Chemistry · Class 12 Science

Ch 15Chemistry in Everyday Life — Class 12 Chemistry, concept-first.

Chemistry is not confined to the laboratory -- it underlies the three basic requirements of everyday life: food, clothing and shelter, all of which are, at bottom, chemical compounds. Life itself can be viewed as a network of interlinked chemical processes.

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Analgesics

Drugs that relieve pain without loss of consciousness, classified as narcotic (morphine) and non-narcotic (aspirin).

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Chapter contents

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Introduction

Chemistry is not confined to the laboratory -- it underlies the three basic requirements of everyday life: food, clothing and shelter, all of which are, at bottom, chemical compounds.

15.1

Drug

A drug, at its simplest, is any substance used to modify or investigate a physiological system or a diseased state for the benefit of the person taking it -- for diagnosis, prevention, or the cure or…

15.1.1

Classification of Drugs

There isn't one single way to classify drugs -- the unit walks through four different, complementary classification schemes, each useful for a different purpose.

15.1.2

Drug–Target Interaction

Ordinary, healthy body function runs on a constant stream of biochemical processes. Metabolism breaks down the food we eat and harvests the released energy as ATP, while simultaneously building the bi…

Enzymes as Drug Targets

Every biochemical reaction inside a living cell runs on an enzyme catalyst, so keeping enzyme activity normal is essential to keeping the whole system running -- and, turned around, disabling a pathog…

Receptors as Drug Targets

A second major class of drug target is the receptor -- a protein whose job is to trigger a response inside a cell when the right molecule docks onto it.

Therapeutic Action of Different Classes of Drugs

Deeper biological understanding of a disease mechanism translates directly into safer, better-targeted drugs -- and the unit uses stomach acidity to make the point concrete.

Tranquilizers

Tranquilizers are neurologically active drugs -- they work directly on the central nervous system, specifically by blocking the neurotransmitter dopamine in the brain.

Analgesics (Non-narcotic)

Non-narcotic analgesics relieve pain without dulling consciousness -- unlike the opioids covered next, they do not sedate or produce dependency in ordinary use.

Opioids (Narcotic Analgesics)

Opioids -- morphine and codeine are the two examples given -- are narcotic analgesics: unlike the non-narcotic class just covered, they relieve pain by inducing sleep and are genuinely addictive, and…

Anaesthetics

Anaesthetics come in two distinct flavours depending on how much of the body they switch off. Local anaesthetics -- the ester-linked procaine and the amide-linked lidocaine are the examples given -- c…

Antacids

Antacids neutralise the excess stomach acid responsible for the burning sensation in the chest or throat known as heartburn, caused by acid reflux.

Antihistamines

Antihistamines -- cetirizine, levocetirizine, desloratadine, brompheniramine and terfenadine are the examples given -- work by blocking histamine release from histamine-1 receptors.

Antimicrobials

Antimicrobials are grouped into five distinct chemical families in the unit, each defined by a different way of disabling a microorganism.

Antiseptics and Disinfectants

Antiseptics and disinfectants share the same basic job -- stopping or slowing the growth of microorganisms -- but differ in where it is safe to apply them.

Antifertility Drugs

Antifertility drugs are synthetic versions of the body's own reproductive hormones, engineered to suppress ovulation or fertilisation.

15.2

Food Additives

Look closely at the ingredient list on any packaged food -- biscuits, chocolates, and the like -- and, alongside the expected main ingredients (wheat flour, edible oil, sugar, milk solids), you'll typ…

15.2.1

Important Categories of Food Additives

Food additives fall into eight broad categories: aroma compounds, food colours, preservatives, stabilizers, artificial sweeteners, antioxidants, buffering substances, and vitamins and minerals.

15.2.2

Preservatives

Preservatives work by inhibiting, retarding or outright arresting the processes -- fermentation, acidification, general decomposition -- that microbial growth causes in food.

15.2.3

Antioxidants

Fats and oils in food are prone to oxidation, and oxidised fat turns rancid -- the unpleasant taste and smell everyone recognises in stale cooking oil or old snack food.

15.2.4

Sugar Substituents

Sugar substituents are compounds used for sweetening in the same way as ordinary sugars like glucose or sucrose, with one crucial difference: they are metabolised by the body WITHOUT needing insulin.

15.2.5

Artificial Sweetening Agents

Artificial sweetening agents are synthetic compounds engineered to produce a sweet taste sensation while carrying little to no actual nutritional (caloric) value -- distinct from the sugar substituent…

15.3

Cleansing Agents

Soap and (synthetic) detergent are the two everyday chemical tools for cleansing, and although they do the same practical job, they are built from different chemistry.

15.3.1

Soaps

Soaps start from animal fat or vegetable oil -- both are glyceryl esters of long-chain fatty acids. Heating these glycerides with a sodium hydroxide solution converts them into soap plus glycerol, the…

15.3.2

Detergents

Synthetic detergents are manufactured products built from either the sodium salt of an alkyl hydrogen sulphate or the sodium salt of a long-chain alkyl benzene sulphonic acid, and they come in three d…

15.4

Polymers

"Polymer" comes from the Greek polumeres, meaning "having many parts" -- an apt name, since a polymer's identity is described entirely in terms of its repeating structural unit, called a monomer.

15.4.1

Classification of Polymers

A single polymer can carry four independent labels at once, because the unit's classification chart sorts polymers along four completely separate axes.

15.4.2

Types of Polymerisation

Polymerisation is simply the process of building one very large, high-molecular-mass polymer out of many small monomer units, and it happens by one of two fundamentally different routes: addition poly…

15.4.3

Preparation of Some Important Addition Polymers

Three specific addition polymers are worked through as examples of everything covered in 15.4.2, each starting from a small, simple monomer.

Condensation Polymers

Condensation polymers work by a fundamentally different logic than the addition polymers just covered: instead of monomers simply adding together, functional groups on adjacent monomers react with eac…

15.4.4

Co-polymers

A co-polymer, by definition, is a polymer built from two or more DIFFERENT kinds of monomer unit, rather than one monomer repeated on its own (a homopolymer).

15.4.5

Natural and Synthetic Rubbers

Natural rubber is a genuinely natural polymer, tapped as latex from cuts made in the bark of the rubber tree.

15.4.6

Biodegradable Polymers

A biodegradable material is one that microorganisms in the environment can readily break down. Natural polymers do this on their own, decomposing over time -- but ordinary synthetic polymers generally…

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