Performic & P2P. Experiments & observations
Swim wrote;
" It was hoped that the modern buffered Performic would do for propenylbenzene that it apparently has done for isosafrole. Well, in my experience it
doesn't. When I first tried the Performic as written up by "Labtop" at the Hive, (the one using a butt load of NaHCO3 ) the results were dissmal on 3
fronts. Only half of the propenyl was converted, a lot of product was lost during/after hydrolysis and less than 10% was ever recovered as P2P.
Results following CA 1975 , using less buffering agent, was a lttle better. More propenyl was convereted to glycol (or what ever the hell it is), more
than than 90%. But still product loss in Hydrolysis with 15% H2SO4 and 15% HCl, and a slight improvement in yield, less than 20% using HCl.
Unbuffered performic produced the best results. No propenyl recovered, and better yield after HCl hydrolysis, 50%. Although once again, product loss
during/after hydrolysis.
For the first stage of the performic 35% H2O2 was mostly used, 86% formic acid and DCM was used.
Hydrolysis was performed with both acids, with and without MeOH and various amounts of, at various tempretures and various times between 2 and max 6
Hrs reflux.
Best results for hydrolysis was achieved using p-Toluene Solphonic acid monohydrate. This was done in various ways, using Dean Stark apparatus with
benzene, toluene, xylene, solventless distillation under vacuum, solventless reflux, solventless heating. Yield up to 65%
The highest yield for conversion of the intermediate product with TsOH was 77% w/w which I think is actually closer to 90% molar yield, but since I
don't know what that glycol is I can't work it out. This sounds good, but, there were many steps and this only worked on the glycol isolated after 15%
H2SO4 reflux. So it seems to me that some of the glycol will convert to P2P with 15% acid reflux and then some of the rest at higher temperetures with
TsOH. If fact
54.8g P2P (68.9%) resulted from 70g propenyl benzene using unbuffered performic with DCM and a 2 stage hydrolysis that included 15% HCl and
distillation from TsOH.
Experiments:
1) Here is a typical run with modified performic using NaHCO3.
101g Propenylbenzene (0.855 moles)
513g DCM
42.6g NaHCO3
214g 86% Formic acid
129g 35% H2O2
Propenylbenzene was made from P1P.
Formic acid from 90% w/w AR grade.
H2O2 was fresh, lab grade containing H3PO4 as stabilizer.
DCM was AR grade.
215g formic acid and 129g 35% H2O2 both about 4¼C was mixed and left at RT for 1 Hr then in the freezer till about 4¼C. Half was placed in a
dropping funnel sitting on a 2L RBF with 101g Propenylbenzene, 42.6g NaHCO3, 513g DCM and stir bar. The other half of the performic sat in an ice
bath.
Almost all of the peracid in the funnel was added before reaction with the carbonate ceased and a tempreture of 39¼C was reached. This took 40
minutes and total addition took 3 hours. This was left to stir for 24Hrs.
Poured into a sep funnel, left for 1 hr, separated and washed aqueous layer with DCM. Distilled off the DCM in a water bath @ 50 - 55¼ then used
vacuum. 125g clear glycol remained.
41.7g glycol, 513g 15% H2SO4 and 85ml MeOH was heated for 3.5 hours. Solution temp was 70 to 78¼C. When cooled, 3 layers were visible, clear acid,
clear middle, and a thin bright yellow layer which blended into the middle overnight.
Extracted 3 X 70ml DCM, washed with NaHCO3, brine, dried, distilled.
Collected 16.4g Propenylbenzene, 1.3g P2P, 10g light green residue.
The rest of the glycol was treated the same way, with some variation in MeOH and reflux time, but results were similar. The combined viscious light
green residue was again put through H2SO4 and resulted in hardly any P2P.
29.4g of that glycol was heated in a Dean Stark trap with 90ml toluene and 0.3g Tosic acid. A small amount of water was collected so another 1.3g was
added. After 3.5 hrs, 1.7ml water (acidic) was collected and colour of solution was orange/red. Neutralised with 60ml 10% NaHCO3, 60ml brine, dried.
Colour was bright yellow.
With bath up to 160¼C @ 5.5mbar, collected 0.8g P2P. Added a small amount of tosic and heated again. P2P with some water came over first then towards
the middle right to the end, P2P came over clear. Collected 24.4g P2P from 29.4g Glycol and 3.3g residue. Pretty fucking good, except that the glycol
represents a fraction of the starting material."
Much more to come, but some questions first. Please note, I am not a trained chemist and my knowledge is very very basic.
1) Is formic acid strong enough to hydrolyse glycol to P2P, or does it at lest contribute in some way? I remember Rhodium saying something about
formic beinng able to open up the the epoxide ring with regards to MDP2P and Dal Carson, in his 93% P2P claim says;
| Quote: |
This conversion was accomplished by dropping an acetone/trans-beta-methylstyrene solution into a stirred solution of hydrogen peroxide in formic acid
[2,3]. The acidic solution was refluxed and, then, neutralized and extracted with CH2Cl2. After Evaporating most of the CH2Cl2, the extracted mixture
of glycol and glycol esters was stirred stirred and heated in a solution of methanol and dilute sulfuric acid.
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Where he says "The acidic solution was refluxed", he is talking about before hydrolysation with H2SO4. So why the reflux here. Would acetone peroxide
be a danger?
2) Can anyone verify that buffered performic (15% H2SO4 or 15% HCL hydrolysis) works for p2p in good yield? That is, over 70% ?
Example 2)
Unbuffered performic.
70g Propenylbenzene (0.59 mole)
148.1g 86% Formic acid
77g 35% H2O2
415g DCM
Formic acid and peroxide were mixed and left at RT for 1 hr, cooled to 0¼C and dripped in keeping temp between 38 and 39 deg. Stirred for 20 hrs.
Extracted with DCM and distilled that off. 128.5g light green/yellow was left.
Half of that was (64.2g) mixed with 90ml MeOH and 500ml 15% HCl and refluxed for 2 hrs. Ex with DCM, washed with 10% NaHCO3, dried, removed DCM and
vacuum fractionally distilled. Collected 20.1g P2P. Yield 50.1%.
The other half was hydrolysed again for 3.5 hrs. Collected 19.3g P2P. Yield 48.6%
The combined residue (31.5g glycol) was vacuum distilled with 2.3g TsOH collecting 19.2g P2P. This was washed with 10% NaHCO3, brine, dried, then all
P2P was combined and fractionally distilled collecting 54.8g P2P. Yield 68.9%
Example 2)
Performic with Na2CO3
250g Propenylbenzene (2.1 mole)
31.7g Na2CO3
528.9g 86% Formic acid
275g 35% H2O2
1,269g DCM
10% more performic acid was used to try and convert all propenyl.
Propenyl, DCM and carbonate was in a 5l RBF and peracid at 7 deg was dripped in. Temp about 38 deg. Stirred for 24 hrs, separated, extracted, then the
1880.9g glycol + DCM was split into 3 groups. 627g representing 83.3g propenylbenzene.
1a) Toluene + TsOH
313.5g of the glycol (41.6g propenyl) was washed with 155ml 10% NaOH then 105ml dH2O. DCM was mostly removed, then set up with a Dean Stark trap with
240ml toluene and 3.5g TsOH. After 3 hrs, 2.3ml H2O was collected.
Washed with 100ml 10% NaHCO3. Colour was honey gold and more red/orange after the 100ml brine wash. Set up for vacuum fractional distillation along
with 0.5g TsOH and distilled some P2P. When this stopped, another 1g was added then P2P came over clear.
Collected 0.9g Propenylbenzene, 27.9g raw P2P with 8.6g residue.
1b) Solventless rearrangement with TsOH (vacuum)
313.5g of the glycol was washed with 155ml10% NaOH then 105ml dH2O. Removed DCM, transfered to a 100ml RBF with 3.2g TsOH and set up for vacuum
fractional distillation.
Collected some water and propenylbenzene, 26.1g raw P2P, with 10.7g residue.
2a) Solventless rearrangement with TsOH
313.5g of the glycol was washed with 2 x 150ml dH2O. DCM mostly removed and transferes to a 100ml RBF and 3.5g TsOH added. Set up for simple
distillation with a recovery tube. The solution heated to a max temp of 131 deg. When the temp reached 130 deg, the oil bath was removed 11 minutes
later. Cooled quickly with fan. Colour was black. Yeh black!
Washed with 200ml 10% NaHCO3, Colour turned light yellow/orange, washed with 85ml brine, dried vacuum distilled.
Collected 2g propenylbenzene, 25.4g P2P with 9.9g residue brown but not polymerised.
Added 0.7g TsOH to the residue and heated again etc, collected a further 3g P2P
Total 28.4g clean P2P.
2b) Solventless rearrangement with TsOH
Repeat of 2a) except that heating was set up with packed claison instead of the recovery tube and liquid temp was held between 127 and 130 deg for 20
minutes.
Collected 1.6g Propenylbenzene, 27g P2P with 10g residue.
Added 0.3g to residue then collected a further 0.6g P2P
Total 27.6g clean P2P.
3) Rearrangement with Xylene and TsOH
627g of the glycol was neutralised with 310ml 10% NaOH, then 200ml brine, dried with MgSO4 and DCM removed, last bit with vacuum. Transfered to a 1l
RBF with 8.4g TsOH with 400ml Xylene and set up with a Dean Stark trap.
Liquid temp reached 141 deg when H2O evolution seemed to stop. It spent 19 minuted from 130 deg to 141 deg, then heat was removed. The extracted water
and reaction liquid was combined and washed with 210ml 10% NaHCO3, then brine. colour was light yellow/orange, dried and vacuum distilled.
Collected 2g propenylbenzene and 15 - 25ml P2P so added 1.1g TsOH. Nothing came over after 5 minutes so added another 1g TsOH. After another 5 minutes
with bath over 154 deg, came clear P2P. Collected 71.4g raw P2P with 13.6g black tar.
Washed and dried then vacuum distilled and collected 65.4g clean P2P with 0.8g green/yellow residue. This is the best yield so far. 69.2% and if you
don't included the recovered propenyl, 70.9%"
Any suggestions? Dudes?
_________________
Be joyful, though you've concided the facts!
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