text: The Sandmeyer reaction relies on a species of this type replacing the diazo group on an aromatic ring.
full_question: The Sandmeyer reaction relies on a species of this type replacing the diazo group on an aromatic ring. An important family of concerted reactions named for these species is carried out in a polar aprotic solvent and is slowed by steric effects. These species rely on leaving groups such as tosylates and halides to create carbocations in a unimolecular family of reactions named for them. For 10 points, name these chemical species that replace a substituent in SN1 and SN2 reactions, ‘attacking’ electrophiles.
first_sentence: The Sandmeyer reaction relies on a species of this type replacing the diazo group on an aromatic ring.