nimgoldman
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Understanding a paper on eugenol extraction from clove oil
I found the following 2015 article about isolation of eugenol from clove oil:
Reactive Extraction Process in Isolation of Eugenol of Clove Essential Oil ( Syzigium aromaticum ) Based on Temperature and Time Process
The paper focuses on an efficient extraction method as there is a growing demand for eugenol in the industry (dentistry, perfumery etc.).
Here is a copy of the abstract for convenience (everything important is already said in the abstract):
| Quote: |
The purpose of this study was to obtained optimum conditions a reactive extraction process in isolation eugenol from clove essential oil associated
with the temperature and time process. Research stage begins by inserting a 100 ml clove essential oil and 0.8 N NaOH solution at a ratio of 1:1.1 to
the reactor. Turn on the hot plate and set the appropriate reaction temperature variables of the study (30, 40 and 50°C) and set the stirrer speed of
100 rpm. After a reaction time achieved according to the study variables (15, 30, 45, 60 and 75 minutes) the reaction product was then separated. The
bottom layer was Na-eugenolat (aqueous layer) and the top layer was organic layer. Na-eugenolat (aqueous layer) was then added 5 N HCl to obtain a pH
of 4. Before placing distillation flask, Na-eugenolat that has been mixed with HCl silenced while for NaCl precipitate formed, then the newly inserted
distillation flask which had been fitted condenser and thermometer. The mixture was then heated with a hot plate at a temperature of 195C and vacuum
pressure of 6.10 kPa for 30 minutes. Distillate was eugenol and the residue was NaCl residual reaction products. |
So they basically heat clove oil with aqueous sodium hydroxide (molar equvalent to the expected eugenol content) while stirring. The eugenol in clove
oil forms a water-soluble salt which is extrated by means of layer separation. The resulting aqueous extract is then acidified and the eugenol is
vacuum-distilled.
The acidified extract should contain oily precipitate of eugenol (clouding the solution instead of making clear layers), sodium chloride (resulting
from neutralization reaction) and some excess hydrochloric acid.
However, the (vacuum) distillation of this solution should yield a water-eugenol mixture not pure eugenol as the article proposes:
| Quote: | | Na-eugenolat (aqueous layer) was then added 5 N HCl to obtain a pH of 4. Before placing distillation flask, Na-eugenolat that has been mixed with HCl
silenced while for NaCl precipitate formed, then the newly inserted distillation flask which had been fitted condenser and thermometer. The mixture
was then heated with a hot plate at a temperature of 195C and vacuum pressure of 6.10 kPa for 30 minutes. |
This does not make much sense: "Na-eugenolat that has been mixed with HCl silenced while for NaCl precipitate formed" - there is a bad english in the
paper and makes it hard to me do decipher. Do you have any idea?
Did they add sodium chloride to salt out eugenol and then separated the resulting layer prior to vacuum distillation?
I think to obtain pure eugenol, one should extract it from acidified extract with something like DCM, then dry the solvent with e.g. anhydrous sodium
sulfate, then evaporate DCM (e.g. with the help of rotavap), filter off the drying agent and finally vacuum-distill the resulting eugenol (to remove
traces of insoluble impurities).
I think mere vacuum distillation of the acidified extract nor the separated eugenol layer won't work.
What do you think?
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Boffis
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Given the phenolic nature of eugenol I don't see much mystery here. Eugenol is a substituted phenol and I suspect that like many phenols it acts like
a weak acid, dissolving in strong alkali solution from which it is liberated by acid.
The language in the paper, however, is another matter.
The main issue looking at your quotations is the ratio of oil to 0.8M NaOH solution of 1 to 1.1. I was under the impression that Clove oil contains
about 80-90% eugenol and has about the same density as water so 100ml should contain about 0.5M of eugenol. Therefore you would need at least 0.5M of
NaOH, say 20g assuming that eugenol reacts as a monobasic acid but 110ml of 0.8M NaOH contains only about 3.5g of NaOH. Are you sure that it says 0.8M
(normal) NaOH and not 8M (8N)?
[Edited on 13-7-2018 by Boffis]
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DraconicAcid
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Agreed. After acdification, extract with an organic solvent and dry with sodium sulphate.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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nimgoldman
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Yes, you can click on the link in OP to see the original paper - it's right in the abstract. I really just copy-pasted the text.
I think they assumed something like 80% purity of the clove oil (which justifies the 0.8 N NaOH concentration), then adjusted it to 1:1.1 instead to
1:1 to add 10% of the solution more to be on the safe side and make sure all the eugenol in 80% oil will get converted.
Maybe they don't get the chemistry right.
It is not completely liberated by acid. Right now I am watching a beaker with eugenol solution with acid added (pH is below 1.0) and the water is
cloudy, not separating to layers at all.
This is where the mystery comes. The author of the paper does not use any organic solvents, they went straight to vacuum distillation.
I think extraction with organic solvent with subsequent drying is really needed. I will look up more literature on the topic...
The article was tempting since it promises to get relatively pure eugenol without using liters of solvent to extract something like 100 ml. I am not a
chemist so I am putting the puzzle together, trying to find economical way of clove oil purification without using excess of solvents or other
chemicals.
[Edited on 15-7-2018 by nimgoldman]
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nimgoldman
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Okay after 30 minutes of stirring, a brown oily precipitate settled on the bottom which I believe is the purified clove oil, i.e. 98% eugenol. I am
afraid it has decomposed a bit as it should be lighter in color (pale yellow, not brown).
I have extracted the oil with four portions of DCM even though the method in original article does not mention use of any organic solvent (!).
Maybe the method in original article is meant to just purify the clove oil a bit, not to extract almost pure eugenol (even though the article title
suggests that).
So - even at 2:1 solvent : oil ratio, processing something like 300 ml of oil would need several liters of DCM (as several pulls are needed and some
more for washing). I though extracting eugenol from clove oil would need much less solvent but it is maybe just the cost of having isolated chemical
at that purity.
 
[Edited on 15-7-2018 by nimgoldman]
[Edited on 15-7-2018 by nimgoldman]
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nimgoldman
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So today I've tried to strip DCM off the eugenol extract (attached image of my apparatus - a simple distillation basically).
The textbook I used said DCM can be distilled off eugenol at 40 °C.
Well that didn't work. I heated the water bath up to 60 °C (with strong stirring) and even pulled 400 mmHg of vacuum and DCM was still coming over.
I think the only effective method for removing DCM is by using a rotavap.
My eugenol looks somewhat dark. I am afraid I overdid it with the acidification step.
I still believe there is an easier method than using lots of solvent - maybe just leaving the acidified liquor sit for a day or two, then separate the
eugenol layer with a sep. funnel and then dry it directly, using distillation or using minimum amount of solvent and drying agent. OR maybe by freeze
separation.
The small amount of water in the eugenol is really not a problem as long as it won't affect its shelf life (I intend to store it in freezer until
further experimentation).
What do you think?
[Edited on 17-7-2018 by nimgoldman]
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DraconicAcid
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Just keep heating it to 60 oC until DCM stops coming over.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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nimgoldman
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Okay so here is my somewhat successful experiment with eugenol isolation from clove oil.
First I prepared acid and base solutions. The acid should be 5M HCl which is close to 5% so I've just used the pre-made 5% HCl I already had. I made
110 ml of 0.8M NaOH (it took 3.52 gams of NaOH):
Next I measured 100 ml of store-bought clove oil:
This has been added to the NaOH solution while moderately stirring and heating - a clouds of precipitated sodium eugenate appear:
The mixture was stirred for 30 minutes at around 40 °C, then transferred to a 250 ml separatory funnel and left to stand for 24 hours. You can see
the bottom aqueous layer containing the product already separates from the organic layer:
The next day, the bottom layer was flushed in a beaker. It was of somewhat syrupy consistency, dense but still pouring easily:
Here are the organic and aqueous phases separated side by side:
Now for the acidification step. I slowly poured the HCl solution by about 10 ml steps to the aqueous eugenolate while stirring:
The pH started at 11.0 and dropped to about 9.0 when acid was added, but quickly returned to 10.0-11.0 range.
Finally the equilibrium was broken and pH started dropping in the acidic range:
Unfortunately it kept dropping under 1.0 so I definitely overshoot it with total of 134 ml 5% HCl. One should be much more careful and wait until pH
stabilizes before each addition.
Anyway. I poured the solution already showing oily bubbles of eugenol in a 1L sep. funnel:
Eugenol quickly consolidates:
I extracted the eugenol with 150 ml of DCM and this was a really clean separation - you can see the bottom DCM layer took up practically all the
eugenol:
In the second extraction (with 100 ml DCM), the DCM layer was only faintly brownish:
I did a third extraction with 50 ml DCM just to be sure everything got extracted.
The combined extractions:
Next I washed the DCM extract with 100 ml dH2O and then with 100 ml 23% saline:
The washed extracted was then mixed with 60 grams of anhydrous sodium sulfate to dry the organic:
The drying agent was filtered off - I should have washed it with fresh dry DCM by this is an experimental run and I believe much eugenol won't be
lost:
Finally a I set up a simple distillation and boiled off most DCM with 60 °C water bath while stirring to even out boil:
I added some alu foil insulation by the end of the distillation to allow last bits of DCM to come over instead of refluxing:
Now it looks like all DCM has boiled off:
Unfortunately, by raising temperature, the liquid started boiling again. I raised the temperature to about 80 °C and waited until boiling ended.
Finally, I pulled some vacuum (-500 mmHg) and see the boiling again!
It took some time, vacuum and temperature (up to 97 °C) until no more DCM seemed to come over.
I think there is still some in the eugenol and the mixture boils at much higher temperature then the b.p. of DCM. I think the only effective way to
remove solvent would be a rotary evaporation, not just distillation at atm. pressure as I read in the literature.
Anyway - I cooled and trasferred the product in a bottle. I haven't smelled any DCM from it, maybe a very faint trace but this can as well be the
eugenol itself.
The total amount of the product is 82 ml of eugenol (~98%) from 100 ml of clove oil, which is the expected yield from a quality oil.
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Boffis
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nimgoldman; a few points and thoughts.
5M hydrochloric acid is about 18% w/v.
The amount you used to neutralize the final extract though was 134ml which is about 6.7g of HCl (assuming 5% w/v) or 0.184 mole. Roughly twice the
amount required to neutralize the 3.52g of NaOH.
Assuming that eugenol acts as a monobasic acid and has a MW of 164.2 your 3.52g (=0.088 moles) of NaOH would only extract 14.45g of eugenol as an
anion. So what is all the rest?
In the original paper the ration figure is not clear but we all seem to have interpreted it as a simple ratio of volumes ie clove oil to 0.8M NaOH
solution but it could be molar ratio of clove of to alkali. In which case you would need about 650-700ml of 0.8M NaOH solution.
Since you seem to have got a better yield than is theoretically possible it raises the question about what you are actually extracting, clearly not
eugenol as a eugenolate anion. I wonder if the eugenolate ion acts as a surfactant and simply emulsifying the oil? Though from your disruption this
does not appear to be the case. However, if it is then the oil you are recovering may be no purer than the starting material.
If I were doing this I would add enough NaOH to extract say 90% eugenol and ten extract the non-ionisable materials with say petroleum ether allowing
plenty of time for the emulsion to separate out (overnight). Separate of the aqueous layer, treat with decolourizing carbon and then add just enough
acid to neutralize the NaOH. You can then use a DCM or similar extraction for the eugenol.
If you heated the DCM extract to 60C under even modest aspirator vacuum I am pretty sure that you will have removed all of the solvent. What makes you
think that you haven't?
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nimgoldman
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I see. I forgot to adjust my source HCl weight by its concentration to get actual hydrogen chloride weight...
It seems not all eugenol has been converted, the aqueous-organic separation was not complete and unconverted eugenol with other stuff has been picked
up by DCM. One such thing could be eugenol acetate.
However, the yield of about 80 ml from 100 ml of clove oil was pretty much the expected amount.
I don't understand the amount in the paper. It seems too little NaOH is used...
This also does not explain why pH was so high (11.0) since all the NaOH should have been consumed by excess eugenol to form Na-eugenate.
Assuming the clove oil is already 100% eugenol, 100 ml of it should contain 106 grams of eugenol (based on density), that is 0.645 mol.
0.645 mol of NaOH is 25.8 grams. Way more than proposed.
According to paper, one should use 110 ml 0.8M NaOH per 100 ml clove oil. 0.8M NaOH is about 32 grams per liter and 110 ml of it is therefore 3.5
grams - what??
They actually used normal concentration (0.8N) but this is equivalent to molar concentration in case of strong bases like NaOH, right? Maybe they
assumed 80% eugenol and 0.8N meant exactly that - molar equivalent to expect eugenol content.
BTW I've seen someone did just vacuum fractional distillation of clove oil to recover eugenol. This seems much easier than a tedious and messy A/B
extraction.
[Edited on 23-7-2018 by nimgoldman]
[Edited on 23-7-2018 by nimgoldman]
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nimgoldman
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Okay so this time I have added 26 grams of NaOH (molar equivalent to 100 ml of pure eugenol rounded up) to 110 ml water and after it dissolved and
temperature was set at 40 °C I added the clove oil.
After about 50 ml of the oil added, the solution solidified:
This indicates the authors of the article probably used weaker NaOH solution or their oil was much lower quality.
So I added 90 ml more water (200 ml in total) and stirred it up until everything dissolved.
The solution is still somewhat thick. I don't know if it's a good or bad thing. One one side, there will be more intimate contact between the
reactacnts, one the other side the may dissolve badly and the layer separation won't be clean.
I will probably dilute it some more (to 300 ml, therefore having 3:1 basic water : oil ratio).
[Edited on 23-7-2018 by nimgoldman]
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Tsjerk
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Please redo your molar calculations, you are off by a magnitude as mentioned before. Please redo them and check here if you did them correctly.
When boiling of DCM have a bit more patience. In mixtures boiling points are not absolute. Better maintain a lower pressure overnight at room temp
than to go all the way too 90-something. I think that is your reason for the brown color.
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nimgoldman
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Quote: Originally posted by Tsjerk  | Please redo your molar calculations, you are off by a magnitude as mentioned before. Please redo them and check here if you did them correctly.
When boiling of DCM have a bit more patience. In mixtures boiling points are not absolute. Better maintain a lower pressure overnight at room temp
than to go all the way too 90-something. I think that is your reason for the brown color. |
I redid the calculations three times already and re-checked with online calculator:
molar masses:
eugenol 164.20 g/mol
NaOH 39.99 g/mol
HCl 36.46 g/mol
100 ml clove oil (assuming 100% eugenol) = 106 g eugenol = 106/164.2 = 0.6455 mol
0.6455 mol of NaOH is 0.6455 * 39.99 = 25.81 grams of NaOH required to react with our 106 grams of eugenol
...
Now the HCl. 0.6455 mol * 36.46 = 23.53 grams of HCl
1000 ml of 35% HCl solution weighs 1180 g, therefore contains 413 g HCl
23.53 g of HCl is therefore 1000 ml * 23.53 g / 1180 g = 19.94 ml of 35% HCl ... this amount will be diluted to allow for titration
...
Please let me know if there are any mistakes.
...
BTW the separatory funnel now shows only a thin organic layer - which makes much more sense than previously - since most (over 80%) of the oil should
have dissolved in the aqueous layer.
...
| Quote: Originally posted by Tsjerk | | When boiling of DCM have a bit more patience. In mixtures boiling points are not absolute. Better maintain a lower pressure overnight at room temp
than to go all the way too 90-something. I think that is your reason for the brown color. |
The distillation took almost 3 hours and only then I increased heat and vacuum only to observe boiling. Maybe the solvent would go away overnight but
my setup unfortunately does not allow unsupervised process. Thanks, I will be more careful about that. I haven't observed a single drop in two minutes
so I assumed nothing will come over.
Unfortunately I have just a hand pump ... I will store the DCM-eugenol until a proper vacuum pump and rotavap arrive and remove the solvent then. Only
hope the DCM won't attack the eugenol smh.
[Edited on 23-7-2018 by nimgoldman]
[Edited on 23-7-2018 by nimgoldman]
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Tsjerk
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I thought you were still using the 0.8 molar NaOH, so yes, the 26 gram should be enough. If you think all DCM came of that should be fine. Can you try
to freeze your eugenol in a freezer? It should freeze at -7,5 degrees, a little of DCM should lower that considerably.
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nimgoldman
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| Quote: Originally posted by Tsjerk | | Can you try to freeze your eugenol in a freezer? It should freeze at -7,5 degrees, a little of DCM should lower that considerably.
|
Yes I did that and will see tommorow.
It seems all the eugenol have been dissolved in water as sodium salt. The remaining organic layer is only 12 ml or so (88% of the oil dissolved - this
correspond to typical eugenol content):
It took almost 400 ml of 5% HCl to acidify the aqueous extract:
The eugenol layer is dark-brown:
I did three extractions with DCM: 200 ml, 100 ml and 50 ml.
In the last extraction, the DCM layer was very slightly tinted and the aqueous layer stays murky:
I have dried and filtered the combined DCM extract. I've put it in a freezer set to -20 °C so I will see the next day how it goes.
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nimgoldman
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The freeze separation didn't work well, at least not down to -12 °C. There was only tiny lining of solids that quickly dissolved after removing the
bottle from the freezer. It might work with lower temperatures.
So my final working procedure for eugenol isolation from clove oil is the following:
- dissolve 26 grams (excess) of NaOH in 300 ml water
- add 100 ml of clove essential oil while stirring
- stir for 30 minutes at 40 °C
- transfer the liquid to a separatory funnel and let it sit for 24 hours for full phase separation
- drain the bottom aqueous layer to a 1L beaker (discard the top organic layer containing mostly eugenol acetate and beta-caryophyllene)
- while stirring, slowly add 15% HCl - a little over 100 ml should suffice - the solution will turn cloudy, then milky with oil droplets, then
brownish; keep adding acid slowly until pH 4.0 is reached
- transfer the liquid to a 1L separatory funnel
- extract three times with DCM (200 ml, 100 ml, 50 ml), discard the liquid
- wash the DCM extract with 100 ml distilled water and then with 100 ml 23% saline
- dry the DCM extract with 50 grams (or more if necessary) of anhydrous sodium sulfate - this can be done by magnetically stirring the solvent with
drying agent for 30 minutes
- filter the DCM extract
- set up a simple distillation, distill off the DCM using hot water bath (60 °C), when no more DCM comes over, slowly pull vacuum up to 500 mmHg and
wait until no solvent comes over; of course, this step can be done conveniently using a rotary evaporator
- the distillation flask now contains approx. 98% eugenol, store it in a sealed (preferably dark) bottle in the fridge
I will later test the extract using TLC and some suitable reagent (e.g. ferric chloride).
If you have any improvements to the method, I welcome it.
[Edited on 27-7-2018 by nimgoldman]
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S.C. Wack
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I didn't see a step where the phenolate is washed with solvent...it could be included...when solvents are part of the process anyways. I'd expect
phenol/phenolate to absorb carbon dioxide and oxygen while stirring in beakers.
For large scale efficiency in these chemophobic times, one would think solvent free methods at the site of the clove oil manufacture would be desired.
The hydroxide exposure might as well be hot and long enough for hydrolysis but not isomerization of whatever, and if (IF) eugenolate perhaps dissolved
in say 2% hydroxide is stable at 100C, steam alone might purify it? Why not then just add CO2 to get maybe rather decent phenolic steam distillate,
and carbonate solution for CO2 generation?
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nimgoldman
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| Quote: | I didn't see a step where the phenolate is washed with solvent...it could be included...when solvents are part of the process anyways. I'd expect
phenol/phenolate to absorb carbon dioxide and oxygen while stirring in beakers.
For large scale efficiency in these chemophobic times, one would think solvent free methods at the site of the clove oil manufacture would be desired.
The hydroxide exposure might as well be hot and long enough for hydrolysis but not isomerization of whatever, and if (IF) eugenolate perhaps dissolved
in say 2% hydroxide is stable at 100C, steam alone might purify it? Why not then just add CO2 to get maybe rather decent phenolic steam distillate,
and carbonate solution for CO2 generation? |
This is why looked over and under but haven't found any solvent-free method to isolate eugenol. The one I found did not work and this is the very
reason for this thread.
The only eugenol isolation methods I found were all about this acid/base extraction with some nonpolar solvent (hexane, DCM etc.) - usually lab
practice protocols from schools. They never use solvent washing though - one method uses water and saline to wash DCM which I used.
Perhaps the most efficient method would to simply fractionally distill the clove oil (under vacuum), separating the middle fraction. Or steam
distillation of the acidic water with eugenol to liberate it from salt, then simply phase separate eugenol from water and dry (don't know how - are
there suitable drying agents for eugenol oil?)
| Quote: | | Why not then just add CO2 to get maybe rather decent phenolic steam distillate, and carbonate solution for CO2 generation? |
Unfortunately, I have no idea what this means. You mean steam distillation under CO2 to avoid some kind of decomposition or oxidation of the product?
Please note I don't need neither large scale nor food grade eugenol. Just couple 100s of milliliters for my home lab syntheses.
[Edited on 28-7-2018 by nimgoldman]
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S.C. Wack
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Surely such washing isn't common practice, but I wonder if common practice is for the best here. There is some old clove powder around...shouldn't be
too much trouble but there's carpentry in the lab...fractionation of clove oil would be best done after further cleanup especially of terpenes and
esters.
| Quote: Originally posted by nimgoldman | | Unfortunately, I have no idea what this means. You mean steam distillation under CO2 to avoid some kind of decomposition or oxidation of the product?
|
Giving a flying fuck much less understanding is of no concern it's something I thought to add to this thread as is. CO2 if it is so easy could be
added with or without the steam after terpenes etc. have gone, but I'm thinking with the steam here, the steam being the final purification; the
eugenol never seeing nonaqueous solvent, acid stronger than carbonic, or temperature higher than the steam, assuming that's worth something. But the
reality of my unknowing and as said the reactivity and volatility of eugenol at high enough temperature and hydroxide concentration may intrude.
| Quote: Originally posted by nimgoldman | | Please note I don't need neither large scale nor food grade eugenol. Just couple 100s of milliliters for my home lab syntheses.
|
Please note I may comment on statements such as these regardless of what scale you're working on or how you're doing it.
| Quote: Originally posted by nimgoldman | The paper focuses on an efficient extraction method as there is a growing demand for eugenol in the industry (dentistry, perfumery etc.)...
...I think to obtain pure eugenol, one should extract it from acidified extract with something like DCM |
[Edited on 28-7-2018 by S.C. Wack]
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andy1988
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| Quote: Originally posted by nimgoldman |
The paper focuses on an efficient extraction method as there is a growing demand for eugenol in the industry (dentistry, perfumery etc.).
|
You've piqued my interest. Sore tooth? 
The authors left some lack of specificity about what "clove oil" was used in their experiment. They don't specify part of plant or explicitly specify
the extraction method which are both pertinent information when dealing with composition. But I suppose everything looks similar enough it shouldn't
matter? In other essential oils there are more substantial differences in composition between plant parts.
They paraphrase sampled compositions of both Syzigium aromaticum and Syzigium caryophyllatum:
| Quote: | Clove essential oil (Syzigium aromaticum L. Myrtaceae) were isolated by hidrodestilasi process, from the analysis of GC-MS has the composition of
eugenol (88.58%), β-caryophyllene (1.39%), 2-heptanone (0.93%) , ethyl hexanoate (0.66%), humulenol [3].
Essential oil of clove leaf (Syzigium caryophyllatum (L.) Alston) from Bangladesh were isolated by hidrodestilasi process, from the analysis of GC-MS
has the composition of eugenol (74.3%), eucalyptol (5.8%), caryophyllene (3.85% ) and αcadinol (2.43%) [4]. |
Following are excerpts from the book Essential Oil Safety: A Guide for Health Care Professionals 2nd Edition, by Robert Tisserand and
Rodney Young, published 2014.
Botanical name: Syzygium aromaticum (L.) Merill et L.M. Perry
Source: Dried flower buds
Key constituents:
Eugenol 73.5–96.9%
b-Caryophyllene 0.6–12.4%
Eugenyl acetate 0.5–10.7%
a-Caryophyllene 0.4–1.4%
Isoeugenol 0.1–0.2%
Methyleugenol 0–0.2%
(Kubeczka 2002, Lawrence 1981 p33–34, 1993 p.36)
Source: Leaves
Quality: May be adulterated with clove stem oil (Singhal
et al 1997).
Key constituents:
Eugenol 77.0–88.0%
b-Caryophyllene 3.5–6.4%
a-Caryophyllene 0.8–1.4%
Eugenyl acetate tr–1.2%
Isoeugenol tr
(Lawrence 1995g p178, p. 198)
Source: Stems
Key constituents:
Eugenol 76.4–84.8%
b-Caryophyllene 3.5–12.4%
Eugenyl acetate 0.4–8.0%
a-Caryophyllene 1.0–1.5%
Isoeugenol 0.1–0.4%
(Lawrence 1993 p. 36, 1995g p. 178, p.198)
This book doesn't exhaustively list constituents due to lack of space. I expect in each case the literature cited should list complete GC-MS
interpretation and method of extraction (the literature cited might also be literature reviews given the composition ranges). It is a great book I
recommend it... a great deal of information in it, with particular attention to allergens/safety.
I'm certainly beginner chemist as well, so I'm not really able to offer much advice there. But I'm guessing, given the information I've provided,
your extraction should also have Methyleugenol and Isoeugenol in it given their similarity to eugenol? Thanks for sharing!
[Edited on 29-7-2018 by andy1988]
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nimgoldman
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Thanks for the results of analyses. The composition of clove oil varies widely depending on source. It seems the eugenol content hovers around 80%
unless it's a really low quality oil.
The clove oil I used was 86.525% eugenol, 0.47% isoeugenol. Other eugenol analogs and beta-caryophyllene content have not been measured. So having
yield over 84-85% should be suspicious as this woudl exceed the practical 97% yield attainable by common A/B extraction.
Yes it is very probably there are impurities like eugenol analogs but the eugenol content should be something like 98%, which is good enough for most
applications.
I think for pure eugenol we would really have to consider more advanced methods like column chromatography.
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DraconicAcid
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I wonder if you could crystallize the sodium salt.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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