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Author: Subject: phenyl acetic acid from phenylalanine
sokay
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biggrin.gif posted on 30-5-2006 at 19:36
phenyl acetic acid from phenylalanine


i searched some old posts that outline synth of paa from phenylalanine, using sodium perchlorate via an intermediate, or something like that, anyone have any detail of possible procedure
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[*] posted on 30-5-2006 at 19:56


There is a route to reduce Phenylalanine to benzyl cyanide and then to PAA........solo

Quote:



psyloxy
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07-10-04 23:17
No 518656
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As it turns out, phenylalanine can also be converted to benzyl cyanide directly:

Syn.Lett.; EN; 4; 2003; 542 - 546 - NBS, ammonium chloride, DMF
J.Amer.Chem.Soc.; EN; 106; 20; 1984; 6075-6076 electrooxidation 80% yield <__ could be interesting OTC-wise
Indian J.Chem.Sect.A; EN; 19; 4; 1980; 325-329. CAT
J.Indian Chem.Soc.; EN; 69; 10; 1992; 642-647 dichloramine-B, perchloric acid
J.Chem.Soc.Perkin Trans.2; EN; 1983; 323-334. chloramine-T
Synthesis; EN; 5; 1996; 600-602.CuBr2 t-BuOLi, 53% yield
J.Chem.Sect.A; EN; 27; 1; 1988; 39-43. chloramine-T, perchloric acid

--psyloxy--


......................source,

Hive archives.........

-----------------------------------------------------------------------------------------------

Quote:
Phenylacetic acid from Benzyl Cyanide [2]


In a silica basin of about 35 cm. diameter, a mixture of 2.5 kilos of benzyl cyanide [3] and 7.5 kilos of 70% sulfuric acid is warmed until a few bubbles of gas appear. The heating is at once stopped, since a very vigorous action now ensues. As the vapors evolved are injurious to health, the basin is covered when the reaction begins with a sliding cover from which the vapors can be led into water. As soon as the reaction ceases, the product is poured upon crushed ice in a large, earthenware vessel. Crude phenyl acetic acid, contaminated on the surface with phenyl acetamide, is precipitated on cooling. In order to remove the amide, the acid is dissolved in lukewarm dilute soda solution. The amide remains undissolved and can be filtered off, while the phenyl acetic acid goes into solution as sodium salt and is reprecipitated in a sufficiently pure state by the addition of dilute mineral acid. After drying it is acceptably pure.



................source

http://www.erowid.org/archive/rhodium/chemistry/phenylacetic...

[Edited on 31-5-2006 by solo]




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[*] posted on 20-9-2017 at 14:36


Indian J.Chem.Sect.A; EN; 19; 4; 1980; 325-329. CAT

Micellar Catalysis in the Chlorination of Anilines by
Chloramine-T—Substituent Effect

P. S. RAGHAVAN, V. S. SRINIVASAN (Sr) & N. VENKATASUBRAMANIAN

https://www.mediafire.com/file/30dt61rbn21x0oy/Indian%20J.Ch...
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[*] posted on 20-9-2017 at 21:43


I once considered trying this, given that the same oxidation reaction can work on another alpha amino acid that we all know and love (glutamic acid to succinic acid).
It must be converted to its ammonium salt and then H2O2 is slowly added.
There is a thread somewhere on the forum but im too lazy to find it.
Chemplayer did a vid on it: https://www.youtube.com/watch?v=kDLSRk068SU

Ive done this several times before and the yield is never particularly great and the product is always somewhat impure, however Phenylacetic acid can be conveniently distilled.

Another similar reaction, which calls for a more mild oxidizer and also stops at the aldehyde is called the strecker degradation. :D
https://en.wikipedia.org/wiki/Strecker_degradation
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[*] posted on 21-9-2017 at 19:34


Just as a note, and Magpie mentioned this in another thread, but we've not been able to repeat the results of the glutamic->succinic experiment. The first batch of MSG we had was not MSG (look at the crystal structure in the video and compare to any brand of MSG out there)! We're still trying to work out what was going on though...



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[*] posted on 21-9-2017 at 21:38



Quote:

Just as a note, and Magpie mentioned this in another thread, but we've not been able to repeat the results of the glutamic->succinic experiment. The first batch of MSG we had was not MSG (look at the crystal structure in the video and compare to any brand of MSG out there)! We're still trying to work out what was going on though...

Well this makes me question what ive actually got sitting in that jar on the shelf. Definitely doing a MP determination this weekend.

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[*] posted on 22-9-2017 at 08:52


I posted recently an OTC synthesis of phenylacetonitrile from phenylalanine in this section. The conversions of phenylacetonitrile (benzyl cyanide) to phenylacetonitrile and phenylacetonitrile acid are clearly described in Organic Syntheses.

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[*] posted on 22-9-2017 at 14:14


chemplayer: H2O2 can under some conditions (acids present) oxidize aldehydes to acids (Baeyer-Villiger oxidation). Is it possible that some of the glutamic acid had degraded to succinaldehyde?

Such a reaction gives a possible method of converting phenylalanine -> PAA via Strecker degradation with dehydroascorbic acid or similar.

AvBaeyer: I assume when you say "... to phenylacetonitrile and phenylacetonitrile acid" you mean to say "to phenylacetamide and phenylacetic acid".
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[*] posted on 23-9-2017 at 05:19


Yes, an unacceptable typo due to not proper proofing. I need to be extra careful as this #@$$% ipad keeps "spell checking" on me and inserting nonsense.

Thanks for catching the nonsense.

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[*] posted on 23-9-2017 at 15:04


My results for the melting point determination of the glutamic acid i had oxidized via the same method done by chemplayer in there video.

I used a test tube to do this and 2 thermometers, one thermometer imursed in the oil and one in the test tube.

At 170*C according to the thermometer in the oil, the crystals on the outer walls of the test tube began to conglomerate and melt together, by 176*C all of the crystals on the outer parts of the test tube had melted and formed a brown liquid puddle at the bottom of the test tube.
There was a coupe crystals on the thermometer inside the test tube.
These crystals began to melt at 170*C according to the thermometer they were clinging to and then had uniformly melted into the puddle by 176*C as well.

Unfortunately this kinda melting point set up isn't the most accurate but i think the result are still conclusive enough to evaluate.

MP of succinic acid is 184*C accoring to wiki.
https://en.wikipedia.org/wiki/Succinic_acid
184-186*C according to sigma.
http://www.sigmaaldrich.com/catalog/product/aldrich/239682?l...

So im fairly confident that the reaction does in fact work, or has atleast worked for me.
Still a melting point that far off the literature would indicate some significant impurities.
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[*] posted on 23-9-2017 at 23:28


Another thought: hypobromite is an effective Strecker reagent, so H2O2 with bromide present might take amino acids to shorter acids.

http://www.agriculturejournals.cz/publicFiles/84631.pdf

Bromide present/not present could explain inconsistent results with peroxide oxidation, maybe?

[Edited on 24-9-2017 by clearly_not_atara]
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