Alcohol, Carboxylic Acids and Esters, what are these?

Alcohol 

Alcohol is a type of organic compound characterized by the presence of a hydroxyl (-OH) functional group attached to a carbon atom. In simpler terms, it’s a chemical that consists of carbon (C), hydrogen (H), and oxygen (O) atoms, with one or more of these groups: -OH. Alcohols come in various forms, but the most commonly known one is ethanol, which is found in alcoholic beverages like beer, wine, and spirits. 

For O-level students, it’s important to understand that alcohol is not just used in drinks; it’s also a versatile compound with various uses. One of the most found use of alcohol in the past few years over the pandemic is the hand sanitizers and pharmaceuticals, which have played a central role in preventing the spread of diseases 

What is taught or tested in the O level Syllabus for alcohol

As per the Chemistry 6092 Syllabus:
describe the alcohols as a homologous series containing the –OH group
(b) draw the structures of branched and unbranched alcohols, C1 to C4, and name the unbranched alcohols methanol to butanol
(c) describe the reactions of alcohols in terms of combustion and oxidation to carboxylic acids 

What is an Carboxylic acid

A carboxylic acid is a type of organic compound that contains a specific functional group called a “carboxyl group.” This carboxyl group consists of a carbon atom (C) double-bonded to an oxygen atom (O) and single-bonded to another oxygen atom (O), which is also bonded to a hydrogen atom (H). The general structure of a carboxylic acid looks like this: -COOH.

What is taught or tested in the O level Syllabus
As per the Chemistry 6092 Syllabus:

(c) describe the reactions of alcohols in terms of combustion and oxidation to carboxylic acids (d) describe the formation of ethanol by the catalysed addition of steam to ethene and by fermentation of glucose
(e) describe the carboxylic acids as a homologous series containing the –CO2H group
(f) draw the structures of carboxylic acids, C1 to C4, and name the unbranched acids methanoic acid to butanoic acid
(g) describe the carboxylic acids as weak acids, reacting with carbonates, bases and some metals

Carboxylic acid general formula

The formula for carboxylic acid is R-COOH, where: 

R represents an organic group or hydrocarbon chain, which can vary and give different carboxylic acids their specific properties.

COOH is the carboxyl group, which is the functional group of carboxylic acids. It consists of a carbonyl group (-C=O) and a hydroxyl group (-OH) bonded to the same carbon atom.

Carboxylic acid functional group

The carboxyl group (-COOH) is the defining feature of carboxylic acids and is responsible for their acidic properties. It is this group that releases hydrogen ions (H+) in water, making carboxylic acids acidic and giving them their distinct sour taste. This functional group is crucial in the chemistry of carboxylic acids and is involved in various chemical reactions and applications.

What are some carboxylic acids in daily life?

Carboxylic acids are commonly encountered in our daily lives, often in the form of natural substances, food and beverages, and common household products. Here are some examples:

Citric Acid (C6H8O7): Naturally occurring in citrus fruits like lemons, limes, and oranges. It’s used as a flavoring and preservative in food and beverages.

Lactic Acid (C3H6O3): Produced during the fermentation of milk, giving yogurt and some cheeses their tangy taste.

Ascorbic Acid (Vitamin C, C6H8O6): A vital nutrient found in fruits and vegetables, used as a dietary supplement and food preservative.

Some of its uses are in:
Preservatives: Carboxylic acids, such as benzoic acid and citric acid, are used as food preservatives to extend the shelf life of various products.

Cosmetics: They are used in cosmetics and skincare products for their acidic and astringent properties.

Pharmaceuticals: Many pharmaceutical drugs contain carboxylic acids, playing a crucial role in their effectiveness.

What is an ester? 

An ester is a type of organic compound that is known for its pleasant and often fruity or sweet smell. Esters are formed when an alcohol and a carboxylic acid (The above two) react in a chemical process called esterification. 

Most commonly, esters are often used in perfumes, flavorings (like in fruity candies), and cosmetics because of their delightful scents.

What is taught or tested in the O level Syllabus for alcohol

(h) describe the formation of ethanoic acid by the oxidation of ethanol by atmospheric oxygen or

acidified potassium manganate(VII)

(i) describe the reaction of a carboxylic acid with an alcohol to form an ester, e.g. ethyl ethanoate

(j) deduce the name and formula of an ester from the unbranched carboxylic acid, C1 to C4, and

alcohol, C1 to C4, and vice versa.

How to name esters?

One of the interesting points of esters is how they are named. To name an ester, it requires that the individual identifies the parent carboxylic acid, name the alkyl, combine the names, and use prefixes for substituted groups.

Ignoring the complex steps needed to do so, here are some of the esters:

CH3COOC2H5 is named “ethyl acetate.”

C6H5COOC2H5 is named “ethyl benzoate.”

CH3COOC3H7 is named “propyl acetate.”