CHM037
Organic Chemistry for
Engineering and Applied Sciences
Sem 1 2020-2021
Ma. Cecilia V. Almeda
Department of Chemistry
CSM. MSU-IIT
CHM037 – Organic Chemistry for
Engineering Technologist
Module 1 – Theories of Acids and
Bases
Ma. Cecilia V. Almeda
Dept. of Chem, CSM, MSU-IIT Iligan City
NOTE: This Power point lecture notes is
intended for classroom use only and
not to be distributed or reproduced.
Acids & Bases
• Bronsted-Lowry definition
– Donates/accepts a hydrogen ion (H+)
– Conjugate A/B
Key point: strong acids
have weak conjugate
bases and weak acids
have strong conjugate
bases.
In each acid-base reaction, an acid reacts with a base to give a
conjugate base and a conjugate acid
Strong acids have weak conjugate bases and weak acids have
strong conjugate bases.
The equilibrium is shifted
towards a weaker species
(with bigger pKas)
Ka & pKa & relative strength of acid
• Organic acid (blue)
– Those that lose a proton from O–H: methanol and acetic acid
– Those that lose a proton from C–H, a carbon atom next to a C=O
double bond (O=C–C–H)
• Organic acid (blue)
• Organic bases
– Have an atom with a lone pair of electrons that can bond to
H+
– -O & -N
• Lewis acids and bases
– accepts & donates an electron pair
• Lewis acids & bases Reactions
Lewis Acids
• The Lewis definition of acidity includes metal cations, such as
Mg2+ : They accept a pair of electrons when they form a bond to a
base
• Group 3A elements, such as BF3 and AlCl3, are Lewis acids
because they have unfilled valence orbitals and can accept
electron pairs from Lewis bases
• Transition-metal compounds, such as TiCl4, FeCl3, ZnCl2, and
SnCl4, are Lewis acids
• Organic compounds that undergo addition reactions with Lewis
bases (discussed later) are called electrophiles and therefore
Lewis Acids
Lewis Bases
• Most oxygen- and nitrogen-containing organic compounds
are Lewis bases because they have lone pairs of electrons
• Some compounds can act as both acids and bases,
depending on the reaction