CHM 247 CH.17
Alcohols and Phenol
• Alcohol: A compound with an –OH group bonded to a saturated, sp -hybridized carbon,
• Phenol: A compound with an –OH group directly bonded to an aromatic ring, ArOH.
• Enol is a hydroxyl group bonded to a carbon in a double bond.
17.1 NamingAlcohols and Phenols
• Can be primary, secondary, or tertiary.
• Rules: 1) Longest chain with the hydroxyl group. Replace the –e with –ol. 2) Number the
chain. 3) List in alphabetical order.
• Phenol is used as the parent name rather than benzene.
17.2 Properties of Alcohols and Phenols
• Alcohols and phenols have a higher than expected BP due to H-bonding.
• Alcohols and phenols are both weakly basic and weakly acidic.
• Weak base:
• Alkoxide ion: The anion RO formed by deprotonation of an alcohol.
• Phenoxide ion: The anion of a phenol, ArO .-
• Weak acid:
• Simple alcohols are about as acidic as water. Phenols are substantially more acidic than
• The bulkier the alcohol the weaker the acid.
• Induction by EWGs polarize the O-H bond and increase acidity.
• Alcohols don’t react with weak bases such as amines or bicarbonate ion.
• Alcohols do react with alkali metals, strong bases (NaOH, NaH, NaNH ),2and Grignard
reagents (RMgX). •
• Phenols are soluble in NaOH due to being more acidic.
• Substituted phenols can be more or less acidic than phenol depending on the substituent
being an EWG or an EDG. Phenols with an EWG are more acidic. Phenols with an EDG
are less acidic.
17.3 Preparation of Alcohols: A Review
• Hydroboration: Syn, non-Markovnikov. Oxymercuration-demercuration: Markovnikov.
• OsO y4elds cis product. Epoxide opening yields trans.
17.4 Alcohols from Carbonyl Compounds: Reduction • Most common method of preparation is the reduction of a carbonyl compound.
Reduction of Aldehydes and Ketones
• Aldehydes are easily reduced to primary alcohols and ketones are reduced to secondary
• Only strong enough to reduce aldehydes and
ketones. Solvents are alcohols.
• Stronger than NaBH .4Reduces other carbonyls like esters
and carboxylic acids, though 2 equivalents of hydride are needed. Reacts violently with
H 2, dry solvents are used (ether, THF).
Reduction of CarboxylicAcids and Esters
• Not as fast as aldehydes or ketones being reduced.
17.5 Alcohols from Carbonyl Compounds: Grignard Reaction
• When a proton is present, Grignard reagents will not work.
• • Carboxylic acids do not give addition products with Grignard reagents because the acidic
carboxyl hydrogen reacts with the basic Grignard reagent to yields a HC and a
• Grignard reagents can’t be prepared from an organohalide if other reactive functional
groups are present on the same molecule.
17.6 Reactions of Alcohols
Conversion ofAlcohols intoAlkyl Halides
• Tertiary alcohols react with HCl or HBr by a S N mechanism. No necessary change in
stereocenter. Primary and secondary alcohols are more resistant to acid and are best
converted with treatment of SOCl o2 PBr th3ough an S 2 mNchanism.