The nitration of methyl benzoate

You may wonder why the nitro group has gone magically onto the 3 position and not onto the 2 or 4 positions. There will be small amounts of the 2 and 4 isomers, although the 3 isomer is the major product of this reaction. This is because the existing (COOCH₃) side chain directs the new substituent (NO₂) into this position. The directing effect of side chains on the benzene ring is not required for your "A" level, but you might want to research it anyway.

If the temperature is allowed to rise multiple nitration may occur, producing a number of possible isomers with more than one nitro group.