On this page:
Introduction What Are Structural Formulae? Organic Compounds and Functional Groups Features and Structure of Carboxylic Acids Features of Carboxylic Acids Naming Carboxylic Acids Esters: Their Structure and Formation Main Structural Features Of Esters How are Esters Formed?: Esterification Properties Of Esters Carboxylic Acids vs Esters Steps to Draw Structural Formulae Why are structural formulae important? Big Picture: Linking Structure to Function
Perhaps you have a nail polish remover and perfume in your kitchen cupboard, or maybe you have even vinegar or fruit flavoring. Even though these items look ordinary, they have common organic compounds. The taste and smell of these compounds exhibit distinct, clear structural patterns.
In Chemistry, they don't just stop at naming a substance. They go further to explain how the atoms are connected. This is where structural formulae come in. They allow the chemists to "see'' the entire molecule. They help to explain how and why some substances behave the way that they do.
In this lesson, the focus will be on the two most important groups of organic compounds: carboxylic acids and esters. By the end of this lesson, you will have a clear ability to describe the structures of these compounds, understand the major characteristics of these compounds, and the everyday uses they are associated with.
A structural formula shows the arrangement of atoms in a molecule and the connections between them. Structural formulas overall contain more information than molecular formulas. For example,
Both compounds (ethanol and dimethyl ether) are C₂H₆O, or C2H6O, which means they have the same molecular formula, but they have different structures and different properties. This illustrates the importance of structure in chemistry.
Importance of structural formula:
The compounds in organic chemistry are based on the element carbon. Carbon's ability to bond with both itself and other elements in a multitude of ways produces a large variety of possible molecular structures.
A functional group is a specific group of atoms in a molecule that determines the properties and reactions of that molecule.
Here are some examples of common functional groups:
Carboxylic acids are organic compounds containing a carboxyl functional group, i.e., -COOH.
A carboxyl functional group comprises a
In this case, R is the hydrocarbon chain (e.g., CH₃–, C₂H₅–).
Examples of this include:
Structure and functional groups of carboxylic acids account for their certain properties:
Physical properties
Chemical properties
Use in Real Life:
The names of the carboxylic acids are based on the prefix of the corresponding alkane:
Methane → Methanoic acid
Ethane → Ethanoic acid
Propane → Propanoic acid
The names always end in "-oic acid".
This provides a framework for you to name linkages, especially while sketching structural formulas.
Esters form a significant class of compounds in organic chemistry primarily due to their characteristic pleasant smell and their utility in the food and fragrance industries.
The structural representation of an ester is [-COO-].
Where:
Ethyl ethanoate: CH₃–COO–CH₂CH₃
This ester is formed from
This process is called esterification.
Describe What Happens
In the reaction of a carboxylic acid and an alcohol, an ester is formed, and water is released.
Overall,
Why is Important Here?
The acid's -COOH group and the alcohol's -OH group rearrange to form the -COO- linkage.
This explains why esters possess unique structures and why they are distinct from both acids and alcohols.
The reaction, of course, involves more conditions, like a catalyst and heat, but the key focus is the atomic rearrangement, which leads to the formation of a new structure.
This difference in functional groups explains why esters behave differently from carboxylic acids.
Physical Properties
Chemical Properties: Esters are not as reactive as carboxylic acids. Esters can undergo hydrolysis, which is a type of reaction where the compound is broken down by the addition of water, yielding an acid and an alcohol.
Everyday Applications: Esters are used in flavoring foods (like those that taste like bananas, pineapples, and strawberries), perfumes and other scented products, paint, nail polish remover, plastics, and fibers.
Even though esters are derived from carboxylic acids, they have different structures and properties.
General structure: R–COOH
Sour and acidic taste
More soluble in water (smaller ones)
Contain –OH group (acidic)
General structure: R–COO–R′
Neutral taste, fragrant smell
Low solubility in water
Lack –OH, have –COO–
This shows that a slight structural change can bring about significant changes in properties.
Remember that the -COOH group is at the end of acids.
The carboxyl group (–COOH) has to be on the end of the carbon chain.
Helpful tips:
In everyday chemistry, structural formulae are important because they show how different substances interact and how they behave in different circumstances.
The ideas from this lesson can be seen in face value, food technology, and the flavor preserving substances.
A change in the structure of a molecule brings about a change in the smell, taste, reactivity, and usefulness of the molecule.
This is how important structure is in chemistry.
A good example of structure determining function in chemistry is carboxylic acids and esters.
A slight modification in structure will result in a large change in the properties.
More studies in Chemistry will introduce you to more functional groups. Reading and writing structural formulae will be important in building confidence in organic chemistry.
To sum up: Different parts of a molecule are represented in structural formulae. Carboxylic acid compounds are due to the -COOH group, which makes them sour and acidic. -COO- group will ensure you of esters, which are pleasant to smell and taste. The chemistry that explains the structure of these compounds is the same that explains the chemistry of the world around us.