BRAINCAKEReactivity of Phenol
In phenol, C6H5OH, an -OH group is bonded directly to the benzene ring. (It is not classed as an alcohol, because the -OH is on an aromatic carbon.)
Phenol undergoes electrophilic substitution much more readily than benzene. The reason is the oxygen atom:
• A lone pair of electrons in a p-orbital on the oxygen overlaps with the π-system of the ring.
• The lone pair is partially delocalised into the ring.
• This increases the electron density of the ring.
• The electron-rich ring attracts electrophiles more strongly and can polarise molecules such as Br2, so no halogen carrier is needed.
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Key terms in this lesson
- electrophilic substitution
- A reaction mechanism in which an electrophile is attracted to and attacks a region of high electron density, such as the delocalised ring in benzene, displacing a hydrogen atom.
- halogen carrier
- A catalyst, such as AlCl3 or FeBr3, that generates a positive electrophile from a halogen or haloalkane for electrophilic substitution on a benzene ring.
More in Benzene
- Phenol
- Halogen Carriers
- Friedel-Crafts Alkylation
- Friedel-Crafts Acylation
- Phenol as a Weak Acid
- Bromination of Phenol
- Nitration of Phenol
- Directing Effects in Aromatic Substitution
All 16 lessons in Benzene · All OCR A-level Organic Chemistry topics