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Author: Subject: Improvement in the yield of racemic PPA*HCl via Akabori reaction (35 % molar)
Quantum_Dom
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[*] posted on 10-9-2010 at 21:40


Quote: Originally posted by Francis Crick  
Sorry about the naming issue QD, brain must have been skim reading your name for a while :o your work is very much admired from these parts

Yes, the aqueous was reduced then aqueous base added to it as it was thought a LOT less base would be needed than was required.

If there is indeed still PPA present in the aqueous, would one expect to see the freebase rise to sit on top as the volume reduces? Or would it be better to acidify with HCl, reduce volume then basify again to get at the freebase?

And is the freebase actually brown or that just a result of byproducts present in the sample prior to the crystallization?


I am still confused as you didnt really answered what I was asking for. I know you reduced the volume (by only 1/5 th of the inital volume). What I am telling you is that:

1. You did not reduce sufficiently the acidic extract volume.
2. Not only you did not reduce the acidic extract enough, you returned to square one by flooding the system with almost 1 L of aqueous base. I mentionned on many occasions, that the freebase of PPA has affinity with water. Too large a volume of water, smaller the yield of extraction with a non-polar solvent.

Please have another look at the write-up in my original post as everything is explained there.

QD




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Melgar
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[*] posted on 11-9-2010 at 17:34


Would there be any harm from heating this reaction for too long? If not, it would seem that if there's both unreacted alanine and unreacted benzaldehyde, letting it react a bit longer, or adding the alanine in portions, might be helpful. If heating too long is harmful though, then those would be bad ideas.
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[*] posted on 12-9-2010 at 17:23


Understood QD, but if the reaction could be done again from scratch it would. I should have made it more clear as I was asking what would be the best approach to take after this most unfortunate of errors.

Either:

1. acidfy the now 1.8 L basic solution, reduce the volume by heating then re-basify to extract with DCM

or

2. reduce the volume of the 1.8L basic solution by heating then extract with DCM

Due to concerns with excess NaCl with all the HCl and NaOH additions, the decision was made to take option 2 and just reduce the solution.

Upon reducing the volume to 600 mL, an obvious orange color has been developing in the aqueous solution so its looking promising. clear solid 'salt like' matter has also been forming in the bottom of the beaker so it may help to filter these prior to DCM extraction. It is planned to continue to reduce the volume to 200mL, vacuum filter the solids out warm, extract with 5 x 200 mL DCM and continue as per the original QD method.

One further question, is removing the DPEA from the aqeuous as sensitive to its concerntration as the PPA? I notice that 3 x 150 mL DCM extactions preceed the reduction in aqeuous volume whilst 3 x 75 mL DCM follow it. Any particular reason for this?

Suggestions are more than welcome. Will post yields soon.
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Quantum_Dom
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[*] posted on 13-9-2010 at 10:33


Quote: Originally posted by Francis Crick  
Understood QD, but if the reaction could be done again from scratch it would. I should have made it more clear as I was asking what would be the best approach to take after this most unfortunate of errors.

Either:

1. acidfy the now 1.8 L basic solution, reduce the volume by heating then re-basify to extract with DCM

or

2. reduce the volume of the 1.8L basic solution by heating then extract with DCM

Due to concerns with excess NaCl with all the HCl and NaOH additions, the decision was made to take option 2 and just reduce the solution.

Upon reducing the volume to 600 mL, an obvious orange color has been developing in the aqueous solution so its looking promising. clear solid 'salt like' matter has also been forming in the bottom of the beaker so it may help to filter these prior to DCM extraction. It is planned to continue to reduce the volume to 200mL, vacuum filter the solids out warm, extract with 5 x 200 mL DCM and continue as per the original QD method.

One further question, is removing the DPEA from the aqeuous as sensitive to its concerntration as the PPA? I notice that 3 x 150 mL DCM extactions preceed the reduction in aqeuous volume whilst 3 x 75 mL DCM follow it. Any particular reason for this?

Suggestions are more than welcome. Will post yields soon.


IMO I would avoid evaporating the water without reacidifying the whole as PPA will steam distill. To what extent, I dont know.

I do not understand the second part.

QD




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[*] posted on 20-9-2010 at 10:30


Quick question... is most of the DPEA left in the nonpolar layer? Also, is the reddish-brown product DPEA? I'm guessing the reason for evaporating most of the solvents and then basing the aqueous layer is to saturate it with salt so less of the PPA base can dissolve in it.
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[*] posted on 17-4-2011 at 06:43


A notice to those few members who brought this otherwise nice thread down to the level of kewls:
All your posts from the recent revival of the thread were split and moved elsewhere where they fit better.

Stop posting junk replies into this thread! If you have something off-topic to discuss on such a kewlish level, at least have the decency to do so in a separate thread in the Beginnings section. Only post here when you have something to add on topic and on the same level of discourse.
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[*] posted on 17-4-2011 at 07:19


There are other ways to work this reaction up. For example, I evaporated away all the liquid, leaving me with PPA HCl and some other junk, then rinsed the other junk away with acetone.

Obviously I'm a student of the "Good Enough" school of philosophy. :P

The more steps I have to take, the more likely I am to screw up something, so this may not be a bad way to go.

[Edited on 4/17/11 by Melgar]
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[*] posted on 17-4-2011 at 22:56


yeah it is a bad way to go about it.
what happens with these kind of amino alcohols is they are volitile with steam
even thier hydrochlorides.
did you take a m.p. afterwards?
and diphenylethanolamine i can't tell you exactly the solubility data i have looked for it in chem abs.
other than to say the scientists at sigma aldrich said it dissolves .6 g/100 ml in ethanol under sonication.
so likely you can easily remove it by simply salting out the aqueous phase at ph 12 and saturating with isopropanol.

also wanted to add that you can suppress the steam volatility of these type of compounds by acidifying it to ph3 or less

that keeps water tied up as the hydronium ion so it does'nt tie up with your substrate.

[Edited on 18-4-2011 by jon]
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[*] posted on 18-4-2011 at 15:37


Well there's an excess of HCl already in the solution; as it gets down to the last little bit, the HCl fumes are quite intense. Did not take a melting point, but I did do a few DCM washes like the OP did, so there shouldn't be too much diphenylethanolamine. With such an excess of benzaldehyde, I don't think there's going to be much alanine left, and most of the rest of the products would evaporate away.
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[*] posted on 18-4-2011 at 21:01


I must agree with the tasting of any known/unknown rxn soultion, as being one of the crazyist things to do, to say the least.
BUT, And I hope this will not only prevent it being repeated, but posibly help identify the substance, or it's main constituant at least.

After reading a post on a body building site, beta alanine/l-alanine, was said to be VERRY SOUR tasting & had to be sweetened with OJ before being used as a pre workout suppliment drink.

apollogies if this is of little or no usefull info, I just thaught it worth mentioning. Xtal
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[*] posted on 18-4-2011 at 23:35


this is standard extraction protocol for ppa.
i found this in a book at the pharmacy library so i would stick with convention it always works for me.
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[*] posted on 20-4-2011 at 02:54


just a thought on the akabori reaction ! I no there is much speculation on the steriochemistry of ppa ,but could someone correct me if i am wrong. but i think that you will get dextro and levro forms of both norephedrine and norpsuedoephedrine is this correct . sorry if im wrong


regards azo
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[*] posted on 14-6-2011 at 00:49


I can make benzaldehyde from cinnamon bark oil but the product I always end up with has still got some cinnamon oil in it.
It is about 80% benzaldehyde and 20% cinnaomon oil.
I'm thinking of just mixing and reacting this solution with the N-methylalanine to make the pseudoephedrine

Do you think the cinnamic aldehyde will react with the n-methylalanine and or even stuff up the reaction some how?
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[*] posted on 25-6-2011 at 23:32


yes i think it would it has the same functional group so it would tie up your alanine i would carefully fractionate it.
or remove it chemically by means of oxidation with acidic potassium permanganate.
you could test for it's presence by adding bromine for a double bond test.

AZO you would get erythro/threo isomers of course.
there are two stereocenters i don't see this reaction being selective chirally.

[Edited on 26-6-2011 by jon]
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[*] posted on 31-8-2011 at 01:02


How would I separate the cinnamon aldehyde from the benzaldehyde by the method you mentioned using acidic potassium permanganate?
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[*] posted on 31-8-2011 at 09:54


The best way to seperate them is by distillation

Benzaldehyde 178
Cinnamaldehyde 248
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[*] posted on 20-9-2011 at 02:24


I would like to ask
After alkalization ,Is the extraction of water phase?or Oily extract?
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[*] posted on 1-10-2011 at 18:15


So has anyone written up an example they would like to share? Since this thread is about improving efficiency I think an efficient example or method should be provided that explains what is actually going on. For example.

"150 ml of DMSO is added to extract impurities such as *insert impurities here* and then the dmso is separated and set aside for recycling."
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[*] posted on 1-10-2011 at 19:03



Quote: Originally posted by Melgar  
There are other ways to work this reaction up. For example, I evaporated away all the liquid, leaving me with PPA HCl and some other junk, then rinsed the other junk away with acetone.

Obviously I'm a student of the "Good Enough" school of philosophy. :P

The more steps I have to take, the more likely I am to screw up something, so this may not be a bad way to go.

[Edited on 4/17/11 by Melgar]



Could youexplain what you did in a little more detail so that we can better understand what your talking about?


Quote: Originally posted by jon  
yeah it is a bad way to go about it.
what happens with these kind of amino alcohols is they are volitile with steam
even thier hydrochlorides.
did you take a m.p. afterwards?
and diphenylethanolamine i can't tell you exactly the solubility data i have looked for it in chem abs.
other than to say the scientists at sigma aldrich said it dissolves .6 g/100 ml in ethanol under sonication.
so likely you can easily remove it by simply salting out the aqueous phase at ph 12 and saturating with isopropanol.

also wanted to add that you can suppress the steam volatility of these type of compounds by acidifying it to ph3 or less

that keeps water tied up as the hydronium ion so it does'nt tie up with your substrate.

[Edited on 18-4-2011 by jon]



[Edited on 2-10-2011 by overload]
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[*] posted on 16-10-2011 at 19:41


The aqueous phase was then treated with small portions of NaHCO3 [11] until fizzing becomes less violent (Figure-6), then small portions of NaOH were added until pH was strongly alkaline. A light brown-yellow oily layer with a strong and biting amine smell separated from the aqueous phase .

I tried to do so,But when it alkalinization after ,In oil layer unknown things have contact .Who can tell me how to clear these things





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[*] posted on 23-12-2011 at 15:37


Quote: Originally posted by Quantum_Dom  
Quote: Originally posted by hector2000  

i know chemistry of drug and i know tasting small amount of ppa is not dangerous also i know PPA has bitter taste but my PPA(by akabori reaction) is sour.

No, tasting (regardless of the quantity involved) a product you do not know the nature or idendity makes you a cook, not a chemist.


If resisting to taste the chemical you just produced without knowing what it is makes you a chemist then even monkeys can be chemists. Simply put a monkey infront of a beaker filled with sulfuric acid and a beaker filled with ethanol get him to pour one into the other and then have him run away. Monkey chemist.

[Edited on 23-12-2011 by cipi]
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[*] posted on 28-12-2011 at 08:55


To expand the possibilities of the akabori different benzaldehydes such as 4-fluorobenzaldehyde or clorobenzaldehyde might be used in place of regular benzaldehyde. "Substituted" benzaldehydes being used in akabori have been discussed before but no results have been posted -so?-
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[*] posted on 14-9-2012 at 21:34


Yield may increase if we Use certain solvents(like DMSO)?

Yuusaku Yokoyama(2007) used DMSO and got 79% yield

Attachment: Yuusaku Yokoyama.pdf (117kB)
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[*] posted on 15-9-2012 at 09:35


i had a hunch about that solvent years ago i fucking knew it.
of course they are using methyl alanine so the yeilds will be higher naturally.
but still it's a rung up.
now we need to optimize solvent ratios i don't understand japanesse.

[Edited on 16-9-2012 by jon]




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[*] posted on 20-9-2012 at 10:44


Holy shit!
This would lead one to believe that yields in the range of 60%-70% are possible, given the right conditions. But seeing as how I'm an uncultured ass, and can't read Japanese (or any other non-English language) I'm not 100% sure I saw what I think I saw. I think.




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