GC_MS (Hive Bee)
09-18-02 11:22
No 357603
      Gattermann and HCN  Bookmark   

The following is hypothetical and hasn't been tested for its validity. SWiM would like to discuss if the following dream is achievable, or just a pile of crap.

Some of the bees might be familiar with the Gattermann reaction. One of its best know applications is the synthesis of asarone via formylation of trimethoxybenzene. The formylation occurs by adding HCN and AlCl3 to the trimethoxybenzene.
Here we notice the use of HCN. SWiM doesn't like HCN since it is a little bit too toxic to handle. An alternative might be the in situ formation of HCN. SWiM's idea is based on something he found in the Hive section of our Russian collegues (http://www.zone.ee/dushist/r&misl/rimisl2t.djvu. SWiM doesn't understand a thing of all those funny characters (although he finally managed to learn how to pronounce them), but he can watch @ the nice figures. On page 94 of that document, there is something about the formation of HCN by a reaction between KCN and MgSO4. Now we still have to deal with KCN (isn't this used to execute the death penalty in some US states?), but in its crystal form, it is safer to handle (but don't be so stupid to check how it smells off course....).
In the Gattermann reaction, HCN may be formed by:

2 KCN + MgSO4 -> K2SO4 + Mg(CN)2
Mg(CN)2 + H2O -> Mg(OH)CN + HCN
Mg(OH)CN + H2O + MgSO4 -> (MgOH)2SO4 + HCN

(taken from above mentioned text)

So, what do the other bees think? Might it be achievable in this particular synthesis, or should SWiM stop his stupid dreams? There are some things that should be considered, viz. the addition of H2O and the use of MgSO4. I can see the later being a disturbing element when adding AlCl3.
Ideas? smile

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(Hive Bee)
09-18-02 11:35
No 357608
      I have never worked with HCN or KCN myself, and ...  Bookmark   

I have never worked with HCN or KCN myself, and Im not particulary eager to do so either. I cannot contribute to the -CN part of your question. What caught my interest was that you mentioned 1,3,4-trimethoxybenzene and AlCl3 together in a reaction. Do you have a reference for this? A patent perhaps?
(Stoni's sexual toy)
09-18-02 11:38
No 357609
      The usual way of preparing anhydrous HCN in situ ...  Bookmark   

The usual way of preparing anhydrous HCN in situ is reaction of Zn(CN)2 with gaseous HCl. This produces HCN and anhydrous ZnCl2, which works as the required Lewis acid catalyst in this reaction.

I'm not fat just horizontally disproportionate.
(Hive Bee)
09-18-02 11:55
No 357611
      Asarone  Bookmark   

Barium, has been part of one of SWiM's previous posts here: Post 333359 (GC_MS: "Asarone: unraveling of a molecular structure", Novel Discourse)- the German article is there, and a link to the translated document (PDF) can be found there as well.


Maybe have a look at this one as well: http://fachschaft.cup.uni-muenchen.de/~schleifi/reaktion/reaction/hoesch.html - don't think AlCl3 in se is important, just the Cl-.
(Hive Bee)
09-19-02 16:01
No 358100
      AlCl3  Bookmark   

OK, big mistake by me... crazy. AlCl3 IS important. Not for the Cl-, but as catalyst. Since it is a Lewis acid, AlCl3 can easily interact with the pi-electron cloud of the aromatic ring (in case of asarone's trimethoxy-pattern, you can guess that the pi-electron cloud is 'extra negative' compared to benzene) to form a sigma-complex. The latter forms the intermediate for a substitution reaction.

I vaguely remember (from the ol'days wink) an example of this reaction for the halogenation of not-activated aromatic compounds, such as the bromination of benzene with Br2.

PhH + Br2 --[AlCl3]--> PhBr

The Lewis acid activates PhH, which makes that the bromination occurs faster. Halogenation of activated compounds (for instance PhOH) don't require this catalyst.

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(Hive Prodigy)
09-19-02 16:03
No 358102
      Backwards  Bookmark   

You have your aromatic electrophillic substitution patterns backwards.

Lewis acids activate halogens/halides which then attack the ring. -OH on an aromatic ring is deactivating to the ring. -OR is activating.


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(Stoni's sexual toy)
09-19-02 16:26
No 358106
      > OH on an aromatic ring is deactivating to ...  Bookmark   

> OH on an aromatic ring is deactivating to the ring. -OR is activating.

No! -OH is even more activating than -OR!

I'm not fat just horizontally disproportionate.
(Hive Bee)
09-19-02 19:15
No 358135
      "Mini-review" of the Scholl formylation reaction  Bookmark   

Didn't want to waste another thread, and since it is related to the formylation of phenyl structures, SWiM puts it in this thread: formylation according to Scholl (using knallquecksilber)

The Scholl formylation reaction is the synthesis of an aldoxime from a carbohydrate, Hg(ONC)2 + 1/2 H2O and hydrous AlCl3. Using anhydrous AlCl3 would mainly yield nitrilles. Consequently, a mixture of AlCl3, AlCl3.6 H2O and Al(OH)3 is used.

Presented syntheses:
- benzaldehyde
- o-toluylaldehyde
- p-toluylaldehyde
- 2,4-dimethylaldehyde
- 2,5-dimethylaldehyde
- 3,4-dimethylaldehyde
- 2,4,6-trimethylaldehyde

Carbohydrates can also condense with formylated secondary amines (formylmethylaniline) in the presence of AlCl3. Patents for the latter method can be found on espacenet: Patent US1807693 (1929), Patent DE519444 (1931) and Patent DE519806 (1931)


(1) Benzaldehyde [a] --- 150 g benzene, 90 g Hg(ONC)2 43-45C in 40 minutes + 120 g AlCl3, 15 g AlCl3.6 H2O, 15 g Al(OH)3. Allow to stand for 3 hours. Yield: 68% aldoxime + 1.2 g aldehyde
(2) o-toluylaldehyde [b] --- toluene, Hg(ONC)2, AlCl3, AlCl3.6 H2O, Al(OH)3
(3) p-toluylaldehyde [b] --- idem.
(4) 2,4-dimethylbenzaldehyde [b] --- idem, but with m-xylene.
(5) 2,5-dimethylbenzaldehyde [b] --- idem, but with p-xylene.
(6) 3,4-dimethylbenzaldehyde [b] --- idem, but with o-xylene.
(7) 2,4,6-trimethylbenzaldehyde [b] --- idem, but with mesitylene. Yield: 3.5 g (of the aldoxime).


[a] Scholl, Ber Dtsch chem Ges 32 (1899) 3498
[b] Scholl, Kacer, Ber Dtsch chem Ges 36 (1903) 324

Most of the information comes from Meyer's Synthese organische Verbindungen from 1938.

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(Chief Bee)
09-19-02 19:28
No 358137
      Help! Knallquecksilber is Mercury Fulminate, the ...  Bookmark   


Knallquecksilber is Mercury Fulminate, the primary explosive! This is worse than tetranitromethane!
(Hive Bee)
09-19-02 19:32
No 358139
      can't help it...  Bookmark   

SWiM can't help it he has a passion for explosive stuff crazy.
For those who understand German, http://www.omikron-online.de/cyberchem/cheminfo/knalllex.htm might be a nice info point. At least we know where "knall"quecksilber comes from...

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