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Author: Subject: The short questions thread (2)
smuv
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[*] posted on 18-10-2009 at 12:28


DJF90: phenylmagnesium bromide might work well in this case; however the mechanism probably would be a little different than you proposed. The first eq of phenylmagnesium bromide would open the epoxide to form the corresponding chlorophenylpropanoate, this should immediately cyclicize, displacing chloride, to form 2-(phenylmethyl)-oxirane. This epoxide will react with the second eq of PhMgBr to form 1,3-diphenyl-propan-2-oate.



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DJF90
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[*] posted on 18-10-2009 at 13:10


Yes sorry wasnt thinking straight. I've drawn the mechanism for that reaction (grignard on epichlorohydrin) before as well! Its been a long day. But yea, I suggest that would be the appropriate way to go, so long as PhMgBr isnt a problem.
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[*] posted on 19-10-2009 at 00:47


Quote: Originally posted by sparkgap  
Hmm, I forgot to take into account that alkyl groups activate aromatic rings towards FC alkylation. :( I was hoping 1,3-diphenyl-2-propanol was as easy as epichlorhydrin + benzene, but I guess I'll look for something else.

There are a couple of examples of Friedel-Crafts alkylation of benzene derivatives with epichlorihydrin, however the products are Ar-CH2CH(OH)CH2Cl or bisalkylated products. See: European Journal of Medicinal Chemistry, 43 (2008) 300-308 (on mesitylene); Khimiya Geterotsiklicheskikh Soedinenii (1985) 1319-1321 (bisalkylation of p-xylene). I could find no examples of ArCH2CH(OH)CH2Ar formation, but you could treat the Ar-CH2CH(OH)CH2Cl with NaOH to form the 3-arylpropene oxide and then do another FC alkylation with it.




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sparkgap
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[*] posted on 19-10-2009 at 06:29


Thanks to Nicodem, smuv, and DJF90. :)

@Nicodem:

"There are a couple of examples of Friedel-Crafts alkylation of benzene derivatives with epichlorihydrin, however the products are Ar-CH2CH(OH)CH2Cl or bisalkylated products."

- As you said, the fact that it stops at the halohydrin isn't too much trouble. :) I'll check those refs now... hopefully an excess of benzene should minimize the polyalkylation products in my case.

@smuv and DJF:

I already thought of that idea, but was asking about FC because I was trying to avoid Schlenk-ware use (long story). :) But I'll fall back on that if FC doesn't pan out.

sparky (~_~)




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DJF90
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[*] posted on 19-10-2009 at 11:14


You shouldnt need schlenk-ware, just normal ground joint glassware. Make the grignard and react it with the epichlorohydrin - the order of addition shouldnt matter - you should get the product regardless of whether you add the epichlorohydrin to the grignard or vice versa.
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[*] posted on 21-10-2009 at 08:40


How much lithium is in cr2032 battery or any of the cr batteries?
This can be calculated and if someone could find the mg of lithium per mAh it would be greatly appreciated:)
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[*] posted on 21-10-2009 at 09:01


Quote: Originally posted by Neo-6  
How much lithium is in cr2032 battery or any of the cr batteries?
This can be calculated and if someone could find the mg of lithium per mAh it would be greatly appreciated:)


These pieces of information are easily available from common references:

  • Electrons per mole (1 Faraday (not a farad))
  • Atomic weight of Li
  • Number of electrons lost when Li is oxidized
  • Coulombs per Faraday
  • 1 A = 1 Coulomb /sec
  • mA in 1 A
  • seconds in 1 hour

The rest is arithmetic and/or algebra

:D
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[*] posted on 21-10-2009 at 20:57


is this correct?

cr3032 has 500mAh = 0,5Ah
0,5Ah * (60min*60sek) = 1800 coulombs
1800 / 96500 = 0,018653 moles
witch is in lithiums case ~ 130mg
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Picric-A
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[*] posted on 22-10-2009 at 10:45
NaHSO4 substituting KHSO4


Can sodium bisulpate replace potassium bisulphate in dehydration reactions, specifically glycerol--> acrolein.
thanks,
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[*] posted on 22-10-2009 at 11:30


Quote: Originally posted by Neo-6  
is this correct?

cr3032 has 500mAh = 0,5Ah
0,5Ah * (60min*60sek) = 1800 coulombs
1800 / 96500 = 0,018653 moles
witch is in lithiums case ~ 130mg


what is "cr3032" ??




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[*] posted on 22-10-2009 at 14:51


Quote: Originally posted by chemrox  

what is "cr3032" ??


An odd case, the newbie knows something a forum regular does not:
http://www.google.com/#q=cr2032


[Edited on 10-22-2009 by 12AX7]




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watson.fawkes
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[*] posted on 22-10-2009 at 14:56


Quote: Originally posted by chemrox  
what is "cr3032" ??
It's the designation of a flat coin cell.
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[*] posted on 27-10-2009 at 10:21


Does anyone know if phosphorus pentoxide attacks glass t temepratures of 250C? I am planning to make a small amount (10mL) of the chemical, by heating P4O10 with NaCl, where POCl3 will be formed at 250C (Gmelin).

I know polyphosphoric acids will attack it, but does P4O10 (with ofcourse traces of polyphosphoris acids present , because the oxide is so incredibly hygroscopic.


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[*] posted on 27-10-2009 at 13:24


According to Perry's Chemical Engineers' Handbook (see References section under Chemical Engineering books for links to access the 7th and 8th editions), chapter 23, glass is slowly attacked by H3PO4, at a concentration of about 35%, from about 300ºF (149ºC) upwards; and attacked more rapidly by concentrations greater than about 35% at about 400ºF (204ºC). I presume that laboratory borosilicate glass, which is somewhat alkaline, is meant; ordinary soda bottle glass would be even more rapidly attacked.
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[*] posted on 27-10-2009 at 23:55


Oh yes, I expect the P4O10 to react with the alkaline glass to form pyrophosphates of sodium. The orthosilicate in the glass easily can give off an oxygen which is taken up by P4O10. Four of such oxygens then can lead to formation of P2O7(4-) ions.

The reaction will not be so fast that your glass is eaten away in a single run, but it will become opaque. You could try the synth and keep that etched piece of glassware for other such etching reactions (reactions involving fluoride or hydrazine-based reactions at elevated temperatures).




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[*] posted on 28-10-2009 at 01:26


In that case I will use cheap glassware. Maybe even a test tube, wich is bent, just like in the synthesis of phosphorus. I think that if I heat slowly, most POCl3 will condense in the other side of the test tube. This is because POCl3 boils quite high, and even if you heat one part of a DURAn test tube very strongly, the other part remains cool. But heating should be slow, so the vapour cannot greatly heat that side of the test tube.
Now i really need some glasswool, to close the test tube. Because i think POCl3 will just chlorinate the OH-groups on cotton wool.
Should be good to preapre about 10mL in a few runs, I hope, wich is enough for my experiments.
Whemn I try, i will post the results.
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[*] posted on 29-10-2009 at 01:57
Hydroflouric acid


A safety inspector that was looking over my lab told me that hydroflouric acid was a watched chemical, but he couldn't say why... thought it was some sort of explosive.

Anybody know what that was about? I'm not in the 'cooking' scene, but I've read parts of the Rhodium archive ... there's a lot of interesting chemistry there ... but never come across requirements for large amounts of HF.
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[*] posted on 29-10-2009 at 07:28


Quote: Originally posted by Paddywhacker  
A safety inspector that was looking over my lab told me that hydroflouric acid was a watched chemical, but he couldn't say why... thought it was some sort of explosive.

Anybody know what that was about? I'm not in the 'cooking' scene, but I've read parts of the Rhodium archive ... there's a lot of interesting chemistry there ... but never come across requirements for large amounts of HF.

Because it is used in the synthesis of nerve agents like sarin. Here sodium fluoride and potassium fluoride, are also watched, although small quantities (less than 250g) is no problem.
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[*] posted on 29-10-2009 at 08:27
Soxhlet Extractor


Thimbles are expencive for Soxhlet extractors.
Will they still work if you bung up the hole with cotton wool instead of a thimble?
I am extracting amygdalin from peach kernels btw :)
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Sedit
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[*] posted on 29-10-2009 at 12:15


I have a couple related questions that should not be to hard.


Question one what temperature does an Ethyl alcohol flame burn at

Question two: How would I beef up the energy and temperature of something like an alcohol lamp. I have considered using a mix of Nitromethane/MeOH like that used in RC cars but better judgement says not to. Any suggestions on a fuel source other then denatured alcohol which is only getting a steady reading with my Pyrometer of 900 degrees F which seems quite low to me(its a bit chilly outside as well though).





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Picric-A
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[*] posted on 29-10-2009 at 14:01


hmm maybe adding ~3% conc (~50%) H2O2 to dry meths?
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Sedit
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[*] posted on 29-10-2009 at 14:13


35% H2O2 is all I have and I don't know if it would be enough to balance the lose of heat associated with the H2O being present in the mixture. Im still thinking about the Nitromethane more now and just diluting it a bit more from the 30% solution down to about 5-10% and seeing how that compairs.

I still have yet to locate the temperature at which EtOH burns and all I keep getting in web searchs is how well alcoholic peoples fat burns in spontaneous human combustion:mad:. God I swear the internet has gone down hill in the last 8 years.





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[*] posted on 29-10-2009 at 15:40


The answer is to use a larger flame or stop using alcohol and graduate to a bunsen or meker burner. A flame temperature is limited by the enthalpy of combustion, gas volume produced, how well it is being mixed with oxygen, and flame size (limits heat transfer to the surrounding air).



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Sedit
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[*] posted on 29-10-2009 at 16:28


Its not really a factor of needing to graduate or anything of that nature its just that I used something simular as This to melt lead a few days ago for the reduction of Pottasium nitrate and it got me to thinking of the range of temperatures that could be achived using different fuels in a simular device. It worked very well and burned for 45 minutes or so on a single charge which kind of impressed me to say the least.

I was under the impression that there is an upper limit to the temperature at which a specific fuel can burn at assuming complete combustion and is independent of flame size.





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[*] posted on 29-10-2009 at 16:51


Quote: Originally posted by Sedit  

I was under the impression that there is an upper limit to the temperature at which a specific fuel can burn at assuming complete combustion and is independent of flame size.


That is correct. It is called as "Adiabatic Flame Temperature".
For a flame (produced by any fuel) that temperature will be way above 900 F or even 900 C.

It seems your problem is not the temperature of the flame but concentrating the flame on to your target.

Remember radiation losses are to the 4th power of absolute temperature of the flame. So if you have a tall and slender flame or multiple small flames then only a vary small portion of the heat will be delivered to your area of application.

gsd
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