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Author: Subject: Piperic acid oxidation to Piperonal
Hexagon
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 Quote: Originally posted by cheeseandbaloney I would think the reason the oxidation of piperic acid usually fails because the strong oxidizers could be tearing up the methylenedioxy bridge. Anything strong enough to rip apart a C=C bond seems like it would do somptin fierce to a R-O-CH2-O-R bond. It would be a surprise to me if the yields on a reaction like this were consistently high...

Nope, the oxidation usually fails because the aldehyde is oxidized all the way to the acid.
Bander
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I made a thread on this a long time ago where I received very useful help from many here, but most notably Tacho's advice. Since then I have done the below to isolate piperine.
 Quote: 113g Black Pepper (4oz) ~600ml Isopropyl Alcohol, anhydrous! ~120ml Acetone, anhydrous! Reflux 113g black pepper in 600ml anhydrous IPA in a 1 L round bottom flask for 2-3 hours. Filter the ~80C olive translucent IPA through coffee filters into temporary jars. Remove the partially extracted ground pepper to save for further extractions and wash the remainder of solids out of the flask with water. *DRY* the water out of the flask completely with acetone wash and hot water bath. Pour the Piperine/IPA back into the ground bottom flask. Add broken glass chips or boiling stones. Distill off and recover the IPA until the viscous remainder starts to stick to and gum up the glassware above the bubble line. This usually happens with around ~30ml (+-10) left. Pour the remainder off and let it sit for a day undisturbed and covered. A cake/mash of orange crystals under a brown oil appears. Crush the fanned out crystal cake under ~20ml acetone (dry! no water). Pour the acetone wash off the powder into a collection jar through a coffee filter for later. It will still contain substantial disolved piperine. Notice the lighter yellow color each time as you repeat this wash and crush three times. The remaining bright yellow <1mm needle crystal powdered piperine at the bottom of the jar should be set out to dry on filters. 2-4g usually results. The waste should be evaporated over 2-3 days to retrieve another crystal cake and the above repeated.

[Edited on 27-8-2010 by Bander]
cheeseandbaloney
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Quote: Originally posted by Hexagon
 Quote: Originally posted by cheeseandbaloney I would think the reason the oxidation of piperic acid usually fails because the strong oxidizers could be tearing up the methylenedioxy bridge. Anything strong enough to rip apart a C=C bond seems like it would do somptin fierce to a R-O-CH2-O-R bond. It would be a surprise to me if the yields on a reaction like this were consistently high...

Nope, the oxidation usually fails because the aldehyde is oxidized all the way to the acid.

aha! I was under the impression that the reaction failed completely and brought a mess of unwanted products. Piperonylic acid still seems useful. I wouldn't consider that a failed reaction! (unless one specifically wanted piperonal obviously).
Nicodem
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 Quote: Originally posted by Gualterio_Malatesta Hence this method is more promising and is favourable to kitchen chemists not because they lack knowledge. This method was tried by several skillfull chemists and failed! I must admit my info is couple of years old, maybe there were some improvements to this oxidation step which actually yielded the desired product - Hexagon's post above (he didn't reply me though).

I'll skip the part about this being a promising method to kitchen chemists and lack of knowledge, because it sounds oxymoronic, but I'm seriously interested in those reports you mentioned of "tried by several skillfull chemists and failed". I don't remember any such report from the Hive and I do more or less regularly follow the developments at the Hyperlab, but I don't remember ever reading about what you talk. If skilled chemists tried and failed, this can mean the oxidations described in the literature are fraudulent, that even ozonolysis on piperine does not work, or that it is not possible to isolate piperonal from the mixture (or a combination of more of such factors). Please provide a few citations from these skilled chemists, so that we can see where the problem resides.

…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)

Gualterio_Malatesta
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2 Nicodem

I will try to find links to those attempts.

Anyways, was there any success that you are aware of involving this method?
Polverone
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Here is the original Annalen paper describing the cleavage of piperine. I don't recall seeing this paper posted before in conjunction with piperine -> piperonal discussions. I know little to no German so it will require much tedious machine translation and dictionary time before I can grasp much of it. It may be useful to anyone in this thread who understands German, though.

Attachment: annalen_1869_25-58.pdf (735kB)

PGP Key and corresponding e-mail address
Bander
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Would it be possible to remove piperonal from solution as it is formed by using a bilsulfite adduct to precipitate it before it is oxidated to the acid? I have used this method after the entire oxidation, but ended up with only ~0.1g of very pale yellow precipitate.
S.C. Wack
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How is it that everyone assumes that piperine isolation and piperic acid oxidation to piperonal have never come up here before?

It's almost as mysterious to me as is staff wasting valuable time in response to obviously clueless or trolling new nyms who refuse to search google or anything, and refuse to post in relevant threads.

Naturally google books has it by now.

The problem with the .txt procedure is that it was...fucked up...and any of these alleged failures by these top notch chemists is caused by their faith in internet teks, not chemistry. No doubt the original directions would be an improvement.

Forming a solid bisulfite adduct is unnecessary and surely lowers yields. I have heard rumors that one trick to the KMnO4 procedure is in the workup.

However any tricks, and possibilities known in the art (KMnO4-related or otherwise), seem ill placed in any thread titled "Seperation of Piperine from resin", much less in response to the posts in this thread.

[Edited on 27-8-2010 by S.C. Wack]

"You're going to be all right, kid...Everything's under control." Yossarian, to Snowden
Hexagon
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AFAIK the adduct you are trying to make is fucked up at anything but neutral conditions, so in the clasic synth. being basic the anvioronment, it's a safe assumption that trying to isolate the aldehyde as it's corresponding bisulfite adduct is not possible. Dunno what you ended with, but I can assure that piperonal is bisulfite aduccut is a powder (when dry) white as snow.

If you have enough piperate you can try the CuSO4 and tartrate/citrate in alkaline media oxidation, dont use an excess of sodium hydroxide since it'll turn the aldehyde in to the alcohol and the acid due to cannizaro, just use enough hydroxide to precipitate de Cu(OH)2 and neutralize the tartaric/citric acid, then add an excess of sodium (bi)carbonate or what ever, it'll foam a little bit at the beggining, after refluxing for 5 hours, I think that the piperonal should be steam distilled and from the resulting aqueous mess, add (meta)bisulfite to isolate the adduct. I tried all that with unproperly hydrolized piperate (turned to be fatty acid salts with a little bit sodium piperate) and obtained a vanillaish smell

Will not try it again with piperate because the hydrolisis of the amide plainly sucks. I'd rather extract pure piperine and then chuck that on a manganese-ammonium alum cell.

Another idea would be to drip very slowly a permanganate solution to boiling aqueous piperate and carbonate, from witch the piperonal is steam distilled as it forms, hopefully.
Polverone
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27-8-2010 at 16:01
euxy
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Antoncho
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1. Extraction of 462 g ground black pepper with boiling acetone (1.5 l + 1 l, circa 1 hr, more isn't needed) gave 39.8 g resin.

2. Boiled for 1 hr with 483 mls 95% EtOH and 117 g urea (as in US Patent 6054585) and cooled overnight in the fridge, decanted from xtals of urea/fatty acids adduct, evaporated most EtOH and added a little water. Crude semi-solid piperine precipitate weighs 31.1 g.

3. Dissolved in 50 mls EtOAc, added 50 mls pet ether, chilled overnight in the freezer. Yield - 11,3 g of nice xtalline piperine .

4. Refluxed for 19 hrs (TLC shows completion at this time) with an equal weight of 85% KOH in 5x volume of 95% EtOH. Cooled, filtered, washed with IPA on the filter. Yield - 101% K piperate.

5. Recrystallized from 5x EtOH + 1x water. After cooling in the freezer 75% yield counting on piperine was obtained. Had an impression that mother liquor still held some piperate.

6. 2 g K-piperate dissolved in 50 mls water, added 50 mls DCM. Placed in ice bath, dripped in saturated aq. solution of 6.2 g KMnO4 with stirring, temp. kept at 5-10 C. Killed remaining oxidant with ascorbic acid. Separated organic layer, extracted with DCM, washed w/5% NaOH, then brine, stripped off solvent. Yield - 500 mg (42,5% on piperate) piperonal, which was solid at RT but melted in hands (lit. mp. 36 C)

The identity of the product was further confirmed by Henry reaction, which proceeded with good yield. Reduction of the intermediate also gave the product with all of the properties that were to bee expected

[Edited on 10-5-2011 by Antoncho]
Antoncho
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Just to not bee confusing - a pound of black pepper gives about 3,5 g of piperonal via the route described in the previous post.

The quantity that the author had actually gotten was about 1.5 g, but only beecause a lot of experimentaion has been made along the way (e.g., oxidation of piperine with CuSO4 was tried and found to bee not working at all).

Thus, a kilo of black pepper could give one about 7 g of piperonal, perhaps even more.
Hexagon
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What can I say? BTW great work antoncho!

Just one thing, did you tried the cuso4 variation with a citrate or tartrate added? looks it needs a cu(ii) complexing agent added.
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Would a loaded salt of Mn+3 reduced to Mn+2 towards piperic acid which gets oxidized with cleavage to piperonal? Is this selective oxidation strong enough to cleave the double bonds of piperic acid?

Strong oxidizer is mentioned in this oxidative cleavage which KMnO4 is, but I'm sure that this also leads to oxidation all the way to the acid.
Mush
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 Quote: Originally posted by euxy The rapodshare link by CherrieBaby is dead, has anyone the articles?

 Code: http://www.4shared.com/zip/xDvE_KC_/200613113482_Piperolal-oxidati.html
thebishop
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The following are mixed together under agitation at ambient temperature:

294.23 g (1.5 mole) of 3,4-methylenedioxy mandelic acid;

562 g of water;

258.75 g of 37% hydrochloric acid being 2.625 moles;

2.1 g of 69% nitric acid being 23 mmoles.

The suspension obtained is heated under agitation at 43°±2° C., then 103.5 mg (1.5 mmole) of sodium nitrite dissolved in 4 g of water is introduced rapidly at this temperature, then 107.5 g of 69% nitric acid, being 1.177 mole, is introduced slowly, over about three hours, in such a way so that the temperature of the reaction medium is maintained at between 40° and 50° C. without using external heating or cooling. At the end of the introduction, the reaction medium is left for one our under agitation at 43°±2° C., then it is cooled down to ambient temperature and finally extraction takes place three times with 600 g of trichloro-1,1,1-ethane. The re-united organic phases are then washed successively, once with water, three times with a saturated aqueous solution of sodium hydrogen carbonate and finally once with water before being concentrated under reduced pressure.

Thus 220 g (1.46 mole) of crude piperonal is isolated which is purified by distillation under reduced pressure.

Thus 178 g (1.186 mole) of pure piperonal is isolated distilling at 106° C. under a vacuum of 2.4 mbars and having a melting point of 37°+1° C. The yield is established at 79% of the theoretically calculated value relative to the 3,4-methylenedioxy mandelic acid used.

http://www.freepatentsonline.com/5095128.html

I expect i'll use DCM rather than trichloro-1,1,1-ethane.
maximumpat
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...thank you. long time lurker here, I shall try and make my first post of consequence a proof of concept on this.
bfesser
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We've tried in the past to perform the permanganate oxidation of piperinic (piperic) acid, and it's possible to do a DCM extract of the reaction mixture and get a tiny tiny amount of something rather nice smelling, but until now nothing isolated. So we tried something different and random:

Preparations:

Solution P (Piperinate):
100ml of water
3.7g of piperinic acid, derived originally from black pepper (17 mmol)
0.68g of sodium hydroxide (17 mmol)

Solution O (Oxidisers):
500ml of water at ~20C
3.9g potassium periodate (17 mmol, 1 x mole equiv)
5.4g potassium permanganate (34 mmol, 2 x mole equiv)

Solution Q (Quench):
75ml of water
5.3g sodium bisulfite (51 mmol)
2.1g sodium hydroxide (51 mmol)

Procedure:

1. Solutions P, O and Q prepared using magnetic stirring in various beakers (P in the large 800ml beaker).
2. 3 ice cubes (~50g) were added to solution P with vigorous stirring.
3. Solution O was agitated with a glass rod (to ensure no residual insoluble periodate had settled).
4. Solution O was added to rapidly stirred solution P over about 15 seconds.
5. Stirring continued and reaction allowed to proceed for 2 minutes.
6. Solution Q added over about 15 seconds, and then the mixture allowed to settle.
7. Mixture filtered (heavy brown-black precipitate), and the precipitate washed with 30ml water.
8. Precipitate washed with 2 x 30ml of dichloromethane.
9. Filtrate (2 layers) placed into separating funnel, shaken, and the bottom DCM layer separated.
10. Aqueous layer extracted with a further 15ml of DCM, and DCM layers combined.
11. DCM dried using anhydrous MgSO4, then decanted and evaporated down (outside, warm day).
12. An oil remained which solidified at room temp into a crystalline pale yellow solid.
13. 0.5g obtained whose melting point range was found to be 34-37C.

Ponderings:

- This was a total guess and we figured we'd see what would happen if periodate and permanganate were combined. We're still not totally sure if the periodate is really playing a responsible role here, but this is the best yield by far we've ever got, an isolated product, and what seems to be a relatively high purity.
- Crude yield is 20% (3.3 mmol) of piperonal from starting piperinic acid.
- Aroma is an incredible vanilla + cherries + toasty buttery ('jelly belly toasted marshmallow flavour') scents. Even slightly 'soapy' and balsamic.

Complete video of the process is here: https://www.youtube.com/watch?v=6r9elLR2WjI

Watch some vintage ChemPlayer: https://www.bitchute.com/channel/chemplayer/
clearly_not_atara
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If you have any more piperic acid, there's an interesting variation where FeSO4 is used to halt the oxidation at the aldehyde stage:

 Quote: The oxidation of ethyl alcohol by the action of potassium per- manganate was first reported by Morawski and Sting1 (72) who found that the alcohol was oxidized to acetic acid. The acid in turn combined with excess of the permanganate to produce po- tassium acetate and a brown unidentified precipitate was formed. Doroshevskii and Bardt (31), working under these conditions, found that with the inclusion of ferrous salts as catalysts in the oxidation of ethyl alcohol by potassium permanganate, the results varied with the catalyst selected. If ferrous sulfate was em- ployed the oxidation stopped with the formation of acetaldehyde, but if ferrous oxalate was used as the catalyst, the product was a mixture of aldehyde and acetic acid.
(^the above procedure is for ethanol, but we were speculating it could extend to alkenes)

There is also a procedure which uses triethylbenzylammonium permanganate as a homogenous oxidant in DCM solution, quenched with aqueous AcOH to yield aldehydes selectively (Et3BnNCl + KMnO4 (DCM) >> Et3BnNMnO4 sol'n):

 Quote: The procedure is as follows: To a stirred solution of endo-dicyclopentadiene (2.27mmol) in dichloromethane (20ml) was added drop- wise the oxidant solution freshly prepared with KMnO4(3.41mmol),7 triethylbenzylammonium chloride (3.41mmol) and dichloromethane (40ml) at such a rate that the temperature was maintained at 0-3°C under cooling with an ice-bath (40-50min). After addition was complete, stirring was continued until permanganate ion was completely consumed (30-40min). The homogeneous dark brown solution was then treated with aqueous solutions of variant pH. When the reaction mixture was treated with 3% NaOH solution (30ml) under nitrogen atmosphere at room temperature for 18 hours, a crystalline product (2), mp 47-52° (lit. 48-51°), was obtained in 83% yield from the organic layer upon usual work-up. The product was identified as the exo,cis-diol (2) by its ir and nmr data, which was previously obtained in 28% yield by the oxidation of endo-dicyclopentadiene in EtoH with aqueous potassium permanganate.8 No other products were detected on tlc and glc. On the other hand, when the reaction mixture was treated with an acetate solution (30ml) at pH 3, the dialdehyde (3), mp 42-44° (lit. 36-42°), was obtained in 81% yield as the single product(tlc,glc). The compound (3) is known as a key intermediate for prostaglandin synthesis and has been synthesized indirectly through periodate oxidation of the diol (2).

The last procedure which I think is really cool is to use horseradish peroxidase, which cleaves anethole (and piperic acid is pretty similar!):

 Quote: Mutti et al. have recently shown that some peroxidases (i.e., horseradish peroxidase, lignin peroxidase, and Coprinus cinereus peroxidase) catalyse the cleavage of a C=C double bond adjacent to an aromatic moiety for selected substrates at the expense of molecular oxygen and at an acidic pH (Scheme 5) [32]. Among the three active peroxidases, HRP turned out to be the most active when an equal concentration of enzyme was employed. A thorough study of the reaction showed that the highest activity was obtained at ambient temperature, at pH 2, and at 2 bars of pure dioxygen pressure. Addition of DMSO as cosolvent up to 15% v v?1 increased the conversion, probably due to the improved solubility of the substrates in the aqueous reaction medium, while a further addition of DMSO led to a progressive decline of the enzymatic activity. Using trans-anethole as substrate (9) (6 g L?1 ) and HRP at low catalyst loading (3 mg, equal to 0.2–0.3 mol%), quantitative conversion was achieved within 24h. The main product was para-anisaldehyde (11) (i.e., 92% chemoselectivity), whereas the side product accounted completely for the vicinal diol (12). The substrate spectrum was quite narrow, since only other two substrates, that is, isoeugenol (10) and indene (13), could be cleaved by HRP with 12% and 72% conversion, respectively.

I'm not entirely sure how to extract horseradish peroxidase from horseradish, but it offers a manganese-free -- hence nontoxic - cleavage of this substrate.

[Edited on 4-7-2016 by clearly_not_atara]
chempropharm
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Nice work.. just a question..

If oxidation of piperine will do the job.. why going to piperic acid intermediate step?
Mush
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 Quote: Originally posted by chempropharm Nice work.. just a question.. If oxidation of piperine will do the job.. why going to piperic acid intermediate step?

Yes, it will do the job .

Forensic Sci Int. 2012 Nov 30;223(1-3):306-13. doi: 10.1016/j.forsciint.2012.10.006

2.4. Piperonal from pepper
2.4.1. Oxidative cleavage of piperine by ozonolysis

A stream of ozone gas. generated by a HAILEA HLO 100 Ozone Steriliser
(— 100 mg of ozone per hour), was passed through a solution of piperine (1.00 g. 331 mmol) in a 5% solution of water in acetone. After 8 h. the ozone generator was switched off and the solution extracted with two 10 mL portions of diethyl ether. The combined ether extracts were dried over anhydrous sodium sulphate and the solvent evaporated in vacuo yielding bright yellow oil. Yield: 508 mg (97%). 'H NMR: see Fig. SI3. GC-MS: see Fig. 2.

2.42. Oxidative cleavege of piperine with aqueous KMn04 in THF
An aqueous solution of KMn04 (2.00 g. 12.6 mmol in 40 ml. of water) was added dropwise over a period of 4 h to a solution of piperine (1.00 g. 3.51 mmol in 40 mL of THF] at 60 C. After the solution had been added, the mixture was stirred for 4 h before the MnO2 precipitate that had formed was filtered off leaving a pale yellow solution. The sample was extracted with diethyl ether and the combined extracts were dried over anhydrous sodium sulphate. The ether was evaporated in vacuo to
yield a dark yellow orange oil that solidified on cooling. Yield: 340 mg (65%). 'H NMR: see Fig. SI4. GC-MS: see Fig. 2.

I believe the authors used this paper as reference:
1, https://erowid.org/archive/rhodium/chemistry/alkene2aldehyde...
2,
 Code: https://pubs.acs.org/doi/abs/10.1021/jo800323x

It worked as it was predicted by Hive members.

Note:
Ozonolysis yields a mixtures of piperonal (1, GC) and 3,4 methylenedioxycinnamaldehyde (6).
Aqueous KMn04 in THF results less byproducts.

[Edited on 3-8-2019 by Mush]
Mush
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Odorographia a natural history of raw materials and drugs used in the
perfume industry intended to serve growers manufacturers and consumers.

John Charles Sawer, 1892, London

Artificial Heliotrope

Piperonal, C8H6O3, , commercially known as " Heliotropine,"
has a very agreeable odour very much like that of heliotrope. The
starting-point in its manufacture is Piperine, C17H19O3. Ground
pepper, preferably the white Singapore pepper, as it contains the
largest amount of alkaloid (9.15 per cent.), is mixed, with twice
its weight of slaked lime and a sufficient quantity of water; the
solution is then evaporated to dryness on a water-bath and the
powder exhausted with commercial ether, from which the piperine
can be obtained nearly pure on evaporation, in large crystals of a
faint straw-yellow colour. To obtain it perfectly pure, it must be
dissolved in alcohol and re-crystallized. Another process of
preparing piperine is to exhaust the pepper with alcohol of sp. gr.
0*833 and distil the tincture to the consistence of an extract.
This extract is to be mixed with potash-lye, which dissolves the
resin and leaves a green powder; by washing this in water, dis-
solving in alcohol, crystallizing and re-crystallizing, it is obtained
colourless *. *Poutet, Journ. de Chim.Med. i.p. 531.

Piperine is converted into potassium piperate by boiling it for
24- hours with its own weight of caustic potash and from 5 to 6
parts of alcohol in a large retort, using an inverted Liebig's
condenser. On cooling, the potassium piperate crystallizes out in
shining yellow laminae. It is washed with cold alcohol and
re-crystallized from hot water. If coloured, it is bleached by animal
charcoal. As thus obtained, it is in nearly colourless crystals,
which become yellow under the influence of light.
One part of potassium piperate is dissolved in from 40 to 50 parts
of hot water, and a solution of 2 parts of potassium permanganate is
gradually poured into the hot liquid with constant stirring. Each
drop of the latter is almost instantly dissolved, and the solution
acquires a very pleasant odour. A pasty mass of brown manganic
hydrate separates, which is placed on a filter and washed with hot
water until the washings cease to smell of heliotropine. These
washings are added together and the whole distilled over an open
fire. The first portions of the distillate contain the largest
proportion of piperonal, the greater part of which crystallizes out
on cooling. The remainder may be obtained by agitation with
ether *. * Chemiker Zeitung, Feb. 1884, and Ann. Ch. Pharm, clii. p. 35.

Piperonal crystallizes from water in colourless, transparent,
highly lustrous prisms, an inch long. It is sparingly soluble in
cold water, easily in cold alcohol, and in all proportions in boiling
alcohol or ether. It melts exactly at 37° and boils without
decomposition at 263°, forming a vapour which has a sp. gr. of 5.18+.
Tiemann and Haarmann state" that the odour of piperonal is
possessed by 'vanillon' a kind of vanilla, which forms thick, fleshy
capsules and is obtained from the West Indies. This sort of vanilla
is employed in perfumery for the preparation of essence of
heliotrope; it contains no piperoral, but vanillin and an oil which
is not yet identified. The perfumers, in preparing essence of
heliotrope, add a little of this oil to the extract of vanillon. If a
little be added to a solution of pure vanilllin, both substances can
be recognized by their smell for some time, but after standing for
months the mixture acquires the smell of heliotrope."
The perfume of " Heliotropine " is completely destroyed by the
action of direct sunlight; it is also injured by heat; it should
therefore be stored in a cool place in the dark, such as a cool cellar,
and be kept in yellow glass bottles, the yellow glass intercepting
the chemical rays.

Attachment: heliotropine, piperonal John Charles Sawer, 1892, London, pages 187-189.rar (637kB)
Mush
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A practical treatise on the manufacture of perfumery

Carl Deite, William T. Brannt, 1892, Philadelphia

Heliotropin or piperonal is of great importance in
the manufacture of perfumes. It forms small, colorless
prismatic crystals, which have an agreeable odor of
heliotrope. Upon the tongue heliotropin produces the same
sensation as oil of peppermint under the same conditions,
the sensation being, however, more lasting. It melts at
about 104 F., and volatilizes at a higher temperature
without leaving a residue. It is soluble in alcohol and
ether, and insoluble in cold water ; in hot water it melts
to an oily liquid which floats upon the water.

Exposed to the action of heat and air, heliotropin
acquires an uncomely appearance, balls together and, under
very unfavorable circumstances, turns brown. It is
then entirely decomposed and useless, and, hence, should
be kept in summer in as cool a place as possible. A
temperature of 95 F. has already an injurious effect
upon the perfume, and it is best not to buy it at all in
the hot summer months. To preserve the perfume in
its entire freshness, it is advisable for consumers in hot
climates to at once dissolve the heliotropin in alcohol
and to keep the solution in a cool place.

Pepper serves as the initial point for heliotropin or
piperonal, the white variety being the best for the purpose.
To obtain piperine, contained in varying quanties
(7 to 9 per cent.) in pepper, the latter is repeatedly
extracted with boiling alcohol. The extract is then
evaporated to one-third its volume, or the greater portion
of the alcohol is distilled off, and the resinous mass,
obtained after the addition of water, is repeatedly washed
in water with the addition of a small quantity, of potash
or soda lye, dissolved in alcohol and purified by repeated
recrystallization. To convert the white-yellow piperine
thus obtained into potassium piperate it is, together with
equal parts of potassium hydroxide and 5 to 6 parts of
alcohol, kept gently boiling for 24 hours in a well-closed
flask provided with an ascending Liebig cooler. A
capacious flask should be used, as the mass pounds quite
vigorously. After cooling, the precipitate, which is
obtained in yellowish, lustrous lamina, is separated through
a filter from the dark-brown mother-lye, washed with
cold alcohol and several times recrystallized from hot
water. A further discoloration may be effected by the

The potassium piperate thus obtained forms nearly
colorless prisms in verucose groups, which, however,
turn yellow when exposed to light. By boiling the
alcoholic mother-lye with 1/3 of the previously used potash-
lye, further small quantities of potassium piperate may
be obtained.

To obtain piperonal from the potassium piperate,
dissolve 1 part of the latter in 40 to 50 parts of hot water,
and then slowly introduce, with constant stirring, a
solution of 2 parts potassium permanganate in 50 parts of
water. This precaution is absolutely necessary, as
otherwise the piperonal formed would be partially further
oxidized and lost. The paste-like mass formed is passed,
while still hot, through a straining cloth, and the residue
repeatedly washed with boiling water until it shows
nothing more of the characteristic odor of heliotrope.
The wash-waters are combined with the first filtrate,
and subjected to distillation over a free fire.

The first distillates are richest in piperonal, it
generally separating already in the cooler. The fractionally
caught distillate is allowed to stand one or two days in
as cool a place as possible, whereby the greater portion
of the piperonal separates in a crystalline form or in fine
lamina. To obtain the piperonal still remaining
dissolved in the water, the mother-lye, after the separation
of the crystals through a filter, may be repeatedly
agitated with ether, whereby the piperonal dissolves in the
ether. The latter is carefully distilled off at as low a
temperature as possible (104 to 122 F.) in the water-bath
or allowed naturally to evaporate.

A practical treatise on the manufacture of perfumery 1892 Piperonal See page 193.djvu

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