1.2- Dibromobenzene, possible isomers

These three structures are different isomers because isomer I has the two bromines between the edges of two squares isomer II has one bromine on the corner of one triangle, and the other bromine on the corner of the other triangle isomer III has the two bromines on the two corners of the same triangle. These are the only three possible isomeric Ladenburg dibromobenzenes. 

Since there is only one possible isomeric product, this dibromobenzene is the para isomer. 

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