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Topic: methylamine vs ammonia  (Read 12892 times)

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pixie

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methylamine vs ammonia
« on: October 11, 2005, 12:57:23 PM »
What chemical tests can be used to distinguish between methylamine and ammonia?

Can you please help because both methyl amine and ammonia turn red litmus blue and fom white clouds with HCl!

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Re:methylamine vs ammonia
« Reply #1 on: October 11, 2005, 02:17:50 PM »
HPLC should do it.
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pixie

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Re:methylamine vs ammonia
« Reply #2 on: October 11, 2005, 02:21:25 PM »
Is there no chemical test you can do?

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Re:methylamine vs ammonia
« Reply #3 on: October 11, 2005, 02:34:25 PM »
Two possibilities:

1.  Scrape off some of the residue of the white cloud with HCl (salt) and check it's melting point.  There is about a 100 C difference between the methylamine HCl and ammonium chloride.

2.  If you have a IR gas cell, collect some off gas in a bag and then flush it through the cell and look for the CH stretch.

Garneck

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Re:methylamine vs ammonia
« Reply #4 on: October 11, 2005, 02:44:25 PM »
I think I know.. so you have ammonium chloride, right? Try to look for Nessler's reagent somewhere.. it's some mercury compound, that has a characteristical reaction with NH4+

Edit: Ok, I found it, it's potassium tetraiodomercurate(II)

http://en.wikipedia.org/wiki/Nessler's_solution
« Last Edit: October 11, 2005, 02:46:24 PM by Garneck »

Karakth

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Re:methylamine vs ammonia
« Reply #5 on: October 11, 2005, 03:28:56 PM »
There are two chemical tests, one is the reaction with HNO2 and the other is burning.

Quote
1.  Scrape off some of the residue of the white cloud with HCl (salt) and check it's melting point.  There is about a 100 C difference between the methylamine HCl and ammonium chloride.

2.  If you have a IR gas cell, collect some off gas in a bag and then flush it through the cell and look for the CH stretch.

A little too complicated, and aren't these physical tests?
   
« Last Edit: October 11, 2005, 03:30:54 PM by Karakth »

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Re:methylamine vs ammonia
« Reply #6 on: October 11, 2005, 03:52:31 PM »
Proton NMR would tell you right away.

IR would too.

You should also be able to smell the difference.
« Last Edit: October 11, 2005, 03:53:53 PM by movies »

CLUB387

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Re:methylamine vs ammonia
« Reply #7 on: October 20, 2005, 03:24:23 PM »
I think you would have a heck of a time trying to take a proton of ammonia or methyl amine since they are both gases.  Smelling them is certainly not recommended since ammonia is toxic and methyamine is a lachrymator. I suggest the addition of benzoyl chloride and characterization of the product by 1H-NMR or melting point.

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Re:methylamine vs ammonia
« Reply #8 on: October 20, 2005, 07:21:55 PM »
Both ammonia and methylamine are totally stable as aqueous solutions which you could definitely get an NMR of those solutions.  You can also buy solutions on methyl amine in THF, MeOH, and EtOH and ammonia solutions in MeOH, EtOH, iPrOH, or dioxane, all of which are fine NMR solvents.  Shouldn't be a problem.  The smell thing should be obvious because it's pretty tough to deal with significant amounts of either of these chemicals without smelling them.

It's also possible to do gas phase NMR, incidentally.

The chemical derivitization is definitely a good way as well, it's just less direct and would take more time.
« Last Edit: October 20, 2005, 07:22:29 PM by movies »

Garneck

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Re:methylamine vs ammonia
« Reply #9 on: October 21, 2005, 04:57:31 AM »
Yeah, but you have to have access to a NMR spectrometer..  ::)

besides, in this case it's like driving 10 meters by car rather than walking the same distance..
« Last Edit: October 21, 2005, 04:59:01 AM by Garneck »

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Re:methylamine vs ammonia
« Reply #10 on: October 21, 2005, 12:56:20 PM »
True, but if you have an NMR, then the whole process would take 10 minutes.  If not, it would take a lot longer to do the derivitization and then the MP.

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