Alcohols

Structure: C–O–H Hybridization: sp³ at carbon and at oxygen Geometry: Tetrahedral at carbon; bent (~108–109°) at oxygen Polarity: Polar; hydrogen bond donor and acceptor Typical reactivity: Weakly acidic at O–H (Chapter 3); the oxygen is nucleophilic, and the hydroxyl can be converted into a leaving group for substitution or eliminated to form an alkene (Chapter 8).

Phenols

Structure: Ar–O–H (hydroxyl attached directly to an aromatic ring) Hybridization: sp² at the ring carbon bearing oxygen; oxygen lone pair conjugates into the ring Geometry: Planar at the point of attachment Polarity: Polar; hydrogen bond donor and acceptor Typical reactivity: More acidic than alcohols (Chapter 3) because the conjugate base (phenoxide) is resonance-stabilized by the ring. The ring is also activated toward electrophilic aromatic substitution (Chapter 17).

Ethers

Structure: C–O–C Hybridization: sp³ at oxygen Geometry: Bent at oxygen, ~109.5° Polarity: Polar bonds, but no O–H means no hydrogen bond donation Typical reactivity: Relatively unreactive; commonly used as solvents rather than reactants. Lack a good leaving group under normal conditions.

Aldehydes

Structure: R–CHO (carbonyl carbon bonded to at least one hydrogen) Hybridization: sp² at the carbonyl carbon Geometry: Trigonal planar, ~120° Polarity: Strongly polar C=O dipole Typical reactivity: Carbonyl carbon is electrophilic and undergoes nucleophilic addition (Chapter 12). Less sterically hindered than ketones, so generally more reactive toward nucleophiles.

Ketones

Structure: R–CO–R′ (carbonyl carbon bonded to two carbon groups) Hybridization: sp² at the carbonyl carbon Geometry: Trigonal planar, ~120° Polarity: Strongly polar C=O dipole Typical reactivity: Undergoes nucleophilic addition (Chapter 12), generally somewhat slower than aldehydes due to greater steric bulk and electron donation from two alkyl groups.

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