Author Topic: Short Question Thread 2.0  (Read 5709 times)

ImAMANGUYS

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Re: Short Question Thread 2.0
« Reply #280 on: January 25, 2013, 07:42:55 PM »
Points made.

On the subject of explosions, i may be incorrect Mr. Roid, but i remember reading about pressure buildup inside the round bottom or flask used for amalgamation when the reflux condenser becomes choked up when it cant handle the amount of methanol or solvent being refluxed. In this case, i would be careful. I dont know how much pressure it creates or if its enough to create any sort of explosion but i just thought itd be a relevant point to touch on.

ImA

d1ssonance

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Re: Short Question Thread 2.0
« Reply #281 on: January 25, 2013, 08:31:16 PM »
Points made.

On the subject of explosions, i may be incorrect Mr. Roid, but i remember reading about pressure buildup inside the round bottom or flask used for amalgamation when the reflux condenser becomes choked up when it cant handle the amount of methanol or solvent being refluxed. In this case, i would be careful. I dont know how much pressure it creates or if its enough to create any sort of explosion but i just thought itd be a relevant point to touch on.

ImA

As far as that is concerned, when the condenser is choked it will usually just cause your material to shoot out of it like a geyser.

From what I have read this reaction is different if you are using Methylamine.hcl or nitromethane, the former needs a bit of a kickstart, a bit of heat to get it going, where the latter will react VERY quickly after about 10 minutes, which is why monitoring the addition rate is important.

RoidRage

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Re: Short Question Thread 2.0
« Reply #282 on: January 25, 2013, 08:37:40 PM »
Points made.

On the subject of explosions, i may be incorrect Mr. Roid, but i remember reading about pressure buildup inside the round bottom or flask used for amalgamation when the reflux condenser becomes choked up when it cant handle the amount of methanol or solvent being refluxed. In this case, i would be careful. I dont know how much pressure it creates or if its enough to create any sort of explosion but i just thought itd be a relevant point to touch on.

ImA

That's probably wrong to be honest. I don't think there is much pressure created from condenser choking, since like d1ssonance said, the reaction mixture will ''geyser'' out of the condenser if the reaction runaway  ;).

As for methylamine al/hg reduction needing heat to kick off, it's not true from my personal experiences. The reduction is actually exothermic enough than I had it runaway when I added all the ketone at once (stupid I know) on a 75g batch. Luckily, wet towels were available and the reaction was controlled  ;)

4studiesonly

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Re: Short Question Thread 2.0
« Reply #283 on: January 25, 2013, 10:58:33 PM »
Found this just now and did not really know where to put it, so if it is useful pls put it where it belongs....
Tried a search for both the name "Francis A. Carey" and "mhhe.com" and all that was linked here was a  course in java.

"On-Line Learning Center for "Organic Chemistry"  (Francis A. Carey) is what i found and at a first glance it looks useful for us noobs and probably for others as well as a quick check reference.
Do not miss to click the "useful concepts"  blob down under chapter 24 for more learning.


mhhe.com/physsci/chemistry/carey5e/
« Last Edit: January 25, 2013, 11:00:52 PM by 4studiesonly »
Bis zum bitteren ende

ImAMANGUYS

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Re: Short Question Thread 2.0
« Reply #284 on: January 25, 2013, 11:49:03 PM »

That's probably wrong to be honest. I don't think there is much pressure created from condenser choking, since like d1ssonance said, the reaction mixture will ''geyser'' out of the condenser if the reaction runaway  ;).

As for methylamine al/hg reduction needing heat to kick off, it's not true from my personal experiences. The reduction is actually exothermic enough than I had it runaway when I added all the ketone at once (stupid I know) on a 75g batch. Luckily, wet towels were available and the reaction was controlled  ;)

I stand corrected than. It was here on the vesp that i read that and have only minimal experience. Thanks for the truth.

ImA

d1ssonance

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Re: Short Question Thread 2.0
« Reply #285 on: January 26, 2013, 02:10:28 AM »
Points made.

On the subject of explosions, i may be incorrect Mr. Roid, but i remember reading about pressure buildup inside the round bottom or flask used for amalgamation when the reflux condenser becomes choked up when it cant handle the amount of methanol or solvent being refluxed. In this case, i would be careful. I dont know how much pressure it creates or if its enough to create any sort of explosion but i just thought itd be a relevant point to touch on.

ImA

That's probably wrong to be honest. I don't think there is much pressure created from condenser choking, since like d1ssonance said, the reaction mixture will ''geyser'' out of the condenser if the reaction runaway  ;).

As for methylamine al/hg reduction needing heat to kick off, it's not true from my personal experiences. The reduction is actually exothermic enough than I had it runaway when I added all the ketone at once (stupid I know) on a 75g batch. Luckily, wet towels were available and the reaction was controlled  ;)

Someone I know usually sticks with nitro, and after the addiction has started it usually takes about 10 minutes for the reflux to start. This guy, in the early days got lazy and instead of a drip, turned it into a stream which resulted in an old faithful like occurrence. Cleaning up mercury and metal is no bueno.

ImAMANGUYS

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Re: Short Question Thread 2.0
« Reply #286 on: January 26, 2013, 02:44:59 AM »
Someone I know usually sticks with nitro, and after the addiction has started it usually takes about 10 minutes for the reflux to start. This guy, in the early days got lazy and instead of a drip, turned it into a stream which resulted in an old faithful like occurrence. Cleaning up mercury and metal is no bueno.

"Addiction" huh? Freud got your tongue :P

4studiesonly

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Re: Short Question Thread 2.0
« Reply #287 on: February 06, 2013, 01:53:15 PM »
I want a source of info on solubility(and other characteristics), not polar or non-polar. But to what extent different compounds are soluble in different types of solvents expressed in mg/ml at a specified temp.
Is there such a source?

As now i check the compound on wiki where i hit the nr(link) to pubchem but i am not satisfied, it is often not specified to anything more then solubility in the usual saltform(sometimes not even that) and/or the solubility in freebase-form(and again, sometimes not) and sometimes the info is dubious(or i do not understand something underlying fundamental).

If i take an example(not interested specifically), magnesium stearate:
Wiki says melting point is 88.5C.
Pubchem says melting point is 88.5C and 132C tech.grade.
Sigma-Aldrich says melting point is 200C tech.grade on their msds.

I guess the merck index is the answer but i have never seen nor owned a copy so...
I found the the merck index online link on wiki but it lookes like shit and makes me want to hurt.... anything.
I guess merck is what i look for but there should be other open and free databases that have the same info?.
« Last Edit: February 06, 2013, 02:54:07 PM by 4studiesonly »
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Gypsy

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Re: Short Question Thread 2.0
« Reply #288 on: February 06, 2013, 02:33:07 PM »
Good day all, quick question: has anyone else noticed a possible beneficial influence of sunlight on Al/Hg reductions on nitropropenes, specifically substituted? Ive found its turned near failures to complete successes.

Whale

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Re: Short Question Thread 2.0
« Reply #289 on: February 06, 2013, 03:37:13 PM »
Maybe some more heat? What do you mean near failures

Gypsy

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Re: Short Question Thread 2.0
« Reply #290 on: February 07, 2013, 02:39:39 PM »
Heat is most certainly not the issue here. The addition of everything is all hot, just below the  BP of methanol. 9 out of 10 times this works like a charm.
The reaction in question started as it should, gained velocity and then just slowed down . No to little evolution of gas.  Temperature dropping sharply. More than adequate stirring throughout. An extra addition of hot methanolic hgcl2 made little difference. So the drum (its semi-transparent ptfe) was put out in the late afternoon sun. Within 30 minutes things were proceeding as though they had never stopped. Didnt bother the yeild any either.

pbinteger

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Re: Short Question Thread 2.0
« Reply #291 on: February 07, 2013, 11:55:47 PM »
Hey Everyone,

Are there any bad things that could happen if one were to use Ethyl Acetate in place of  (C2H5)2O for doing acid / base extractions?

RoidRage

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Re: Short Question Thread 2.0
« Reply #292 on: February 08, 2013, 01:13:27 AM »
Hey Everyone,

Are there any bad things that could happen if one were to use Ethyl Acetate in place of  (C2H5)2O for doing acid / base extractions?

Definitly not optimal. Ethyl acetate is fairly polar, so it's soluble in water a bit + non-optimal to dissolve freebase amines (probably won't really solubilise them either). Why not use toluene, xylenes or dichloromethane?
« Last Edit: February 08, 2013, 11:25:39 PM by RoidRage »

Happyman

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Re: Short Question Thread 2.0
« Reply #293 on: February 08, 2013, 05:16:54 PM »
Hi, does anyone have a write up for a Strecker Degredation of alanine to acetaldehyde, preferably with an easy to get oxidation agent like bleach. I've ran the rxn about a dozen different times and just can't get a distilate. Vinegar was used as a a catalytic amount of acetic acid to prevent polymerization.

P.S. Last time I ran it with Ca(OCl)2 I got a run away which produced acetyl chloride. That should be interesting to someone.

fishinabottle

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Re: Short Question Thread 2.0
« Reply #294 on: February 08, 2013, 07:53:29 PM »
Heat is most certainly not the issue here. The addition of everything is all hot, just below the  BP of methanol. 9 out of 10 times this works like a charm.
The reaction in question started as it should, gained velocity and then just slowed down . No to little evolution of gas.  Temperature dropping sharply. More than adequate stirring throughout. An extra addition of hot methanolic hgcl2 made little difference. So the drum (its semi-transparent ptfe) was put out in the late afternoon sun. Within 30 minutes things were proceeding as though they had never stopped. Didnt bother the yeild any either.
I suppose there was no more stirring when the drum was moved outside?

/ORG

pbinteger

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Re: Short Question Thread 2.0
« Reply #295 on: February 08, 2013, 09:32:58 PM »
Quote
Definitly not optimal. Ethyl acetate is fairly polar, so it's soluble in water a bit + non-optimal to dissolve freebase amines. Why not use toluene, xylenes or dichloromethane?

Diethyl Ether doesn't form emulsions when washing with Na cation h2o and also has a nice low boiling point for easy evaporation -- also I have a huge bottle of ACS Ethyl Acetate lying around. (I like to use things that I have on hand rather than order more)

Also a taaaad scared of making Ether...

_Pbint_

Balkan Bonehead

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Re: Short Question Thread 2.0
« Reply #296 on: February 08, 2013, 11:22:43 PM »
Hi, does anyone have a write up for a Strecker Degredation of alanine to acetaldehyde, preferably with an easy to get oxidation agent like bleach. I've ran the rxn about a dozen different times and just can't get a distilate. Vinegar was used as a a catalytic amount of acetic acid to prevent polymerization.

P.S. Last time I ran it with Ca(OCl)2 I got a run away which produced acetyl chloride. That should be interesting to someone.


Lol, you're not going to get acetyl chloride from alanine and bleach.

RoidRage

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Re: Short Question Thread 2.0
« Reply #297 on: February 08, 2013, 11:35:15 PM »
Quote
Definitly not optimal. Ethyl acetate is fairly polar, so it's soluble in water a bit + non-optimal to dissolve freebase amines. Why not use toluene, xylenes or dichloromethane?

Diethyl Ether doesn't form emulsions when washing with Na cation h2o and also has a nice low boiling point for easy evaporation -- also I have a huge bottle of ACS Ethyl Acetate lying around. (I like to use things that I have on hand rather than order more)

Also a taaaad scared of making Ether...

_Pbint_

I agree than DCM is a bitch with emulsions most of the time. What about xylenes/toluene then? It's fairly high boiling but not too bad to remove using a rotovap/vacuum distillation.

Electro´S

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Re: Short Question Thread 2.0
« Reply #298 on: February 09, 2013, 01:09:17 AM »
What is the problem with Hexane? I don´t read people extracting with hexane and it works perfectly, while is warm emulsions are broken in seconds.

Electro´S

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Re: Short Question Thread 2.0
« Reply #299 on: February 09, 2013, 01:14:39 AM »
Can any one help me about the exact ratio DMSO-Benzyl Alcohol oxidation to the aldehyde.
In rhodium papers with air flow in the reactions DMSO is 7eq and catalyzed with HBr DMSO is 14eq around.
Can any one says me the theorycal rate?