Sciencemadness Discussion Board

Benzaldehyde from Benzyl Chloride and Nitromethane

twodogs - 27-3-2011 at 00:48

I found this but can't find any references for it. Has anyone seen this before and perhaps have a writeup?

Benzyl chloride can be converted into benzaldehyde by treatment with nitro methane and base. The reaction involves initial conversion of nitro methane into its anion, followed by SN2 reaction of the anion with benzyl chloride and subsequent E2 reaction.

reaction.jpg - 17kB

[Edited on 27-3-2011 by twodogs]

jwarr - 27-3-2011 at 05:40

a quick search on scifinder did not turn up anything for this reaction

madscientist - 27-3-2011 at 08:16

Where did you find it?

twodogs - 27-3-2011 at 11:31

I googled and found

I am a bit dubious. I can't figure out how to balance the equation. Where does the chlorine end up?

[Edited on 27-3-2011 by twodogs]

Sedit - 27-3-2011 at 12:00

Im under the assumption that the Chlorine ends up with the base used but im confused as to what the final results of the nitromethane would be. Is there some sort of resonance setup?

Im also having a bit of trouble understanding it but this is not one of my strong points in the first place. Im left to assume a 2x molar excess of base being used as it seems to suggest to me that the Chlorine adds to the first mol of base while a second mol attacks the intermediat compound to finish off the product.

Ephoton - 27-3-2011 at 14:34 :)

Anions derived from aliphatic nitro compounds are capable of covalency formation at either
carbon or oxygen. Although the carbon alkylate is stable, and is isolated without difficulty, the
oxygen alkylate is unstable and the carbonyl compounds corresponding to the alkyl halides are
obtained. In general, nitroparaffin salts undergo oxygen alkylaton with little, if any, concomitant
carbon alkylation; indeed, this is the basis of a useful synthesis of aldehydes and ketones
(Scheme 5.1).1 However, there are some exceptions to give the C-alkylation, the reaction of
p-nitrobenzyl chloride with the salt of 2-nitropropane give the C-alkylation exclusively [see the
section of 7.1.1 radical substitution (SRN1)].

should work and there are reports from some of the guys on WD or now known as
the collective of it working from memory.

it is referenced too

Hass, H. B., and M. L. Bender. Org. Synth., ", 932 (1963).

ill dig it up and post it here if I can.

[Edited on 27-3-2011 by Ephoton]

Ephoton - 27-3-2011 at 14:43

case closed :)

Organic Syntheses, Coll. Vol. 4, p.932 (1963); Vol. 30, p.99 (1950).
Submitted by H. B. Hass and Myron L. Bender1.
Checked by Arthur C. Cope and Malcolm Chamberlain.
1. Procedure
Eleven and one-half grams (0.5 g. atom) of sodium is dissolved in 500 ml. of absolute ethanol in a 1-l. round-bottomed flask. Forty-six grams (0.52 mole) of 2-nitropropane is added, then 92.5 g. (0.50 mole) of o-xylyl bromide (Note 1). The flask is attached to a reflux condenser connected to a drying tube and shaken at intervals for 4 hours. The reaction mixture, originally at room temperature, becomes warm spontaneously, and a white precipitate of sodium bromide forms (Note 2).
After a reaction period of 4 hours the sodium bromide is separated by filtration and the ethanol is removed by distillation on a steam bath. The residue of product and sodium bromide is dissolved in 100 ml. of ether and 150 ml. of water. The ether layer is washed with two 50-ml. portions of 10% sodium hydroxide solution to remove any acetoxime and excess 2-nitropropane and is then washed with 50 ml. of water. The ether layer is separated and is dried with 15 g. of anhydrous sodium sulfate, and the ether is removed by distillation on a steam bath.
The crude product is distilled from a Claisen flask under reduced pressure. The yield of o-tolualdehyde boiling at 68–72°/6 mm., n25D 1.5430, is 41–44 g. (68–73%) (Note 3).
2. Notes
1. o-Xylyl bromide may be obtained from the Eastman Kodak Company or may be prepared by the light-catalyzed bromination of o-xylene.2
2. The solution is originally supersaturated with the sodium salt of 2-nitropropane, and a precipitate of this salt may be mistaken for sodium bromide.
3. This is a general method for the preparation of substituted benzaldehydes. The following aldehydes have been prepared by the same general procedure.3


Yield, %











Ephoton - 27-3-2011 at 14:51

I think you get a better yeild from hexamine though

twodogs - 27-3-2011 at 17:32

Thanks for that.

Ephoton - 27-3-2011 at 22:17

no probs my friend I wouldnt post if but for your effort to forward the cause.

good luck with your search.

Nicodem - 28-3-2011 at 10:06

Quote: Originally posted by Ephoton  
case closed :)


Eleven and one-half grams (0.5 g. atom) of sodium is dissolved in 500 ml. of absolute ethanol in a 1-l. round-bottomed flask. Forty-six grams (0.52 mole) of 2-nitropropane is added

It says "2-nitropropane" which is not what the question was about. The oxidation of alkyl halides and sulfonates via the decomposition of alkyl nitronates derived from 2-nitropropane is a common and well known method (there are plenty of references posted in other threads). But the original poster asked about the reaction of benzyl chloride with nitromethane derived nitronate which is certainly neither common or well known.

Ephoton - 28-3-2011 at 13:01

true good point there nicodem I should have taken that into account.

case is open then till some one tries it.

the measurements should be the same and the theory and balancing of equations would
be the same as well.

twodogs - 28-3-2011 at 22:28

So is sodium ethoxide or perhaps sodium methoxide necessary to create an anion. I was hoping simple NaOH would suffice.

[Edited on 29-3-2011 by twodogs]

Ephoton - 29-3-2011 at 00:17

I think sodium methyl nitronate is what is made when we make the big flame from nitromethane
and sodium hydroxide so I would think it should work.

I belive from my experiance with nitronates they use 2 nitro propane as it is not as reactive
when making the nitronate salt.

I could be wrong here but from what I have seen the larger the alkyl chain on the nitro the less likely
you are going to have the fire from hell burn your lab down.

still I have made the salt with nitromethane then done a neff reaction to formaldehyde so I can not
see how it would not work with normal sodium hydroxide.

I think they like to use ethoxide as it is in alcohol making the bromide precipitate.

also the reaction looks quite anhydrous from what I can tell so maby hydroxide is not so good.

maby if one was to make the nitronate salt first then dry it very carefully then use this in IPA as
this alcohol is easier to get anhydrous then add the benzyl chloride it might work.

Ephoton - 29-3-2011 at 01:41

on second thoughts I think you would be better off just using sodium hydroxide ethanol
and toluene or xylene. then distill of azeotrope to form the ethoxide ready for use.

I dont think its the sodium hydroxide that would be a problem but rather the water.

this would save you the danger of isolating and drying the nitronate salt.

kmno4 - 30-3-2011 at 04:50

It seems to be simple to do. All substrates are at hand: sodium, anh. ethanol, CH3NO2, benzyl chloride.
I am going to test this in a few days.

[Edited on 30-3-2011 by kmno4]

kmno4 - 31-3-2011 at 13:03

Solution of sodium ethoxide has beeen prepared from 1,07 g Na and ~40 cm3 ethanol. Next I have added equimolar amount CH3NO2 in ethanol. I have got white suspension, however liquid had blue tinge. Equimolar amount of benzyl chloride has been added to this suspension. The only effect is that liquid has green tinge now. No reaction seems to take place, even after standing 12 h at room temp. I am going to heat to reflux this mixture tomorrow.
I had no time to reflux it. After 24 hours there is still white suspension but liquid is yellow now and misture starts to smell like isocyanide :o
Something happens....

[Edited on 1-4-2011 by kmno4]

kmno4 - 2-4-2011 at 20:48

Product of refluxing (5 hours) looks very shitty.
It is just brown, not transparent solution, with brown sediment (possibly contaminated NaCl) and isocyanide smell. It is not worth taking a picture, the most adequate place for such things is water-closet.
But I will try to do "something" with it.

Ephoton - 4-4-2011 at 01:22

doesnt sound too good kmno4 thanx heaps for the test run.

I would have thought nitromethane to be more reactive than
the other nitroparifins.

nitroethane and nitropropane do not release anywere near
as much heat when mixed with dry NaOH as nitromethane.

[Edited on 4-4-2011 by Ephoton]

kmno4 - 4-4-2011 at 07:50

I had no idea so I refluxed it additionally during ~12 hours.
(it is because some papers give procedures with 14 h refluxing and longer).
Isocyanide smell became weaker, but a new one - benzaldehyde - appeared. It all is not so simple because benzaldehyde can exist in this mixture as benzaldoximes (in some papers they extract them with NaOH sol. from chlorofom sol. of reaction product).
However I think that this smell confirms existence of benzaldehyde (as one of the products of reaction).
It would be good is someone else would perform this experiment and present results here.

Slash - 8-4-2011 at 14:19

This is very interesting kmno4! Keep up the good work i wish i could help

MeSynth - 25-8-2011 at 21:31

Quote: Originally posted by Ephoton  
I think you get a better yeild from hexamine though

I found this in another forum... It needs to be revised.

140 g HMTA are finely grinded up and suspended into 4000 ml Ethanol (60%). To this suspension are added 125 g Benzyl Chloride, and the mixture is refluxed with stirring on a water bath for 5-6 h. After the reaction is finished, there are added 2000 ml H2O, and the mix is transferred into a distillation flask. After the alcohol distillated off, the stirrer speed was turned up, and the Benzaldehyde was steam distilled by the steam that generates from the boiling water in the flask. The Benzaldehyde presents as a separate layer in the receiving flask and is very probably pure enough to leave out further purification. (If desired, the BA can be extracted with DCM or ether, and can then be isolated as the Bisulfite adduct)
The yield of Benzaldehyde is 75 - 90 g (60 - 72%)

another post clip

the sommellete I would do with just water. setup for reflux with water
then when the condensor does not smell like amine or chloride change
condensor for distil setup.

when distilling drip in water into reaction flask at the rate that water
comes over at. keep distilling till no organics come over.

sep distallate with dcm then dry with MgSO4, filter then.
evap dcm to get a very clean

another post clip
Just be sure to do a bisulfite workup to get rid of any remaining benzyl chloride.

MeSynth - 30-8-2011 at 21:19

I found a couple more... XD (these are by faaa the best I've read about)

Benzaldehyde from Benzal Chloride Using Hydrochloric acid.
[by Friedrich Bruhne and Karl-August Lipper : Krefeld Germany November 6, 1978]

322 g (2 mols) of benzyl chloride and 750 g of 25 percent strength hydrochloric acid are heated to the reflux tempurature in a 1 liter three-necked flask with a stirrer, reflux condencer, gas inlet tube and thermometer, whilst stirring vigerously, and the mixture is kept under light reflux for 2 hours. A sump tempurature of 106* C. is established. A weak stream of nitrogen is passed through the flask during the reaction . The off-gas escaping from the reflux condencer is absorbed in a washing tower, packed with Raschig rings, wish 600 g of water, which are circulated by means of a pump. After cooling the mixture, 204 g of a light yellow coloured oil which, according to the titrimetric determination contains 98.1% of benzaldehyde (=200.1 g pure benzaldehyde), are obtained as the organic phase. This corresponds to a yield of 94.3% of theory. The benzaldehyde contains 0.06% of residue which cannot be distilled. *I skip the rest

Benzaldehyde from Benzal Chloride using Zinc Chloride
[by General Aniline New York, New York February 17, 1960]

To 700 parts by weight of distilled benzal chloride there was added 2 parts by weight of anhydrous zinc chloride and the two were mixed thoroughly with stirring while heating to 105—110°C. As soon as the reaction mixture was at 105—110°C. the addition of water was begun at a slow rate, while maintaining the reaction temperature at 110—120°C. The addition of water was continued until a total of 85 parts by weight of water had been added (approximately 5% excess) at which time the evolution of hydrogen chloride ceased. Reaction temperature was maintained for another hour to be sure that all the HC1 had been removed, and the benzaldehyde was then removed by vacuum distillation. The yield of benzaldehyde recovered at non distillation was 95% of theory and the purity of the product better than 96.5% Source General Aniline 1962

Manufacture of Benzaldehyde from Benzyl Chloride using Hexamine
[by Fabriques Issy, France March 7, 1912]

A solution of 14 kilos of hexamethylenetetramine in 40 litres of alcohol of 60 per cent. strength is mixed with 12.5 kilos of benzyl chloride and the mixture is heated on then water bath in a reflux apparatus for 5-6 hours; 20 litres of water are then added, the greater part of the alcohol distilled away and the residue carried over with steam. The liquid carried over is extracted by means of a volatile solvent and the aldehyde is purified by means of its bisulphite compound. The yield of purified benzaldehyde amounts to 7.5 to 9 kilos. The reaction may also be carried out without addition of alcohol,
that is to say in an aqueous solution. Thus, 12.65 kilos of benzyl chloride are heated for two hours with a solution of 14 kilos of hexamethylenetetramine in 60 litres of water, and the aldehyde is then distilled with steam; after purification with sodium bisulphite a good yield of benzaldehyde is obtained. Source: Fabriques 1914

2bfrank - 8-11-2012 at 01:21

The initial reaction in this thread was a question in the prescribed text, namely McMurray 6E/ i.e. Describe the mechanism when the base produced anion of nitromethane reacts with benzyl chloride. This tells me its in the literature. Im on an interem spell from Uni, and lost access to the searching journal capabilities, till I return for more punishment, but Im sure that its out and waiting to be discovered. I might play around with reaction conditions myself.