Sciencemadness Discussion Board

Benzyl Iodide/Benzyl Cyanide Synthesis

CRK - 30-9-2014 at 19:47

One of the most common ways to synthesize benzyl cyanide is to start from benzyl chloride. Is it possible to substitute benzyl chloride for benzyl iodide? If so, how would one approach this? I would imagine it would work if you bubble I2(g) through Toluene at ~100 degress Celsius, the same process you would use if you were making benzyl chloride with chlorine. Would that work, or how could you synthesize benzyl iodide? Iodine is a lot safer to handle compared to chlorine.

Chemosynthesis - 30-9-2014 at 19:58

Unfortunately, the most common production method I have seen for alkyl iodides is a halide swapping reaction from the chloride, known as the Finkelstein reaction. Iodides also tend to be difficult to store.

UnintentionalChaos - 30-9-2014 at 20:38

Iodine cannot substitute for Br2 or Cl2 in this reaction as far as I know. Other complications are the significant instability of benzyl iodide and it's extremely lachrymatory nature. According to a PhD student I know, the iodide is far worse than the chloride and bromide despite lower volatility. Additionally, as as alkylating agent, the iodide is the most potent of the three and is thus the most dangerous benzyl halide to handle.

CRK - 30-9-2014 at 21:15

Okay, well since I will be abandoning that idea. Would ClO2 react with Toluene? I'm planning on mixing NaClO and HCl to produce Chlorine gas, but ClO2 is a side product, will this interfere with the reaction?

forgottenpassword - 1-10-2014 at 02:09

It would be simpler to react benzyl alcohol with hydrochloric acid. Using chlorine gas and toluene will likely give you a mixture of products and a separation problem.

CuReUS - 1-10-2014 at 04:10
Quote:
CRK -why dont you try making benzyl iodide from benzene diazonium chloride(aniline +NaNO2 +excess HCl) with methyl iodine
i have seen a similar reaction with benzene diazonium chloride with nitromethane to form nitromethyl benzene(N-phenyl nitro methane) but that may be due to the electron withdrawing effect on the nitro group so you may have to use a catalyst.


thinking of it now,maybe you could just react benzene diazonium chloride with acetonitrile to get benzyl cyanide instead of an aralkyl halide route:D


[Edited on 1-10-2014 by CuReUS]

[Edited on 1-10-2014 by CuReUS]

Metacelsus - 1-10-2014 at 06:45

Benzyl bromide is the easiest to prepare, given that bromine is a liquid. I've done the reaction before myself. The bromide should work fine for making benzyl cyanide.

Mercedesbenzene - 1-10-2014 at 12:21

I have made benzyl chloride from toluene and chlorine using TCCA and hydrochloric acid. The reaction worked quite well and the mixture of the mono/di chlorinated derivatives were easy to separate by distillation. The bromide should be even easier to make because as previously mentioned bromine is a liquid which simplifies handling.

Oxirane - 1-10-2014 at 14:33

This reaction is actually described in Versuchschemie, but there are many variations to it. Easiest would be to mix benzyl alcohol and hydrochloric acid. Most difficult, though used in industry, is to react chlorine gas with toluene under strong UVB light source. Benzyl cyanide synthesis is described in couple of sites and it should be quite easy.

Does anyone have any data on benzyl cyanide toxicity, by the way? I generally classify all common cyanides in the highest safety class, but somebody mentioned once that benzyl cyanide toxicity is substantially lower than common salts.

CRK - 1-10-2014 at 22:15

I attempted to synthesize benzyl chloride. 100mls of Toluene was place in a 500ml two neck round bottom flask fitted with a reflux condenser and a vacuum receiver with tubing leading into the Toluene (Not the best way it could've been performed, but it sufficed). NaClO and HCl were mixed to produce chlorine with ClO2 as a side product. The chlorine was bubbled through the Toluene as it was gently boiling and a 60 Watt lamp was my light source. The rfinal product I ended up with was a clear/yellow solution, normally I'd be ecstatic since benzyl chloride has a slightly yellow tint, but I'm thinking some ClO2 dissolved in it to give it the yellow colour. Do you think the reaction was successful or unsuccessful? The next time I attempt this I'm going to use KMnO4 and HCl to avoid the chlorine dioxide by product. Also, I haven't had time to check the boiling point of the solution.

forgottenpassword - 2-10-2014 at 05:18

Quote: Originally posted by CRK  
Do you think the reaction was successful or unsuccessful? The next time I attempt this...

Why not complete this reaction first, rather than planning your next attempt? It is a waste of time attempting any reaction if you will then only look at the colour and think "no good, try again". Separate your products by distillation and record the boiling points. Then you can tell us if it was successful, and what quantity of each product you synthesised.

Metacelsus - 2-10-2014 at 08:38

Did your eyes burn? That's a good (though maybe not so safe) way to detect formation of benzyl halides.

Steam - 2-10-2014 at 18:45

I have worked with benzyl chloride before and let me tell you from experience, it is a nasty chemical. It seams to penetrate clothes and for some reason once you smell it it lingers in the back of the nose for hours.

It also tends to polymerize in storage to a thick yellow gunk...