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17.1 Carboxylic Acids17.2 Physical Properties of Carboxylic Acids

17.3 Acidity of Carboxylic Acids

Chapter 17 Carboxylic Acids And Esters

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The carboxyl group: Is a carbonyl group (C=O) attached to a

hydroxyl group (OH). Is found on carbon 1 in carboxylic acids. Is written in different ways. O CH3—C—OH CH3—COOH CH3—CO2H

Carboxyl Group

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Models of Carboxylic Acids

The three-dimensional models show the geometry of atoms in carboxylic acid molecules.

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The IUPAC names of carboxylic acids: Replace the -e in the alkane name with -oic acid.

CH4 methane HCOOH methanoic acid

CH3—CH3 ethane CH3—COOH ethanoic acid Number substituents from the carboxyl carbon 1.

CH3

|CH3—CH—CH2—COOH

4 3 2 1 3-methylbutanoic acid

IUPAC Names

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The common names of simple carboxylic acids: Use formic acid (1C), acetic acid (2C), propionic

acid (3C), and butyric acid (4C). HCOOH formic acidCH3—COOH acetic acid

Locate substituents by assigning , , γ to the carbon atoms adjacent to the carboxyl carbon. CH3

γ | CH3—CH—CH2—COOH -methylbutryic acid

Common Names

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Names and Sources of Some Carboxylic Acids

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Aromatic Carboxylic Acids

Benzoic acid: Is the aromatic carboxylic acid. Locates substituents by assigning 1 to the

carbon attached to the carboxyl group. Has common names that assign prefixes

ortho, meta, and para for 2 substituents.ortho 1, 2 locationmeta 1, 3 location para 1, 4 location

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Aromatic Carboxylic Acids

Benzoic acid

4-Aminobenzoic acidp-Aminobenzoic acid

3-Chlorobenzoic acid m-Chlorozenoic acid

COOH

NH2

COOH

Cl

COOH

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Alpha Hydroxy Acids

Alpha hydroxy acids (AHAs):

Occur naturally in fruit, milk, and sugarcane.

Are used in skin care products.

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Preparation of Carboxylic Acids Carboxylic acid can be prepared by oxidizing

primary alcohols or aldehydes. The oxidation of ethanol produces ethanoic acid

(acetic acid).

OH O O | [O] || [O] ||CH3—CH2 CH3—C—H CH3—C—OH

Ethanol ethanal ethanoic acidEthyl alcohol acetaldehyde acetic acid

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Boiling Points

Carboxylic acids: Have higher boiling points than alcohols,

ketones, and aldehydes of similar mass. Form dimers in which hydrogen bonds form

between two carboxyl groups. O H—O

|| |CH3cC C—CH3

| ||

O—H O A dimer of acetic acid

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Solubility in Water

Carboxylic acids: With 1-4 carbon

atoms are very soluble in water.

Form hydrogen bonds with many water molecules.

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Boiling Points and Solubility

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Acid Dissociation Constants

Carboxylic acids: Are weak acids.

CH3—COOH + H2O

CH3—COO– + H3O+

Exist mostly as molecules and a few ions in aqueous solutions.

Have small Ka values.

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Salts of Carboxylic Acids

Carboxylic acid salts are: Formed when a carboxylic acid is neutralized by

a strong base.CH3—COOH + NaOH CH3—COO– Na+ + H2O

acetic acid sodium acetate (carboxylic acid salt) Used as preservatives and flavor enhancers.