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Author: Subject: The short questions thread (3)
Formatik
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[*] posted on 13-10-2011 at 12:44


Quote: Originally posted by hkparker  
I"ve thought about doing it and capturing the gas(ses) for observation, however now that I am away from my lab that is not an option. I would be very interested to see the results however.


I wouldn't try this out. Shrapnel pictures due to the reaction of ethanol vapor with TCCA (acetaldehyde formation attempt) are seen on page 2 of this thread: http://www.versuchschemie.de/hartmut.php?t=12979 The blast seen there was due to ethyl hypochlorite which accumulated and exploded.

A mixture of 30 to 35% pure calcium hypochlorite and absolute alcohol is reported to warm up on its own. Sandmeyer has distilled ethanol with calcium hypochlorite and obtained chloroform-containing ethyl hypochlorite. Sandmeyer characterized ethyl and methyl hypochlorite in the literature. The organic hypochlorites thread has more info: http://www.sciencemadness.org/talk/viewthread.php?tid=1896

The 'chlorine bomb' is due to virgorous exothermic oxidation of the alcohol releasing gases, of which organic hypochlorites might contribute to the explosion.
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[*] posted on 14-10-2011 at 13:50


What is the difference between xylitol and arabitol? Why are they different isomers? Should they both not be able to interconvert with eachother since there are no unsaturated bonds?

[Edited on 14-10-2011 by AndersHoveland]




I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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[*] posted on 15-10-2011 at 06:29


Quote: Originally posted by AndersHoveland  
What is the difference between xylitol and arabitol? Why are they different isomers? Should they both not be able to interconvert with eachother since there are no unsaturated bonds?

[Edited on 14-10-2011 by AndersHoveland]


No, these are chiral compounds. If you make models of the two, you will find that there is no way to overlap them atom by atom, regardless of how many bonds you rotate. The only way to interconvert them is by breaking and making bonds.

Chiral alcohols similar to xylitol and arabitol can be interconverted by oxidizing them to the ketone, then reducing them back to the alcohol. If this is done under achiral conditions, you will obtain a mixture of the R and S isomer, but this is such a useful interconversion that there are a wide variety of reaction conditions available to let you choose which isomer your reaction produces. I don't know whether this interconversion has been published for this particular substrate.
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[*] posted on 18-10-2011 at 20:45


Will Tetrahydrafuran react with pure copper in anyway?
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[*] posted on 19-10-2011 at 00:02


Quote: Originally posted by Pope  
Will Tetrahydrafuran react with pure copper in anyway?


I am fairly certain there would not be any reaction.
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[*] posted on 19-10-2011 at 04:15
Calcium Nitrate with out Nitric Acid


What is the best way to synthesize Calcium Nitrate with out using nitric acid...

NaNO<sub>3</sub> + CaCO<sub>3</sub> = Na<sub>2</sub>CO<sub>3</sub> + Ca(NO<sub>3</sub>;)<sub>2</sub>
Extract by the solublility but still bad contamination

NH<sub>4</sub>NO<sub>3</sub> + Ca(OH)<sub>2</sub> = NH<sub>4</sub>OH + Ca(NO<sub>3</sub>;)<sub>2</sub>
Extract by Decomposing the Ammonium Hydroxide and leave Calcium Nitrate

NH<sub>4</sub>NO<sub>3</sub> + CaCO<sub>3</sub> = (NH<sub>4</sub>;)<sub>2</sub>CO<sub>3</sub> + Ca(NO<sub>3</sub>;)<sub>2</sub>
Extract by decomposing Ammonium Carbonate and leaving Calcium Nitrate

Are there any possible routes other then i said up the top?




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[*] posted on 19-10-2011 at 11:19


Perhaps refluxing calcium carbonate, ammonia, and hydrogen peroxide together.

Quote: Originally posted by Formatik  
conditions can ammonia be oxidized to NH4NO2, the Ber. ref. from Hoppe-Seyler describes it... strong solutions of H2O2 with a few drops of NH4OH or solutions of ammonium carbonate (with or without NaOH or Na2CO3) can be let to stand 24 hours without any nitrite formation occurring. But upon longer standing, even with a small amount of hydroxide then nitrite forms. H2O2 forms (even in very dilute solutions) nitrite very rapidly, if the H2O2 solution is mixed with a few drops of NH4OH and a little NaOH or Na2CO3, and this then boiled in a retort to a very small volume. They suggest this nitrite formation as a demonstration experiment because it is very quick to do, and then after acidification of the colorless liquid with H2SO4, the HNO2 can be nicely be proven to be present. Excess H2O2 would oxidize the NH4NO2 to NH4NO3.




I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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[*] posted on 20-10-2011 at 04:36


So in other words, Calcium Carbonate and Ammonium Nitrate would work? just heap both up untill Calcium nitrate forms, and then boil off the Ammonia?



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[*] posted on 28-10-2011 at 22:35


Is there much UV absorption to the silicone rubbers? They share the Si-O linkage with quartz like materrials and if one were to speculate from this the conclusion coud be its unlikely they absorb (the silicone rubbers that is). Does anyone know of additives for the rurbbers that allow they to absorb if in fact they don't. Any links to good sites on this topic woud be appreciated.



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[*] posted on 7-11-2011 at 09:33


It's always cold when you put your hand in a dessicator.
I know why, do you? :P

[Edited on 7-11-2011 by Endimion17]




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[*] posted on 10-11-2011 at 15:46


Quote: Originally posted by Endimion17  
It's always cold when you put your hand in a dessicator.
I know why, do you? :P

[Edited on 7-11-2011 by Endimion17]

No




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[*] posted on 10-11-2011 at 17:53


Because the inside air is very dry. If you stick your hand inside, the equilibrium is greatly shifted towards the evaporation of water from your hand, which requires energy that hand readily provides.
It's the same, whether it's winter or summer. If the desiccant is very strong, like it ought to be, you'll experience a cool sensation.




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[*] posted on 15-11-2011 at 01:17


Quote: Originally posted by Endimion17  
Because the inside air is very dry. If you stick your hand inside, the equilibrium is greatly shifted towards the evaporation of water from your hand, which requires energy that hand readily provides.
It's the same, whether it's winter or summer. If the desiccant is very strong, like it ought to be, you'll experience a cool sensation.


I was only answering your question not asking a further question.

OMG WTF PWNT!,,,,,,m,,,
:D
Am only joking, I thought it would be something obvious, thought about it for a few days.




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[*] posted on 26-11-2011 at 18:14


Does anyone know the resonance frequency of the Benzene ring, IE: What frequency of Electromagnetic radiation would effect it in a similar fashion that Microwaves resonate NH3?


I post a more complex question once I get a responce to this one.





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[*] posted on 27-11-2011 at 13:59


Does anyone know if one could use and over-head stirrer type assembly(greased metal bar) through a rubber septum for an air-tight seal? If not is there any cheap quick DIY fix?



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[*] posted on 29-11-2011 at 10:33


Quote: Originally posted by smaerd  
Does anyone know if one could use and over-head stirrer type assembly(greased metal bar) through a rubber septum for an air-tight seal? If not is there any cheap quick DIY fix?

It would only be air-tight if there is not much pressure difference and if the hole was well cut and tight. If you use a balloon to keep the internal overpressure, then the air-tightness is not much of a problem (if inert atmosphere is all you need, rather than trying to control gas leakage).
A too wide diameter of the shaft might also cause friction related problems. You might just as well use a radial shaft seal of the corresponding size. It would also do a better job in keeping the spinning shaft aligned to prevent rough vibrations.
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[*] posted on 3-12-2011 at 22:31


Quote: Originally posted by smaerd  
Does anyone know if one could use and over-head stirrer type assembly(greased metal bar) through a rubber septum for an air-tight seal? If not is there any cheap quick DIY fix?


Vacuum or over pressure?
For vacuum, a ground glass joint, the minimum size that fits your shaft, once perfectly in place and firmly clamped can be packed out with teflon tape. Basically tie the teflon tape onto the shaft above the joint, turn on the stirrer and with tenion let the tape unwind down the shaft, build up a knob that will creep down into the cavity between the shaft and the joint, applying tighter tenion from time to time pushes the knob down until it has filled the joint.
Take some practice but is quite simple to master. You can then lower the shaft further if wear occurs duing your run. Placement of hose clamp above he knob wll help with creep upwards in case you haven't got the tension right.

Over pressure is trickier.




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[*] posted on 3-12-2011 at 22:33


Quote: Originally posted by Nicodem  
Quote: Originally posted by smaerd  
Does anyone know if one could use and over-head stirrer type assembly(greased metal bar) through a rubber septum for an air-tight seal? If not is there any cheap quick DIY fix?

It would only be air-tight if there is not much pressure difference and if the hole was well cut and tight. If you use a balloon to keep the internal overpressure, then the air-tightness is not much of a problem (if inert atmosphere is all you need, rather than trying to control gas leakage).
A too wide diameter of the shaft might also cause friction related problems. You might just as well use a radial shaft seal of the corresponding size. It would also do a better job in keeping the spinning shaft aligned to prevent rough vibrations.


Is there a reason balloons seem to be used for these pressure situations and not just the regulator from the cylinder directly?




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[*] posted on 4-12-2011 at 05:39


I assume a balloon is used because it can handle overpressures generated within your system (from heat or generated gas). Sometimes reducing the input flow of gas to zero is not enough.

[Edited on 4-12-2011 by bbartlog]
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[*] posted on 4-12-2011 at 08:06


Quote: Originally posted by Panache  


Is there a reason balloons seem to be used for these pressure situations and not just the regulator from the cylinder directly?


Because they are flexible. If the pressure rises in your system, the balloon expands, if the pressure falls the balloon contracts, and if it goes too far in either direction the balloon breaks. You don't put excessive force on any of your expensive glassware.
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[*] posted on 4-12-2011 at 12:12


Can I make soap from of the greasy runoff from a George Foreman grill?




it's all about chemistry.
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[*] posted on 27-12-2011 at 01:27


I was wondering if some one could answer a question on butyl lithium reagents.

Sauron posted a quite controvercial Suzuki based synthesis that required the metalation of a halo indole
with tert butyl lithium so as to make the boronic acid.

I belive this was due to the inability of a grignard to form with the halide rather than working with the
indolic nitrogen.

Is it possible to use other lithium reagents for instance the less reactive and less pyrophoric n butyl lithium
for this kind of reaction.

my personal beliefe would be yes but as of yet I have very little working experiance with lithium compounds
other than methyl lithium.

having read a reasonable chunk of the chemistry of organolithium compounds I found that differnt
butyl isomers make for different sites in the molecule being metalated.

would this also be true when a halogen is the target of metalation ?





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[*] posted on 28-12-2011 at 01:31


Is there any other regent that can substitute for hydrogen iodide HI for selectively reducing ketones?
Something not as harsh as NaBH4, but easier to prepare than AlH3. I read that SH2 is actually a weaker reducing agent than anhydrous HI.

How does PH3 and SiH4 compare?
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[*] posted on 3-1-2012 at 17:17


Hi, can someone please help me write a balanced equation for the reaction of lead(II)acetate with sodium bicarbonate which, yields basic lead carbonate(Pb3(OH)2(CO3)2 .

I am having a hard time balancing this reaction I think the hydroxide part of the carbonate is throwing me off. Some guidance will be greatly appreciated.

[Edited on 4-1-2012 by Squall181]
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[*] posted on 3-1-2012 at 18:20
Lead(II) Acetate + Sodium Bicarbonate


okay I think I finally figured it out: here's what I got

3Pb(CH3OO)2(aq) + 6NaHCO3(s) --> Pb3(CO3)2(OH)2(s) + 6NaCH3OO(aq) + 4CO2(g) + 2H2O(l)

[Edited on 4-1-2012 by Squall181]
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