Final answer:
To form a new bond on a benzylic radical, two fishhook arrows are needed, one from the benzylic radical and another from the radical it is reacting with. Each fishhook arrow represents the movement of a single electron, and the combination of two unpaired electrons results in the formation of a new covalent bond.
Step-by-step explanation:
To answer the question how many fishhook arrows are needed to form a new bond on a benzylic radical, we need to consider how radicals react in chemistry. A radical is an atom or a group of atoms with an unpaired electron, and in the case of a benzylic radical, this unpaired electron resides on the carbon atom adjacent to a benzene ring. Fishhook arrows, or half-headed arrows, represent the movement of a single electron. To form a new bond, two radicals must combine their unpaired electrons, thus necessitating the use of one fishhook arrow from the benzylic radical and another from the other radical participating in the bond formation.
The overall process can be understood in the context of the reaction between a benzylic radical and another radical species, where the unpaired electrons pair up to complete a new covalent bond. This step is vital in various organic reactions, including polymerizations and transformations that involve radical intermediates. The diagram of benzene provided and the related content on aromatic stabilization and electrophilic reactions emphasize the stability and reactivity unique to aromatic compounds.
It's important to note that benzene, as shown, exhibits resonance, where the double bonds in the hexagonal ring are not fixed but instead shift positions, indicating delocalized electrons. This resonance contributes to the stability of aromatic compounds, which is not directly related to formation of new bonds with benzylic radicals but is essential knowledge for understanding aromatic chemistry as a whole.