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Organikum
resurrected
Posts: 2344
Registered: 12-10-2002
Location: Europe
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Mood: frustrated
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The benzene synthesis from sodium benzoate shows that (II) salts are not actually necessary, I used in this reactions always sodium benzoate and made
an iron salt from the acetic or propionic acid and from all of this I made a slurry. But I added coarse steelwool and lots of it as the problem is
heattransfer in special with calcium salts which make a solid rock. The steelwool transfers the heat insides and cracks the salts so the product can
get out. And don't heat at the bottom only but the sides too. gas-burner and a tent for the hot air to go up along the sides of the vessel.
Glassware is much too precious for this. I used old solvent cans and just threw them out after the reaction.
I feel there is a lot of over-thinking going on here.
PS: Rubber is crap, but if you use silicone rubber and wrap it in thick (0,2 mm) PTFE tape..... Helps your cork a lot too....
[Edited on 1-9-2023 by Organikum]
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Boffis
International Hazard
Posts: 1927
Registered: 1-5-2011
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It’s been a will since I was active in may lab due to the pressures of work and family but I am now got back into the swing,  . I have prepared some sodium and barium butanoates and will try the dry distillation
of these in the near future but because I had a lot of butanoic aid left I thought I would give the Org. Synth procedure a go.
I carried out the reaction at half the scale give in Org.Synth. (ie 2 Molar scale) and used atomised iron powder from an Ebay supplier rather than
reduced iron specified. Because I though this might be less reactive than the hydrogen reduced iron I ran the dissolution part for 8 hours instead of
the 5 hours given in Og Synth. I also added a few drops of 1M copper sulphate solution to activate the iron powder. After 8 hours I was left with a
thick black viscous boiling gloop. I let it cool a little so I could shift the reflux condenser to the distillation position and while I was at it, I
added 0.1g of boric acid powder. I then very slowly raised the temperature until distillation began. The total time for the heating up and
distillation was 3.5 hours. To my pleasant surprise distillation occurred easily and largely as described. The only slight problem I encountered was
that the distillate tends to condense into a mist that is difficult to trap and I found it necessary to run the delivery spout from the condenser
below the surface of the liquid; this helps but doesn’t completely eliminate the problem. I have just completed the distillation and have recovered
just over 100ml of pleasant-smelling liquid so it looks like the yield is comparable with that given in the Org. Synth. Procedure.
I will provide a more detailed report later along with my further dry distillation experiments.
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Boffis
International Hazard
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The final work up from ~4.5 Moles of butanoic acid was 156g of heptanone and about 30ml of higher boiling material with a faint earthy smell and
boiling around 155 C. This appears to be 4-heptanol. Presumable this results from the conversion of FeO to Fe3O4 which appears to be the main
component of the black ash left at the end of the reactions.
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Fery
International Hazard
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I wonder whether the nascent atomar hydrogen (2 C3H9COOH + Fe -> Fe(C3H9COO)2 + 2 H) couldn't reduce the acid into butanol (2 H + C3H9COOH ->
C4H11OH + H2O) then also butyl butyrate could be a sideproduct as you had an excess of butyric acid. But its b.p. is 166 C and has tutti frutti scent
(I synthesized it years ago from butanol and butanoic acid).
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Hexabromobenzene
Hazard to Others
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You can prepare iron salts using this method. Use of calcium salts is preferable. In the case of free acids, you may not need a diaphragm.
https://www.sciencemadness.org/whisper/viewthread.php?tid=16...
>I wonder whether the nascent atomar hydrogen (2 C3H9COOH + Fe -> Fe(C3H9COO)2 + 2 H) couldn't reduce the acid into butanol (2 H + C3H9COOH
-> C4H11OH + H2O) then also butyl butyrate could be a sideproduct as you had an excess of butyric acid.
This is practically impossible. Iron has too low a hydrogen overpotential.
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bnull
National Hazard
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Isn't iron plus acetic acid used for reduction of nitroaromatics?
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Boffis
International Hazard
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Hi Guys, thanks for the comments. I have already thought about most of these possibilities. Its actually very difficult to reduce simple aliphatic
acid to the equivalent alcohol and it is very unlikely that the abundant hydrogen evolved could bring about this reduction to any significant degree.
If it did why would people use use expensive and hazardous LAH to achieve this end? If a small amount of butanol had been formed it would have been
lost to the head fraction during distillation but this fraction was very small and consisted mainly of an azeotrope of 4-heptanone and water which
boils at about 94 C and separates out into two phases when condensed. The final residue in the flask charred to a crude oil like viscous substance
that I burned and then washed the flask with dichromate and sulphuric acid. Distillation stalled at 160 C and white smoke began to appear in the flask
so I stopped distillation but the was less than 20ml of residue by this point.
The residue in the flask at the end of distillation is soft and friable black magnetic oxide. If this is formed during the decomposition of the iron
salt of the organic acid it implies oxidation of part of the iron oxide and hence reduction of something else. I believe that a small amount of
4-heptanol is a direct pyrolysis product. To confirm that the fraction boiling around 155-156 C is mainly heptanol I decided to try oxidising it to
4-heptanone using the dichromate procedure I had successfully used on 2 and 3 pentanols. This appears to have worked, the 30 ml of "4-heptanol has
yielded about 20ml f heptanone smelling product. I am currently working on characterising the product. I may try to derivatise it rather than distill
it.
One final comment was the clean of the flask. To my surprise I have found that if the pyrolysis is carried out to the bitter end the residue is soft
and readily removed from the flask leaving a thin black film that is readily removed with warm dilute sulphuric acid containing a little dichromate.
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