Carboxylic acids contain the carboxyl functional group (-COOH). They form hydrogen bonds between molecules, giving them higher boiling points than similar molecular weight compounds. Carboxylic acids are soluble in water and organic solvents due to hydrogen bonding. Common carboxylic acids include formic acid, acetic acid, and butanoic acid.

1. Carboxylic Acids
• Formula -COOH
• Oxygen atoms NOT
joined together.
• General formula when
rest of structure is an
alkyl group R-COOH.
Carboxyl group

2. STRUCTURE OF CARBOXYLIC ACIDS
• contain the carboxyl functional group
-COOH
• the bonds are in a planar arrangement
• include a carbonyl (C=O) group
and
a hydroxyl (O-H) group

3. METHANOIC ACID ETHANOIC ACID PROPANOIC ACID
Carboxylic acids form a homologous series
BUTANOIC ACID 2-METHYLPROPANOIC ACID

4. Acids are named according to standard IUPAC rules
1. select the longest chain of C atoms containing the
-COOH group
2. remove the “-e” and add “-oic” acid after the basic
name
3. number the chain starting from the end nearer the
COOH group
4. as in alkanes, prefix with alkyl substituents
5. side chain positions are based on the C in -COOH
being 1
e.g. CH3 - CH(CH3) - CH2 - CH2 - COOH
4-methylpentanoic acid
NAMING CARBOXYLIC ACIDS

5. Naming Practice
• Name these structures
Butanoic acid
Octanoic acid
Pentanedioic acid

6. NAMING CARBOXYLIC ACIDS
Many carboxylic acids are still known under their trivial names, some having
been called after characteristic properties or their origin.
Formula Systematic name (trivial name) origin of name
HCOOH methanoic acid formic acid latin for ant
CH3COOH ethanoic acid acetic acid latin for vinegar
C6H5COOH benzenecarboxylic acid benzoic acid from benzene
101°C 118°C 141°C 164°C
PHYSICAL PROPERTIES
BOILING POINT
Increases as size increases - due to increased van der Waals forces

7. PHYSICAL PROPERTIES
BOILING POINT
Carboxylic acids have high boiling points for their relative
mass
arises from inter-molecular hydrogen bonding due to
polar O—H bonds
The effect of hydrogen bonding on the boiling point of
compounds of similar mass
Compound Formula Mr b. pt. (°C) Comments
ethanoic acid CH3COOH 60 118
propan-1-ol C3H7OH 60 97 H-bonding
propanal C2H5CHO 58 49 dipole-dipole
butane C4H10 58 - 0.5 basic V der W

8. PHYSICAL PROPERTIES cont…
SOLUBILITY
• carboxylic acids are soluble in organic solvents
• they are also soluble in water due to hydrogen bonding
HYDROGEN
BONDING
• small ones dissolve readily in cold water
• as mass increases, the solubility decreases

9. Carboxylic Acids
• Carboxylic acids exhibit dipole-dipole interactions
because they have polar C=O and O—H bonds.
• They also exhibit intermolecular hydrogen bonding.
• Carboxylic acids are held together by two
intermolecular hydrogen bonds.
Physical Properties

10. Carboxylic Acids
Interesting Carboxylic Acids
Butanoic acid is an oxidation product that contributes
to the disagreeable smell of body odor. It’s common
name, butyric acid, is derived from the Latin word
butyrum, meaning “butter”, because butyric acid
gives rancid butter its peculiar odor and taste.
Acetic acid is the sour component of vinegar. The air
oxidation of ethanol to acetic acid is the process that
makes “bad” wine taste sour (acidus). Acetic acid is
an industrial starting material for polymers used in
paints and adhesives.
Formic acid has an acrid odor and a biting taste, and is
responsible for the sting of some types of ants. The name
is derived from the Latin word formica, meaning “ant”.

11. More Interesting Carboxylic Acids
Caproic acid, the common name for hexanoic
acid, has the foul odor associated with dirty
socks and locker rooms. Its name is derived from
the Latin word caper, meaning “goat”.
Oxalic acid (Rhubarb) and lactic acid are simple carboxylic acids that are quite prevalent in
nature.
Salts of carboxylic acids are commonly used as preservatives. Sodium benzoate is a
preservative used in soft drinks and baked goods.

12. These red ants, like other ants, make the simplest of the organic
acids, formic acid. The sting of bees, ants, and some plants contains
formic acid, along with some other irritating materials. Formic acid
(methanoic acid) is HCOOH.
Salad Dressing?

13. PREPARATION OF ESTERS(Esterification)
Reagent(s) alcohol + carboxylic acid
Conditions reflux with a strong acid catalyst (e.g. conc. H2SO4 )
Equation e.g.) CH3CH2OH(l) + CH3COOH(l) CH3COOC2H5(l) + H2O(l)
ethanol ethanoic acid ethyl ethanoate
Notes Conc. H2SO4 is a dehydrating agent - it removes
water causing the equilibrium to move to the right
and thus increases the yield of the ester
CH3
C O CH2
CH3
O
Acid part of ester Alcohol part of ester

14. ETHYL METHANOATE
METHYL ETHANOATE
Naming Esters:
Named from the original alcohol and carboxylic acid
CH3OH(l) + CH3COOH(l) CH3COOCH3 (l) + H2O(l)
from ethanoic acid CH3COOCH3 from
methanol
METHYL ETHANOATE

15. CH3
C O CH2
CH3
O
ethyl ethanoate (IUPAC)
CH3 CH C O CH3
CH3
O
methyl 2-methylpropanoate

16. ethyl pentanoate
Br
O
Et
O
1
2
3
4
5
6
CH3
CH2
CH2
CH2
C O CH2
CH3
O
ethyl 5-bromo-3,4-dimethylhexanoate
DON’T Have To Know!

17. Esters as Flavoring Substances
Isopentyl acetate Ethyl butyrate
banana pineapple
Isobutyl propionate Octyl acetate
rum orange
Propyl acetate Methyl butyrate
pear apple
CH3 C O CH2 CH2 CH3
O
CH3
CH2
C O CH2
CH CH3
O
CH3
CH3 C O CH2 CH2 CH2
O
CH2 CH2 CH2
CH2 CH3
CH3 CH2 CH2 C O CH2 CH3
O
CH3 C O CH2 CH2 CH
O
CH3
CH3
CH3 CH2 CH2 C O CH3
O
Solvents: nail varnish remover - ethyl ethanoate
octyl ethanoate
ethyl butanoate
propyl ethanoate methyl butanoate
NOT IUPAC!

18. SUMMARY OF THE CLASSES OF ORGANIC COMPOUNDS
• alkanes – single bonds
• alkenes – double bond
• alkynes – triple bond
• aromatic – benzene ring
C6H5 –
• organic halides – halogen
R = hydrocarbon chain/group
R – X
(X = halogen)
• alcohols – hydroxyl group
R(H) = hydrocarbon chain/group or
can be hydrogen
R – OH
• carboxylic acids – carboxyl group
R – COOH
• esters – ester group
–COOC–
R1(H)COOCR2