15_Carboxylic Acids and Esters.pdf

CHAPTER 15

CARBOXYLIC ACIDS

Contains the carboxyl group –COOH

on one end of chain. Named with an

-oic acid ending.

Carboxylic acid Carbonyl group

R

C

O

NOMENCLATURE OF CARBOXYLIC ACIDS

Determine the parent compound, the longest continuous

carbon chain bearing the carboxyl group.

Number the chain so that the carboxyl carbon is carbon #1.

Replace the –e ending of the parent alkane with the suffix

–oic acid. If there are two carboxyl groups, the suffix –dioic acid is used (common in biology).

GIVE THE IUPAC

NAME FOR….

O

OH

O

HO

Br

Br Br

O

OH O

COMMON NAMES

Common names are usually derived from some Latin or Greek word that is related to a source for the acid.

Append the suffix “–ic” acid.

− The positions of substituents are denoted by Greek letters rather than numbers with

reference to the carbonyl carbon (C₁), e.g., C₂ is alpha (a), C₃ is beta (b), C₄ is gamma

COMMON NAMES FOR THE FIRST SIX

MONOCARBOXYLIC ACIDS

 Table 16.1

COMMON NAMES FOR THE FIRST SIX

DICARBOXYLIC ACIDS

 Table 16.2

POLYFUNCTIONAL CARBOXYLIC ACIDS

PCAs contain at least one or more functional groups other

than carboxyl group

PCAs are commonly found in living organisms an play an

important role in human body

 Occur in many fruits

 Used in over the counter skin care products and prescription drugs Common types of PCAs:

UNSATURATED ACIDS

Contain at least one carbon-carbon double bond (C=C): Examples:

 Propenoic acid (acrylic acid) used in the manufacture of polymeric materials.

 Futenedioic acid - has two forms

 Fumaric acid : trans-form  Maleic acid: cis-form

HYDROXY ACIDS

Contain at least one hydroxyl group and are naturally present in many foods

Examples:

 Glycolic acid: present in juice from sugar cane and sugar beets  Lactic acid: Present sour milk, sauerkraut, and dill pickles

 Malic acid and tartaric acid occur naturally in fruits

KETO ACIDS

Contain a carbonyl (C=O) group within a carbon chain. Example:

 Pyruvic acid - simplest keto acid with odor

resembling that of vinegar (acetic acid) and it is also a metabolic acid

O O

OH

METABOLIC ACIDS

Metabolic acids: Polyfunctional acids formed as

intermediates of metabolic reactions in the human body. There are eight such acids that will appear repeatedly in

the biochemistry chapters

Metabolic acids are derived from:

− Propionic acid, (C₃ mono acids): lactic, glyceric, and pyruvic acids − Succinic acid (C₄ diacid): fumaric, oxaloacetic, and malic acids − Glutaric acid (C₅ diacid): a-ketoglutaric and citric acids

PHYSICAL PROPERTIES

Carboxylic acids have hydrogen bonding to themselves and to water.

Result: High boiling points and high water solubility.

THE SOLUBILITY OF

SATURATED

PREPARATION OF CARBOXYLIC ACIDS

• Non-aromatic carboxylic acids: Oxidation of primary

alcohols or aldehydes, using an oxidizing agent such as

K₂Cr₂O₇

• Aromatic carboxylic acids: Oxidation of a carbon side chain

(alkyl group) on a benzene derivative

HO _O HO

O

Ethanol Acetaldehyde Acetic acid

[O] _[O]

CH₂CH₂CH₃

K2Cr2O7

H2SO4

COOH

ACIDITY OF CARBOXYLIC ACIDS

In water they dissociate to release protons (H+) and form carboxylate ion (RCOO-_{) = Dissociation reaction}

Monocarboxylic acids release one H+ to form one negative charge

CARBOXYLIC ACID SALTS

Reaction of an acid and a base is a neutralization

reaction. It produces a salt and water

O

OH

+ NaOH

O

O Na+

+ H₂O

Summary of reactions

involving

PRACTICE: CARBOXYLIC ACID

REACTIONS

 Name the acid and write the product of the reaction below

STRUCTURE OF ESTERS

 An ester is a carboxylic acid derivative in which the —OH portion

of the carboxyl group has been replaced with an —OR group

ESTERIFICATION

Esters are produced by an esterification reaction

Esterification reaction: Reaction of a carboxylic acid with an alcohol (or phenol) to produce an ester

Esterification reaction require a strong acid catalyst such as H₂SO₄

NOMENCLATURE FOR ESTERS

Use the alkyl or aryl portion of the alcohol name as the first name

The –ic acid ending of the name of the carboxylic acid is replaced with –ate and follows the first name

O

O _O

O

Ethyl butanoate

Copyright © _{2001 Houghton Mifflin Company. All rights reserved.}

PHEREMONES

O O

ISOMERISM FOR CARBOXYLIC ACIDS & ESTERS

Functional Group Isomers:

Skeletal Isomers:

Positional Isomers:

PHYSICAL PROPERTIES (RESEMBLE ETHERS)

Boiling Points:

 Lower than alcohols and carboxylic acids, due to lack of hydrogen

bonding

Soluble in Water (less than 3 carbons)

 Moderate solubility between 3 and 5 carbons

CHEMICAL REACTIONS OF ESTERS

Ester Hydrolysis: breaking the carbon–oxygen single (C-O) bond that holds the “alcohol part” and the “acid part” in an ester (reverse esterification)

CHEMICAL REACTIONS OF ESTERS

Ester Saponification: hydrolysis of an organic compound,

PRACTICE: ESTERS

SULFUR ANALOGS OF ESTERS

• Thioester: A sulfur-containing analog of an ester in which an —SR

group has replaced the —OR group.

 The most important naturally occurring thioester is acetyl

coenzyme A

POLYESTERS

Polymers are formed by reacting difunctional monomers Examples: dicarboxylic acids and dialcohols are used for

the formation of polyesters Two important polymers:

ACID CHLORIDES

 Acid Chloride: A carboxylic acid derivative in which the “-OH”

ACID ANHYDRIDES

• Acid Anhydrides: A carboxylic acid derivative in which the

“-OH” portion of the carboxyl group has been replaced with a “acyl” group.

• Two types of acid anhydrides:

− Symmetrical acid anhydrides

− Mixed anhydrides

• General reaction

R C

O

OH C R'

O

HO

+ _{R C}

O

O C R'

O

ESTERS OF INORGANIC ACIDS

Inorganic acids such as sulfuric, phosphoric, and nitric acids react with alcohols to form esters (similar to carboxylic acids)

PHOSPHORIC ACID ANHYDRIDES

Three biologically important

phosphoric acids are phosphoric acid, diphosphoric acid, and

triphosphoric acid

Examples of such esters in the human body include adenosine diphosphate (ADP), and

Summary of reactions

involving