Aniline to Azobenzene

[GreyDergal]

I heard about a process for turning Nitrobenzene to Aniline by refluxing it with NaOH and some Zn causing for Sodium zincate and Aniline to be formed. Then turning the Aniline into Azobenzene, the question is how do you turn the aniline into azobenzene, the simpler the better.

 

 

[tiny529]

I heard about a process for turning Nitrobenzene to Aniline by refluxing it with NaOH and some Zn causing for Sodium zincate and Aniline to be formed. Then turning the Aniline into Azobenzene, the question is how do you turn the aniline into azobenzene, the simpler the better.

 

 

 

NaNO2 in HCl should give you a diazonium chloride salt.

[Horza2002]

Ok, there's a little confusion here. Do you want how to make a diazomnium salt of benzene or how to make azobenzene? They are two different compounds.

 

As tiny529 said, reacting the aniline with sodium nitrite and HCl will do it. The HCl and sodium nitrite react first to generate nitrous acid which then reacts to form the diazonium salt. This is a useful intermediate as the N2 group is a vrey good leaving group and so can be used in as a range on intermediates (e.g. Sandmeyer reaction to convert the aryl amine into an aryl halide).

 

However, if you want azobenzene, then you reduce nitrobenzene with zinc and acetic acid.

 

http://en.wikipedia.org/wiki/Azobenzene

[mississippichem]

I'll add that everyone should be careful with diazonium salts as they can be explosively unstable above 5 C. Always keep a thermometer in the reaction mixture! But yes, the HCl after sodium nitrite is a Sandemeyer reaction and it leads to the diazonium salt which is different from an azo-compound.

 

 

vs.

 

Edited February 20, 2011 by mississippichem

[Horza2002]

Yes, azo compounds tend to be rather unstable at relatively mild temperatures...they also tend to be highly coloured resulting from the highly conjugated pi-system. Have a look at the dye topic thats in the organic chemistry section if you want more details as I've sready described them once!

[John Cuthber]

IIRC you can get azobenzene from the reaction of aniline with nitrobenzene or by oxidation of aniline (but the yield's not great)

[tiny529]

IIRC you can get azobenzene from the reaction of aniline with nitrobenzene or by oxidation of aniline (but the yield's not great)

 

According to my textbook (granted, I think my textbook is crap), aniline treated with NaNO2 and HCl will form the diazonium ion and an azo compound (though the yield is low). Sorry... I guess I tend to assume that everyone on here is doing this primarily on paper. =)