Acids and Bases: Molecular Structure and Behavior

Home

Table of Contents

Introduction

Molecular Structure

Ionization Constants

Salts

Buffers

Lewis Theory

Carboxylic Acids

There are many organic molecules that contain the carboxyl functional group (-CO₂H). This group has a hydrogen bonded to an oxygen (an electronegative atom) and can act as an acid (or donate a proton). Common carboxylic acids include acetic acid (vinegar), citric acid (found in citrus fruit), oxalic acid (occurs widely in plants, including spinach and rhubarb), and lactic acid (responsible for the taste of sour milk).

Formic acid causes the sting of red ant bites. In the strucure of formic acid below, click on the hydrogen that will be acidic (or donated to a base).

Remember that being bonded to an electronegative atom makes a hydrogen more acidic.

Good! The other hydrogen in this molecule is not acidic.

Amines

Amines are compounds containing nitrogen making three covalent bonds and having a non-bonded electron pair. Common amines include norephinephrine and adrenaline (stimulants in the human nervous system). Many drugs (codeine, novocaine, and the decongestant ephedrine are some) are derivatives of amines.

Three nitrogen containing compounds are shown below. Which one is an amine and will be able to act as a base?

Remember that a molecule must have a lone pair of electrons to act as a base.

Good! A nitrogen must have a lone pair of electrons to act as a base.

The non-bonded pair of electrons must be on the nitrogen in order to be an amine.