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Author: Subject: The short questions thread (2)
sonogashira
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[*] posted on 22-9-2009 at 13:42


Quote: Originally posted by Jor  
Now what i forgot is possible hydrolysis. Is it possible that at those temperatures a lot of my 3-nitrophthalhydrazide hydrolysed?


I would imagine it is more difficult to hydrolyse than a normal amide as the adjacent nitrogen causes more delacalization into amide bond - so I would think it is not a big problem - but that is only a guess.:)

[Edited on 22-9-2009 by sonogashira]
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[*] posted on 23-9-2009 at 18:07


Does styrene react with aqueous HCl to make 1-phenyl,1-chloroethane? Trying to make styrene from styrofoam worked horribly bad, but I think I can perfect it.
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[*] posted on 23-9-2009 at 18:16


Quote: Originally posted by ketel-one  
Does styrene react with aqueous HCl to make 1-phenyl,1-chloroethane? Trying to make styrene from styrofoam worked horribly bad, but I think I can perfect it.


No.

Dry HCl or HBr is usually used in an organic solvent or by passing directly into the compound to be hydrohalogenated, assuming it is a liquid.




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[*] posted on 23-9-2009 at 18:42


Ok, that's logical. No reason HCl would ever want to leave a polar solution.
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[*] posted on 23-9-2009 at 18:52


Perhaps a phase transfer catalyst and hard stirring could work I would think.

To make styrene from styrofoam sounds like a mess due to the huge bulk. I have had fine success on the Pyrolysis of polystyrene forks one time. Its so cheep and easy to get I would never go that way if I really wanted it as it would be much easier to just distill from over the counter products.





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[*] posted on 23-9-2009 at 19:06


Firstly perhaps this thread should be restarted as No.3, its getting somewhat long.

When nichrome wire is used in/as a heating element it is typically coiled in a small diameter coil (~3mm), then this coil is coiled around some ceramic mounting. Is small coiling simply to maximise the length and hence surface area of nichrome over a minimum volume or is it neccessary for some inductive effect and hence critical to the nichrome's resistance and heating ability.
Why is thicker nichrome wire seemingly rarely used?




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not_important
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[*] posted on 23-9-2009 at 21:04


Quote: Originally posted by Panache  
...
Why is thicker nichrome wire seemingly rarely used?


Resistance inversely is proportional to cross-sectional area, and thus to the square of the diameter. Double to the diameter and thus quarter the resistance.

As most heaters run from the mains, a fixed voltage level, cutting the resistance to 1/4 means pulling 4 times as much current, and generating 4 times as much heat per given length of wire. Continue to increase the diameter and you reach a point where the mains can't supply the current, or the heating becomes excessive and the resistance wire fails.

This is made worse because the radiative surface is proportional to the diameter (pi*2r) and so the area able to radiate heat increases linearly with increasing diameter while the heat generated increases as the square of diameter.

You can use four times the length of the twice-as-think wire, and draw the same amount of current and generate the same amount of heat, but now you've used 16 times as much nichrome - 4 times the cross section area x 4 times the length. And the heat generated per unit length decreases to 1/4 that of the thinner wire, giving the opposite problem of above - now the heating element may be too cool.

You could run the wire at 1/2 the voltage, giving 1/2 the current and thus the same amount of power dissipation. But transformers are heavy and expensive, so there is little call for that unless you need a short section of wire running hot.


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[*] posted on 24-9-2009 at 18:52


I have a 1 ohm resistor that's wound open-frame with fairly heavy nichrome, probably around 12 gauge. It's probably good for about 300W, being about 8" long, 3" across, 1" thick (the winding is on a hollow rectangular ceramic form).

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[*] posted on 25-9-2009 at 09:50


Does anyone know of a fairly simple synthesis of diacetyl? (butane-2,3-dione) Vogel's has precisely diddle on the matter and a benzoin condensation is worthless on enolizable substrates.



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[*] posted on 25-9-2009 at 10:35


I think benzyl chloride posted a easy synthesis of diacetyl, from butanone oxime, after nitrosatation of MEK IIRC, or something similar.. It was a text or pdf paper, part of a multistep synthesis..

EDIT: Gotcha:

http://www.sciencemadness.org/talk/viewthread.php?tid=11966#...

Ask benzylchloride1 for details regarding the preparation of diacetyl, looks pretty easy to do.

[Edited on 25-9-2009 by Klute]




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[*] posted on 25-9-2009 at 12:45


Concerning the ariel oxidation of benzaldehyde. If i left a small dish of around 2ml of 'Almond flavouring' (which uses i guess benzaldehyde) out in the open for 12 hour then boiled off the alcohol/water the next morning would i be left with benzoic acid (presuming it contained benzaldehyde) crystals?
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[*] posted on 25-9-2009 at 12:53


Quote: Originally posted by Klute  
I think benzyl chloride posted a easy synthesis of diacetyl, from butanone oxime, after nitrosatation of MEK IIRC, or something similar.. It was a text or pdf paper, part of a multistep synthesis..

EDIT: Gotcha:

http://www.sciencemadness.org/talk/viewthread.php?tid=11966#...

Ask benzylchloride1 for details regarding the preparation of diacetyl, looks pretty easy to do.

[Edited on 25-9-2009 by Klute]


Thanks! I remember that thread, but not well enough to have gone looking for it.

[Edited on 9-25-09 by UnintentionalChaos]




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[*] posted on 26-9-2009 at 00:08


Quote: Originally posted by ketel-one  
Does styrene react with aqueous HCl to make 1-phenyl,1-chloroethane? Trying to make styrene from styrofoam worked horribly bad, but I think I can perfect it.

Yes, you can prepare 1-chloro-1-phenylethane by refluxing styrene with conc. HCl(aq) and then steam distilling. You will need a few milligrams of 2,6-di-t-butyl-4-methylphenol or some other hydrophobic polymerisation inhibitor (hydroquinone might not work well or give only low yields).
See also JOC, 45, 3527-3529 (I think the paper was already posted on this forum so UTFSE).




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[*] posted on 26-9-2009 at 10:28


I have some 3-nitrophthalhydrazid now, and as I have not recieved my sodium dithionite yet, I'm looking for another way to make luminol. I will only use about 20% of my current batch, and reduce the rest with sodium dithionite.

What would be my best bet? I was thinking of Sn/HCl, so add 250mg 3-nitrophthalhydrazid to 1mL conc. HCl, and add 300-400mg of tin. Then reflux (test-tube). The problem is that the starting material is insoluble, and tin is a solid as well.
How long should I reflux it?
Do you think this works, or do you have alternative methods?
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[*] posted on 26-9-2009 at 11:00


Jor, you could probably make enough dithionite for a 250 mg reduction by stirring some NaHSO3 up with Zn dust.

Alternatively I would expect SnCl2 or sodium sulfide to reduce the nitro group.

If you want to use Sn metal, you might check to see if the hydrazide is soluble in AcOH. If so, you could use Sn/AcOH I believe.

Try it on an even smaller scale than 250 mg, if possible.
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[*] posted on 27-9-2009 at 01:04


I have tryed Sn/HCl method- failure.
I also tryed the folowing method taken from ORganic Chemistry by P.J.Durrant. one gram of the solid was dissolved in 10ml of water and 8g of NaOH was dissolved in the water as well. A steady stream of H2S was then bubbled in until the NaOH stopped absorbing the gas then the mix was refluxed for 30 mins. Yield- none. No ppt was formed after addition of GAA.
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[*] posted on 27-9-2009 at 15:03


A (hopefully) easy question: how to destroy nitrate (NO3-) ions in an aqua regia solution after dissolving metals presumed to contain precious ones. The protocol which I have read says to boil the liquid down until it's syrupy, add concentrated HCl, repeat twice more. This seems to me both wasteful and toxic. What I propose to do is to add urea (CO(NH2)2) and heat, assuming that the reaction 6 HNO3 + 5 CO(NH2)2 -> 5 CO2 +8 N2 + 13 H2O is possible. I haven't found anything explicit either way: what I do find is that urea is used to remove excess NO2 from nitric acid solutions.... is the analogy likely? Thanks for any pointers!
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[*] posted on 27-9-2009 at 15:45


The Energetic Materials crowd can offer better advice, but might you not form urea nitrate, which I believe can be explosive under certain cirumstances? Just a thought.
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[*] posted on 27-9-2009 at 16:46
EDA from EDTA


Can anyone offer some suggestions or point me in the right direction on how I would cleave an acetate function from an amine?

My goal is to synthesis Ethylenediamine from Ethylenediamine tetraacetate or NaEDTA respectively. I have found some information on using a dilute (aq)solution of Ammonia but this all takes place at high temperatures and pressures which I would like to avoid if possible. I remember seeing a suggestion in another threed sometime back on how to handle a situation like this but I can not for the life of me seem to find it anymore.

Thanks in advance for anyhelp,
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[*] posted on 27-9-2009 at 16:57


I can obtain some a-Benzoin oxime for a acceptable price. Google doesn't give much useful hits, only that it can be used to detect metals and seperate some metals from eachother.

Are there any interesting complexes wich can be isolated, with this compounds as the ligand, or other interesting uses?
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[*] posted on 30-9-2009 at 14:35
What's good for dissolving HDPE?


I've come up with a list of some compounds based on some listed incompatabilities (just below), but am asking also anyone with experience in dissolving the plastic.

Thionyl chloride, chlorosulfuric acid, aqua regia, nitric acid (95% plus), oleum, H2CrO4/H2SO4, bromine, ethylene chlorohydrin, halogenated hydrocarbons (tetrachloroethylene, perchloroethylene, chlorobenzene, chloroform, dichloromethane, tetrachloromethane, etc.), hydrocarbons and others (cyclohexane, ethylbenzene, kerosene, turpentine, diethyl ether, petroleum ether, and the like).

I remember using Et2O a while back to attack HDPE allowing the plastic to soak for some days, but it didn't do a good job. The same with dichloromethane. Neither dissolved significant amount of the plastic.
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[*] posted on 30-9-2009 at 15:20


HDPE is in effect an alkane, mostly CH2 groups with a small amount of branching giving tertiary hydrogens, and a tiny amount of unsaturation. Anything immiscible with petroleum ether and that doesn't readily chemically attack the same is not going to do much to HDPE.

Solvents based on aromatics and halocarbons are the best bet, and generally need to be hot to boiling. You still don't get a good solution, often a gel is the result. General hydrocarbons, including kerosene, and other compounds that have long carbon chains (biodiesel) will also act as solvents when rather hot.

I believe that ethylene under very high pressure dissolves PE, I remember reading a paper on MW fractionating polyethylene during production by controlling the pressure of the remaining ethylene with higher MW PE dropping out first as the pressure was reduced.

Solvents based on phenols or hydrogen donors such as tetralin and decalin 'dissolve' HDPE by enhancing thermal degradation to random mixtures of mostly linear chain alkanes over a wide range of carbon numbers.





[Edited on 30-9-2009 by not_important]
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[*] posted on 30-9-2009 at 20:51


Phenolic hydroxy groups don't count as alcohols and don't react with HCl to replace the hydroxy with a chlorine, right? Also I don't suppose there's any easy way to turn a phenolic hydroxy group to a phenolic methoxy group, right?
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[*] posted on 30-9-2009 at 20:52


Phenolic hydroxy groups don't count as alcohols and don't react with HCl to replace the hydroxy with a chlorine, right? Also I don't suppose there's any easy way to turn a phenolic hydroxy group to a phenolic methoxy group, right?
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[*] posted on 30-9-2009 at 21:03


Quote: Originally posted by ketel-one  
Phenolic hydroxy groups don't count as alcohols and don't react with HCl to replace the hydroxy with a chlorine, right? Also I don't suppose there's any easy way to turn a phenolic hydroxy group to a phenolic methoxy group, right?


As far as I can tell you can't replace phenolic OH with something else

Making methoxy is easy, there are several threads about methylating agents. Phenolic OH easily turns into a phenolate salt, which can undergo Williamson ether synthesis.
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