CBSE Class 12 Chemistry Chemistry in Everyday Life Exam Notes

CBSE Class 12 Chemistry Chemistry in Everyday Life Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Chemistry in everyday life covers the drugs and medicines that act on the body, their classification, how they interact with enzymes and receptors, and their use as antacids, antihistamines, tranquilizers, analgesics, antimicrobials, antiseptics and disinfectants. This Class 12 Chemistry exam notes page also explains antifertility drugs, artificial sweetening agents, food preservatives, soaps and detergents, with their structures and examples, followed by additional questions with answers.

Topics Covered

1. Drugs and medicines and their classification
2. Drug-target interaction
3. Antacids, antihistamines and tranquilizers
4. Analgesics, antimicrobials, antiseptics and disinfectants
5. Antifertility drugs and artificial sweetening agents
6. Food preservatives
7. Soaps and detergents
8. Additional questions

Drugs are low molecular mass (100-500 u) substances which interact with targets in the body and produce a biological response.

DRUGS AND MEDICINES

Medicines: The chemicals which cause a therapeutic and useful biological response.
Chemotherapy: The use of chemicals for a therapeutic effect.

CLASSIFICATION OF DRUGS

1. Pharmacological effect: Drugs are classified according to the particular type of problem they are used for, such as analgesics and antiseptics.
2. Drug action: Drugs are classified according to their action on a particular biochemical process, such as antihistamines.
3. Chemical structure: Drugs with common structural features often have similar pharmacological activity.
4. Molecular targets: Drugs interact with biomolecules such as carbohydrates, lipids, proteins and nucleic acids. These are also called target molecules or drug targets.

DRUG-TARGET INTERACTION

Enzymes: Enzymes are biological catalysts, which are proteins.
Receptors: Receptors are proteins which act as the communication system of the body.

(a) Catalytic action of enzymes:
(i) The enzyme holds the substrate on the active site in a suitable position, through a variety of interactions, for a chemical reaction.
(ii) The enzyme provides functional groups that attack the substrate and carry out the chemical reaction.

(b) Drug-enzyme interaction:
Drugs which act as enzyme inhibitors stop the activity of enzymes in two ways. Competitive inhibitors block the binding site of the enzyme and prevent the binding of the substrate. Other drugs bind to a different site of the enzyme, called the allosteric site, and deform the active site.

Antagonists: Drugs that bind to the receptor site and inhibit its natural function.
Agonists: Drugs that mimic the natural messenger by switching on the receptor.

ANTACIDS

Antacids are chemical substances which neutralise excess acid in the gastric juices and give relief from acid indigestion, acidity, heartburn and gastric ulcers. Examples are Eno, Gelusil and Digene.

Excess acid in the stomach causing pain is normally treated with sodium hydrogen carbonate or a mixture of aluminium and magnesium hydroxide. Excess use of these antacids results in the production of even more acid. These treatments control only the symptoms.

ANTIHISTAMINES

Antihistamines are chemical substances which diminish or abolish the effects of histamine released in the body, and hence prevent allergic reactions. Examples are brompheniramine (Dimetapp) and terfenadine (Seldane). They are also useful in other allergies such as conjunctivitis and rhinitis, and allergic response to pollen.

Brompheniramine and terfenadine act as antihistamines. They interfere with the natural action of histamine by competing with histamine for the binding sites of the receptor where histamine exerts its effect. These antihistamines do not affect the secretion of acid in the stomach, because antiallergic and antacid drugs work on different receptors.

For the treatment of hyperacidity, cimetidine (Tagamet) is used, which prevents the interaction of histamine with the receptors present in the stomach wall. Zantac is also used for this purpose.

TRANQUILIZERS

Tranquilizers affect the message transfer mechanism from nerve to receptor. They are used for the treatment of stress and mild or even severe mental diseases.

A low level of noradrenaline causes depression. In such cases, antidepressant drugs help by inhibiting the enzymes which catalyse the degradation of noradrenaline. Examples are iproniazid and phenelzine.

Chlordiazepoxide and meprobamate are relatively mild tranquilizers, suitable for relieving tension. Equanil is used in controlling depression and hypertension.

Barbiturates: Derivatives of barbituric acid, such as veronal and amytal, are hypnotic. Some other substances used as tranquilizers are valium and serotonin.

ANALGESICS

Analgesics are drugs which reduce or abolish pain.

(a) Non-narcotic (non-addictive) analgesics:
Aspirin inhibits the synthesis of prostaglandins, which stimulate inflammation in the tissue and cause pain. It is helpful in arthritis, is also used as an antipyretic (to reduce fever), and has anti-blood-clotting action, which helps in the prevention of heart attacks.

(b) Narcotic analgesics:
These relieve pain and produce sleep. They produce stupor, coma and convulsions, and ultimately death.

ANTIMICROBIALS

Antimicrobials destroy or prevent the development of, or inhibit the pathogenic action of, microbes such as bacteria, fungi and viruses.

(a) Antibiotics:
An antibiotic is a substance produced wholly or partly by chemical synthesis, which in low concentrations inhibits the growth of, or destroys, microorganisms by intervening in their metabolic processes.

Arsphenamine (salvarsan) was the first effective medicine for syphilis. Prontosil is another antibacterial used for syphilis, because of its similar structure.

Antibiotics have either a cidal (killing) effect or a static (inhibitory) effect on microbes.

Classification of antibiotics on the basis of their spectrum of action:
- Broad spectrum antibiotics: Antibiotics which kill or inhibit a wide range of Gram-positive and Gram-negative bacteria.
- Narrow spectrum antibiotics: Antibiotics effective against a single organism or disease. They are referred to as limited spectrum antibiotics.
- Wide range spectrum: Antibiotics effective against several different types of harmful microorganisms. Chloramphenicol can be given orally in the case of typhoid, dysentery, acute fever, certain forms of urinary infection, meningitis and pneumonia.

In India, penicillin is manufactured at Hindustan Antibiotics, Pimpri.

(b) Antiseptics: Antiseptics are applied to living tissues such as wounds, cuts, ulcers and diseased skin surfaces. Examples are furacine and soframicine.
- Dettol is a mixture of chloroxylenol and terpineol.
- Bithional is a compound added to soaps to impart antiseptic properties.
- Iodine is a powerful antiseptic. Its 2-3 per cent solution in an alcohol-water mixture is known as tincture of iodine. It is applied on wounds.
- Iodoform is also used as an antiseptic for wounds.
- Boric acid, in dilute aqueous solution, is a weak antiseptic for the eyes.

(c) Disinfectants: Disinfectants are applied to inanimate objects such as floors, drainage systems and instruments. A 0.2 per cent solution of phenol is an antiseptic, while its 1 per cent solution is a disinfectant.

ANTIFERTILITY DRUGS

Birth control pills essentially contain a mixture of synthetic oestrogen and progesterone derivatives. Both of these compounds are hormones. Progesterone suppresses ovulation. Synthetic progesterone derivatives are more potent than progesterone. An example is norethindrone.

ARTIFICIAL SWEETENING AGENTS

Artificial sweetening agents are used to control the intake of calories.
- Saccharin (ortho-sulphobenzimide) is the first popular artificial sweetening agent.
- Aspartame is 100 times as sweet as cane sugar. It is the methyl ester of a dipeptide formed from aspartic acid and phenylalanine. It is only used in cold foods, as it is unstable at cooking temperature.
- Alitame is avoided, because it is difficult to control the sweetness of food when using it.
- Sucralose (a trichloro derivative of sucrose) is stable at cooking temperature.

FOOD PRESERVATIVES

Food preservatives include table salt, sugar, vegetable oils and sodium benzoate (C₆H₅COONa).
Antioxidants are added to food to prevent the oxidation of fats and oils, which prevents the food from becoming rancid. Examples are BHA (butylated hydroxy anisole) and BHT (butylated hydroxy toluene).

SOAPS

Soaps are sodium and potassium salts of higher fatty acids. Only sodium and potassium soaps are soluble in water, and they are used for cleaning purposes. Potassium soaps are soft to the skin.

[Figure: Preparation of soap by saponification. A glyceryl ester of stearic acid (fat) reacts with 3 molecules of sodium hydroxide to give 3 molecules of sodium stearate (soap) and 1 molecule of glycerol (or glycerine)]

Types of soaps:
- Soaps that float in water are made by beating tiny air bubbles into the soap before it hardens. They are sold in small broken pieces.
- Transparent soaps are made by dissolving the soap in ethanol and evaporating the excess solvent.
- Medicated soaps have medicinal value, as medicinal substances are added to them.
- Shaving soaps contain glycerol to prevent rapid drying.
- Laundry soaps contain fillers such as sodium rosinate, sodium silicate and borax.

Advantages of soaps: Soap is a good cleansing agent and is 100% biodegradable, that is, micro-organisms present in sewage water can completely oxidise soap. Therefore, soaps do not cause any pollution problems.
Disadvantages of soaps: Soaps cannot be used in hard water, because hard water contains metal ions such as Ca²⁺ and Mg²⁺, which react with soap to form a white precipitate of calcium and magnesium salts.

DETERGENTS

Anionic detergents: Anionic detergents are prepared from alcohols or aromatic hydrocarbons. They are used for household work and in toothpastes.

Lauryl alcohol is converted to sodium lauryl sulphate in two steps:
CH₃(CH₂)₁₀CH₂OH → (H₂SO₄) → CH₃(CH₂)₁₀CH₂OSO₃H (lauryl hydrogensulphate) → (NaOH, aq.) → CH₃(CH₂)₁₀CH₂OSO₃Na (sodium lauryl sulphate, an anionic detergent)

Dodecylbenzene is converted to sodium dodecylbenzenesulphonate in two steps:
CH₃(CH₂)₁₁C₆H₅ → (H₂SO₄) → CH₃(CH₂)₁₁C₆H₄SO₃H (dodecylbenzenesulphonic acid) → (NaOH, aq.) → CH₃(CH₂)₁₁C₆H₄SO₃Na (sodium dodecylbenzenesulphonate)

Cationic detergents: Cationic detergents, such as cetyltrimethyl ammonium bromide, are used in hair conditioners. They have germicidal properties, but they are expensive, and therefore they are of limited use.

[Figure: Structure of cetyltrimethyl ammonium bromide. A positively charged nitrogen atom bonded to three methyl groups (CH3) and one CH3(CH2)15 chain, with a bromide ion (Br-) as the counter-ion]

Non-ionic detergents: Non-ionic detergents are used in liquid detergents, emulsifying agents and wetting agents. Their structure has a hydrophobic part and a hydrophilic part.

Biodegradability of detergents: Unbranched chains can be biodegraded more easily, and hence pollution is prevented. Detergents with highly branched chains are not easily biodegraded.

ADDITIONAL QUESTIONS

Q1. Sleeping pills are recommended by doctors to the patients suffering from sleeplessness but it is not advisable to take its doses without consultation with the doctor. Why ?

Answer:
Most of the drugs taken in doses higher than recommended may cause harmful effects and act as poison. Therefore, a doctor should always be consulted before taking medicine.

Teacher's Note:
a) Sleeping pills are drugs, and a drug can become a poison at a high dose.
b) The correct dose depends on the patient, so the doctor must decide it.

Q2. With reference to which classification has the statement, "ranitidine is anantacid" been given?

Answer:
This statement refers to the classification according to the pharmacological effect of the drug, because any drug which is used to counteract the effect of excess acid in the stomach is called an antacid.

Teacher's Note:
a) Classification by pharmacological effect groups drugs by the problem they treat.
b) Ranitidine belongs to the antacid group because it treats acidity.

Q3. Following type of non-ionic detergents are present in liquid detergents, emulsifying agents and wetting agents. Label the hydrophilic and hydrophobic parts in the molecule. Identify the functional group(s) present in the molecule.
C₉H₁₉-C₆H₄-O(CH₂CH₂O)_xCH₂CH₂OH

Answer:

Functional groups present: ether group (-O-) and primary alcohol group (-OH).

Teacher's Note:
a) The long hydrocarbon part repels water, and the oxygen-rich chain attracts water.
b) Ether and alcohol groups are both present in the polyoxyethylene part.

Q4. Which forces are involved in holding the drugs to the active site of enzymes?

Answer:
Either of the following forces can be involved in holding drugs to the active sites of enzymes.
(i) Ionic bonding
(ii) Hydrogen bonding
(iii) Dipole-dipole interaction
(iv) van der Waals force

Teacher's Note:
a) These are weak or medium-strength interactions, so the drug can bind and also be released.
b) Hydrogen bonding is the most common of these forces in drug-enzyme binding.

Q5. Low level of noradrenaline is the cause of depression. What type of drugs are needed to cure this problem ? Name two drugs.

Answer:
Anti-depressant drugs are needed to counteract the effect of depression. These drugs inhibit the enzymes catalysing the degradation of the neurotransmitter noradrenaline. As a result, the neurotransmitter is slowly metabolised, and it can activate its receptor for longer periods of time.

Two anti-depressant drugs are:
(i) Iproniazid
(ii) Phenelzine

Teacher's Note:
a) Antidepressants raise the level of noradrenaline by slowing its breakdown.
b) Iproniazid and phenelzine are both named in the notes under tranquilizers.

Q6. Why are cimetidine and ranitidine better antacids than sodium hydrogen carbonate or magnesium or aluminium hydroxide?

Answer:
Antacids such as sodium hydrogen carbonate, magnesium hydroxide and aluminium hydroxide work by neutralising the excess hydrochloric acid present in the stomach. However, the root cause of the release of excess acid remains untreated.

Cimetidine and ranitidine are better antacids. These drugs prevent the interaction of histamine with the receptors present in the stomach walls. Consequently, there is a decrease in the amount of acid released by the stomach.

Teacher's Note:
a) Simple antacids only neutralise the acid that is already present.
b) Cimetidine and ranitidine reduce the production of acid at its source.

Q7. What are biodegradable and non-biodegradable detergents? Give one example of each.

Answer:
Detergents that can be degraded by bacteria are called biodegradable detergents. Such detergents have straight hydrocarbon chains. For example, sodium lauryl sulphate.

Detergents that cannot be degraded by bacteria are called non-biodegradable detergents. Such detergents have highly branched hydrocarbon chains. For example, sodium 4-(1, 3, 5, 7-tetramethyloctyl) benzene sulphonate.

Teacher's Note:
a) Straight chains are broken down by bacteria, but branched chains persist in water.
b) Non-biodegradable detergents cause water pollution, which is why they are no longer preferred.

Q8. What is the chemical name of antiseptic chloroxylenol ?

Answer: 4-Chloro-3, 5-dimethyl phenol.

Teacher's Note:
a) Chloroxylenol is the main active ingredient of Dettol.
b) The name shows a phenol ring with one chlorine and two methyl groups.

Q9. Which alkaloid is used to control hypertension ?

Answer: Reserpine.

Teacher's Note:
a) Reserpine is an alkaloid obtained from plants.
b) Hypertension means high blood pressure.

Q10. Which alkaloid is used to treat malaria ?

Answer: Quinine.

Teacher's Note:
a) Quinine is obtained from the bark of the cinchona tree.
b) It is used to treat malaria, which is caused by a parasite.

Q11. What is the use of the following compound :
[Figure: Structure of a benzene ring with an OCOCH3 group at one position and a COOH group at the adjacent position]

Answer:
Analgesic. 2-Acetoxy benzoic acid (aspirin) inhibits the synthesis of prostaglandins, which stimulate inflammation of the tissue and cause pain.

Teacher's Note:
a) Aspirin is a non-narcotic analgesic, as noted in the analgesics section.
b) The OCOCH3 group is an acetyl ester group and the COOH group is a carboxylic acid group.

Q12. Name the antibacterial present in toothpaste.

Answer: Triclosan.

Teacher's Note:
a) Triclosan is added to toothpaste to reduce the bacteria in the mouth.
b) It is an antibacterial, not an analgesic.

Q13. Identify the drug :
[Figure: Structure of a penicillin drug: a benzene ring attached to CH2-C(=O)-NH on a beta-lactam ring with a sulphur atom, two CH3 groups and a COOH group]

Answer: Penicillin G.

Teacher's Note:
a) Penicillin G is a bactericidal antibiotic, as listed in the notes.
b) The beta-lactam ring is the key part of the structure of penicillins.

Q14. Which antibiotic contains NO₂ group attached to aromatic nucleus in its structure ?

Answer: Chloramphenicol.

Teacher's Note:
a) Chloramphenicol is a broad spectrum antibiotic.
b) The NO₂ group is attached to the benzene ring in its structure.

Q15. Give an example of a drug that is antipyretic as well as analgesic.

Answer: Paracetamol.

Teacher's Note:
a) An antipyretic reduces fever, and an analgesic reduces pain.
b) Aspirin is also both an analgesic and an antipyretic.

Q16. Out of morphine, N-Acetyl-para-aminophenol, Diazepam and tetrahydrocatenol, which can be used as analgesic without causing addiction ?

Answer: N-Acetyl-para-aminophenol.

Teacher's Note:
a) Morphine is a narcotic analgesic, which causes addiction.
b) N-Acetyl-para-aminophenol is a non-narcotic analgesic, so it is non-addictive.

Q17. Pick the odd one amongst the following on the basis of their medicinal properties mentioning the reason.
(i) Luminal, seconal, phenacetin, equanil
(ii) Chloroxylenol, phenol, chlorampherical, bithional

Answer:
(i) Phenacetin is an antipyretic, while all the rest are tranquilisers.
(ii) Chlorampherical is an antibiotic, while all the remaining are antiseptics.

Teacher's Note:
a) Luminal and seconal are barbiturates, and equanil is a tranquilizer.
b) Chloroxylenol, phenol and bithional are antiseptics.

Q18. What is the purpose of adding antioxidants to food ? Give two examples of antioxidants.

Answer:
They are added to prevent the oxidation of fats and oils present in food, thus preventing food from becoming rancid.
Examples: BHA (butylated hydroxy anisole) and BHT (butylated hydroxy toluene).

Teacher's Note:
a) Rancid food has an unpleasant smell and taste because the fats have been oxidised.
b) Antioxidants are added in small amounts and do not change the taste of food.

Q19. (a) Boric acid is a weak antiseptic than tincture of iodine. Give reason.
(b) Tincture of iodine is preferred over iodoform as antiseptic. Why?
(c) How can you overcome the problem of premature ageing by specific intake of food items. Name some food items that slows down the ageing process. Explain how they act ?

Answer:

(a) Iodine is a powerful antiseptic, because it kills microbes by reacting with their proteins. Boric acid is a weak acid, and in dilute solution it has only a mild antiseptic action, so it is a weaker antiseptic than tincture of iodine.

(b) Tincture of iodine contains free iodine, which is a powerful antiseptic. Iodoform releases iodine slowly, is less effective, and has an unpleasant smell. So tincture of iodine is preferred.

(c) Premature ageing is largely caused by free radicals, which damage cells by oxidation. Antioxidants in food react with these free radicals and make them harmless. Foods rich in antioxidants, such as vitamin C (citrus fruits, amla, guava), vitamin E (nuts, seeds and vegetable oils) and beta-carotene (carrots, papaya, green leafy vegetables), help to slow down the ageing process.

Teacher's Note:
a) Part (a) is based on the strength of iodine as an antiseptic, while boric acid is weak in dilute form.
b) Vitamin C, vitamin E and beta-carotene are the main antioxidants that slow the ageing process.
c) A balanced diet with fresh fruits and vegetables supplies these antioxidants.

Enzymes-biological catalysts proteins.

Receptors-proteins act as communication system