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Author: Subject: The short questions thread (3)
Nicodem
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[*] posted on 29-7-2010 at 23:49
The short questions thread (3)


The old thread has become too long so please continue here. Those who never received a proper reply in the old thread, please feel free to repost the question.

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This is a thread where you can post all those short questions you always wanted to ask but did not consider them worthy of a new thread. You can ask amateur science related questions of all kind as long as you think they are simple enough to be answered by other forum members in a preferably single post.
Consequently, self discipline in avoiding off topic replies is expected.




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Nicodem
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29-7-2010 at 23:49
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[*] posted on 30-7-2010 at 01:08


Quote: Originally posted by mewrox99  
Anyone know what the PiHKAL cover is meant to be? Is it like a mountain or something

I guess this was one of the last unanswered questions in the last short questions thread. Having some experience with how cover designers think and work, I would guess that being more or less clueless on the specific content of the book, he/she resorted to use stereotypes and therefore used a stylised picture of Mount Sinai as a symbolism for spiritual revelation or cognitive illumination that the pop culture associates with the use of psychedelics. It is just a guess, but when it comes to book covers you can be pretty sure they try to use stereotypes to have a major impact on the potential book buyer.


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psychokinetic
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[*] posted on 30-7-2010 at 02:12


I was thinking similarly

Could also be a 'peak', as in 'peaking' and the obvious mountain 'peak'. (Along with a potential pronunciation of the book, 'peak-al').




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Picric-A
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[*] posted on 1-8-2010 at 10:55


Does anybody know the best solvent for 4-Aminobenzoic acid?

I am looking to purify a load of PABA to get rid of the starch impurity so i want to dissolve as much 4-Aminobenzoic acid in as little solvent as possible.

Thanks
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JohnWW
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[*] posted on 1-8-2010 at 13:30


It should be soluble in water, and in polar organic solvents such as acetone, diethyl ether, ethanol, isopropanol, tetrahydrofuran, dioxane, pyran, etc.
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DJF90
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[*] posted on 1-8-2010 at 13:31


Where the hell did the starch come from?! Purification of Laboratory Chemicals says:

Quote:

p-Aminobenzoic acid [150-13-01] M 137.1, m.p. 187-188*C, pK1 2.45, pK2 4.85.
Purified by dissolving in 4-5% aqueous HCl at 50-60°C, decolorising with charcoal and carefully precipitating with 30% Na2CO3 to pH 3.5-4 in the presence of ascorbic acid. It can be crystd from water, EtOH or EtOH/water
mixtures.
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Picric-A
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[*] posted on 2-8-2010 at 00:13


Quote: Originally posted by DJF90  
Where the hell did the starch come from?! Purification of Laboratory Chemicals says:

Quote:

p-Aminobenzoic acid [150-13-01] M 137.1, m.p. 187-188*C, pK1 2.45, pK2 4.85.
Purified by dissolving in 4-5% aqueous HCl at 50-60°C, decolorising with charcoal and carefully precipitating with 30% Na2CO3 to pH 3.5-4 in the presence of ascorbic acid. It can be crystd from water, EtOH or EtOH/water
mixtures.


As i said in my post.... i am purifying the 4-aminobenzoic acid from PABA vitamin supplements and so the starch is present as the filler i am guessing. They were in caps so i meerly pulled the cap open and poured out the powder.

It is only very slightly soluble in water, 4.9g/kg so this is out. I think i will try EtOH or MeOH.
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[*] posted on 2-8-2010 at 09:17


Will the amine from alpha -trans-methylcinnamaldehyde produce stereoisomers of the l enantiomer or the d, or a recimic product of l-(+/-) , or d-(+/-)....i"ve read from the links below , but still not clear to me......solo

http://en.wikipedia.org/wiki/Diastereomer

http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/ster...




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[*] posted on 2-8-2010 at 13:43
Red/Yellow benzaldehyde?


Someone who is me tried to make 3,4,5-trimethoxybenzaldehyde from 5-bromo-vanillin. After Ullmann and methylation an oil was obtained which distilled in a narrow range of 102-104°C - so far so good. But what was really strange: in the beginning of the distillation the distillate was a pale yellow oil which then crystallized to a distinctly red solid. An absolutely weird sight, more so considering that usually it's the other way round: slightly coloured oil giving colourless crystalls. Question: how comes?

My only explanation, although not very convincing, is that in the beginning of the distillation there was a small amount of polymeric stuff bumping into the receiver. When crystallizing, the red impurity was concentrated on the outside of the crystals, making it much more visible than when mixed with the liquid distillate.

IMG_2669.JPG - 106kB
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[*] posted on 3-8-2010 at 00:50
NH4NO3 Odour?


Today was the first time using some AN I bought a month or so ago.

It claims to be Lab grade prills.

For some reason it seems to have a very slight unusual odor that one my friends was also able to notice.

Anyone have any clues what it could be (my guess is small amounts of NH3 or N2O)
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[*] posted on 3-8-2010 at 22:06


NH3 makes sense, mewrox99.



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Nicodem
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[*] posted on 4-8-2010 at 14:07


Quote: Originally posted by solo  
Will the amine from alpha -trans-methylcinnamaldehyde produce stereoisomers of the l enantiomer or the d, or a recimic product of l-(+/-) , or d-(+/-)....i"ve read from the links below , but still not clear to me......solo

http://en.wikipedia.org/wiki/Diastereomer

http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/ster...

You mean the product of reductive amination? The transformation of CHO into CH2NH2? That would give beta-methyl-cinnamylamine. This compound has no chirality so it has no enantiomers (the -CHO is not a prochiral). It can have two diasteromers though, the E and Z isomers. However, which of the isomers would be the main or sole product depends on the reaction conditions and the configuration of the starting compound. If the conditions are not such as to cause E/Z-isomerization then the product will retain the same configuration around the C=C double bond. For example if you start with the E diastereoisomer you end up with the E diastereoisomer of the product. But only if the reaction conditions are not such as to cause E/Z-isomerization, either in the starting or ending compound.

Also, mind that some methods of reductive amination would also cause the reduction of the double bond. That double bond is also quite electrophilic so it can also alkylate amines via the Michael reaction. In short, the reductive amination of that aldehyde is not trivial and only few methods apply.




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[*] posted on 5-8-2010 at 01:43


Quote: Originally posted by Nicodem  
Also, mind that some methods of reductive amination would also cause the reduction of the double bond.

I guess that's the product solo is talking about? Evidently you would get the racemate, as it is not a diastereomer. The result would be the same for the cis- and trans-isomers of the reactant.
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[*] posted on 5-8-2010 at 12:31


This is probably a very trivial question but here we go;

How does one form formate (methanoate) esters?

I know conc H2SO4 reacts with conc formic acid producing carbon monoxides so i guess if one were to try make the ester the usual way (acid + alcohol + conc H2SO4) you would just be left with a bunch of alcohol and CO. So how does one actually go about it? I would specifically like to make ethyl formate (from conc formic acid and methylated spirit)
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[*] posted on 5-8-2010 at 12:36


Any strong acid will catalyze the Fischer esterification reaction. You can use hydrochloric acid instead of sulfuric acid. Using a Dean-Stark trap or a similar device will improve the yield.
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[*] posted on 5-8-2010 at 12:46


Formic acid is strong enough to catalyse its own esterification; no added catalyst is necessary.
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[*] posted on 5-8-2010 at 13:04


Quote: Originally posted by Picric-A  
I would specifically like to make ethyl formate (from conc formic acid and methylated spirit)

Why don't you use Google before asking, lazy bastard.

http://pubs.acs.org/doi/abs/10.1021/ed027p245
I cannot upload the PDF since it's larger than 2MB.
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[*] posted on 5-8-2010 at 15:12


Quote: Originally posted by turd  
Quote: Originally posted by Picric-A  
I would specifically like to make ethyl formate (from conc formic acid and methylated spirit)

lazy bastard.
.


Wow calm down! Bit strong!

Thanks for all the proper informative responses.
Will refluxin formic acid and an excess of ethanol produce said ester? Seems very simple.

[Edited on 5-8-2010 by Picric-A]
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[*] posted on 5-8-2010 at 15:20


The yield of uncatalized n-propyl formate with 12hrs of reflux is said to be around 65%, so I would expect ethyl formate yields to be similair. Also couldnt one use p-tsa as a catalyst? I have heard of it being used in some esterifications, and it does not have the same dehydrating properties sulfuric acid has.
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[*] posted on 5-8-2010 at 15:48


I made methyl formate from formic acid (98%) and methanol. Just refluxed and then distilled the very volatile ester. That was a long time ago can't find my notes.

In fact dehydration of formic acid would require a fair quantity of sulphuric acid, unlike the catalytic quantity used for esterification and sulphuric acid diluted in formic acid doesn't dehydrate it, whereas formic acid diluted in sulphuric acid dehydrates on warming. But as we are saying, catalysis is not required for the esterifcation of alcohols with formic acid, maybe zeolites or magnesium sulphate would help by removing water.




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[*] posted on 5-8-2010 at 15:49


@Nicodem: regarding the Pihkal cover, the mountain looks just as much (if not a bit more) like Mt Diablo, which Shulgin's house/lab overlooks.

For my own question, does metabisulfite hydrolyze into two bisulfite ions or one bisulfite ion and one SO2 molecule?
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[*] posted on 5-8-2010 at 16:11


Quote: Originally posted by panziandi  
I made methyl formate from formic acid (98%) and methanol. Just refluxed and then distilled the very volatile ester. That was a long time ago can't find my notes.

In fact dehydration of formic acid would require a fair quantity of sulphuric acid, unlike the catalytic quantity used for esterification and sulphuric acid diluted in formic acid doesn't dehydrate it, whereas formic acid diluted in sulphuric acid dehydrates on warming. But as we are saying, catalysis is not required for the esterifcation of alcohols with formic acid, maybe zeolites or magnesium sulphate would help by removing water.


Thanks Panziandi, i will try making both the methyl and ethyl ester tommorow. Although maybe a bit trivial, i have 2.5L of formic acid and havnt realy found a use for it. Also making an ester with such a low boiling point will be good tecnique practice.
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[*] posted on 6-8-2010 at 00:36


Quote: Originally posted by Picric-A  

Wow calm down! Bit strong!

Apparently not strong enough. First of all you refused to search for yourself, and then instead of fetching the reference I posted detailing the synthesis for students (J. Chem. Education), you continue the begging for being spoon fed. If that's not the behaviour of a lazy bastard, I wonder what is. :P Hint: the interesting part is not so much the catalyst but the question whether your product forms azeotropes with the reactants and byproducts.
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[*] posted on 6-8-2010 at 04:12


Quote: Originally posted by turd  
Quote: Originally posted by Picric-A  

Wow calm down! Bit strong!

Apparently not strong enough. First of all you refused to search for yourself, and then instead of fetching the reference I posted detailing the synthesis for students (J. Chem. Education), you continue the begging for being spoon fed. If that's not the behaviour of a lazy bastard, I wonder what is. :P Hint: the interesting part is not so much the catalyst but the question whether your product forms azeotropes with the reactants and byproducts.


I did not continue 'begging' to be spoon fed, i got my question answered and there was no need for you to lash out.
I have done research and yes i know methyl formate forms an azeotrope with both water and diethyl ether. The ether azeotrope boils at 31.5. Enough research for you?!?! now back off.
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[*] posted on 6-8-2010 at 11:55


does anyone know if potassium iodide is very soluble in glacial acetic acid? i want to try an electrolysis experiment to obtain methyliodide. the iodide shouldn't oxidize to iodine right? because acetic acid is a weak non-oxidizing acid correct?

thanks




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