General orrganic and biological chemistry structures off liffe 5th by karen timberlake16 worked examples

Propanoic acid has the highest boiling point, 141 °C, because carboxylic acids can form stable dimers through hydrogen bonding to increase their effective molar mass and therefore their

Give the IUPAC and common name for the following carboxylic acid:

Sample Problem 16.1 Naming Carboxylic Acids

Solution

Step 1 Identify the longest carbon chain and replace the e in the corresponding alkane name with oic acid The IUPAC

name of a carboxylic acid with four carbons is butanoic acid; the common name is butyric acid

Step 2 Name and number any substituents by counting the carboxyl group 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 α specifies the carbon atom next to the carboxyl carbon, α-methylbutyric acid.

Study Check 16.1

Give the IUPAC and common name for the following:

Continued

Sample Problem 16.1 Naming Carboxylic Acids

The boiling point increases when the molecules of a compound can form hydrogen bonds or have dipole–dipole

attractions Pentane has the lowest boiling point, 36 °C, because alkanes cannot form hydrogen bonds or dipole–dipole attractions 2-Butanol has a higher boiling point, 100 °C, than pentane because an alcohol can form hydrogen bonds Propanoic acid has the highest boiling point, 141 °C, because carboxylic acids can form stable dimers through hydrogen bonding to increase their effective molar mass and therefore their boiling points

Study Check 16.2

Why would methanoic acid (molar mass 46, bp 101 °C) have a higher boiling point than ethanol (molar mass 46,

bp 78 °C)?

Answer

Two methanoic acid molecules form a dimer, which gives an effective molar mass that is double that of a single acid molecule Thus, a higher boiling point is required than for ethanol

Match each of the compounds 2-butanol, pentane, propanoic acid with a boiling point of 141 °C, 100 °C, or 36 °C

(They have about the same molar mass.)

Sample Problem 16.2 Boiling Points of Carboxylic Acids

A chemical equation for the dissociation of a carboxylic acid includes the reactants, a carboxylic acid and water, and the products, carboxylate and hydronium ions

Study Check 16.3

Write the balanced chemical equation for the dissociation of formic acid in water

Answer

Write the balanced chemical equation for the dissociation of propanoic acid in water

Sample Problem 16.3 Dissociation of Carboxylic Acids in Water

A chemical equation for the neutralization of carboxylic acid includes the reactants, a carboxylic acid and a base, and the products, a carboxylate salt and water

Study Check 16.4

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

Answer

butanoic acid (butyric acid)

Write the balanced chemical equation for the neutralization of propanoic acid (propionic acid) with sodium hydroxide

Sample Problem 16.4 Neutralization of Carboxylic Acid

In an esterification equation, a carboxylic acid and an alcohol react to form an ester and water The ester product of the esterification of butanoic acid and methanol is methyl butanoate

Study Check 16.5

The ester that smells like plums can be synthesized from methanoic acid and 1-butanol Write the balanced chemical

equation for the formation of this ester

An ester that has the smell of pineapple can be synthesized from butanoic acid and methanol Write the balanced

chemical equation for the formation of this ester

Sample Problem 16.5 Writing Esterification Equations

Continued

Sample Problem 16.5 Writing Esterification Equations

Step 1 Write the name for the carbon chain from the alcohol as an alkyl group The alcohol part of the ester is from

propanol (propyl alcohol) The alkyl group is propyl

What are the IUPAC and common names of the following ester?

Sample Problem 16.6 Naming Esters

Step 2 Change the ic acid of the acid name to ate The carboxylic acid part of the ester is from propanoic (propionic)

acid, which becomes propanoate (propionate) The ester is named propyl propanoate (propyl propionate)

Replacing the ic acid in the common name propionic acid with ate gives propionate The common name for the

ester is propyl propionate

Study Check 16.6

Draw the line-angle structural formula for ethyl heptanoate that gives odor and flavor to grapes

Answer

Continued

Sample Problem 16.6 Naming 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?

Sample Problem 16.7 Acid Hydrolysis of Esters

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 —H to complete the alcohol The acetic acid in the products gives the odor of vinegar to a sample of aspirin that has hydrolyzed

Study Check 16.7

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

Answer

propanoic acid and ethanol (propionic acid and ethyl alcohol)

Continued

Sample Problem 16.7 Acid Hydrolysis of Esters

Ethyl acetate is a solvent used in fingernail polish, plastics, and lacquers Write the balanced chemical equation

for the hydrolysis of ethyl acetate with NaOH

Sample Problem 16.8 Base Hydrolysis of Esters

Sample Problem 16.8 Base Hydrolysis of Esters

Study Check 16.8

Draw the condensed structural formulas for the products from the hydrolysis of methyl benzoate with KOH

Answer