Transcript SAMPLE PROBLEM 16.1 Naming Carboxylic Acids

SAMPLE PROBLEM
16.1
Naming Carboxylic Acids
Give the IUPAC and common name, if any, for each of the following carboxylic acids:
SOLUTION
a. 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.
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 2methylbutanoic acid. For the common name, the Greek letter a specifies the carbon atom next to the
carboxyl carbon, a-methylbutyric acid.
Timberlake: General, Organic & Biological Chemistry
Copyright ©2010 by Pearson Education, Inc.
SAMPLE PROBLEM
16.1
Naming Carboxylic Acids (Continued)
Give the IUPAC and common name, if any, for each of the following carboxylic acids:
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.
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 thecommon name, the —Cl is on the meta (m) carbon, which
gives meta-chlorobenzoic acid or m-chlorobenzoic acid.
STUDY CHECK
Draw the condensed structural formula of 3-phenylpropanoic acid.
Timberlake: General, Organic & Biological Chemistry
Copyright ©2010 by Pearson Education, Inc.
SAMPLE PROBLEM
16.2
Preparation of Carboxylic Acids
Write an equation for the oxidation of 1-propanol and name each product.
SOLUTION
A primary alcohol oxidizes to an aldehyde, which can oxidize further to a carboxylic acid:
STUDY CHECK
Draw the condensed structural formula of the carboxylic acid produced by the oxidation of 1-butanol.
Timberlake: General, Organic & Biological Chemistry
Copyright ©2010 by Pearson Education, Inc.
SAMPLE PROBLEM
16.3
Properties of Carboxylic Acids
Put the following organic compounds in order of increasing boiling points: butanoic acid, pentane, and 2-butanol.
SOLUTION
The 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.
STUDY CHECK
Why would methanoic acid (molar mass 46, bp 101 ˚C) have a higher boiling point than ethanol
(molar mass 46, bp 78 °C)?
Timberlake: General, Organic & Biological Chemistry
Copyright ©2010 by Pearson Education, Inc.
SAMPLE PROBLEM
16.4
Ionization of Carboxylic Acids in Water
Write the equation for the ionization of propionic acid in water.
SOLUTION
The ionization of propionic acid produces a carboxylate ion and a hydronium ion:
STUDY CHECK
Write an equation for the ionization of formic acid in water.
Timberlake: General, Organic & Biological Chemistry
Copyright ©2010 by Pearson Education, Inc.
SAMPLE PROBLEM
16.5
Neutralization of a Carboxylic Acid
Write the equation for the neutralization of propanoic acid (propionic acid) with sodium hydroxide.
SOLUTION
The neutralization of an acid with a base produces the salt of the acid and water:
STUDY CHECK
What carboxylic acid will give potassium butanoate (potassium butyrate) when it is neutralized by KOH?
Timberlake: General, Organic & Biological Chemistry
Copyright ©2010 by Pearson Education, Inc.
SAMPLE PROBLEM
16.6
Writing Esterification Equations
The 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?
— of the ester group and add —H and —OH to give the original alcohol and
(Hint: Separate the O and C—O
carboxylic acid.)
Timberlake: General, Organic & Biological Chemistry
Copyright ©2010 by Pearson Education, Inc.
SAMPLE PROBLEM
16.7
Naming Esters
Write the IUPAC and common names of the following ester:
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.
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 CHECK
Draw the condensed structural formula of ethyl heptanoate that gives odor and flavor to grapes.
Timberlake: General, Organic & Biological Chemistry
Copyright ©2010 by Pearson Education, Inc.
SAMPLE PROBLEM
16.8
Acid Hydrolysis of Esters
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?
SOLUTION
To 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:
STUDY CHECK
What are the names of the products from the acid hydrolysis of ethyl propanoate (ethyl propionate)?
Timberlake: General, Organic & Biological Chemistry
Copyright ©2010 by Pearson Education, Inc.
SAMPLE PROBLEM
16.9
Base Hydrolysis of Esters
Ethyl acetate is a solvent widely used for fingernail polish, plastics, and lacquers. Write the equation of the
hydrolysis of ethyl acetate by NaOH.
SOLUTION
The hydrolysis of ethyl acetate by NaOH gives the salt of acetic acid and ethyl alcohol:
STUDY CHECK
Draw the condensed structural formulas of the products from the hydrolysis of methyl benzoate by KOH.
Timberlake: General, Organic & Biological Chemistry
Copyright ©2010 by Pearson Education, Inc.