From the data which are now available it may be safely concluded that a halogen meta to the nitro group does increase the mobility of the halogen: in the para position. Also when piperidine is used as the reagent for reactive halogen, a steric effect seems to be of importance. Drake and McElvain “,'have shown that with piperidine a rate determining factor in the halogen replacement reaction is the ability of the reagent to approach the carbon ...
