Chemistry in Everyday Life is the final chapter of the Class 12 syllabus and connects chemical principles to the products and processes that surround us daily. The chapter focuses on three major areas: drugs and medicines, the chemistry of cleansing agents such as soaps and detergents, and a brief survey of food preservatives and chemicals used in daily life. This chapter demonstrates the enormous impact that chemical research has on human health and comfort.
The chapter begins with the classification of drugs and the concept of drug-target interaction. Drugs are classified based on their pharmacological effect, chemical structure, or target site. The mechanism of drug action is explained through the interaction of drugs with biomolecules such as enzymes and receptors. Enzyme inhibitors, in particular, form the basis of many therapeutic drugs, and the differences between competitive and non-competitive inhibition are explained.
The second half of the chapter covers cleansing agents. Soaps are sodium or potassium salts of long-chain fatty acids, prepared by the saponification of oils and fats. Synthetic detergents were developed to overcome the problems of soaps in hard water and include anionic, cationic, and non-ionic types. The chapter also briefly introduces antiseptics, disinfectants, antimicrobials, antifertility drugs, and antacids, and concludes with the role of food preservatives and artificial sweeteners in modern food technology.
Drugs are chemical substances that interact with biological targets to produce therapeutic effects. They are classified in several ways:
Important classes include: - Analgesics: Aspirin (acetylsalicylic acid) for pain and inflammation, and paracetamol. Aspirin also prevents blood clotting and reduces the risk of heart attacks. - Antipyretics: Paracetamol, phenacetin, and aspirin reduce fever. - Antiseptics: Applied to living tissues to kill or reduce microorganisms, e.g., iodine, boric acid, and chloroxylenol (Dettol). - Disinfectants: Applied to inanimate objects to kill microorganisms, e.g., phenol, chlorine. Disinfectants in low concentrations act as antiseptics. - Antacids: Neutralise excess stomach acid, e.g., sodium bicarbonate, magnesium hydroxide, aluminium hydroxide, and ranitidine (which prevents histamine from stimulating acid secretion). - Antihistamines: Relieve allergy symptoms such as sneezing and runny nose, e.g., diphenhydramine, chlorpheniramine. - Antimicrobials: Antibiotics that kill or inhibit microorganisms, e.g., penicillin, and antibacterial sulpha drugs. - Antifertility drugs: Birth control pills containing estrogen and progesterone derivatives. - Tranquillisers: Relieve anxiety, stress, and mental disorders, e.g., barbiturates and benzodiazepines.
Enzymes are proteins that catalyse biological reactions. Many drugs act by inhibiting enzymes. The active site of an enzyme is the region where the substrate binds. A drug that blocks the active site prevents the substrate from binding, thereby inhibiting the reaction.
An example is the inhibition of the enzyme that synthesises cholesterol by certain drugs. Sulpha drugs act by competing with p-aminobenzoic acid (PABA), which bacteria require to synthesise folic acid.
Receptors are proteins embedded in the cell membrane that receive chemical messengers. Drugs that bind to receptors and mimic natural messengers are called agonists, while drugs that bind and block the receptor are called antagonists. Antihistamines, for example, block histamine receptors and prevent allergic reactions.
Food preservatives prevent spoilage caused by microbial growth. They either kill microorganisms or prevent their growth. Examples include: - Sodium benzoate: Used in acidic foods such as jams and squashes. - Sodium metabisulphite: Used in pickles. - Sorbic acid: Used in bakery products. - Common table salt and sugar also act as preservatives by creating a hypertonic environment.
Artificial sweeteners provide sweetness without the calories of sugar. Examples include: - Saccharin: The oldest artificial sweetener, about 550 times sweeter than cane sugar. - Aspartame: About 100 times sweeter than sugar; it loses its sweetness on heating. - Alitame: About 2000 times sweeter than sugar. - Sucralose: About 600 times sweeter than sugar.
Antioxidants prevent the oxidation of food by oxygen and retard rancidity. Examples include butylated hydroxy anisole (BHA) and butylated hydroxy toluene (BHT), which are added to fats and oils.
Soaps are sodium or potassium salts of long-chain carboxylic acids, such as sodium stearate. They are prepared by the hydrolysis of fats and oils (triglycerides) with alkali, a process called saponification.
Soaps have two parts: a long hydrophobic hydrocarbon tail and a hydrophilic carboxylate head. This amphiphilic nature allows soap to emulsify oil and grease. Soap micelles form around grease particles, with the hydrophobic tails embedded in the oil and the hydrophilic heads facing the water, allowing the grease to be washed away.
Soaps form insoluble scum with hard water containing calcium and magnesium ions, which reduces their cleansing action. This led to the development of synthetic detergents.
Synthetic detergents are amphiphilic molecules that cleanse like soaps but do not form scum with hard water. They are classified as:
Biodegradable detergents have linear alkyl chains, whereas non-biodegradable detergents have branched chains that resist degradation by bacteria and cause water pollution.
| Drug | Category | Use |
|---|---|---|
| Aspirin | Analgesic, antipyretic | Pain, fever, heart attack prevention |
| Paracetamol | Analgesic, antipyretic | Pain, fever |
| Ranitidine | Antacid | Excess stomach acid |
| Diphenhydramine | Antihistamine | Allergies |
| Penicillin | Antibiotic | Bacterial infections |
| Chloroxylenol | Antiseptic | Wound disinfection |
| Feature | Soap | Synthetic Detergent |
|---|---|---|
| Source | Fats and oils | Petrochemicals |
| Hard water | Forms scum | No scum |
| Biodegradability | Biodegradable | Some non-biodegradable |
| Structure | Na/K salt of fatty acid | Sulphonate/sulphate head |
| Example | Sodium stearate | Sodium alkyl benzene sulphonate |
Chemistry in Everyday Life shows how fundamental chemical principles are translated into products that improve human health, comfort, and nutrition. The classification of drugs and the mechanisms of drug-target interaction explain how medicines work at the molecular level, while the distinction between competitive and non-competitive inhibition provides a framework for designing enzyme inhibitors. Food preservatives, artificial sweeteners, and antioxidants protect our food and enhance its safety and appeal. The chemistry of soaps and detergents illustrates the importance of molecular structure in determining function, and the problems caused by hard water and non-biodegradable detergents highlight the environmental dimension of chemical design. This chapter concludes the Class 12 curriculum by demonstrating the profound relevance of chemistry to everyday life and preparing students to think critically about the chemical products that surround them.