Timberlake: General, Organic & Biological Chemistry Copyright ©2010 by Pearson Education, Inc. SAMPLE PROBLEM16.1 Naming Carboxylic Acids SOLUTION a. STEP

Timberlake: General, Organic & Biological Chemistry Copyright ©2010 by Pearson Education, Inc.

SAMPLE PROBLEM 16.1

Naming Carboxylic Acids

SOLUTIONa. STEP 1 In the IUPAC system, name the longest carbon chain containing

the carboxyl group by replacing the e in the alkane name with oic acid. A carboxylic acid with four carbon atoms is named butanoic acid; the common name is butyric acid.

Give the IUPAC and common name, if any, for each of the following carboxylic acids:

STEP 2 Give the location and names of the substituents on the carbon chain by counting the carboxyl carbon as carbon 1. With a methyl group on the second carbon, the IUPAC name is 2-methylbutanoic acid. For the common name, the Greek letter a specifies the carbon atom next to the carboxyl carbon, a-methylbutyric acid.


SAMPLE PROBLEM 16.1

Naming Carboxylic Acids (Continued)

SOLUTION

b. STEP 1 In the IUPAC system, name the longest carbon chain containing the carboxyl group by replacing the e in the alkane name with oic acid. An aromatic carboxylic acid is named as benzoic acid.

Give the IUPAC and common name, if any, for each of the following carboxylic acids:

STEP 2 The carbon attached to the carboxyl group is carbon 1. With the —Cl on carbon 3, the IUPAC name is 3-chlorobenzoic acid. For the common name, the —Cl is on the meta (m)

carbon, which gives meta-chlorobenzoic acid or m-chlorobenzoic acid.

STUDY CHECKDraw the condensed structural formula of 3-phenylpropanoic acid.


SAMPLE PROBLEM 16.2

Preparation of Carboxylic Acids

Write an equation for the oxidation of 1-propanol and name each product.

STUDY CHECKDraw the condensed structural formula of the carboxylic acid produced by the oxidation of 1-butanol.

SOLUTIONA primary alcohol oxidizes to an aldehyde, which can oxidize further to a carboxylic acid:


SAMPLE PROBLEM 16.3

Properties of Carboxylic AcidsPut the following organic compounds in order of increasing boiling points: butanoic acid, pentane, and 2-butanol.

STUDY CHECKWhy would methanoic acid (molar mass 46, bp 101 ˚C) have a higher boiling point than ethanol(molar mass 46, bp 78 °C)?

SOLUTIONThe boiling point increases when the molecules of a compound can form hydrogen bonds or have dipole–dipole attractions. The alkane has the lowest boiling point because alkanes cannot hydrogen bond. Alcohols and carboxylic acids have higher boiling points than alkanes because they form hydrogen bonds. However, carboxylic acids can form stable dimers to increase their effective molar mass and therefore their boiling points.


SAMPLE PROBLEM 16.4

Ionization of Carboxylic Acids in WaterWrite the equation for the ionization of propionic acid in water.

STUDY CHECK

Write an equation for the ionization of formic acid in water.

SOLUTIONThe ionization of propionic acid produces a carboxylate ion and a hydronium ion:


SAMPLE PROBLEM 16.5

Neutralization of a Carboxylic AcidWrite the equation for the neutralization of propanoic acid (propionic acid) with sodium hydroxide.

STUDY CHECK

What carboxylic acid will give potassium butanoate (potassium butyrate) when it is neutralized by KOH?

SOLUTIONThe neutralization of an acid with a base produces the salt of the acid and water:


SAMPLE PROBLEM 16.6

Writing Esterification EquationsThe ester that is present in apples and pineapples can be synthesized from butyric acid and methyl alcohol. What is the equation for the formation of the ester in apples?

SOLUTION

STUDY CHECK

What carboxylic acid and alcohol are needed to form the following ester, which gives flavor and odor to apricots? (Hint: Separate the O and C—O of the ester group and add —H and —OH to give the original alcohol and carboxylic acid.)

——


SAMPLE PROBLEM 16.7

Naming Esters

SOLUTION

STEP 1 Write the name of the carbon chain from the alcohol as an alkyl group. The alcohol that is part of the ester is propanol, which is named as the alkyl group propyl.

Write the IUPAC and common names of the following ester:

STEP 2 For the IUPAC name, replace the ic acid in the carboxylic acid name with ate. The carboxylic acid with three carbon atoms is propanoic acid. Replacing the ic acid with ate gives the IUPAC

name of propyl propanoate. The common name of propionic acid gives the common name for the ester of propyl propionate:

STUDY CHECKDraw the condensed structural formula of ethyl heptanoate that gives odor and flavor to grapes.


SAMPLE PROBLEM 16.8

Acid Hydrolysis of Esters

STUDY CHECKWhat are the names of the products from the acid hydrolysis of ethyl propanoate (ethyl propionate)?

Aspirin that has been stored for a long time may undergo hydrolysis in the presence of water and heat. What are the hydrolysis products of aspirin? Why does a bottle of old aspirin smell like vinegar?

SOLUTIONTo write the hydrolysis products, separate the compound at the ester bond. Complete the formula of the carboxylic acid by adding —OH (from water) to the carbonyl group and an —H to complete the alcohol. The acetic acid in the products gives the vinegar odor to a sample of aspirin that has hydrolyzed:


SAMPLE PROBLEM 16.9

Base Hydrolysis of Esters

STUDY CHECKDraw the condensed structural formulas of the products from the hydrolysis of methyl benzoate by KOH.

Ethyl acetate is a solvent widely used for fingernail polish, plastics, and lacquers. Write the equation of the hydrolysis of ethyl acetate by NaOH.

SOLUTIONThe hydrolysis of ethyl acetate by NaOH gives the salt of acetic acid and ethyl alcohol:

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Timberlake: General, Organic & Biological Chemistry Copyright ©2010 by Pearson Education, Inc. SAMPLE PROBLEM16.1 Naming Carboxylic Acids SOLUTION a. STEP