and that might overreact his product. If, however, he considers it to be 35% and it is really ~27%, then he will use too little hydrogen peroxide and will be able to reclaim the unreacted isosafrole. <br><br>If he's performing the reaction based off of the notes on your page, then he should be fine either way, since I think the reaction calls for an 8x molar excess of peracetic acid anyway, and also for a large excess of acetic acid to hydrogen peroxide.<br><hr>Sed quis custodiet ipsos custodes?
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<font color="#ff0000">Osmium</font><br>
<i>(<span title="The user's title at the time of posting">Stoni's sexual toy</span>)</i><br>
<span title="Posting date">12-07-01 02:56</span><br>
<span title="Link to this post by using the markup [245147]">No 245147</span><br>
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<b title="The subject of this post">Re: Fully buffered peracetic</b>
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> he will use too little hydrogen peroxide and will be able<br>> to reclaim the unreacted isosafrole. <br><br>The isosafrole which didn't react will be largely decomposed in side reactions. <br><br>> I think the reaction calls for an 8x molar excess of<br>> peracetic acid <br><br>No way that much is used.
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Chromic<br>
<i>(<span title="The user's title at the time of posting">Hive Addict</span>)</i><br>
<span title="Posting date">12-07-01 20:31</span><br>
<span title="Link to this post by using the markup [245359]">No 245359</span><br>
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<b title="The subject of this post">Re: Fully buffered peracetic</b>
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The scent of acetic acid remained in the extracted epoxide. I can't stress the importance of NaOH washes, even if it was "buffered". UGH. I'll still run the samples, but I'm not expecting much. I guess it's back to Oxone...
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