Author Topic: Benzaldehyde + MEK acid catalyzed aldol  (Read 11161 times)

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bio

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Benzaldehyde + MEK acid catalyzed aldol
« on: August 03, 2003, 07:28:00 AM »
I am prepared to do the subject reaction with Bayer Villager oxidation to P2P. Where I am now I have no access to a library only the internet for references. Does anyone have anymore details on this procedure? I feel the sketchy details in

Post 245942

(twodogs: "New method for P2P", Novel Discourse)
are fraught with pitfalls and I sure don't want to waste my analytical grade $80 a liter PhCHO. Also I have been searching the internet for other catalysts other than Hydrogen Chloride which would be suitable for this type reaction to no avail. Any references or pointers would be highly appreciated. The Organic Reactions volumes referenced don't seem to be available on-line and the Patents referenced aren't very helpful. Anyway I will try it on a small scale soon and will let you all know how it turns out.

twodogs

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Benzaldehyde + MEK
« Reply #1 on: August 03, 2003, 10:49:00 PM »
Sketchy details?? Jesus Christ ...how much detail do you want? If you follow the procedure exactly as I have mentioned you will get a result.

bio

  • Guest
Benzaldehyde + MEK
« Reply #2 on: August 05, 2003, 03:07:00 AM »
OK, Two Dogs thanks for the encouragment. Perhaps sketchy was a poor choice of words. So I assume you have had success with this reaction. It does seem fairly simple to do. Apparently a little H2O is not detrimental to the condensation product yield as they performed it in an open beaker at freezing temperature. This puzzled me somewhat as water is eliminated and usually I used a Dean Stark tube or at least a drying tube in a sealed system for similar PhCHO condensations. Also I wonder if the relatively low yields are partly due to doing atmospheric distillation. At those high temps it seems a lot of decomposition could occur. I will try a test batch tomorrow and see if it will crystallize after removing the excess MEK. If you have done this reaction could you share some more thoughts? I want to scale it up and think the oxidation step could get by with way less MeCOOH.

twodogs

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Benzaldehyde + MEK acid catalyzed aldol
« Reply #3 on: August 05, 2003, 04:19:00 AM »
Bio...yes I have had sucess with this reaction but I felt that 35% was too low for me. The aldol condensation part is very easy and as I mentioned can be done with refluxing conc. HCl or with H2SO4 but you get the best result with dry HCl. With the oxidation part, I would use peracetic acid or performic acid if I were you as the perborate makes for a messy workup. If you use less Acetic with the perborate you will end up with such a solid mass that you won't be able to stir it. I don't do this shit any more but have a look at this site from time to time but I know two another ways to the ketone from the unsaturated ketone that is formed from the aldol condensation. The unsaturated ketone can be oxidised with NaOCl to give the alpha- methyl cinnamic acid. This can be decarboxylated to give phenyl propene that can be worked up with performic etc or the methyl cinnamic can be oxidised with oxone and the resulting epoxy acid decarboxylated to give the ketone. I was looking at these reactions when I figured out that the Baeyer-villager worked as well and that seemed easier. It is a pity you don't have a library handy as I think that the Baeyer-Villager would work much better with a catalyst.

viki

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peracetic oxidation
« Reply #4 on: August 05, 2003, 05:49:00 AM »
question for two dogs.what strength peracetic would you recommend for the oxidation?would 30-35 %work? viki

twodogs

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Benzaldehyde + MEK acid catalyzed aldol
« Reply #5 on: August 05, 2003, 06:17:00 AM »
Viki,yes that would work. Have a look at all the patents under Baeyer-Villager and you will see all the different oxidisers used. Boesken used peracetic.

bio

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Benzaldehyde + MEK acid catalyzed aldol
« Reply #6 on: August 06, 2003, 05:32:00 AM »
Yea, twodogs the peracetic makes sense. I bought some 30% H2O2 intending to try it or even regenerate the Na Perborate. Can the peracetic or performic be made insitu? and would the same molar ratios be used. Also I have the perborate tetrahydrate a monohydrate is also available, the 4 hydrate which is NaBO3.H2O2.3H20 is ca. 10% O2. What is the actual mole ratio needed of O2 for the Baeyer Villiger?

Again thanks for your assistance as the library here is in the wrong language and only goes to the 10th grade (sic).

twodogs

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Baeyer-Villager
« Reply #7 on: August 06, 2003, 07:11:00 AM »
Bio
I am sorry but this was a while ago and I don't have any notes. I would have thought that you would need at least 50% H2O2 to make a strong enough peracetic. Performic pretty much has to be made on the spot as it deteriorates quite quickly. Peracetic needs a catalyst like H2SO4 to form and that may need to be neutralised before use. I had alot of difficulty in figuring out the percentage of peracetic formed by combining H2O2 and acetic acid. A lot of posts on the topic here at the Hive I think are wrong in that they assume too high a percentage of peracetic in the final product. It is one of those reactions where 1+1 doesn't equal 2. I couldn't buy peracetic and this is the main reason why I went with the perborate as the quantities needed are easier to work out. Have a look at US Patent 4988825 where I got the idea of using perborate.

Rhodium

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twodogs

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Peracid concentrations
« Reply #9 on: August 06, 2003, 11:39:00 AM »
Thanks Rhodium. That is what I had read.. if you use 90% H2O2 with acetic acid you can get the high concentrations of peracetic but 30% H2O2 only gives about 8%. I don't believe that you can buy 90% H2O2 any more. 35% peracetic seems to be the reaction grade.

bio

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Peracid concentrations
« Reply #10 on: August 07, 2003, 06:33:00 AM »
OK, twodogs and Rhodium, thanks for the references. Doing my research now. By the way Rhodium can P2P be distilled at atmospheric without decomposition (or only minimal)? I always used about 10 torr and it stayed water white for days.

Rhodium

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P2P distillation
« Reply #11 on: August 07, 2003, 08:21:00 AM »
Yes, P2P can be distilled without vacuum, but you might get 10% better yield by using vacuum. 10 mmHg is excellent in this case.

bio

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Benzaldehyde + MEK acid catalyzed aldol
« Reply #12 on: August 09, 2003, 06:16:00 AM »
Hi twodogs and Rhodium. The condensation went quite smoothly I added about half the HCL gas before the color change started and it was just as you said the next morning. I will try to crystallize my little test batch tonight without distilling. Did you ever have any luck with this? When I crystallized phenyl nitropropene w/o distillation it worked but only by seeding with a grain or two of fine sand and this without removing the solvent or chilling. I presume not as you mention the freezer trip. Anyway I will try it as it would save a lot of work especially when scaled to the proportions planned. PhCHO is sold as bacteriacide around here so it's about as common as formaldehyde.

bio

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Benzaldehyde + MEK acid catalyzed aldol
« Reply #13 on: August 09, 2003, 10:57:00 PM »
OK, It crystallized after freezing with scratching and seeding. Now trying to determine a suitable recrys solvent. Any ideas. Will try abs IPA and Hexane or Benzene first.

Herr_Ovalmeister

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Post 208702 Post 451381 I've seen MEK (methyl...
« Reply #14 on: August 15, 2003, 02:28:00 AM »

Post 208702

(Antoncho: "The easiest synth of benzaldehyde from toluene", Chemistry Discourse)


I've seen MEK (methyl ethyl ketone) sold at one hardware store OTC.

bio

  • Guest
CeMolybdate
« Reply #15 on: September 09, 2003, 03:36:00 AM »
The CeMolybdate vapor phase method is INMHO the best. See my other posts.

chilly_willy

  • Guest
tried this...
« Reply #16 on: September 25, 2003, 03:40:00 AM »
Someone I know tried this reaction a while back.  Seemed too good to be true!  Was it?  During the condensation he found it impossible to weigh the gassed liquid to determine any amount of absorbed HCl.  Digi(good one) weighed NO appreciable weight change. <--missing something here??.. He just kept gassing and gassing until everything got blood red brown.  It was left overnight..washed, extracted, and distilled...a yellow oil was left over that still smelled like cherries.  What the hell??  Instinct told him something went wrong.  Anyway..for shits and giggles he left everything in some ice..and to his surprise the whole lot of yellow oil solidified the next day..still smelled like cherries..but crystals..yea!  The cherry-smelling sulfur crystals were added to the perborate w/ gaa..and heating started...a little too fast.  Whoops..a little boil-over.  Shit! vinegar smell all over..oh well..fan took care of that.  Heating was properly maintained..crap...the crystasls werent dissoving.  Kept heating.  Left for a couple hours...seemed as though perborate and cherry xtals didnt dissove at all.  That cant be right since the p2p comes from the cherry xtals...?  Dumped the whole mess.  What the hell happened?  Bio please post as to what happened during your oxidation step.  Ne1 else please enlighten as to what happened/went wrong....


placebo

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Or you could steam distill the p2p.
« Reply #17 on: September 25, 2003, 12:26:00 PM »
Or you could steam distill the p2p.


bio

  • Guest
sodium perborate tetrahydrate
« Reply #18 on: October 08, 2003, 04:54:00 AM »
two dogs.......Please could you clarify for me if the ca. 8% peracetic from 30% H2O2 will oxidize the ester we discussed, given the perborates ca. 10% H2O2? I did get the unsat ketone to crys w/o distill.

bio

  • Guest
it worked
« Reply #19 on: October 21, 2003, 07:08:00 AM »
just like you said twodogs, thankyou very much. Only thing is I got a slightly better yield