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Chapter 16 Chemistry in Everyday Life
Drugs and their Classification
Chemistry significantly impacts human life, contributing to areas like cleanliness (soaps, detergents), clothing (synthetic fibres, dyes), food (additives, preservatives), health (medicines), and various materials (explosives, fuels, building materials).
Drugs are chemical substances with low molecular masses, typically ranging from 100 to 500 u. They interact with biological macromolecules within the body, known as **drug targets**, to produce a biological response. When this response is beneficial for diagnosing, preventing, or treating diseases, these drugs are called **medicines**.
It's important to note that most drugs used as medicines can be poisonous if taken in doses exceeding those recommended. The use of chemicals for therapeutic effects to treat diseases is termed **chemotherapy**.
Classification of Drugs
Drugs can be classified based on several criteria:
(a) Based on Pharmacological Effect: This classification focuses on the drug's effect on the body. It's useful for medical professionals as it groups drugs by the type of problem they treat. Examples include analgesics (pain relievers) or antiseptics (substances that kill or stop microbial growth).
(b) Based on Drug Action: This classification relates to the drug's action on specific biochemical processes. For example, antihistamines block the action of histamine, which is involved in inflammatory responses.
(c) Based on Chemical Structure: This groups drugs that share similar chemical structures. Drugs with common structural features often exhibit similar pharmacological activities. Sulfonamides, for example, are a class of drugs sharing a common structural unit.
(d) Based on Molecular Targets: This is considered the most useful classification for medicinal chemists. Drugs interact with specific biomolecules in the body like carbohydrates, lipids, proteins, or nucleic acids. These biomolecules are the **drug targets**. Drugs with similar structural features may interact with the same molecular target via the same mechanism.
Drug-Target Interaction
Biomacromolecules in the body perform various functions. Proteins act as enzymes (biological catalysts) and receptors (involved in communication). Nucleic acids store genetic information. Lipids and carbohydrates are structural components.
Enzymes as Drug Targets
Enzymes are proteins that catalyse biochemical reactions. They perform two main functions in catalysis:
1. Holding the substrate (reactant) in their **active site** in a suitable orientation for the reaction to occur.
2. Providing functional groups within the active site that attack the substrate and facilitate the chemical reaction.
Drugs can interfere with the catalytic activity of enzymes. Drugs that block or inhibit enzyme activity are called **enzyme inhibitors**. They can inhibit substrate binding or the catalytic process itself.
Drugs inhibit substrate binding in two main ways:
(i) **Competitive Inhibitors:** These drugs have a structure similar to the natural substrate and compete with the substrate for binding to the enzyme's active site (Figure 16.2).
(ii) **Non-competitive Inhibitors:** These drugs bind to a different site on the enzyme, called the **allosteric site**, which is distinct from the active site. Binding at the allosteric site changes the enzyme's shape, including the active site, making it unable to bind the substrate or carry out catalysis (Figure 16.3).
If an inhibitor forms a strong covalent bond with the enzyme, the enzyme is permanently blocked and must be degraded and replaced by the body.
Receptors as Drug Targets
Receptor proteins are vital for the body's communication system. Many receptors are embedded in cell membranes, with their active site exposed on the outside of the cell surface (Figure 16.4).
Receptors have specific binding sites with unique shapes and chemical compositions, allowing them to selectively interact with particular chemical messengers (like neurotransmitters, hormones). Binding of a messenger causes the receptor's shape to change, transmitting the message into the cell without the messenger entering the cell itself (Figure 16.5).
Drugs targeting receptors are either **antagonists** or **agonists**.
- **Antagonists:** Bind to the receptor site and block the natural messenger's function. Useful when the signaling pathway needs to be blocked.
- **Agonists:** Mimic the natural messenger, binding to the receptor and activating it. Useful when there is a deficiency of the natural messenger.
Therapeutic Action of Different Classes of Drugs
Various classes of drugs act on specific targets to produce therapeutic effects.
Antacids
Antacids are chemicals used to counteract excessive acid production in the stomach (hyperacidity), which causes pain, irritation, and potentially ulcers. Historically, sodium hydrogencarbonate or mixtures of aluminium and magnesium hydroxides were used.
Sodium hydrogencarbonate can cause excessive alkalinity, triggering more acid production. Metal hydroxides are preferred as they don't raise pH above neutrality. These older treatments only addressed symptoms.
A major advancement came with the understanding that histamine stimulates stomach acid secretion. Drugs like **cimetidine (Tagamet)** and later **ranitidine (Zantac)** were developed to block the interaction of histamine with specific receptors in the stomach wall, reducing acid release. These receptor antagonists were more effective than older antacids.
Antihistamines
Histamine is a chemical messenger with various functions, including causing inflammation, contracting smooth muscles in bronchi/gut, relaxing fine blood vessel walls, and contributing to nasal congestion/allergic responses.
Antihistamines are synthetic drugs (e.g., **brompheniramine (Dimetapp)**, **terfenadine (Seldane)**) that block histamine's action. They do this by competing with histamine for binding sites on histamine receptors. It's important to note that antihistamines used for allergies block different histamine receptors than those in the stomach responsible for acid secretion (which are targeted by drugs like ranitidine).
Neurologically Active Drugs
These drugs affect the nervous system and message transfer mechanisms.
Tranquilizers: Chemical compounds used to treat stress, anxiety, irritability, excitement, and mental illnesses. They promote well-being and are components of sleeping pills.
Some tranquilizers work by affecting neurotransmitters. For example, low levels of noradrenaline (a neurotransmitter involved in mood) are linked to depression. Antidepressant drugs (like **iproniazid** and **phenelzine**) inhibit enzymes that degrade noradrenaline, allowing it to activate receptors longer, thus counteracting depression.
Mild tranquilizers like **chlordiazepoxide** and **meprobamate** relieve tension. **Equanil** is used for depression and hypertension. Barbiturates (derivatives of barbituric acid, e.g., veronal, amytal, nembutal, luminal, seconal) are hypnotic (sleep-inducing) tranquilizers. Other examples include **valium** and **serotonin** (though serotonin is a neurotransmitter, not a drug itself, related drugs affect its levels/receptors).
Analgesics: Drugs that reduce or eliminate pain without causing unconsciousness, mental confusion, or other nervous system disturbances. Classified as non-narcotic or narcotic.
(i) Non-narcotic (non-addictive) analgesics: Examples include **aspirin** and **paracetamol**. Aspirin works by inhibiting the synthesis of prostaglandins, chemicals that cause pain and inflammation. Effective for skeletal pain (arthritis). Also has antipyretic (fever-reducing) and anti-platelet (prevents blood clotting) effects; used in preventing heart attacks.
(ii) Narcotic analgesics: Examples include **morphine** and its derivatives (opiates, from opium poppy). Relieve severe pain and induce sleep in medicinal doses. Can cause stupor, coma, and death in poisonous doses, and are addictive. Used for post-operative pain, cardiac pain, terminal cancer pain, and during childbirth.
Antimicrobials
Antimicrobials are drugs used to destroy or inhibit the growth and pathogenic action of microbes (bacteria, fungi, viruses, parasites). They include antibiotics, antiseptics, and disinfectants.
Antibiotics: Originally defined as substances produced by microorganisms that inhibit or kill other microorganisms. Now, the definition includes wholly or partly synthetic substances that inhibit or destroy microbes at low concentrations by interfering with their metabolism. Antibiotics have selective toxicity, affecting microbes more than host cells. Early search by Paul Ehrlich led to arsenic-based salvarsan for syphilis, the first effective treatment. He noted structural similarity between salvarsan's –As=As– linkage and azodyes' –N=N– linkage and the selective staining of tissues by dyes. This led to the discovery of prontosil, an azodye, which is metabolised in the body to sulphanilamide, the active compound. This initiated the development of sulpha drugs (sulfonamide analogues like sulphapyridine).
The discovery of penicillin by Alexander Fleming in 1929 revolutionized antibacterial therapy. Antibiotics can be bactericidal (killing bacteria, e.g., Penicillin, Aminoglycosides, Ofloxacin) or bacteriostatic (inhibiting growth, e.g., Erythromycin, Tetracycline, Chloramphenicol).
Antibiotic effectiveness is described by its spectrum of action: broad spectrum (against wide range of Gram-positive and Gram-negative bacteria, e.g., Chloramphenicol, Vancomycin, Ofloxacin), narrow spectrum (mainly Gram-positive or Gram-negative, e.g., Penicillin G), or limited spectrum (against a single organism).
Antiseptics and disinfectants: Chemicals that kill or prevent microbial growth.
- Antiseptics: Applied to living tissues (wounds, cuts, ulcers, skin surfaces). Not ingested. Examples: furacine, soframicine. Dettol is a common antiseptic mixture (chloroxylenol + terpineol). Bithionol is added to soaps for antiseptic properties. Tincture of iodine (2-3% solution in alcohol-water) is a powerful antiseptic for wounds. Iodoform is also used for wounds. Dilute aqueous boric acid is a weak antiseptic for eyes.
- Disinfectants: Applied to inanimate objects (floors, drains, instruments). The same substance can be an antiseptic or a disinfectant depending on concentration (e.g., 0.2% phenol is antiseptic, 1% phenol is disinfectant). Examples: chlorine (0.2-0.4 ppm in water), sulphur dioxide (very low concentrations).
Antifertility Drugs
Used to control population growth, mainly by preventing conception. Birth control pills commonly contain synthetic derivatives of estrogen and progesterone (hormones). Progesterone suppresses ovulation. Synthetic progesterone derivatives like **norethindrone** are more potent. Often combined with estrogen derivatives like **ethynylestradiol (novestrol)**.
Intext Question 16.1. 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 drugs, including sleeping pills, have specific recommended dosages for therapeutic effect. Taking doses higher than recommended can be harmful or even fatal, as many drugs act as **poisons** at excessive concentrations. Additionally, some drugs can be addictive or have significant side effects. Only a qualified doctor can assess the patient's condition, determine the appropriate drug and dosage, consider potential interactions with other medications, and monitor for adverse effects. Taking sleeping pills or any medication without consulting a doctor is risky due to the potential for toxicity, addiction, or misuse.
Intext Question 16.2. With reference to which classification has the statement, “ranitidine is an antacid” been given?
Answer:
The statement "ranitidine is an antacid" is given with reference to the classification based on **pharmacological effect**. Antacids are defined by their therapeutic action, which is to counteract or reduce stomach acid. Ranitidine's pharmacological effect is reducing stomach acidity, hence it is classified as an antacid based on its function in the body, even though its mechanism of action (blocking histamine receptors) is distinct from traditional antacids like metal hydroxides.
Chemicals in Food
Chemicals are added to food for various reasons: preservation, enhancing appeal (colour, flavour, sweetness), and adding nutritive value. Main categories of food additives include colours, flavours, sweeteners, emulsifiers, stabilisers, flour improvers, antioxidants, preservatives, and nutritional supplements (minerals, vitamins, amino acids).
Most additives (except nutritional supplements) don't add nutritive value but improve shelf life or appearance.
Artificial Sweetening Agents
Used as sugar substitutes, mainly by diabetics or those controlling calorie intake, as natural sweeteners like sucrose add calories. **Saccharin** (ortho-sulphobenzimide) was the first artificial sweetener (discovered 1879), about 550 times sweeter than sugar. It is excreted unchanged and considered inert and harmless. Other artificial sweeteners are listed below:
| Artificial sweetener | Structural formula | Sweetness value in comparison to cane sugar |
|---|---|---|
| Aspartame | 100 | |
| Saccharin | 550 | |
| Sucralose | 600 | |
| Alitame | 2000 |
**Aspartame** is a very common, widely used sweetener (about 100 times sweeter than sugar). It's a methyl ester of a dipeptide (aspartic acid + phenylalanine). Unstable at cooking temperatures, limited to cold foods/drinks.
**Alitame** is a high-potency sweetener (about 2000 times sweeter). More stable than aspartame but difficult to control sweetness accurately.
**Sucralose** is a trichloro derivative of sucrose (about 600 times sweeter). Stable at cooking temperature and does not provide calories.
Food Preservatives
Added to food to prevent spoilage caused by microbial growth. Common examples: table salt, sugar, vegetable oils, and **sodium benzoate** ($\textsf{C}_6\text{H}_5\text{COONa}$). Sodium benzoate is used in limited amounts and is metabolised. Salts of sorbic acid and propanoic acid are also used as preservatives.
Antioxidants in Food
Additives that help preserve food by retarding the action of oxygen, preventing oxidation that can cause rancidity or spoilage. They function via various chemical mechanisms. Examples: **butylated hydroxy toluene (BHT)** and **butylated hydroxy anisole (BHA)**. Adding BHA to butter significantly increases its shelf life. Sulphur dioxide and sulfites are antioxidants used in wines, beers, syrups, and dried fruits/vegetables.
Intext Question 16.3. Why do we require artificial sweetening agents ?
Answer:
We require artificial sweetening agents primarily for two reasons:
1. **Calorie control:** Natural sugars like sucrose add calories to the diet. Artificial sweeteners provide sweetness with little to no calories, which is beneficial for individuals trying to manage their weight or reduce calorie intake.
2. **Diabetes management:** People with diabetes need to control their blood glucose levels. Natural sugars are metabolised into glucose, causing a rise in blood sugar. Artificial sweeteners are generally not metabolised into glucose and do not affect blood sugar levels, making them suitable for diabetics.
Cleansing Agents
Cleansing agents are substances used for cleaning, typically by helping to remove grease and dirt. The two main types are soaps and synthetic detergents.
Soaps
Soaps used for cleaning are typically **sodium or potassium salts of long-chain fatty acids** (e.g., stearic acid, oleic acid, palmitic acid). Sodium soaps are made by heating fat (glyceryl ester of fatty acid) with aqueous sodium hydroxide (NaOH) solution, a process called **saponification**. Glycerol is produced as a byproduct. Potassium soaps (softer) are made using potassium hydroxide (KOH).
$\textsf{Fat} + \textsf{NaOH} \rightarrow \textsf{Soap} + \textsf{Glycerol}$
Only sodium and potassium soaps are water-soluble and used for cleaning. Insoluble calcium and magnesium soaps form when using hard water.
Various types of soaps exist based on manufacturing processes and additives:
- Toilet soaps: Better quality fats, less alkali, added colour/perfume.
- Floating soaps: Air bubbles beaten in before hardening.
- Transparent soaps: Dissolved in ethanol and evaporated.
- Medicated soaps: Contain medicinal substances.
- Shaving soaps: Contain glycerol to prevent drying, rosin for good lather.
- Laundry soaps: Contain fillers (sodium rosinate, sodium silicate, borax, sodium carbonate).
- Soap chips: Thin sheets of dried soap.
- Soap granules: Dried miniature soap bubbles.
- Soap powders/Scouring soaps: Contain soap, abrasive (pumice, sand), builders (sodium carbonate, trisodium phosphate) to speed up action.
Why soaps don't work in hard water: Hard water contains calcium ($\textsf{Ca}^{2+}$) and magnesium ($\textsf{Mg}^{2+}$) ions. When soaps (sodium or potassium salts) are used in hard water, these ions react with the soap anions to form insoluble calcium and magnesium soaps. These form a precipitate called **scum**, which separates out, reducing the effective concentration of the soap for cleaning and adhering to surfaces like fabric fibres and hair, hindering good washing.
$2\textsf{RCOONa (Soap)} + \textsf{Ca}^{2+}\text{(from hard water)} \rightarrow \textsf{(RCOO)}_2\text{Ca (Insoluble calcium soap/scum)} + 2\textsf{Na}^+$
Synthetic Detergents
Synthetic detergents are cleansing agents that are not soaps but possess similar properties and advantages, particularly working well in **hard water** because their calcium and magnesium salts are soluble and do not form scum. Some even work in ice-cold water.
Classified into three main categories:
- (i) Anionic Detergents: Sodium salts of sulphonated long-chain alcohols or hydrocarbons. The anionic part of the molecule is the cleansing agent. Prepared by reacting long-chain alcohols with concentrated sulfuric acid to form alkyl hydrogensulphates, which are then neutralised with alkali. Alkyl benzene sulphonates are another important class, made by neutralising alkyl benzene sulphonic acids. Used mostly for household cleaning and in toothpastes.
- (ii) Cationic Detergents: Quaternary ammonium salts containing a long hydrocarbon chain and a positive charge on the nitrogen atom. Acetates, chlorides, or bromides are the anions. Example: cetyltrimethylammonium bromide, used in hair conditioners. They have germicidal properties but are more expensive than anionic detergents, limiting their use.
- (iii) Non-ionic Detergents: Do not contain any ions. Formed by the reaction between stearic acid and polyethyleneglycol. Liquid dishwashing detergents are often non-ionic. Their cleansing action (removing grease and oil by micelle formation) is similar to that of soaps.
Environmental Impact of Detergents: Highly branched hydrocarbon chains in detergents are poorly degraded by bacteria, leading to accumulation and pollution (foaming in rivers, ponds). Modern detergents use hydrocarbon chains with minimal or no branching, as unbranched chains are more easily biodegradable, reducing environmental problems.
Intext Question 16.4. Write the chemical equation for preparing sodium soap from glyceryl oleate and glyceryl palmitate. Structural formulae of these compounds are given below.
(i) ($\textsf{C}_{15}\text{H}_{31}\text{COO})_3\textsf{C}_3\text{H}_5$ – Glyceryl palmitate
(ii) ($\textsf{C}_{17}\text{H}_{32}\text{COO})_3\textsf{C}_3\text{H}_5$ – Glyceryl oleate
Answer:
Sodium soap is prepared by saponification, the alkaline hydrolysis of a fat (glyceryl ester of fatty acid) using sodium hydroxide. The products are sodium salts of the fatty acids (soap) and glycerol.
(i) Preparation of sodium palmitate soap from glyceryl palmitate:
$(\textsf{C}_{15}\text{H}_{31}\text{COO})_3\textsf{C}_3\text{H}_5 \text{ (Glyceryl palmitate)} + 3\textsf{NaOH (aq)} \xrightarrow{Heat} 3\textsf{C}_{15}\text{H}_{31}\text{COONa} \text{ (Sodium palmitate/Soap)} + \textsf{C}_3\text{H}_5\text{(OH)}_3 \text{ (Glycerol)}$
(ii) Preparation of sodium oleate soap from glyceryl oleate:
$(\textsf{C}_{17}\text{H}_{32}\text{COO})_3\textsf{C}_3\text{H}_5 \text{ (Glyceryl oleate)} + 3\textsf{NaOH (aq)} \xrightarrow{Heat} 3\textsf{C}_{17}\text{H}_{32}\text{COONa} \text{ (Sodium oleate/Soap)} + \textsf{C}_3\text{H}_5\text{(OH)}_3 \text{ (Glycerol)}$
Intext Question 16.5. 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.
Answer:
The structure provided is a long hydrocarbon chain attached to a polyethyleneglycol chain, terminating in a hydroxyl group. This is a typical non-ionic surfactant structure.
Labeling the parts:
- The long hydrocarbon chain ($–\textsf{CH}_2\text{–CH}_2\text{–CH}_2\text{–CH}_2\text{–CH}_2\text{–CH}_2\text{–CH}_2\text{–CH}_2\text{–CH}_2\text{–CH}_2\text{–CH}_2\text{–CH}_2\text{–}$) is non-polar and oil-soluble. This is the **hydrophobic part** (or lipophilic part).
- The polyethyleneglycol chain ($–\textsf{O–CH}_2\text{–CH}_2\text{–O–CH}_2\text{–CH}_2\text{–O–CH}_2\text{–CH}_2\text{–O–CH}_2\text{–CH}_2\text{–OH}$) contains multiple polar ether linkages and a terminal hydroxyl group. These polar parts can form hydrogen bonds with water. This is the **hydrophilic part** (or lipophobic part).
Identifying the functional groups present in the molecule:
- Ether groups (–O–) within the polyethyleneglycol chain.
- A **hydroxyl group** (–OH) at the end of the polyethyleneglycol chain.
Summary
Chemistry plays a vital role in everyday life, especially in health, food, and cleaning. **Drugs** are chemicals used for therapeutic purposes (chemotherapy), interacting with biological **targets** like enzymes and receptors. Drugs are classified by pharmacological effect, action, structure, or molecular target. They can inhibit enzymes (competitive or non-competitive inhibitors) or mimic/block receptor messengers (agonists/antagonists). Important drug classes include antacids (reducing stomach acid, e.g., ranitidine), antihistamines (blocking histamine effects, e.g., terfenadine), neurologically active drugs (tranquilizers for stress/mental illness, e.g., valium; analgesics for pain, e.g., aspirin/morphine), antimicrobials (killing/inhibiting microbes, e.g., antibiotics like penicillin/chloramphenicol, antiseptics like dettol, disinfectants like phenol), and antifertility drugs (preventing conception, e.g., norethindrone/ethynylestradiol).
**Chemicals in food** include additives for preservation, appeal, and nutrition. Artificial sweeteners (saccharin, aspartame, sucralose) provide sweetness without calories. Food preservatives (sodium benzoate) prevent microbial spoilage. Antioxidants (BHT, BHA) prevent oxidation.
**Cleansing agents** (soaps, synthetic detergents) help remove dirt and grease. Soaps are sodium/potassium salts of fatty acids, made by saponification. They form insoluble scum in hard water. Synthetic detergents work in hard water and are classified as anionic (sodium alkyl sulphonates), cationic (quaternary ammonium salts with germicidal properties), or non-ionic (no ions). Biodegradable detergents (with unbranched hydrocarbon chains) are preferred environmentally over non-biodegradable branched-chain ones.
Exercises
Questions covering definitions (polymer, monomer, chemotherapy, target molecules, functional monomers, polymerisation types), classifications (polymers by source, structure, forces, polymerisation mode; drugs; vitamins; detergents), structures, properties (elasticity, boiling point, solubility), preparation (addition/condensation polymerisation, vulcanisation, specific polymers, soaps, detergents), reactions (free radical mechanism, crosslinking, working in hard water, cleansing action), types of isomerism, environmental impact of polymers and detergents, uses, and identifying monomers/polymers/structures.
Intext Questions
Question 16.1. 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:
Question 16.2. With reference to which classification has the statement, “ranitidine is an antacid” been given?
Answer:
Question 16.3. Why do we require artificial sweetening agents ?
Answer:
Question 16.4. Write the chemical equation for preparing sodium soap from glyceryl oleate and glyceryl palmitate. Structural formulae of these compounds are given below.
(i) $(C_{15}H_{31}COO)_3C_3H_5$ – Glyceryl palmitate
(ii) $(C_{17}H_{32}COO)_3C_3H_5$ – Glyceryl oleate
Answer:
Question 16.5. 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.
Answer:
Exercises
Question 16.1. Why do we need to classify drugs in different ways ?
Answer:
Question 16.2. Explain the term, target molecules or drug targets as used in medicinal chemistry.
Answer:
Question 16.3. Name the macromolecules that are chosen as drug targets.
Answer:
Question 16.4. Why should not medicines be taken without consulting doctors ?
Answer:
Question 16.5. Define the term chemotherapy.
Answer:
Question 16.6. Which forces are involved in holding the drugs to the active site of enzymes ?
Answer:
Question 16.7. While antacids and antiallergic drugs interfere with the function of histamines, why do these not interfere with the function of each other ?
Answer:
Question 16.8. Low level of noradrenaline is the cause of depression. What type of drugs are needed to cure this problem ? Name two drugs.
Answer:
Question 16.9. What is meant by the term ‘broad spectrum antibiotics’ ? Explain.
Answer:
Question 16.10. How do antiseptics differ from disinfectants ? Give one example of each.
Answer:
Question 16.11. Why are cimetidine and ranitidine better antacids than sodium hydrogencarbonate or magnesium or aluminium hydroxide ?
Answer:
Question 16.12. Name a substance which can be used as an antiseptic as well as disinfectant.
Answer:
Question 16.13. What are the main constituents of dettol ?
Answer:
Question 16.14. What is tincture of iodine ? What is its use ?
Answer:
Question 16.15. What are food preservatives ?
Answer:
Question 16.16. Why is use of aspartame limited to cold foods and drinks ?
Answer:
Question 16.17. What are artificial sweetening agents ? Give two examples.
Answer:
Question 16.18. Name the sweetening agent used in the preparation of sweets for a diabetic patient.
Answer:
Question 16.19. What problem arises in using alitame as artificial sweetener ?
Answer:
Question 16.20. How are synthetic detergents better than soaps ?
Answer:
Question 16.21. Explain the following terms with suitable examples
(i) cationic detergents
(ii) anionic detergents and
(iii) non-ionic detergents.
Answer:
Question 16.22. What are biodegradable and non-biodegradable detergents ? Give one example of each.
Answer:
Question 16.23. Why do soaps not work in hard water ?
Answer:
Question 16.24. Can you use soaps and synthetic detergents to check the hardness of water ?
Answer:
Question 16.25. Explain the cleansing action of soaps.
Answer:
Question 16.26. If water contains dissolved calcium hydrogencarbonate, out of soaps and synthetic detergents which one will you use for cleaning clothes ?
Answer:
Question 16.27. Label the hydrophilic and hydrophobic parts in the following compounds.
(i)
(ii)
(iii)
Answer: