Carboxylic Acids

A carboxylic acid contains a carboxyl group, which is a carbonyl group attach to a hydroxyl group.

carbonyl

group

O

CH3 — C—OH hydroxyl group or CH3COOH

carboxyl group

Carboxylic Acids

CH3CO2H

• The common names use prefixes “form-” and “acet-” for the first

two carboxylic acids.

H-COOH methanoic acid formic acid

CH3-COOH ethanoic acid acetic

acid

CH3-CH2-COOH propanoic acid

CH3-CH2-CH2-COOH butanoic acid

Naming Carboxylic Acids

Naming Carboxylic Acids– Identify the root. Name the parent alkane. Drop the –e on the parent

alkane to get the root.– Identify the suffix. For carboxylic acid, the suffix is –oic acid. No

numbers in the suffix because the carboxyl group is always carbon 1.– Identify the prefix. Name and number any alkyl side groups on the

main chain. – Name the compound. Combine the prefix, root, and suffix

13

3-Methylbutanoic acid

OH

OOH15

5-Hydroxylhexanoic acid

CH3─CH2─CH─COOH

CH2 – CH3

2-Ethylbutanoic acid

2CH3─CH─CH2─COOH

CH3 1

Draw 2-ethylpentanoic aicd

CH3

O

OH

CH3

Physical properties of Carboxylic Acids

1- The carboxyl group contains three polar covalent bonds;

C=O, C-O, and O-H. So they are so polar.

2- Carboxylic acids have higher boiling points than other types of organic compounds (with the same molecular weight) because of hydrogen bonding.

3- They are more soluble in water than alcohols, ethers, aldehydes, and ketones because of stronger hydrogen bonding.

4- Liquid carboxylic acids have sharp and disagreeable odors.

5- They taste sour (exist in pickle, lime, and lemon).

H3C C

O

O

H

CH3C O

O

H- +

+ -

Hydrogen bondingbetween two molecules

Esters

Formation of Esters

RC O HO

A carboxylic acid

=

Fischer Esterification

RCOR'O

RC-OHO

H- O R '

==

An alcoholA carboxylic acid An ester

H2SO4

+ H2O

Naming Esters

1. Identify the root. Identify part of ester that contains carbonly group (from acid). Name the parent carboxylic acid. Drop the suffix of the of the acid to form the root

2. Identify the suffix. The suffix for an ester is –oate

3. Consider the part of the ester that is associated with the alcohol. Name only the alkyl group.

4. Name the compound. Combine the prefix, root and suffix.

acid alcohol

methyl

CH3 — C—O —CH3

ethanoate IUPAC: methyl ethanoate

Naming of Esters

O

propyl

CH3 — C—O —CH2—CH2—CH3

Propyl ethanoate (IUPAC)

CH3—CH2 —C—O—CH2—CH3

Ethyl propanoate

Naming of Esters

O

O

Name the following ester

• Parent carboxylic acid is

3-methylbutanoic acid

Root: 3-methylbutan

Suffix: -oat

Alcohol: ethanol

Prefix:ethyl

Name: ethyl 3-methylbutanoate

CH3

O

O

CH3

CH3

Draw butyl propanoate

• Alcohol: butanol

• Acid: propanoic acid

CH3

O

O CH3

Esters give flowers and fruits their pleasant fragrances and flavors.

Properties of Esters

Hydrolysis: reaction with water.

(breaking a bond and adding the elements of water)

RCOR'O

RC-OHO

H- O R '

= =An alcoholA carboxylic acidAn ester

+ H2O +Heat

Acid

Chemical properties of Carboxylic Acids

3- Fischer Esterification:

- A carboxylic acid reacts with an alcohols to form an ester.

- Using an acid catalyst such as concentrated sulfuric acid.

CH3C-OHO

H-OCH2CH3

H2SO4CH3COCH2CH3

OH2O

Ethanoic acid(Acetic acid)

++

Ethyl ethanoate(Ethyl acetate)

Ethanol(Ethyl alcohol)

The best way to prepare an ester.