Sandmeyer's reaction. This reaction is used to prepare arial halides from dylzonium salt. Am I no benzene? That is anyline is reactivit nitrous acid in the presence of NNO2 plus HCl at 273278 kWh. Here goes benzene dylzonium chloride salt. And this benzene dylzonium salt is used to prepare arial halides. Nitrogen in this benzene dylzonium salt is replaced by chlorine, bromine and cyanogrop. This reaction is called as Sandmeyer reaction. For example, dylzonium salt is reactivit COCl. Here goes chlorobenzene. Dylzonium salt is reactivit COBr. Here goes bromobenzene. And dylzonium salt is reactivit COCl. Here formation of cyanobenzene. In this reaction, this nitrogen it is replaced by chlorine, bromine and cyanogrop.