OCR A2 Chemistry F324: Arenes

General definitions:

• Arenes - Are aromatic hydrocarbons containing one or more benzene rings.
• Electrophile - An electron pair acceptor.
• Electrophilic substitution of Benzene - A H atom on the benzene ring is replaced by an electrophile. The electrophile is attracted to the electron-rich pi bond where it accepts a pair of electrons from the pi bond to form a new covalent bond with a C atom of the ring.
• Reflux - The continuous boiling and condensing of a liquid mixture.
• Phenol's common uses - Antiseptics, disinfectants, plastics and resins in paints.

Reactions (simplified, without conditions or reagents):

- Nitration of Benzene

C₆H₆ + HNO₃ --> C₆H₅NO₂ + H₂O

(Where one of the H atoms is replaced by an NO₂ group)

- Chlorination (or Bromination) of Benzene

C₆H₆ + Cl₂ --> C₆H₅Cl + HCl

(Where one of the H atoms is replaced by a Cl atom)

- Phenol (‘acid’) + Alkali

C₆H₅OH + NaOH_(aq) --> C₆H₅ONa + H₂O

(Where O^- and Na⁺ form an ionic bond)

- Phenol (‘acid’) + Sodium

C₆H₅OH + Na_(s) --> C₆H₅ONa + ½H₂

(Where O^- and Na⁺ form an ionic bond)

- Phenol + Br₂

C₆H₅OH + 3Br₂ --> C₆H₂Br₃OH + 3HBr

(Where 3 H atoms are replaced by Br atoms (C₆H₂Br₃OH = 2,4,6-tribromophenol))

Evidence against Kekulé’s model of…