Presentation about carboxylic acids and their general characteristics.

1. Carboxylic acids
BY: garima (b.sc biotech)

2. Contents
Definition
Nomenclature and IUPAC names
Structure and bonding
Physical properties
Acidity of carboxylic acids
Effects of substituents on acid
strength

3. Definition of carboxylic acid
A carboxylic acid contains
a hydroxyl group (-OH)
attached to a carboxyl
group (C=O).
3

4. Nomenclature
4
Generally, these organic compounds are referred to by their trivial names, which contain the
suffix “-ic acid”. An example of a trivial name for a carboxylic acid is acetic acid (CH3COOH). In
the IUPAC nomenclature of these compounds, the suffix “-oic acid” is assigned.
The guidelines that must be followed in the IUPAC nomenclature of carboxylic acids are listed
below.
● The suffix “e” in the name of the corresponding alkane is replaced with “oic acid”.
● When the aliphatic chain contains only one carboxyl group, the carboxylic carbon is
always numbered one. For example, CH3COOH is named as ethanoic acid.
● When the aliphatic chain contains more than one carboxyl group, the total number of
carbon atoms is counted and the number of carboxyl groups is represented by Greek
numeral prefixes such as “di-”, “tri-“, etc.
● A carboxylic acid is named by adding these prefixes and suffixes to the parent alkyl
chain. Arabic numerals are used for indicating the positions of the carboxyl group.
● The name “carboxylic acid” or “carboxy” can also be assigned for a carboxyl substituent
on a carbon chain. An example of such nomenclature is the name 2-carboxyfuran for the

5. Iupac names of carboxylic acids
● The name of the carboxylic acid of benzene ,is
benzoic acid.
● The carbon in the carbonyl group is bonded to
carbon 1 in the benzene ring.
● The ring is numbered to give the lowest possible
numbers for any substituents.
● The prefixes ortho, meta and para may be used to
show the position of one other substituents.

6. 6
Common names of carboxylic acids
➢ Many carboxylic acids are still named by their
common names that include prefixes, form ,
acet , propion , butyr.
➢ When using the common names , the greek
letters alpha(α), beta(β) and gamma(𝛄) are
assigned to the carbons adjacent to the
carboxyl carbon.

7. Structure and bonding
Structure of carboxylic acid group
Carboxylic acids are organic compounds which incorporate a
carboxyl functional group, CO2H. the name carboxyl comes from the
fact that a carbonyl and a hydroxyl group are attached to the same
carbon.
7

8. The carbon and oxygen in the carbonyl are both sp2
hybridized which give a carbonyl group a basic trigonal shape.
The hydroxyl oxygen is also sp2 hybridized which allows one of
its lone pair electrons to conjugate with the pi system of the
carbonyl group planar and can be represented with the
following resonance.
8

9. Carboxylic acids are named such because they can
donate a hydrogen to produce a carboxylate ion.
9

10. Physical properties
● Carboxylic acid molecules are polar due to the presence of two
electronegative oxygen atoms.
● They also participate in hydrogen bonding due to the presence of the
carbonyl group (C=O) and the hydroxyl group.
● When placed in nonpolar solvents, these compounds form dimers via
hydrogen bonding between the hydroxyl group of one carboxylic acid and
the carbonyl group of the other.
10

11. ● The solubility of compounds containing the carboxyl
functional group in water depends on the size of the
compound. The smaller the compound (the shorter the R
group), the higher the solubility.
● The boiling point of a carboxylic acid is generally higher than
that of water.
● These compounds have the ability to donate protons and are
therefore Bronsted-Lowry acids.
● They generally have a strong sour smell. However, their
esters have pleasant odours and are therefore used in
perfumes.
11

12. Acidity of carboxylic acids
12

13. Why carboxylic acid is more acidic than alcohol ?
13
1. Lesser the pKa greater the acidity = pKa value for acid is 4-5 and alcohol
is 14-16.
2. Ionization of carboxylic acid leads to delocalozation or shifting of
negative charge from one oxygen to another hence separation and
creation of unlike charge to produce force drive to ionize.
● So , the equilibrium shifted to right side and carboxylic acid
ionizes faster than alcohol.
● Ionization of alcohol to produce anion and there is no delocalization of
charge and hence ionizes slowly and equilibrium shifted to left.

14. 14
3. There is difference in electronegativity between carbon and
oxygen , there is partial positive charge on carbonyl carbon which
induces polarization of electron in O-H bond.
● Electron withdrawing effect of carbonyl carbon weakens OH
bond and facilitates ionization of carboxylic acid compared to
alcohol.

15. Effect of substituents on acidic strength of carboxylic acid
15
❏ Electron withdrawing group (Cl , Br ,F) increases acidity -
electron withdrawing group withdraws electron density
from the carboxyl group and equilibrium shifted to right
that increases acidity of carboxylic acid.
❏ Electron donating group (OH ,NH2 ) decreases the acidity -
electron donating group adds electron density to carboxyl
group and equilibrium shifted to left that decreases acidity
of carboxylic acid.

16. Thank you
16