General Chemistry Principles, Patterns, and Applications, 2011

alcohols are even weaker acids than water. The acidic strength of phenols, however, is about a million
times greater than that of ethanol, making the pKa of phenol comparable to that of the NH4 + ion (9.89
versus 9.25, respectively):
Equation 24.8
C6H5OH + H2O H 3O + + C6H5O -
Note the Pattern
Alcohols undergo two major types of reactions: cleavage of the O–H bond and cleavage of the C–O bond.
Cleavage of the C–O bond in alcohols occurs under acidic conditions. The –OH is first protonated, and
nucleophilic substitution follows:
In the absence of a nucleophile, however, elimination can occur, producing an alkene (Figure 24.13).
Ethers lack the –OH unit that is central to the reactivity of alcohols, so they are comparatively unreactive.
Their low reactivity makes them highly suitable as solvents for carrying out organic reactions.
Aldehydes and Ketones
Aromatic aldehydes, which have intense and characteristic flavors and aromas, are the major components
of such well-known flavorings as vanilla and cinnamon (Figure 24.17 "Some Familiar Aldehydes and Their
Uses"). Many ketones, such as camphor and jasmine, also have intense aromas. Ketones are found in
many of the hormones responsible for sex differentiation in humans, such as progesterone and
testosterone. (For more information on aldehydes and ketones, see Chapter 4 "Reactions in Aqueous
Solution", Section 4.1 "Aqueous Solutions".)
Figure 24.17 Some Familiar Aldehydes and Their Uses
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