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Fery
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[*] posted on 24-2-2020 at 11:34
allyl alcohol


This is continuation of the synthesis describe in the allyl bromide thread. For allyl bromide, there is OK to use allyl alcohol + water azeotrope. But for an allyl alcohol ester preparation it is better to have higher alcohol concentration than 72,9 wt %.
here the preparation of allyl alcohol from anhydrous glycerol and 85% formic acid:
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...

the whole thread with allyl bromide:
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...

Here my attempt to concentrate the alcohol:
The distillates (approx 500 ml) were processed this way:
150 g of K2CO3 added (it was an overkill, less could be enough, a lot of did not dissolve), some CO2 evolved (very likely formic acid) and was shaken few times during 24 hours, then separated the upper layer which was distilled using Vigreux column. On steam bath, 50 ml of condensate collected with about 2 ml of water phase separated at the bottom (azeotrope allyl formate + allyl alcohol + H2O), thermometer in distillation adapter showed 80 C, no more distillate obtained, although about 400 ml of mixture still stayed in the distillation flask.
So the steam bath removed and the flask heated using flame burner and boiling plate.
Additional 250 ml of of distillate collected upto 94 C (so totally 300 ml with the first portion from steam bath), and then last 60 ml portion boiling above 94 C collected separately which was the most concentrated allyl alcohol obtained.

The total 300 ml of distillate in first fractions will be later treated with NaOH to decompose allyl formate and to obtain allyl alcohol again (this one with lower concentration, then will be salted out using K2CO3 to increase its concentration).

Another interesting concentration method is distilling at slightly reduced pressure 200-300 mm Hg where azeotreope containing 90% of allyl alcohol should distill, boiling points 60 C at 200 mm Hg, 70 C at 300 mm Hg.
Azeotrope at normal pressure boils at 88,2 C, contains 72,9 wt% of allyl alcohol and has density 0,905 g/ml. Pure allyl alcohol b.p. 97 C.

Densities of allyl alcohol + water mixtures at 20 C are:
0,920 g/ml (65%)
0,911 g/ml (70%)
0,902 g/ml (75%)
0,893 g/ml (80%)
0,884 g/ml (85%)
0,875 g/ml (90%)
0,865 g/ml (95%)
0,854 g/ml (100%)
the table of densities is here: http://www.orgsyn.org/Content/pdfs/procedures/CV1P0042.pdf

I determined the density of my 60 ml last fraction using 50,0 ml calibrated volumetric flask and obtained this result:
29,720 g empty
73,197 g full

43,477g of allyl alcohol 50,0 ml
density 0,86954 g/ml

so according the table of densities it is 93 wt% allyl alcohol
quite good

The allyl formate present in the mixture behaved similarly to benzene - breaking the azeotrope allyl alcohol + H2O, carrying out some of H2O when distilling ternary azeotrope allyl formate + allyl alcohol + H2O (which is probably richer in H2O than binary azeotrope allyl alcohol + H2O), then 72,9 wt% binary azeotrope distilled which carried out more of water and partially concentrated allyl alcohol distilled at the end.

IMG_20200224_192107_0_sm.jpg - 35kB IMG_20200224_193101_3_sm.jpg - 34kB

[Edited on 24-2-2020 by Fery]




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Fery
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[*] posted on 27-2-2020 at 02:52
anhydrous allyl alcohol


To the 300 ml fraction was added 10 g NaOH which dissolved completely and formed bottom water layer. Then another 10 g added which did not dissolve completely. This was refluxed for 30 minutes and the bottom water layer was separated and discarded. The upper alcohol layer was refluxed 2x with 30 g K2CO3 each time and the lower water layer discarded, the second rfx was much less efficient than the first one (a lot of K2CO3 did not dissolve at all) so I decided to change the way to go (the idea when allyl formate distilled in which water bottom layer formed).

The alcohol was transferred into 1 L RBF, the 60 ml fraction (93 wt %) added too and then 200 ml of hexane (if you are focused on maximizing the yield, probably 50 ml would be enough... hexane boils with some amount of allyl alcohol on distillation which decreases the yield). Boiling chips added and the flask was stirred in hand vigorously to ensure some of hexane entered the bottom phase and some water and allyl alcohol entered the upper phase (otherwise sudden vigorous boil onset which could not be coped by the condenser when they mix later spontaneously during rfx !!!). RBF was inserted into a steam bath, Dean-Stark trap adapter attached with rfx condenser and distillation started. Bottom water phase was collected from the trap adapter and every 15 ml was treated with K2CO3, after its treatment the bottom water layer discarded and upper concentrated alcohol phase returned back into the apparatus. This was very slow process and approx. 75 ml of distillate from Dean-Stark trap apparatus was treated by K2CO3 from which the alcohol layer was returned into the apparatus through the condenser and small funnel on its top after the Dean-Stark trap was again fully filled with new bottom layer (that ensured that the most of the returned layer did not sink into the Dean-Stark trap but passed through its arm into the RBF, only after that process the Dean-Stark trap was drained and the liquid treated with K2CO3 as described).

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https://en.wikipedia.org/wiki/Azeotrope_tables
Ternary mixture H2O : allyl alcohol : n-hexane boils at 59,7 C and has composition 5 : 5 : 90 wt % which separates spontaneously into upper layer with composition 0,5 : 3,6 : 95,9 wt% which is returning back into the RBF automatically and bottom layer 80,9 : 17,7 : 0,4 (this layer is treated with K2CO3 and then returned back into the apparatus manually through the top of condenser after the Dean-Start trap again fully filled with fresh bottom layer).
This was very slow process and lasted 7 hours. When the treatment with K2CO3 did not yield significantly some water to discard, the dehydratation was done. Another sign was that the rate at which the bottom phase separated decreased significantly (3-4 times) - there was still some bottom phase but now without H2O, it was allyl alcohol without water now. The hexane was distilled out in a way that it was drained from the Dean-Stark trap (this is very quick process for only few minutes).

Allyl alcohol from the 1 L RBF was poured into 500 ml RBF and distilled from an oil bath, collecting fraction 96-98 C (b.p. 97 C lit.).

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Some K2CO3 stayed in the RBF (it is slightly soluble in allyl alcohol and very soluble in water present in allyl alcohol).

yield:
fraction boiling upto 96 C 56,1 g (250 ml FBF with glass stopper behind the yellow hose)
fraction boiling 96-98 C 131,1 g (amber flask in the front right)

200 ml of hexane enriched with allyl alcohol was kept for allyl valerate esterification (250 ml FBF with glass stopper behind the 56,1 g fraction of the alcohol).

[Edited on 27-2-2020 by Fery]




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[*] posted on 29-2-2020 at 11:07


Nice write-up Fery! I particularly like the idea of partially drying the allyl alcohol by azeotropic distillation before using potassium carbonate or the like.

I have had rather mixed results with azotropic distillation to drive esterification so its good to hear of a success.

[Edited on 29-2-2020 by Boffis]
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[*] posted on 1-3-2020 at 07:42


Boffis it was very slow process (7 hours) but quite efficient. I've chosen a solvent not miscible with water which has its b.p. far enough from the product (allyl alcohol b.p. 97 C) and which was not too much toxic (unlike benzene). Not pure hexane but a mixture of isomers of hexane could be easily obtained as Pharma Benzine (hydrogenated fraction with b.p. But the lower b.p. the less water in the azeotrope. So e.g. pentane could be even easier to separate from allyl alcohol but less efficient in removing water (partial pressure of water much lower at lower temperature).
Here they used CCl4 for dehydratation http://www.orgsyn.org/Content/pdfs/procedures/CV1P0042.pdf
Perhaps it was done in less hours than 7 and during last hours only allyl alcohol separated in the Dean-Stark Trap adapter, I did not check that.




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[*] posted on 4-3-2020 at 22:11


This channel may interest you, scoop it up before it gets deleted; unfortunately I'm pretty sure he's going for the synthesis of Safrole via grignard ultimately....

https://www.youtube.com/watch?v=Npa9Twp3dlo
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[*] posted on 5-3-2020 at 09:53


Thx for the video link, very nice video.
By my experience the inert gas was not necessary (steam replaced the air quickly).
What was important was the heating intensity - too weak heating = acrolein byproduct, too strong heating = too little of glycerin monoformate. Heating the flask for the first time when it is full of glycerin and for the third time when there is approx 1/3 of original glycerin required different heating intensity (if you apply the same intensity as for the first run then it is heated approx twice faster for the third run).
What is ultimately is a thermometer inserted into the reaction flask, once it reaches 195 C start collecting the product, upto reaction reaches temperature 260 C. The distillate below 195 C was collected separately (it is high in formic acid which could be recovered).
And instead of wasting NaOH I just led a hose from the vacuum take off adapter to the outside of my house.
I did not stir the content in the reactor flask, the boiling did the task instead.
Do not use CaCl2 for drying alcohols (used in the video).




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[*] posted on 20-10-2020 at 01:21
allyl alcohol from glycerin and formic acid, for the second time in my life


this is my second synthesis of allyl alcohol in my life, now in advance of preparation of allyl phenoxyacetate (pineapple fragrance)
apparatus: 1 L RBF with 2 necks, 1 neck with thermometer 0-300 C, 1 neck with empty 25 cm long column, distillation head with thermometer 50-150 C, condenser, vacuum take off adapter to which a hose is connected and its end was led OUTSIDE OF BUILDING (second choice is to submerge into solution of NaOH), 250 ml receiving flask

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serie No 1
Into 1 L RBF was placed boiling chips, 330 g of anhydrous glycerin, 100 g of 85% formic acid and thoroughly mixed well (not so easy, glycerol is quite thick syrup, it's better to mix the glycerin in a beaker with most of the acid, pour into flask using a wide (!) funnel (to keep ground glass joints clean to apply a grass to them later easily) and wash the beaker with the remaining acid and add it into the flask)

serie No 1, round No 1
The 1 L RBF was heated with flame burner using smallest possible flame.
Time +45 minutes the distillation started, T inside flask 130 C, T in head 102 C which raised to 105 C for the most of time.
Time +90 minutes T in head fell to 100 C and was further decreasing, nothing distilled temporary, the content from receiving flask collected and empty flask attached back into the apparatus. 48,8 g of water and diluted formic acid obtained.
The column was insulated with one sheet of newspaper turned around it in few layers.
When T in flask raised to 210 C the distillation resumed, T in head 97C.
Time +165 minutes the T in flask 255 C, T in head 70 C and falling down, no more distillate in condenser, 108,9 g allyl alcohol collected in receiving flask which was removed and kept aside
content in 1 L flask at the beginning and at the end



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serie No 1, round No 2
thermal insulation from column removed, when the content in 1 L RBF temperature fell to 100 C, 100 g of 85 % formic acid added (now it mixes well spontaneously as the glycerin is hot), started to heat using the smallest possible flame, which was few times turned off and on to allow reflux for 20 minutes (always just before vapor reached the distillation head the flame was turned off) - this time was to allow esterification to proceed
time +20 minutes T in flask 125 C, T in head 102 C, H2O and diluted formic acid distills, T in head reached 105 C in few minutes and stayed at that temperature for long time, the removed thermal insulation from column allows some formic acid to flow back into the reaction
time +60 minutes, T in head decreasing to 100 C and further falling down, no more distillate condensing, T in flask 220 C, 55,9 g H2O + formic acid collected from receiving flask, column thermally insulated with newspaper
then allyl alcohol distills, T in head 97 C, droplets in column observed caried up by CO2 stream evolution from the reaction (that's why I used an empty column to allow most of droplets to return back into the flask)
time +90 minutes T in head below 70 C and falling down further, no more distillate condensing, T in flask 255 C, 80,5 g allyl alcohol collected from receiving flask


serie No 1, round No 3
thermal insulation from column removed, when the content in 1 L RBF temperature fell to 100 C, 100 g of 85 % formic acid added, started to heat using the smallest possible flame, which was few times turned off and on to allow reflux for 20 minutes
time +20 minutes distillation of H2O and diluted formic acid started, T in flask 120 C, T in head 102 C which later raised to 105 C for most of time
time +60 minutes, T in head 100 C and falling down, no more distillate condensing, 62,0 g H2O + diluted formic acid collected in receiving flask, removed and kept aside
thermal insulation of column installed and soon distillation resumed, now allyl alcohol distilling, T in head 97 C
time +100 minutes, T in head below 70 C, no more distillate condensing, T in flask 260 C, end of round 3, end of serie 1, 53,3 g allyl alcohol collected from receiving flask, kept aside and thermal insulation from column removed

the content in 1 L RBF approx 50-100 g of red glycerol

IMG_20201019_135459_9_sm.jpg - 20kB



serie No 2

serie No 2, round No 1
into the red remaining glycerol in 1 L RBF was added 270 g of fresh anhydrous glycerol mixed with 100 g of 85 % formic acid and heating started with lowest possible flame which was few times turned off and on to allow reflux and esterification to proceed for 20 minutes
time +20 minutes, T in flask 130 C, T in head 102 C, distillation of H2O and diluted formic acid, some of formic acid returns back through the column (that's why thermal insulation of column temporary removed)
time +60 minutes T in flask 200 C, T in head 100 C and falling, condensate from receiving flask removed and kept aside, 48,2 g H2O and diluted formic acid collected, thermal insulation of column installed back (few turns of newspaper sheet)
soon distillation resumed, now allyl alcohol distilling
time +135 minutes, T in flask 245 C, T in head 65 C and falling, no more distillate condensing, 83,0 g allyl alcohol collected and thermal insulation from column removed

serie No 2, round No 2
when T in 1 L RBF dropped to 100 C, 100 g 85% formic acid added and heating started with lowest possible flame, which was few times turned off and on to allow reflux for 20 minutes and the esterification to proceed
time +20 minutes, T in flask 126 C, T in head 102 C, H2O and diluted formic acid distilling, some part of formic acid returns back into the 1 L RBF through the column
time +25 minutes, T in flask 130 C, T in head 105 C
time +65 minutes, T in flask 210 C, T in head 100 C and falling down, no more distillate condensing, 49,9 g H2O + formic acid removed from receiving flask
continued heating, thermal insulation to column installed, soon allyl alcohol started to distill
time +120 minutes, T in flask 250 C, T in head dropped to 60 C, no more distillate condensing, 72,5 g allyl alcohol collected from receiving flask, thermal insulation from column removed

serie No 2, round No 3
when T in 1 L RBF dropped to 100 C, 100 ml 85% formic acid added, heating started with lowest possible flame which was few times turned off and on to allow reflux for 20 minutes and esterification to proceed
time +20 minutes, distillation started, T in flask 122 C, T in head 102 C and further raising upto 105 C where it stayed for most of time, H2O and diluted formic acid distilling
time +55 minutes T in flask 215 C, T in head 100 C and falling down, 54,1 g H2O + formic acid collected, thermal insulation to column installed and continued heating
allyl alcohol started to distill, T in head 97 C
time +115 minutes, T in 1 L RBF 260 C, T in head 60 C, finished, 58,2 g allyl alcohol collected in receiving flask

remainder in 1 L RBF (full flask weighed, then glycerol removed, flask washed with water and dried)
378,9 g - 287,7 g = 91,2 g

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the remaining 91,2 g of glycerol could be perhaps later reacted with azeotrope formic acid recovered from distillates (just my idea to use it)

theoretical calculations:
total glycerol reacted 330 + 270 - 91,2 = 508,8 g (5,52 mol)
total 85% formic acid entered the reaction 600 g
total water + formic acid fraction 318,9 g
total crude allyl alcohol fraction 456,4 g

if assuming that the whole difference 330,5 g escaped as CO2 = 7,58 mol which is 1,37 times more than the moles of glycerol reacted. There is a chance that the glycerol remaining if flask is not pure glycerol, maybe contains some glycerol formate, water, longer carbohydrates etc so more glycerol reacted... also some acrolein (side reaction) could escape with CO2 as vapors (b.p. 53 C) and maybe some of formic acid decomposed to CO and some of allyl alcohol as droplets on the walls of flask, column, head, condenser...

workup will follow (recovering some allyl alcohol from H2O + formic acid fraction, I expect distilling it out of the mixture as allyl formate b.p. 83-85 C using a hempel column packed with rashig rings and then decomposing it with NaOH) and concentrating the allyl alcohol fraction (+ decomposing allyl formate here and neutralisation of formic acid with NaOH, salting out the alcohol using K2CO3 and further dehydratation using Dean-Stark trap adapter and hexane as a solvent to drive out H2O)

[Edited on 20-10-2020 by Fery]




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