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Author: Subject: The Short Questions Thread (4)
PHILOU Zrealone
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[*] posted on 17-2-2017 at 10:18


Quote: Originally posted by fastbre4k  
It is possible to do an Schmidt reaction in Ethylacetate?

What would be the carboxilic acid, keton or aldehyd involved?




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fastbre4k
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[*] posted on 17-2-2017 at 17:22


I would like to know for all three :)
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PHILOU Zrealone
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[*] posted on 17-2-2017 at 18:50


I'm not sure but:
Maybe that the HN3 will attack the acetic moeity of the ethyl acetate...
CH3-CH2-O2C-CH3 + HN3 --?--> CH3-CH2OH + N3-CO-CH3
If this happens, then this would preclude the use or ethyl acetate for all 3 cases.

Maybe that the carbo acid will induce transesterification with the acetate...
R-CO2H + CH3-CH2-O2C-CH3 <====> CH3-CH2-O2C-R + CH3-CO2H
If this happens, then this would preclude the use of an acid with ethyl acetate...but would be no problem for the keton or aldehyd

The related alternative Schmid reaction with N2H4 and carbo-acid would be a no go since acethydrazide (CH3-CO-NH-NH2) would be formed aside with ethanol.
CH3-CO-NH-NH2 + HONO --> CH3-CO-N3 + 2 H2O

[Edited on 18-2-2017 by PHILOU Zrealone]




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[*] posted on 20-2-2017 at 11:02


I have been doing the synthesis of pentanoic acid via the kmno4 oxidation of pentanol, would anyone like a procedure and writeup with pics and if so then where should i post it.



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[*] posted on 20-2-2017 at 11:10


You can post it in Organic Chemistry, and if it is well-written and repeatable, it can stay there. If it has considerable flaws I will move it to Beginnings so that people can give you advice for your future write-ups. Either way, please do post it.



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[*] posted on 20-2-2017 at 12:14


Alright then, over the next week i will repeat the procedure while taking pictures then post



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[*] posted on 21-2-2017 at 06:10


I was cleaning my sintered funnel with a bit of piranha solution. After I thought that the hydrogen peroxide in the solution had decomposed, I rinsed it thoroughly with acetone. Now there is a small amount of white solid at the bottom of the flask that I fear may be acetone peroxide. If it is, what is a safe and proper way to get it out of the flask and dispose of it?
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[*] posted on 22-2-2017 at 08:38


From the sciencemadness wiki:

" Acetone peroxide can be rendered relatively benign by dissolving it in toluene. Even if the solution is saturated, there is almost no risk of detonation. "
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[*] posted on 22-2-2017 at 08:45


What are ground glass reagent bottles good for? They don't seem airtight unless sealed with vacuum grease, and I don't want vacuum grease in my products... can they actually be used for long term storage of reagents?



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[*] posted on 22-2-2017 at 09:22


Quote: Originally posted by TheNerdyFarmer  
I was cleaning my sintered funnel with a bit of piranha solution. After I thought that the hydrogen peroxide in the solution had decomposed, I rinsed it thoroughly with acetone. Now there is a small amount of white solid at the bottom of the flask that I fear may be acetone peroxide. If it is, what is a safe and proper way to get it out of the flask and dispose of it?


Ok thanks i will get on that right away. :D
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PHILOU Zrealone
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[*] posted on 22-2-2017 at 14:32


Quote: Originally posted by TheNerdyFarmer  
I was cleaning my sintered funnel with a bit of piranha solution. After I thought that the hydrogen peroxide in the solution had decomposed, I rinsed it thoroughly with acetone. Now there is a small amount of white solid at the bottom of the flask that I fear may be acetone peroxide. If it is, what is a safe and proper way to get it out of the flask and dispose of it?

Simply add more aceton and it will redissolve then trow into the toilet and flush...
Or simply collect when moist (I think there can't be much more than a few mg) so no risk of injury and put into a some toilet paper then light with a lighter...it will burn without explosion and make a tiny flash.




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[*] posted on 22-2-2017 at 14:46


Quote: Originally posted by JJay  
What are ground glass reagent bottles good for? They don't seem airtight unless sealed with vacuum grease, and I don't want vacuum grease in my products... can they actually be used for long term storage of reagents?

Without grease, parafin oïl, candle wax or silicon oil...it is not 100% airtight and so any volatile, oxygen sensitive compounds are storable only for a limited amount of time (like wiskey carafe --> one year).

If you use the correct grease/viscous paraffin wax...it is unreactive and will remain onto the rough ground glass...then it can store for example concentrated HNO3...then use with care a pipette into the center to take the liquid without touching the sides of the bottle mouth to avoid contamination with the grease...some flasks do have the pipette integrated into the glass roded cap...

If your product is non volatile, non hygroscopic and non sensitive to air (O2, NH3 or CO2, volatile acids)...then it is OK without grease/wax





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[*] posted on 22-2-2017 at 15:33


often the vapours of stored liquids condense into the ground glass joint, sealing it somewhat.

one of my school chemistry memories is how during summer,
bottles of reagents with ground glass joints would 'vent' excess pressure occasionally by pushing up the stopper a little, releasing a puff of vapour.
I would not store ammonia solution, or conc. acids, especially HCl, in this way
as my chem. lab is also my 'workshop' and electronics lab,
and I value my tools and equipment :P




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[*] posted on 28-2-2017 at 16:15


I want to use my oxy acetylene torch but running hydrogen instead of acetylene.
Is this completely unsafe? If anyone has direct experience with trying this what 'observations' would you remark on?




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[*] posted on 28-2-2017 at 18:19


Quote: Originally posted by Panache  
I want to use my oxy acetylene torch but running hydrogen instead of acetylene.
Is this completely unsafe? If anyone has direct experience with trying this what 'observations' would you remark on?


I do not have any direct experience. However from memory the flame velocity of a hydrogen oxygen mixture is higher than oxygen acetylene mixture. That means flash back in a premixed torch is more likely but that can be corrected easily by increasing the gas flow or by using a nozzle with a smaller hole.

For safety you should be operating the torch with flashback arrestors in the gas lines, which may not work correctly for the higher flame velocity of hydrogen.
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[*] posted on 28-2-2017 at 18:30


Quote: Originally posted by wg48  
Quote: Originally posted by Panache  
I want to use my oxy acetylene torch but running hydrogen instead of acetylene.
Is this completely unsafe? If anyone has direct experience with trying this what 'observations' would you remark on?


I do not have any direct experience. However from memory the flame velocity of a hydrogen oxygen mixture is higher than oxygen acetylene mixture. That means flash back in a premixed torch is more likely but that can be corrected easily by increasing the gas flow or by using a nozzle with a smaller hole.

For safety you should be operating the torch with flashback arrestors in the gas lines, which may not work correctly for the higher flame velocity of hydrogen.


Ok great, I have flame arresters directly off the regulators on the bottles but there's about 10metres of hose after that, hydrogen cannot burn with an oxidant so at worst my torch might strike back.
Also I forgot to ask hydrogen oxygen mixtures burn at almost all proportions/ratio's (3-95% from memory) however what about detonation, do hydrogen oxygen mixtures detonate and is there a safe working pressure where the mixture will only burn not detonate. Converse from some people I don t want a detonation.




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[*] posted on 1-3-2017 at 08:08


Quote: Originally posted by Panache  
Quote: Originally posted by wg48  
Quote: Originally posted by Panache  
I want to use my oxy acetylene torch but running hydrogen instead of acetylene.
Is this completely unsafe? If anyone has direct experience with trying this what 'observations' would you remark on?


I do not have any direct experience. However from memory the flame velocity of a hydrogen oxygen mixture is higher than oxygen acetylene mixture. That means flash back in a premixed torch is more likely but that can be corrected easily by increasing the gas flow or by using a nozzle with a smaller hole.

For safety you should be operating the torch with flashback arrestors in the gas lines, which may not work correctly for the higher flame velocity of hydrogen.


Ok great, I have flame arresters directly off the regulators on the bottles but there's about 10metres of hose after that, hydrogen cannot burn with an oxidant so at worst my torch might strike back.
Also I forgot to ask hydrogen oxygen mixtures burn at almost all proportions/ratio's (3-95% from memory) however what about detonation, do hydrogen oxygen mixtures detonate and is there a safe working pressure where the mixture will only burn not detonate. Converse from some people I don t want a detonation.


Yes Hydrogen does not burn with out oxygen. However if for some reason one of the gases flows down the supply pipe of the other gas the flash back arrester will stop the gas flow and or stop a flame. Its particularly need when using an acetylene bottle because the oxygen can be at a much higher pressure than the acetylene.

Detonation: Most if not all fuel oxygen mixtures with the correct stoichiometry can detonate if ignited. Acetylene can even detonate in the absence of oxygen.

Assuming your torch is a regular oxy/acetylene torch it is the flow velocity thru the nozzle that must be higher than the flame velocity to prevent the flame travelling back in to the torch nozzle and possibly detonating in it. But that mixed gas volume in the torch is small and the torch is designed to withstand the occasional blowback . Hydrogen is less powerful than acetylene.

So NO there is not a hydrogen pressure to prevent blowback as it depends on both the hydrogen and oxygen pressure and the nozzle hole size ie flow velocity
i
The normal procedure is to light the torch with only the fuel on. Then adjust oxygen for the required flame. That will be near to stoichiometric and near to the fastest flame velocity. So you use a nozzle with an outlet diameter such that the gas flow is greater than the flame velocity or the flame will blow back into the torch. Too higher velocity and the flame will blow out.
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[*] posted on 3-3-2017 at 08:36
Confused about distillation


I'm adapting a synth of ethyl acetoacetate from here. In the workup I am very confused about the distillations.

Quote:

The liquid divides into two layers the upper one, consisting of acetoacetic ester and unchanged ethyl acetate, is carefully separated and distilled collecting fraction passing at 100° C. The distillate is redistilled and collected in fractions, that distilling at 175-185° C is nearly pure acetoacetic ester.


The boiling point of ethyl acetoacetate is more than 100 degrees higher than ethyl acetate, so I wouldn't think very much would come over at 100 C. Am I missing something? Why would most of the product come over at 100 C in the first distillation, but then in the second one come over between 175 and 185 C?

Any answer is appreciated.

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[*] posted on 3-3-2017 at 09:22


Quote: Originally posted by Geocachmaster  


The boiling point of ethyl acetoacetate is more than 100 degrees higher than ethyl acetate, so I wouldn't think very much would come over at 100 C. Am I missing something? Why would most of the product come over at 100 C in the first distillation, but then in the second one come over between 175 and 185 C?

Any answer is appreciated.



Maybe the ethyl acetoacetate is being co-distilled with the ethyl acetate at the lower temperature and then fractionally distilled further from the resulting distillate? If there's a lot of unreacted ethyl acetate then that would explain why they're expecting a lot to come over at 100 C
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[*] posted on 5-3-2017 at 07:28


I want to remove a large amount of water from a solution, using calcium chloride, however I dont know what hydratate will form.
If I cool the solution to below 30C, hexahydratate should form? (Hexahydratate decomposes at 30C)
How long will it take? Is it something fast or slow?
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[*] posted on 5-3-2017 at 08:27


If you have a large amount of water, you'll form saturated calcium chloride solution. It forms quickly, and you should be able to decant the organic layer. Sodium sulphate and other ionic drying agents will act similarly.



Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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[*] posted on 5-3-2017 at 10:01


Thanks, it doesnt work for what I wanted it for, but I learned something :D

I wanted to concentrate H2O2, and I saw somewhere that you could do it with drying agents like CaCl2, however if it separates completelly, I dont want it as I stay away from explosives, and if it doesnt separate at all, it doesnt work either.
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[*] posted on 7-3-2017 at 04:46
KMnO4 solubility


Why is there no solubility for KMnO4 in water after 60 C ?



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[*] posted on 7-3-2017 at 05:09


25 g/100ml at 65°C, 32 g/100 ml at 75°C. That's pretty much highest temperatures which allow more or less accurate measurement of KMnO4 solubility, at higher temperatures it quickly decomposes, thus leading to huge errors in measurement.
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[*] posted on 7-3-2017 at 05:47


Quote: Originally posted by TheMrbunGee  
Why is there no solubility for KMnO4 in water after 60 C ?


google gave me this;

4 KMnO4 + 2 H2O = 4 KOH + 4 MnO2 + 3 O2




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