Carboxylic acid – ester – propanoic acid methyl ethanoate

14.1 Carboxylic AcidsStructure • Carboxylic acid groups consist of two very polar functional groups – Carbonyl group – Hydroxyl group • Carboxylic acid groups are very polar Carboxylic

Functional Group Formulas

14.1 Carboxylic Acids

Structure

• Carboxylic acid groups consist of two

very polar functional groups

– Carbonyl group

– Hydroxyl group

• Carboxylic acid groups are very polar

Carboxylic acid – Ester –

propanoic acid methyl ethanoate

Physical Properties

• Low molecular weight carboxylic acids

• High molecular weight carboxylic acids

• Low molecular weight carboxylic acids are water

soluble due to hydrogen bonding with:

• Determine the parent compound: 4C – butane

• Number the chain so that the carboxyl carbon

is carbon 1: from right to left

• Replace the – e ending with – oic acid

– Butanoic acid

– If two carboxyl groups are present use –dioic acid

• Complete naming as usual – bromine on C-3

3 4

Carboxylic Acid Naming Examples

Common Names

• Use Latin or Greek prefixes

• Suffix is –ic acid

• Greek letters indicate the position of the

Names and Structures of Some

Common Carboxylic Acids

Some Important Carboxylic Acids

Reactions Involving Carboxylic Acids

• Carboxylic acids are prepared by

oxidation of primary alcohols and aldehydes

H2CrO4Warm

Acid-Base Reactions

• Carboxylic acids behave as acids because when they are dissolved in water they will deprotonate to form a carboxylate ion and the hydronium ion

• Carboxylic acids are weak acids with

dissociations of less than 5%

Acid-Base Reactions

• Carboxylic acids DO react with strong

bases to form carboxylate salts

– A process of neutralization– Acid protons are removed by the –OH- to form

H2O and carboxylate ion

– Equilibrium shifts to the right with removal of

Using Acid-Base Reactions

• What is the product of each of the following reactions?

Salts of Carboxylic Acids

• Uses of carboxylic acids

14.2 Esters

Structure and physical properties

• Esters are mildly polar, somewhat water soluble

• Frequently found in natural foodstuffs

• Many have pleasant aromas

• Boil at approximately the same temperature as

carbonyls with comparable molecular weight

Form from the reaction of a carboxylic acid with an

alcohol, which is reflected in the naming

1 Use the alkyl group as the first name

(Alcohol part of the ester)

2 Base the name for the acid part of the structure

from the longest chain ending in the C=O

(Carboxylic acid part of the ester)

3 Change the –oic acid of the acid name to –oate

Naming Esters

Name the following esters:

• Alkyl portion = first name ethyl

• Parent carboxylic acid = butanoic acid

• Change suffix to reflect ester = Ethyl butanoate

• Alkyl portion = first name proply

• Parent carboxylic acid = ethanoic acid

• Change suffix to reflect ester = Propyl ethanoate

Naming Esters

Naming esters is much like naming the salts

of carboxylic acids:

• Alkyl portion = first name ethyl

• Parent carboxylic acid = ethanoic acid

• Change suffix to reflect ester =

Reactions Involving Esters

Preparation

O

CH3+ H2O

Hydrolysis of Esters

• The main reaction of esters is hydrolysis, reaction with water

– This reaction is also called hydration =

cleavage of any bond by the addition of a water molecule

• However, the uncatalyzed reaction is slow and requires heat

• Mineral acid is used as a catalyst

Acid hydrolysis of Esters

Acid hydrolysis products are:

Base hydrolysis of Esters

The base catalyzed hydrolysis of an ester:

• Saponification or soap-making

• Products are:

– Acid salt – Alcohol

• Acid can’t exist in basic conditions, so the product is the salt of the carboxylic acid using the cation of the base catalyst

• Saponification (soap-making) is:

Simplified Action of Soap

Condensation Polymers

• Polyesters are condensation polymers

• They are formed by eliminating a small

molecule (e.g., H2O) when combining:

• Each of the combining molecules has two

reactive functional groups, highlighted in red

Polethylene terphthalate, PETE

14.3 Acid Chlorides and

Acid Anhydrides

acids having the general formula:

• Are named:

name with –oyl chloride

Acids Chlorides

Acid chlorides

• Noxious, irritating chemicals requiring great

care in handling

• Slightly polar, boiling near the

corresponding carbonyl’s temperature

• React violently with water

• Are good acyl group transfer reagents

CH2C

O OH

Hydrolysis of Acid Chlorides

Acid chlorides react violently with water in a hydrolysis reaction

• Reforming the acid and HCl

• Substitution of the –OH for the –Cl occurs at

the acyl carbon

Acid Chloride Substitution

• Acid chlorides react with alcohols to form

esters and HCl

• Substitution of the –OR for the –Cl occurs at

the acyl carbon

Acid Anhydrides

• Acid anhydrides have the formula:

• The molecule is 2 carboxylic acid molecules

with a water molecule removed

– Anhydride means without water

• Symmetrical anhydrides are those with both

acyl groups the same

• Symmetrical anhydrides are named by

replacing the -acid ending of the acid with –

Formation of Acid Anhydrides

• Acid anhydrides are not typically formed in

a reaction between the parent carboxylic acids

• One pathway is the reaction between:

Acid Anhydride Reactions

14.4 Nature’s High Energy Compounds:

Phosphoesters and Thioesters

• Phosphoric acid reacts with alcohols to

produce a phosphate ester or phosphoester

• The ester can then react with a second or

third acid to give phosphoric acid

anhydrides

• ADP and ATP of biochemistry fame are

important examples of phosphate esters

adenosine triphosphate, ATP

P

O O

O O O

N

OH OH

O

N

N N

P

O O

Phosphoric Acid Esters

Ester bond Anhydride bonds

• In biochemistry, acetyl coenzyme A (acetyl

CoA-SH) reacts with acyl groups to “activate” them for further biological reaction by forming

a thioester

CH3C

O CoA-S

COOC

-CH2COO-

O H

3 Acid chloride synthesis

4 Acid anhydride synthesis

5 Phosphoester formation

Summary of Reactions