Chapter 17: Alcohols and Phenols Dr. Sivappa Rasapalli Chemistry and Biochemistry University of Massachusetts Dartmouth
Coverage and Objectives • Coverage: • 1. Structure and Bonding; Physical Properties of Alcohols • 2. Acidity of Alcohols and Phenols • Formation of Alkoxides and Phenoxides • Preparation of Alcohols including Review Reactions • and Ring-opening Reactions of Epoxides (+ Mechanisms). • 5. Reactions of Alcohols + Mechanisms • Objectives: • 1. Know all mechanisms discussed in class. • Know how to predict the relative acidities of substituted alcohols and phenols. • Know reactions and reagents for preparation of alcohols including review reactions. • Know reactions of alcohols and mechanisms.
CO + 2H2 CH3OH Oldest known synthesis: fermentation Sugar + yeast ethyl alcohol + CO2
Problem 1: Classify each of the following either as a phenol, or as a 1º, 2º, 3º, or vinyl alcohol
IUPAC Rules for Naming Alcohols 3-hydroxycyclohexanone
Nomenclature of Phenols Problem 2: Name the following using IUPAC system
17.2 Physical Properties: miscible miscible 0.6% soluble
Acidity of Phenols Summary of EDG/EWG Substituents on p-Bonding Systems • donating and withdrawing ability measured relative to hydrogen
Retrosynthesis R R C O H OH C H H R R H:– H OH C O C R' R' H:–
Reducing agents i-Butyl H H – + – + H H H Li Na H H Al Al B H iButyl H Lithiumaluminum hydride Diisobutylaluminum hydride both reagents act as donors of hydride (H-) donors Sodiumborohydride
Sodium borohydride Aldehydes are reduced to 1° alcohols Ketones are reduced to 2° alcohols The reagent adds the equivalent of hydride to the carbon of C=O and polarizes the group as well
NaBH4 Vs LiAlH4 synthons precursors = NaBH4 reduces aldehydes to primary alcohols NaBH4 reduces ketones to secondary alcohols NaBH4 does not react with esters or carboxylic acids
Grignard + Ester • Grignard attacks the carbonyl and OEt ion leaves. Ketone intermediate
Grignard + Acid Chloride • Grignard attacks the carbonyl and Chloride ion leaves. Ketone intermediate
How would you synthesize... • Using an aldehyde or ketone. Using an acid chloride or ester.
Grignard Reagents and Other Functional Groups in the Same Molecule • Which Solvents (if any) Would be OK for Handling RMgBr?, • Which substrates could be converted into RMgBr, and Subsequently reacted with CH3CHO?
Some Reactions of Alcohols Two general classes of reaction • At the carbon of the C–O bond • At the proton of the O–H bond