What is the role of sodium amide in the formation of benzyne from chlorobenzene?

[[Leo]]

1)I can't find what will happen if 3C2H2 reacts with Cu2Cl2 . C6H6 can't be , or does it ?
2) after several reactions i got unknown compound which reacts with 2NaNH2(in the ether ) and product is C6H4 . How it can be C6H4 ? Does anybody know what unknown compound can be ?

 

[tandoorichicken]

If I am doing this right, 3C2H2 in Cu2Cl2 will give you one molecule of unreacted C2H2 and vinyl ethyne, or CH2-CH-CCH, which if you add up all the carbons and hydrogens, you get 6C and 6H.

As to the second question, I don't think C6H4 exists, but it is listed as a hypothetical byproduct in some benzene-related reactions. Imagine a six-carbon chain where all of the carbons are double bonded and the end carbons each have two hydrogens, and you have C6H4. I think it would be called 1,2,3,4,5-pentahexene or something like that. However, I don't think you could get that from a reaction with Na-NH2 or any other strong base (NaOH, NaH, etc.).

 

[chemisttree]

Benzyne is a derivative of benzene or a substituted benzene. Some of these derivatives of benzene can be driven to produce benzyne by the action of a strong base such as sodium amide. It is not a six-carbon chain at all but rather a six-carbon ring. You must figure out why TWO molecules of sodium amide are required to produce the benzyne.

I'll give you a hint: if chlorobenzene were reacted with ONE molecule of sodium amide, benzyne (C6H4) could be produced (base-assisted dehydrohalogenation).