Class 12 Chemistry Notes Chapter 16 (Chemistry in Everyday Life) – Examplar Problems Book

Detailed Notes with MCQs of Chapter 16, "Chemistry in Everyday Life." This chapter is quite important, not just for its direct applications but also because questions frequently appear in various government exams based on the specific examples and classifications discussed here. Pay close attention to the names of chemicals, their categories, and functions.

Chapter 16: Chemistry in Everyday Life - Detailed Notes

1. Introduction:
Chemistry plays a vital role in meeting human needs for food, healthcare, and materials. This chapter focuses on the application of chemical principles in three major areas: Medicines, Food Materials, and Cleansing Agents.

2. Drugs and Medicines:

• Drugs: Chemicals of low molecular mass (~100-500 u) that interact with macromolecular targets (like proteins, carbohydrates, lipids, nucleic acids) and produce a biological response.
• Medicines: Drugs used for therapeutic effect, i.e., in the diagnosis, prevention, and treatment of diseases. Most drugs used as medicines are potential poisons if taken in doses higher than recommended.
• Chemotherapy: Use of chemicals for therapeutic effect.

3. Classification of Drugs:
Drugs are classified based on different criteria:
* (a) Based on Pharmacological Effect: Based on the effect on the body. Useful for doctors.
* Example: Analgesics (pain killing), Antiseptics (kill/arrest growth of microorganisms), Antipyretics (reduce fever).
* (b) Based on Drug Action: Based on the action on a specific biochemical process.
* Example: Antihistamines (inhibit the action of histamine, which causes inflammation).
* (c) Based on Chemical Structure: Drugs sharing common structural features often have similar pharmacological activity. Useful for chemists.
* Example: Sulphonamides (contain -SO2NH2 group).
* (d) Based on Molecular Targets: Drugs interact with biomolecules called target molecules (e.g., enzymes, receptors, nucleic acids). This is the most useful classification for medicinal chemists.

4. Drug-Target Interaction:

• Enzymes as Drug Targets:
  • Catalytic Action of Enzymes: Enzymes have active sites that bind substrates through various interactions (ionic, hydrogen bonding, van der Waals, dipole-dipole).
  • Drug-Enzyme Interaction: Drugs can inhibit enzyme activity.
    • Competitive Inhibitors: Drugs compete with the natural substrate for attachment to the active site.
    • Non-Competitive Inhibitors (Allosteric Inhibition): Drugs bind to a different site (allosteric site), changing the shape of the active site so the substrate cannot bind.
• Receptors as Drug Targets:
  • Receptors: Proteins crucial to the body's communication system, embedded in cell membranes. Their active site shape accommodates specific chemical messengers.
  • Chemical Messengers: Chemicals that transmit signals between nerve cells or to muscles.
  • Drug Action:
    • Agonists: Drugs that bind to the receptor and mimic the natural messenger, switching on the receptor.
    • Antagonists: Drugs that bind to the receptor and block its function, inhibiting the natural messenger. Useful when blocking of message is required.

5. Therapeutic Action of Different Classes of Drugs:

• (a) Antacids:

  • Function: Neutralize excess stomach acid, providing relief from acidity and heartburn.
  • Mechanism: Initially, basic salts like Sodium bicarbonate (NaHCO3) or mixtures of Aluminium hydroxide [Al(OH)3] and Magnesium hydroxide [Mg(OH)2] were used. These only neutralize acid. Later, drugs preventing acid production were developed.
  • Histamine's Role: Histamine stimulates secretion of pepsin and HCl.
  • H2-Antagonists: Drugs like Cimetidine (Tagamet) and Ranitidine (Zantac) were designed to prevent the interaction of histamine with H2 receptors in the stomach wall, reducing acid production. Omeprazole and Lansoprazole are newer, more effective proton pump inhibitors.

• (b) Antihistamines:

  • Function: Combat the effects of histamine (released during allergic reactions), which causes vasodilation, nasal congestion, itching, etc.
  • Mechanism: They act as antagonists, competing with histamine for binding sites on receptors (H1 receptors), thus preventing histamine from exerting its effects.
  • Examples: Brompheniramine (Dimetapp), Terfenadine (Seldane), Cetirizine.
  • Note: Antiallergic and antacid drugs work on different histamine receptors (H1 vs H2).

• (c) Neurologically Active Drugs: Affect the message transfer mechanism from nerve to receptor.

  • Tranquilizers:
    • Function: Treat stress, mild or severe mental diseases. Relieve anxiety, stress, irritability, or excitement by inducing a sense of well-being. Essential component of sleeping pills.
    • Mechanism: Affect neurotransmitters like Noradrenaline (mood regulation). Low levels cause depression.
    • Examples:
      • Antidepressants: Iproniazid, Phenelzine (increase noradrenaline by inhibiting breakdown enzymes).
      • Mild Tranquilizers (anxiety relief): Chlordiazepoxide, Meprobamate (Equanil).
      • Hypnotics (sleep-inducing): Derivatives of barbituric acid (Barbiturates) like Veronal, Amytal, Nembutal, Luminal, Seconal.
      • Non-hypnotic: Diazepam (Valium).
  • Analgesics:
    • Function: Reduce or abolish pain without causing impairment of consciousness, mental confusion, paralysis, or other nervous system disturbances.
    • Classification:
      • Non-narcotic (Non-addictive): Aspirin, Paracetamol.
        • Mechanism: Inhibit the synthesis of prostaglandins, which stimulate inflammation and cause pain.
        • Uses: Pain relief (arthritis), fever reduction (antipyretic), blood clot prevention (aspirin).
        • Side Effects: Aspirin can cause stomach bleeding/ulcers; toxic to the liver. Paracetamol is a common alternative.
      • Narcotic (Addictive): Morphine and its derivatives (Heroin, Codeine).
        • Uses: Relief from postoperative pain, cardiac pain, terminal cancer pain, childbirth.
        • Side Effects: Produce sleep and unconsciousness in high doses; addictive.

• (d) Antimicrobials: Destroy/prevent development or inhibit the pathogenic action of microbes (bacteria, fungi, viruses, parasites).

  • Antibiotics:
    • Definition: Chemical substances produced wholly or partly by chemical synthesis, which in low concentrations inhibit the growth or destroy microorganisms. Originally derived from microorganisms (bacteria, fungi, molds).
    • Discovery: Penicillin by Alexander Fleming (1929) from Penicillium notatum.
    • Types based on Action:
      • Bactericidal: Kill bacteria (e.g., Penicillin, Aminoglycosides, Ofloxacin).
      • Bacteriostatic: Inhibit bacterial growth (e.g., Erythromycin, Tetracycline, Chloramphenicol).
    • Types based on Spectrum:
      • Broad Spectrum: Effective against a wide range of Gram-positive and Gram-negative bacteria (e.g., Ampicillin, Amoxycillin, Chloramphenicol, Vancomycin, Ofloxacin).
      • Narrow Spectrum: Effective mainly against Gram-positive OR Gram-negative bacteria (e.g., Penicillin G).
      • Limited Spectrum: Effective against a single organism or disease.
    • Important Examples: Penicillin, Streptomycin, Chloramphenicol (typhoid fever), Tetracycline.
  • Antiseptics:
    • Function: Applied to living tissues (wounds, cuts, ulcers, diseased skin) to kill or prevent the growth of microbes. Not ingested.
    • Examples:
      • Dettol: Mixture of Chloroxylenol and Terpineol.
      • Bithionol: Added to soaps for antiseptic properties.
      • Tincture of Iodine: 2-3% solution of Iodine in alcohol-water mixture. Powerful antiseptic.
      • Iodoform (CHI3): Antiseptic for wounds.
      • Boric Acid (H3BO3): Dilute aqueous solution is a weak antiseptic for eyes.
  • Disinfectants:
    • Function: Applied to inanimate objects (floors, drains, instruments) to kill microorganisms. Harmful to living tissues.
    • Examples:
      • Phenol: 1% solution is disinfectant; 0.2% solution is antiseptic.
      • Chlorine: 0.2 to 0.4 ppm in aqueous solution for water sterilization.
      • Sulphur Dioxide (SO2): In very low concentrations.
    • Note: The same substance can act as an antiseptic or disinfectant depending on concentration.

• (e) Antifertility Drugs:

  • Function: Birth control pills / oral contraceptives. Control the female menstrual cycle and ovulation.
  • Mechanism: Contain a mixture of synthetic estrogen and progesterone derivatives, which suppress ovulation.
  • Examples: Norethindrone (synthetic progesterone derivative), Ethynylestradiol (Novestrol - synthetic estrogen derivative). Mifepristone is used as a "morning after pill".

6. Chemicals in Food:
Added to food for preservation, enhancing appeal (colour, flavour, sweetness), and adding nutritive value. Main categories:
* (a) Food Preservatives:
* Function: Prevent spoilage due to microbial growth.
* Examples: Table salt, Sugar, Vegetable oils, Sodium benzoate (C6H5COONa - used in limited quantities, metabolized in the body), Salts of sorbic acid and propanoic acid.
* (b) Artificial Sweetening Agents:
* Function: Provide sweetness without adding calories. Important for diabetics and weight-conscious people.
* Examples:
* Saccharin (ortho-sulphobenzimide): First popular sweetener. 550 times sweeter than cane sugar. Excreted unchanged in urine.
* Aspartame: Most successful/widely used. Methyl ester of dipeptide (aspartic acid + phenylalanine). 100 times sweeter than sugar. Unstable at cooking temperatures; limited to cold foods/soft drinks.
* Alitame: High potency sweetener. More stable than aspartame. 2000 times sweeter than sugar. Difficult to control sweetness.
* Sucralose: Trichloro derivative of sucrose. Appearance/taste like sugar. Stable at cooking temperatures. 600 times sweeter than sugar. Does not provide calories.
* (c) Antioxidants:
* Function: Help in food preservation by retarding the action of oxygen on food (prevent oxidative spoilage). More reactive towards oxygen than the food material they protect.
* Examples: Butylated hydroxy toluene (BHT), Butylated hydroxy anisole (BHA). Ascorbic acid (Vitamin C) is also used.

7. Cleansing Agents: Improve cleansing properties of water. Help in removal of fats which bind other materials to fabric or skin.
* (a) Soaps:
* Definition: Sodium or potassium salts of long-chain fatty acids (e.g., stearic, oleic, palmitic acids).
* Preparation: Saponification - heating fats (esters of fatty acids and glycerol) with aqueous NaOH solution.
* Cleansing Action: Form micelles. The hydrophobic hydrocarbon tail dissolves in oil/grease, and the hydrophilic carboxylate head dissolves in water, emulsifying the grease and washing it away.
* Limitations: Do not work well in hard water (containing Ca2+, Mg2+ ions). Form insoluble precipitates (scum).

• (b) Synthetic Detergents:
  • Definition: Cleansing agents with properties of soap but are not salts of fatty acids. Can be used in both soft and hard water.
  • Classification:
    • Anionic Detergents: Largest group. Anionic part involved in cleansing.
      • Examples: Sodium salts of sulphonated long-chain alcohols or hydrocarbons.
        • Sodium alkylbenzenesulphonates (derived from hydrocarbons from petroleum). Branched chains are non-biodegradable, causing pollution. Straight chains are biodegradable.
        • Sodium lauryl sulphate (from lauryl alcohol treated with H2SO4).
      • Uses: Household detergents, toothpaste.
    • Cationic Detergents: Quaternary ammonium salts of amines with acetates, chlorides, or bromides as anions. Cationic part has a long hydrocarbon chain and a positive charge on Nitrogen.
      • Examples: Cetyltrimethylammonium bromide.
      • Properties: Germicidal, expensive.
      • Uses: Hair conditioners, germicides.
    • Non-ionic Detergents: Do not contain any ion. Formed by reaction of polyethylene glycol with stearic acid or lauryl alcohol.
      • Mechanism: Cleansing action similar to soaps (micelle formation).
      • Uses: Liquid dishwashing detergents.
  • Biodegradability: Detergents with highly branched hydrocarbon chains are poorly biodegradable, leading to water pollution. Straight chain hydrocarbons are preferred as they are easily degraded by bacteria.

Multiple Choice Questions (MCQs):

1. Which of the following is used as an antacid?
   (a) Ranitidine
   (b) Aspirin
   (c) Morphine
   (d) Chloramphenicol

2. Aspirin is chemically known as:
   (a) Methyl salicylate
   (b) Acetylsalicylic acid
   (c) Phenyl salicylate
   (d) Salicylic acid

3. Which of the following acts as an antidepressant?
   (a) Equanil
   (b) Iproniazid
   (c) Cimetidine
   (d) Paracetamol

4. Dettol is a mixture of:
   (a) Chloroxylenol and Bithionol
   (b) Chloroxylenol and Terpineol
   (c) Phenol and Iodine
   (d) Terpineol and Bithionol

5. Which of the following is a broad-spectrum antibiotic?
   (a) Penicillin G
   (b) Erythromycin
   (c) Chloramphenicol
   (d) Streptomycin

6. Which artificial sweetener contains chlorine?
   (a) Aspartame
   (b) Saccharin
   (c) Sucralose
   (d) Alitame

7. Which of the following is a cationic detergent?
   (a) Sodium lauryl sulphate
   (b) Sodium stearate
   (c) Cetyltrimethylammonium bromide
   (d) Sodium dodecylbenzenesulphonate

8. Bithionol is generally added to soaps to function as a/an:
   (a) Softener
   (b) Dryer
   (c) Buffering agent
   (d) Antiseptic

9. Which class of drugs is used to treat stress and mental diseases?
   (a) Analgesics
   (b) Antiseptics
   (c) Tranquilizers
   (d) Antihistamines

10. The drug that inhibits the synthesis of prostaglandins is:
    (a) Morphine
    (b) Ranitidine
    (c) Paracetamol
    (d) Terfenadine

Answers to MCQs:

1. (a) Ranitidine (H2-antagonist used to reduce acid production)
2. (b) Acetylsalicylic acid
3. (b) Iproniazid (Inhibits enzyme that degrades noradrenaline)
4. (b) Chloroxylenol and Terpineol
5. (c) Chloramphenicol
6. (c) Sucralose (Trichloro derivative of sucrose)
7. (c) Cetyltrimethylammonium bromide (Quaternary ammonium salt)
8. (d) Antiseptic
9. (c) Tranquilizers
10. (c) Paracetamol (Also Aspirin, which is a non-narcotic analgesic)

Remember to revise these examples and classifications thoroughly. Understanding the basic function and category of each chemical mentioned is key for your exams. Good luck with your preparation!