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Author: Subject: Benzoic Acid, Carbamid>Benzamid>Anilin?
dr. nick
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[*] posted on 25-7-2005 at 07:45
Benzoic Acid, Carbamid>Benzamid>Anilin?


Swim talked to a real skilled friend who gave him the hint to get anilin from benzoic acid and carbamid via benzamid and bleach (chlor), so he decided to try a test run on this:

1g Carbamid and 2g Benzoic Acid where finely grinded and mixed in a mortar, then filled into a large test tube and fitted with a stopper and a rubber hose leading into a jar of water to avoid any mean smells.

While heating the mix it completely liquefied (clear, slight yellow).

after cooling it re-solidified again.
(Swim's a real pro, so the first thing he did after pulling off the stopper was taking a deep smell - now his nasal cavities will probably stay clear for quite a time ...)

Then some 40ml around 3% Chlorine Bleach where added. After some bubbling, foaming, fuming and changing colours from slight red over redbrown the liquid turned to a nearly black brown. He decided not to smell it this time as he likes his Erythrocytes as they are.

Can anyone give his appraisal on this? is this of any worth? should the black/brown liquid contain some Aniline now? if so, how to get it out there? destillation?
Or can anyone help with some more info on this? temps needed, amounts of bleach needed, is there a better way to benzamid, and so on? maybe to use some hcl with the benzoic acid and the carbamid??

Any hint welcome!

Thanks!

[Edited on 25-7-2005 by dr. nick]
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[*] posted on 25-7-2005 at 08:14


Can you come up with a mechanism for this?

Also, I suspect carbamide is urea? Or what is it? Wouldn't you expect to get the condensation product, Phe-CO-NH-CO-NH-CO-Phe ? Did you see moisture appearing after you melted the mix?

Anyway, if this is the product, I don't see how the nitrogen would suddenly move to the Phe. But I don't know enough about this type of chemistry.

As to tests for aniline- that's an easy one. You could diazotise it, turn it into some dye.

For it's potential isolation, add ether/ehtanol, the aniline should precipitate as the hydrochloride salt (check solubilities first)




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[*] posted on 25-7-2005 at 10:06


i'm sorry, i'm in the dark myself on this, i wasn't able to get more info on this yet. on the other hand: maybe i simply didn't understand ...

here's what i found in a mail from the mentioned friend:

1. a mentioned possible side reaction:
--------------------------------------------------------------------
One side reaction may cause trouble:

NH2-CO-NH2 + 2 HOOC-Ph --> CO2 + H2NCO-Ph + NH4+ -OOC-Ph--

2. a hint for the benzamid step:
--------------------------------------------------------------------
--you may need to add some acid, like HCl or NaHSO4, which is stronger than benzoic acid, to displace the ammonium ion.--

3. a hint to complete the whole thing
--------------------------------------------------------------------
--cook to make benzamide. Second, add a cool bleach solution to the benzamide and let stir for a couple hours. Finally, add some base and heat the mixture up to complete rearrangement and decarboxylation.
An oily layer of aniline will separate, which canbe extracted with nonpolar solvents.

That's all i can tell at the moment. Possibly i'll be able to talk to him again sometime.
I'll go on with my test runs and will post the results here if somebody is interested ...
unfortunately i'm not much of a chemist yet so all i can do is to describe what i see ...

[Edited on 25-7-2005 by dr. nick]
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[*] posted on 25-7-2005 at 17:15
Ah, I knew it, this rang a bell!


It's the Hoffmann Rearrangement what you are talking about!

Check this for instance!!

In the case of acetamide ---> methylamine:
Quote:
The Hoffmann Rearrangement

2 CH3CONH2 + Ca(OCl)2 → 2 CH3CONHCl + Ca(OH)2

2 CH3CONHCl + Ca(OH)2 → (CH3CONCl)2Ca + 2 H2O

(CH3CONCl)2Ca + 2 NaOH → 2 (CH3CONCl)-Na+ + Ca(OH)2

(CH3CONCl)-Na+ --Heat--> CH3CON + NaCl --Rearr.--> CH3N=C=O

CH3N=C=O + H2O + 2 NaOH → CH3NH2 + Na2CO3

CH3NH2 + HCl → CH3NH3+ Cl-

In this experiment, acetamide is first converted into N-chloroacetamide, which, in the presence of alkali, eliminates hydrogen chloride and undergoes rearrangement to form methylisocyanate. Hydrolysis of the latter gives methylamine which is isolated as the hydrochloride. It should be pointed out that the elimination of hydrogen chloride from N-chloroacetamide in the presence of alkali, actually consists of the removal of the hydrogen as a proton to form the alkali salt of N-chloroacetamide; the chloride ion is apparently released from the anion of this salt.


For experimental details, see the above link too. I'd use a modified procedure from the above.

What remains is the making of benzamide in the first place. I don't know the usual synthesis routes, however, in the analogous case, acetamide is made by heating & melting ammonium acetate, so maybe the same could be done with ammonium benzoate.




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[*] posted on 25-7-2005 at 17:39


Excerpt from Helv. Chim. Acta 29, (1946) pp. 1440-1:

Exemples d'acidolyse de l'urée.

Formamide: 15,8 gr. d'acide formique chauffés avec 18 gr. (une molécule) d'urée à
140—150° jusqu'à cessation du dégagement de gaz (quelques heures) fournissent par
distillation dans le vide 11,3 gr. de formamide passant à 113° sous 20 mm (rendement
84%). — Berend[Ann. 128, 335 (1863)]) a déjà décrit l'action, qualifiée par lui de «déshydrante», de l'urée
sur le formiate d'ammonium et indiqué qu'en chauffant ce sel avec la moitié de son poids
d'urée (environ une demi-molécule) à 140°, on pouvait préparer la formamide avec un
rendement meilleur (mais qu'il n'indique pas) que par simple chauffe du sel: il a formulé
l'équation:

2 HCOONH4 + NH2CONH2 = 2 HCONH2 + C03(NH4)2

Mais c'est bien la réaction qui intervient: en prenant seulement 3/4 de mol. d'urée
(ce qui fournit après acidolyse de 1/2 mol. d'urée un mélange qui contient pour 2 molécules
de formiate d'ammonium une molécule d'urée, à côté de l'amide déjà formée), on obtient
avec la même quantité d'acide seulement 10 gr. d'amide; or l'urée mise en oeuvre fournit
par acidolyse 10,1 gr. de formamide (soit 8,4 gr. si l'on tient compte du rendement de 84%
de l'essai précédent), de sorte que la formation d'amide par déshydratation du sel ammoniacal
est peu importante.

Acétamide: 10 gr. d'urée et 10 gr. d'acide acétique (quantités équimoléculaires)
chauffés dans un ballon à tube ascendant à l'ébullition dégagent du gaz carbonique dès
que la température du mélange atteint 110°. Poursuivant la chauffe deux ou trois heures,
on voit la température de la liqueur s'élever à 220°, avec dégagement non seulement de
CO2, mais aussi d'ammoniaque. La distillation fournit 9,5 gr. d'acétamide (rendement
95%) pratiquement pure, passant à 223°. L'acétate d'ammonium se comporte de même
avec l'urée. Ici encore, la formation d'amide par déshydratation directe du sel ammoniacal
est relativement peu importante: en chauffant l'acide acétique avec la moité de
son poids d'urée dans les mêmes conditions, on n'obtient que 66% (par rapport à l'acide)
d'amide.

Benzamide: La réaction est ici un peu plus lente et ne débute qu'à environ 150°.
Chauffant des quantités équimoléculaires d'acide benzoïque et d'urée 1 heure à 200—230°,
on obtient un produit qui, extrait au benzène bouillant, fournit par refroidissement de
la solution obtenue, de la benzamide identifiée par son p. de f. et le dosage d'azote. Il
reste sur le filtre une certaine quantité de produits de transformation de l'urée (ac. cyanurique,
etc.). Rendement environ 60%.
...
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[*] posted on 25-7-2005 at 17:51


Great ref, S.C. wack.
In other words, it can indeed be made with urea.
If it hasn't been obvious:
The reaction is a little slower here (with benzamide) and begins at approximately 150° C. Heating equimolar quantities of benzoic acid and urea for 1 hour at 200-230°, one obtains a recrystallised product that when extracted with hot benzene. On the filter paper, there remains a certain quantity of other products such as urea (cyanuric acid, etc). Yield approximately 60%.




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[*] posted on 25-7-2005 at 18:08


Translation:

-------
Example of urea acidolysis

Formamide: 15,8 g of formic acid heated with 18 g (one mol) of urea at 140-150° until cessation of gas formation (couple of hour) yield by vaccuum distillation 11,3 g of formamide melting at 113° under 20 mm (yield: 84%). - Berend[Ann. 128, 335 (1863)]) has already described the action, qualified by him as deshydrating, of urea on ammonium formate and has noted that heating this salt with half his weight of urea (about half a mol) at 140°, we could separation the formamide with a better yield (but he doesn't indicate it) than by simple heating of the salt: he has formulated the equation:

2 HCOONH4 + NH2CONH2 = 2 HCONH2 + C03(NH4)2

But it's really the reaction that intervenes: by taking only ¾ mol of urea (which yield after acidolysis of ½ mol of urea a mix that already contain for 2 mol of ammonium formiate on mol of urea, beside the already formed amide), we obtain with the same acid quantity only 10 g of amide; but the urea already converted by the acidolysis give 10,1 g of formamide (8,4 g if we count the 84% yield of the precedent try), so the formation of amide by dehydratation of the ammoniacal salt is not very important.

Acetamide: 10 g of urea and 10 g of acietic acid (equimolar quantity) heated in a round bottom flask until boiling give out CO2 as soon as the temperature reach 110°. Continuin the heating during two or three hour we see the temperature of the solution going up to 220°, with release of CO2 and NH3. The distillation yield 9,5 g of acetamide (yield of 95%) praticly pure, melting at 223°. The ammonium acetate is reacting the same way with urea. Here too, the formation of amide by direct deshydratation of the ammoniacal salt is relatively not important: by heating the acetic acid with half his weight of urea in the same conditions, we obtain only 66% (by comparing with the acid) of amide.

Benzamide: The reaction is here a bit slower and start only at about 150°. Heating equimolar quantity of benxoic acid and urea 1 hour at 200-230°, we obtain a product which, once extracted with boiling benzene, yield by cooling of the solution, benzamide identified by it's melting point and the nitrogen proportioning. There is still on the filter a quantity of by-product of the urea transformation (i.e. cyanuric acid, etc.) Yield about 60%
-------

Hope it's good




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dr. nick
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smile.gif posted on 26-7-2005 at 04:59


Yow! Thanks all!
That's allmost exhausting :)
I feared i was asking again stupid questions no one even knows what i want to know ... :)

Comes another problem: Getting Benzene from Calciumhydroxide and Sodium Benzoate to clear the benzamide before going on to aniline ...

every task turns out to be a never ending story :)
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[*] posted on 26-7-2005 at 05:34


Cool, that's an even simpler route to benzamide than "benzoic acid-(92%)->methyl benzoate-(93%)->benzamide" (described on my page).
Defineately gonna try the nearest days :o
Btw, I'm sure the benzene can be substituted. One could probably recryst the product from hot water or aqueous methanol..

For the Hoffmann rearrangement, should one use same conditions as for the alifatic amides? IIRC this was discussed in another thread.. humm

[Edited on 26-7-2005 by frogfot]
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[*] posted on 26-7-2005 at 05:51


I hope it will work! would you give me some more info if you made it? i don't get it done practically at the moment, funny thing is:

when the mixture begins to "boil" a lot of it crystallizes at the walls of the vessel (i guess it's the benzoic acid, but not sure), so most of it isn't reacting but hanging around at the glass ...

maybe better using a HB solvent? But how to get the product out of that afterwards? would that work at all?
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[*] posted on 26-7-2005 at 06:57


Just started a small batch and I get same problem.. the benzoic acid sublimes on walls of the flask.. Maybe this wouldn't decrease the yield on bigger scale.. I dunno..

Couldnt one add a small amount (with regard to the total reaction mix) of solvent with high bp.. like xylene (~140*C).. maby it will continiously wash down the benzoic acid.. A small amount of it hopefully wouldn't affect the temp in the reaction mix. Or am I totally wrong?

Anyway, I'll continiue with this batch and extract it with ether or heptane..
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[*] posted on 26-7-2005 at 17:39


Not urea, but since I'm posting aniline experimentals here and this is not interesting enough to put anywhere else - an excerpt that I happen to have from JOC 29, 2576 (1964):

"When benzoic acid is heated with nitromethane in
polyphosphoric acid (PPA), aniline is formed in good
yield along with carbon monoxide and carbon dioxide.

...p-Chloroaniline. Reaction of p-Chlorobenzoic Acid with
Nitromethane.-A mixture of 100 g. of PPA, 12.52 g. (0.08 mole)
of p-chlorobenzoic acid and 9.76 g. (0.16 mole) of nitromethane
was heated with stirring at 115' for 90 min. (or until gas evolution
ceased), poured into 200 g. of crushed ice, stirred, and filtered.
p-Chlorobenzoic acid, 3.1 g., was recovered. The filtrate was
then made strongly alkaline with KOH, cooled for 2 hr. at 0,
and filtered. p-Chloroaniline, m.p. 69, 6.1 g. (60% conversion,
80% yield), was isolated; lit. m.p. 70. A mixture melting point
with an authentic sample of p-chloroaniline showed no depression.
The infrared spectrum was superimposable on that of an authentic
sample of p-chloroaniline.

In a similar fashion the following amines were prepared in the
indicated yields from the corresponding carboxylic acids: aniline
(68%), p-toluidine (73%,), and o-toluidine (19%). The low yield
from o-toluic acid may be attributed to steric inhibition of resonance
caused by the o-methyl group and resulting in decreased
protonation of the carboxyl group.

Use of benzoyl chloride instead of benzoic acid gave aniline in
about the same yield (71%,) but in a shorter time. Use of nitroethane
instead of nitromethane gave aniline in 53%, yield from
benzoic acid. Use of 2-nitropropane instead of nitromethane
gave oxides of nitrogen but no aniline..."

I'm sure that everyone will be rushing to make or buy the nitroalkanes to use them to make aniline.
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[*] posted on 26-7-2005 at 23:01


S.C.Wack, that info is just to good to be true :o
Just gotta search the preparation of polyphosphoric acid..

The urea experiment didn't go well, though I'm sure it never reached 200*C (and lots of benz. a. was on the walls). On prolonged extraction with ether and aqueous Na2CO3 nearly whole mass didn't dissolve. The ether gave a small amount of crystalls (probably benzamide).
Everything smelled like almond.. could it be cyanuric acid? couldn't find its smell on google..

Next time gonna reflux the stuff with half amount of acetamide (bp 222*C)..

[Edited on 27-7-2005 by frogfot]
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[*] posted on 27-7-2005 at 01:10


Quote:
Just gotta search the preparation of polyphosphoric acid..


It is made by dissolving P2O5 in 85% phosphoric acid (H3PO4). There is also a preparation in an old Organikum stating it can be made by boiling off water from 85% H3PO4 under vacuum for 6h at 150°C, but I have some doubts that this gives polyphosphoric acid (perhaps it was meant to make a near 100% H3PO4).

Quote:
Everything smelled like almond.. could it be cyanuric acid?


Cyanuric acid is a nonvolatile solid without smell. Probably you meant hydrogen cyanide (HCN). It is unlikely that your experiment produced that. Note that bezaldehyde also smells like almond, but I don't see how urea could reduce benzoic acid.

You don't have to heat up to 200°C for the conversion of an acid to amide with urea. No wander everything sublimates off. Use an oil bath to regulate the temperature at 160-170°C. The reaction works perfectly at this temperature. Anything above will lower the yields due to urea decomposition to biuret, cynuric acid, melamine and other crap. You can tell the reaction is going on well by the evolution of CO2 in tinny bubbles and the ammonia smell. No solvents is needed and if used it would surely lower the yield since urea is not soluble in xylene and similar non polar solvents.

You can wash the product solution in toluene (or what ever you are going to use for extraction) with a solution of NaOH or Na2CO3 to remove any unreacted benzoic acid.

see also: https://sciencemadness.org/talk/viewthread.php?tid=4074

PS: The Hoffman rearrangement is not made like described in the first post of this thread. It is done on the amide and not on a reaction mixture containing urea and all kind of other crap that consumes the hypochlorite. And it is necessary to first let the hypochlorite form the N-chloroamide at a low temperature since at above 50°C the disproportionation of NaOCl to NaCl and NaClO3 occurs rapidly. Only after this induction period at <20°C is the reaction mixture heated to 60-80°C in order for the N-chloroamide to rearrange.




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[*] posted on 27-7-2005 at 02:51


hm. i'm trying a little learning by doing here - do i get this right: the benzamide first has to be cleaned (mix with NP and wash with NaOH) before proceeding, right?

Just one more question: is benzamide of any use for any other interesting task?

Thanks!
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[*] posted on 15-6-2006 at 10:44


hey!

had a little spare time, so i decided to give it another try -
everything like every time, just did not let the temp rise above 150 C.

then mixed with NP (Cleaning Benzin), heated, filtered and washed the
solid in the filter with 200ml 10% NaOH solution -
and was pretty surprised that it all dissolved ... now he has two layers -
one NP on top of the aquaeous layer and both are somehow dirty now -
Aquaeous is yellowish and there are floating solids in the NP ...

is this good or bad or ... ?
and if it's good - what to do now?

completely confused now!

swid doesn't understand anything now anymore ...

can anyone help, please?

thanks!

ps.: found some info at last, but still not clear what to do now -
it's says amides are polar, so when there was any benzamid present it should be in the NaOH-Solution now?

as far as i understood amides are also rather basic, even if not as much as
amines, but how would one get them out of the solution, now? they will probably not form a top layer like amines, so they can't be salted out with HCL, or can they? Or just evaporating the water?

oh man ...

[Edited on 15-6-2006 by dr. nick]
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[*] posted on 15-6-2006 at 15:58


interesting discussion...

I want to make pentafluoro aniline from pentafluoro benzoic acid.
the procedure posted by S.C. Wack looks atractive to me, however I'm afraid the poorly nucleophilic oxygenes of C6F5COOH would hinder any reaction that include protonation of the COOH...
the only way I found 'till now that uses (relatively) simple reagents is this:

C6F5COOH ---> C6F5COCl (using SOCl2)
C6F5COCl ---> C6F5COONH2 (by addition of hydroxyl amine)
C6F5COONH2 ---> C6F5NH2 (-CO2 by heating with K2CO3)


any thoughts anyone?:)
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[*] posted on 6-12-2006 at 11:05


Hey!

Can anyone give me (or hint me to) an instruction to the "destructive distillation" of Indigo? You know, Otto Unverdorben and stuff :)
Can not find it, lots and lots of hits on google, but they all only include the same text from wikipedia and that's of no use for me.

Just got some kg of Indigo and don't know what to do with it there
this old project came to mind again :)


Would be great!

Thanks!
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[*] posted on 6-12-2006 at 12:04


How is it possible that I never saw this thread?
I have produced and investigated the properties of benzamide (though my target product was benzonitrile).
I produced it by dripping benzoyl chloride into cooled excess conc. ammonia solution under vigorous stirring.
People without access to Benzoyl chloride will of course choose to go the urea route.

Benzamide can be recrystallized from water, but it must not be brought together with alkali because it will hydrolyze and dissolve (product is destroyed then).
I might consider doing a documented synthesis of benzamide and aniline from benzoic acid.

To separate benzamide from unreacted benzoic acid, ammonia solution is added. Only the benzoic acid dissolves, the benzamide remains undissolved (when kept cold).

Aniline was produced from indigo by dry distillation with lime (Ca(OH)2).


Oh, and amond smell during production of benzamide is benzonitrile (dehydration product of benzamide, an oil which is slightly soluble in water). This smells very similar to benzaldehyde.

BTW, are you still reading here Frogfot?

[Edited on 6-12-2006 by garage chemist]




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[*] posted on 6-12-2006 at 13:00


that's very interesting - information on simple benzamid is only very sparely available -
be it on the net or in the books available to me!

I have to use the urea/benzoic acid variant so do you have maybe a suggestion how to do it? The sublimation of the benzoic acid every time spoiled any success ...

Quote:
I might consider doing a documented synthesis of benzamide and aniline from benzoic acid.

yes, please, do so - that would be so cool - i already gave it up. My last idea (haven't tried it) was to put the mixed urea/benzoic acid into a aluminum can, than flatten it, closing the ends tight and to heat it in an oil bath, hoping it will not build too much pressure.

Thankful for any hint!

ps.:
Quote:
Aniline was produced from indigo by dry distillation with lime (Ca(OH)2).

could you describe that a bit more in detail? How to do it and so on? Is it maybe like with benzene from sodium benzoat and lime?
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[*] posted on 6-12-2006 at 13:38


I have made phthalimide from phthalic anhydride and urea, and sublimation of the phthalic anhydride is also a problem there. The problem is solved by heating fast enough so that the reaction is over in 5 minutes. Only a small amount of sublimation occurs then.
If the heating would have to be done for maybe an hour, sublimation would be a big problem.

I will try to make benzamide from benzoic acid this weekend (I can only experiment on weekends) and report my findings.
I am interested in this because benzoyl chloride is really too expensive and valuable to use it up for making benzamide.

If sublimation turns out to be a problem, I will try to enclose the mixture into a test tube which will be melted shut (e.g. an ampoule) or enclose it into a test tube with ground glass joint and stopper. Though I hope to be able to work in a normal round- bottom flask.

I do not have any references on the production of aniline from indigo, but I know that it was made by dry distillation with lime.
For me this information would already be enough to start experimentation (if I needed aniline, which isn't the case).

BTW, I have a detailed synthesis of aniline from benzamide. It's in Organikum. I can put a short summary here if there is interest. However, sodium hypobromite is used. If sodium hypochlorite would have to be used instead, its concentration would have to be exactly known.
In the lab, NaOBr is very much favored over NaOCl because it can be made fresh and of exactly known concentration from bromine, NaOH solution and ice.




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dr. nick
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[*] posted on 7-12-2006 at 00:54


Hey, thank you -

that's very encouraging, going to give it another try then, too - i had no idea how long the reaction would need to finish. Maybe the "juice can idea" isn't that stupid in the end, too.

Hm, Bromine is a problem, maybe on could get it from Bromine pool tabs?
I wonder how to do that.

Looking forward to your report, aniline so-to-say OTC is a long harbored dream of mine!

ps: the dry distillation: all i can think of would be like using the same procedure like for Benzene from sodium benzoat and lime ... think i'll give it a try. thanks!

[Edited on 7-12-2006 by dr. nick]
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Pabpa
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[*] posted on 7-12-2006 at 11:47


Hi,

I've done this reaction several times. It's very easy: 1kg benzoic acid, 2kg urea and 10ml phosphoric acid are heated for 2h at 170°C (should be carried out in an efficient hood or outside). Benzamide is purified by recrystallization from H2O and then from 9% ammonia solution.
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[*] posted on 7-12-2006 at 23:26


Quote:
The sublimation of the benzoic acid every time spoiled any success ...


Are you sure about the sublimation of benzoic acid? The white stuff might be ammonium cabonate. ;)
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dr. nick
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[*] posted on 8-12-2006 at 00:33


Quote:
Are you sure about the sublimation of benzoic acid? The white stuff might be ammonium cabonate.

Are you sure? That would be great - got to check that out - gonna heat some of my benzoic acid alone to see what happens and will report again!

Thanks!

Btw.: the Phosphoric acid might maybe help to prevent the sublimation (or what ever) by washing the stuff down again - maybe my error is the too small scale? i always do it in a test tube.
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