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MistaMiyagi
Dream Team
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| Joined: 06 Feb 2005 |
| Posts: 50 |
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19.22 Points
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Piperonal from Piperic Acid, CuSO4*5H20, NaOH
Fri Feb 25, 2005 9:55 am |
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This is a condensed version of a Hive post. Unfortunately, I never saved a copy of the thread before the Hive went down.
If there are any enterprising individuals out there, the thread was accessed by this url:
https://www.the-hive.ws/forum/showflat.pl?Cat=&Number=321699--Post408765
Materials
5g piperic acid
16.9g NaOH
25.6g CuSO4 * 5H2O
150mL DCM
205mL H2O
suff. HCl(aq) to acidify
Procedure
- Combine piperic acid, NaOH, CuSO4 * 5H2O, and H2O.
- Reflux for 8 hours.
- Collect liquid via suction filtration, discarding solids.
- Acidify with HCl(aq).
- Extract product with 3x50mL DCM.
- Distill extract to recover DCM, if desired.
Yield: 4.5g piperonal
Last edited by MistaMiyagi on Sat Feb 26, 2005 8:36 am; edited 1 time in total |
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monkichi
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| Joined: 24 Feb 2005 |
| Posts: 16 |
| Location: A tree |
25.16 Points
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Sat Feb 26, 2005 7:34 am |
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| Combine all ingredients except HCl and DCM? |
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MistaMiyagi
Dream Team
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| Joined: 06 Feb 2005 |
| Posts: 50 |
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19.22 Points
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thanks
Sat Feb 26, 2005 8:37 am |
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Monkichi,
The post has been edited for clarification... thanks!
MM |
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CherrieBaby
chouchou
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| Joined: 01 Mar 2005 |
| Posts: 67 |
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3070.02 Points
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Tue Mar 01, 2005 9:14 pm |
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| Quote: |
5g piperic acid
Yield: 4.5g piperonal
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The MWt of piperic acid = 218.21 and the MWt of piperonal = 150.13.
The quoted yield is impossible. |
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MistaMiyagi
Dream Team
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| Joined: 06 Feb 2005 |
| Posts: 50 |
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19.22 Points
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Sat Mar 05, 2005 9:22 pm |
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CB,
Thanks for spotting that incredibly obvious error. I need to locate my original reference somehow - it was a thread on the hive I was participating in that had hCiLdOdUeDn and I were participating in. He posted a pdf of a photocopy of a patent. Perhaps the intent was a 90% overall yield?
MM |
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Tue Mar 08, 2005 6:46 am |
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Looks like an extrapolation of the oxidation of 3,5-dimethoxy-4-hydroxypropenylbenzene to syringaldehyde.
This is all based on the power of Cu(II) as a mild oxidising agent.
Is this speculative, or has anyone successfully performed this oxidation of piperic acid? |
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CherrieBaby
chouchou
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| Joined: 01 Mar 2005 |
| Posts: 67 |
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3070.02 Points
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Sat Mar 12, 2005 3:29 pm |
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+ * + * + * + * + * + * + * + * + * + *
This oxidation is being discussed on Sciencemadness and the original article [Fittig & Mielch, Ann. 152, 25-58 (1869)] describing the preparation from piperic acid and permanganate is here: http://www.sciencemadness.org/talk/viewthread.php?action=attachment&tid=1369&pid=37022
A translation of the actual procedure used in the article (from the German is here):
http://www.sciencemadness.org/talk/viewthread.php?tid=3007&page=2
+ * + * + * + * + * + * + * + * + * + *
MargaretThatcher "Cu(II) as a mild oxidising agent"
Well in classical chemistry copper sulphate, alkali and tartaric acid are used to make Fehlings solution and that will oxidise an aldehyde to an acid (Fehlings solution is used as a characteristic test for aldehyde group). In Fehlings solution the CuO is complexed with Tartaric acid and is more easily available (because it can be transported by the tartarate).
(a) So perhaps tartarate would catalyse this reaction? What if the copper sulphate / and alkali were slowly added as soon as used up so that fresh tartaric-CuO complex was constantly being replenished?
(b) But if Fehlings oxidises aldehyde to acid what is to stop the reaction from producing piperonylic acid as the final product (with or without the tartarate)? I think this was partially answered on the old hive but that is lost now.
(c) There are 2 double bonds present in piperic acid. What is the final product (and by-product).
(d) Do both double bonds get oxidised at the same time or is one preferentially oxidised? Is the benzyllic bond more easily oxidised? - I seem to vaguely remember that it might be.
(e) If we assume that the first reaction is:
CH2O2:C6H3.CH=CH-CH=CH.COOH --> CH2O2:C6H3.CHO + OHC-CH=CH.COOH
What happens next? Are the aldehydes oxidised to acids or is the other double bond also oxidised?
CH2O2:C6H3.CHO --> (a) CH2O2:C6H3.COOH
OHC-CH=CH.COOH --> (b) HOOC-CH=CH.COOH
or --> (c) OHC-CHO + OHC.COOH
This is exactly the kind of reaction which someone with actual analytical equipment needs to optimise and work out.
I have exactly the same reservations about the permanganate (and any other) oxidation too.
I'm not saying don't do it. I'm saying it needs to be properly worked out to get optimal yields.
+ * + * + * + * + * + * + * + * + * + *
I thought I had this oxidation worked out in theory but my old hive post is no longer available and I can't even find what I wrote on my drive. |
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Fehlings Reagent
Tue Mar 15, 2005 6:53 am |
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Fehlings reagent does not react with aromatic aldehydes (this is a standard test), which I think indicates that the Cu(II) is not strong enough to oxidize piperonal to piperonylic acid. I think that the Cu(II) ions are complexed in Fehlings and Benedict's reagents to keep them in solution, rather than to catalyse the reaction. It may be that complexing the ions would reduce the large volume of water otherwise required for this method and piperic acid. I did stumble upon another example of alkaline copper sulphate being used for an organic oxidation in my searches but have lost it. Cu(II) seems to have just the right strength for this oxidation so that even a surplus would not yield piperonylic acid.
Maybe KMnO4 would have to be used in a similar way to the oxidation of ephedrine to methcathinone to prevent over oxidation. It certainly creates piperonylic acid in the warm:
http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv2p0538
As to your options, I am guessing that (c) would happen.
In the details at the top of this thread, I was wondering how the ratio for piperic acid to copper sulphate was arrived at, i.e. has this been done or is it just fantasy? |
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CherrieBaby
chouchou
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| Joined: 01 Mar 2005 |
| Posts: 67 |
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3070.02 Points
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Thu Mar 24, 2005 11:09 pm |
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(1) Yes, overoxidation with KMnO4 gives piperonylic acid. It's hard to stop that over-oxidation even when using mild KMnO4. You will always get some piperonylic acid unless you protect the aldehyde as it is formed (perhaps by including an amine so that a schiff's base will be formed in situ as soon as the aldehyde is produced). But that's all theory, CuSO4 is more interesting because it's easier to get hold of in bulk.
(2) I can't understand how the ratios above were arrived at. I didn't make the first post. Above, we have:
| Code: |
wt MWt moles
----------------------------------------------
piperic acid 5 218.21 0.023
NaOH 16.9 40 0.42
CuSO4.5H2O 25.6 249.68 0.102
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That's about 4 moles of Cu(II) and 16 moles of NaOH for each mole of Piperic acid. I estimate that you'd need at least 3 moles of (O) for this reaction series:
MDP-CH=CH-CH=CH-COOH + 3(O) --> MDP-CHO + HOOC-CH=CH-COOH
If:
CuSO4 + 2NaOH --> Na2SO4 + CuO + H2O
and:
2CuO --> Cu2O + (O)
4 moles of CuSO4 give 2 moles of (O) which is the least amount. required for this reaction:
MDP-CH=CH-CH=CH-COOH + 2(O) --> MDP-CHO + OHC-CH=CH-COOH
Why is so much alkali needed?
I would use more CuSO4; at least half as much again as in the top of the thread post. I would use 7 moles of Cu(II) per mole of piperic acid. |
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CherrieBaby
chouchou
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| Joined: 01 Mar 2005 |
| Posts: 67 |
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3070.02 Points
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Fri Mar 25, 2005 12:15 am |
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Here is an old hive post I found that used CuSO4 to oxidise a benzylic alkene bond.
| Quote: |
from Post 293365 EXAMPLE VII: Syringaldehyde from ... Bookmark Reply
from Antoncho: "Double bond ox. cleavage (to aldehyde) with CuO" (Chemistry Discourse)
EXAMPLE VII: Syringaldehyde from the isolated intermediate
Syringaldehyde may also be prepared by oxidizing the isolated 3,5-dimethoxy-4-hydroxypropenylbenzene of Example V with nitrobenzene in alkali or other low potential oxidizing agents.
Thus 195 parts 3,5-dimethoxy-4-hydroxypropenylbenzene are added to a cupric oxide mixture freshly prepared from 1000 parts hydrated copper sulfate, 660 parts sodium hydroxide, and 8000 parts of water and the resulting mixture is
heated to boiling under reflux for eight hours. The separated red cuprous oxide is filtered and washed with water. The alkaline filtrate and washings are acidified and extracted with ether.
Bisulfite purification of the ether extract should yield approximately 155 parts or 90% syringaldehyde.
Other alkaline copper oxidizing agents such as Fehling's Solution, Benedict’s Solution, may be used with the same results. An alkaline copper oxidizing agent is particularly advantageous for replacing the propenyl group with the aldehyde group because the strength of its action in changing from a cupric to a cuprous compound is definitely adequate to oxidize to the aldehyde, and at the same time insufficient to continue the oxidation to the acid further or to destruction. However, in large scale operation, it will be obvious that oxidizing agents having no such automatic action may be employed for reasons of economy, and the extent of the reaction controlled by controlling the amount of the reagent.
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CherrieBaby
chouchou
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| Joined: 01 Mar 2005 |
| Posts: 67 |
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3070.02 Points
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Fri Mar 25, 2005 12:25 am |
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How do I identify Piperonal if I make it?
Heliotropin (aka Piperonal)
from: S Arctander, Perfume & Flavour Chemicals, Arctander, NY, 1969, pp 183-184
Physical Constants. heliotropin is marketed as a colourless, crystalline solid possessing the characteristic mild heliotrope odour. Its physical constants are:
Melting point, °C 37
Boiling point, °C 263(760);135(10)
Solubility 1 vol. in 3 vols of 70% alcohol
Oxime, mp. °C 110
Phenylhydrazone, mp. °C 103
Semicarbazone, mp. °C 234
2,4 dinitrophenyl-hydrazone, mp. C 265
The Essential Oil Association of USA has adopted the following standards for heliotropin:
Colour, odour and Appearance: White lustrous crystals having a sweet, flowery odour resembling heliotrope and free of safrole odours.
Congealing Point: At least 35° C
Aldehyde Content: At least 99% calculated as heliotropin.
Solubility in Alcohol: 1 gram is soluble in 4 mL. of 70% alcohol. |
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CherrieBaby
chouchou
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| Joined: 01 Mar 2005 |
| Posts: 67 |
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3070.02 Points
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Fri Mar 25, 2005 12:38 am |
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Here is another extract from the same perfume book as above indicating that chromate can be used to oxidise a benzilic alkene (Isosafrole) to piperonal (aka heliotropin).
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Manufacture. - The only practical source of heliotropin today is safrole which is found in a number of oils, notably, sassafras and camphor. Very large quantities of camphor are normally produced and the safrole is crystallised out from certain fractions of this oil. Brazilian sassafras oil (Ocotea cymbarum) is also used as a source of safrole since it contains over 92% of this compound.
The first step in the preparation of heliotropin is the conversion of safrole into isosafrole. This is done by heating safrole with alcoholic potassium hydroxide or with alcoholates under pressure(31). A simple commercial procedure consists of dissolving 60 parts of potassium hydroxide in 100 parts of alcohol by stirring and heating to reflux. About 60 parts of pure safrole are then added to the alkali solution and the mixture gently refluxed to bring about the conversion of the allyl group to the propenyl group. The reaction takes 15-20 hours and is followed by taking periodic samples to determine the degree of conversion by noting the index of refraction of the samples which have been washed free of alcohol and dried. Since the index of refraction of safrole at 20° C is 1.5360, and that of isosafrole, 1.5780, the end of the reaction is easily determined. When the reaction is complete, the mixture is cooled, diluted with water, and most of the alcohol distilled off. The separated crude isosafrole is fractionally distilled to remove impurities, and used for oxidation to piperonal. The alkali solution can be re-used in a following batch operation.
Oxidation is best carried out by means of a dichromate-sulfuric acid mixture. First the dichromate solution is prepared by dissolving 58 pounds of sodium dichromate in 130 pounds of water. Addition of small quantities of sulfanilic acid is reported to increase the yields appreciably. To this mixture is added 33 pounds of the crude isosafrole obtained as above. The mixture is stirred at room temperature and 180 pounds of technical sulfuric acid (36° Baume) added slowly with constant stirring. It is necessary to employ a vessel with a cooling jacket because the reaction is exothermic, and for good results a close control of temperature is imperative. The temperature is gradually allowed to rise at the rate of 5° C for every fifteen minutes and the rate of addition of sulfuric acid so regulated that all of it is added within three hours. Stirring is continued for a further half hour and then 100 pounds of benzene or toluene are added in order to extract the crude reaction product from the mixture. The mixture is stirred for half an hour and allowed to stand until the benzene or toluene layer is clearly separated. It is then drained off, the acid mixture extracted once more at 40° C with a further 40 pounds of benzene, and the extract combined with the previous benzene or toluene layer. The benzene solution is washed with water and neutralized with cold sodium carbonate solution, then distilled to remove the solvent.
The crude heliotropin remaining as a residue in the still is subjected to a vacuum fractional distillation and heliotropin is obtained as a semi-solid product in yields of about 85 per cent.
The last step involves crystallisation from a suitable solvent such as an equal weight of 95 % alcohol. The mixture is heated to effect complete solution of crude heliotropin in the solvent. It is then filtered if necessary through decolorizing charcoal in order to remove impurities which may affect the color of the finished product. The solution is cooled and the crystals formed are centrifuged and dried at low temperatures in special drying shelves.
To obtain heliotropin of the highest purity, free from by-odours, each step must be carried out under rigid control. Many variations of this method can be employed, depending upon the equipment used and the experience of the operator(32).
31. Nagai, J. Soc. Chem. Ind., 29 (1926) 364.
32. McLang, Chem. Trade J., 79 (1926) 359.
Wagner, Riechstoff Ind., I (1926) 65.
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CherrieBaby
chouchou
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| Joined: 01 Mar 2005 |
| Posts: 67 |
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3070.02 Points
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