Aspirin (acetylsalicylic acid, C9H8O4) is an analgesic (relieves pain); it also has antipyretic and anti-inflammatory properties. Streptomycin and chloramphenicol (Chloromycetin) are antibiotics; penicillin is an antibiotic.
Boric acid and dilute hydrogen peroxide are mild antiseptics; they are not "strong" antiseptics. Statements b, c and d are correct: disinfectants are generally too harsh for living tissues; phenol concentration distinctions and chlorine/iodine as strong disinfectants are correct.
Antagonists bind to receptor sites and block or inhibit the receptor's natural response. Agonists bind and activate the receptor. Enzymes and molecular targets are not the correct terms here.
Aspirin is acetylsalicylic acid (aspirin = salicylic acid in which the phenolic OH is acetylated). Formula: C9H8O4.
Nylon-6,6 is formed by condensation of hexamethylenediamine (H2N–(CH2)6–NH2) and adipic acid (HOOC–(CH2)4–COOH). The repeating unit is \[ -NH-(CH_2)_6-NH-CO-(CH_2)_4-CO- \]_n (so the structure representing the amide linkage between the diamine and diacid corresponds to the correct option).
d
Natural rubber is cis-1,4-polyisoprene and has essentially all cis-configuration, which gives it elasticity.
Nylon is a polyamide — its repeating units contain amide (–CONH–) linkages formed by condensation of diamines and diacids (or from amino acids).
Terylene is a polyester (polyethylene terephthalate, PET), formed by condensation of ethylene glycol and terephthalic acid.
Neoprene (polychloroprene) is obtained by polymerization of chloroprene (2‑chloro‑1,3‑butadiene), CH2=CCl–CH=CH2, corresponding to option (a).
PHBV (polyhydroxybutyrate-co-hydroxyvalerate) is a biodegradable biopolymer produced by bacteria. HDPE, PVC, and nylon-6 are not readily biodegradable.
Non-stick coatings (Teflon) are polytetrafluoroethylene (PTFE), polymerized from tetrafluoroethylene (CF2=CF2), i.e. 1,1,2,2-tetrafluoroethene (often written tetrafluoroethylene).
Assertion is true: isoprene (2‑methyl‑1,3‑butadiene) is the monomer of natural rubber (polyisoprene). Reason is false: natural rubber is biosynthesised by enzyme-catalysed addition (not by anionic polymerisation in vivo); the polymerisation mechanism is not anionic synthetic polymerisation.
PHBV is a copolymer (polyhydroxybutyrate‑co‑hydroxyvalerate). Orlon (polyacrylonitrile), PVC (polyvinyl chloride) and Teflon (PTFE) are homopolymers.
PAN (polyacrylonitrile) fibres are used as acrylic fibres (artificial wool) in blankets and sweaters.
Cross‑linked/network polymers require multifunctional (tri‑ or higher) monomers to form three‑dimensional networks. Bifunctional monomers alone give linear polymers. Thus the statement that they are formed from bi‑ and tri‑functional monomers (implying bifunctional is sufficient) is incorrect.
Answer: Antibiotics are substances (natural or synthetic) that kill or inhibit the growth of microorganisms, especially bacteria, at low concentrations. They can be bactericidal or bacteriostatic; examples include penicillin and streptomycin.
Both aspirin and paracetamol relieve pain (analgesic) and reduce fever (antipyretic). Example: aspirin (acetylsalicylic acid) is commonly used for both purposes.
Aspirin (acetylsalicylic acid) or paracetamol (acetaminophen).
Synthetic detergents are man‑made surfactants used for cleaning. Types include anionic (e.g. linear alkylbenzene sulfonates, LAS), cationic (e.g. quaternary ammonium salts), nonionic and amphoteric. They perform well in hard water (form soluble salts) unlike soap; earlier branched detergents were poorly biodegradable—now linear structures (LAS) are used which are biodegradable. Applications: laundering, dishwashing, industrial cleaning.
Synthetic detergents are surfactants (anionic, cationic, nonionic or amphoteric) produced from petrochemical or oleochemical feedstocks; they lower surface tension and emulsify oils and dirt.
Antiseptics inhibit or kill microbes on living tissues (skin, wounds) and are of lower toxicity (e.g. dilute iodine, hydrogen peroxide, boric acid). Disinfectants are used to destroy microbes on non‑living surfaces (floors, instruments) and are generally too corrosive or toxic for use on skin (e.g. concentrated phenol, bleach, strong chlorine solutions).
Antiseptics are safe for use on living tissues to prevent infection; disinfectants are stronger agents used on inanimate surfaces and usually harmful to living tissues.
Food preservatives inhibit microbial growth or oxidative rancidity. Chemical preservatives include benzoates (sodium benzoate), sorbates (potassium sorbate), sulphites, nitrates/nitrites (in cured meats), and antioxidants like BHA/BHT. Natural preservation methods include salt, sugar, drying, smoking and refrigeration. Preservatives are chosen to be effective at low concentrations and safe for consumption.
Food preservatives are substances added to foods to prevent spoilage by microbes or oxidation, thus extending shelf life.
A drug is any chemical substance that, when taken into a living organism, alters one or more of its functions. Common classifications: (1) By pharmacological effect: stimulants (e.g., caffeine), depressants/tranquillizers (e.g., diazepam), analgesics (e.g., morphine, paracetamol), antibiotics (e.g., penicillin), antipyretics, antihistamines, narcotics, hallucinogens; (2) By therapeutic use: antidiabetic, antihypertensive, contraceptives, etc.; (3) By source: natural (opium), semisynthetic (heroin), synthetic (aspirin). This multiway classification is used in medicine and pharmacy.
Drugs are substances that produce physiological effects in the body. They are classified by effect (stimulants, depressants, analgesics, tranquillizers, antibiotics, hallucinogens, narcotics, etc.), by therapeutic use (antibiotics, antacids, antihypertensives), and by origin (natural, synthetic).
Tranquillizers reduce anxiety and produce calming by altering neurotransmission in the brain. Minor tranquillizers (e.g., diazepam) bind to GABA_A receptors and increase the frequency of Cl− channel opening → hyperpolarization of neurons → CNS depression (anxiolytic, sedative). Major tranquillizers/antipsychotics (e.g., chlorpromazine) act chiefly by blocking dopamine (D2) receptors in the brain → reduce psychotic symptoms. Both classes lower neural excitability but by different receptor targets.
Tranquillizers depress central nervous system activity: minor tranquillizers (benzodiazepines) enhance GABA_A receptor–mediated chloride influx (increasing inhibition); major tranquillizers (antipsychotics) block dopamine D2 receptors.
Aspirin (acetylsalicylic acid) is the acetyl ester of salicylic acid. Condensed structural form: C6H4(OH→OCOCH3)(COOH) or more precisely 2-(acetyloxy)benzoic acid. In chemical notation: \(\text{C}_9\text{H}_8\text{O}_4\) and structure: aromatic ring with –COOH at position 1 and –OCOCH3 (acetoxy) at position 2 (ortho).
Aspirin is acetylsalicylic acid: 2-(acetyloxy)benzoic acid, formula C9H8O4. Structural description: a benzene ring bearing a carboxylic acid (–COOH) and an adjacent acetoxy group (–OCOCH3).
Soap/detergent molecules have a long nonpolar hydrocarbon tail (hydrophobic) and a polar/ionic head (hydrophilic). In water they orient at interfaces and above a critical concentration form micelles: nonpolar dirt/oil is solubilized in the micelle core while the polar heads face water. Mechanical action disperses these micelles; rinsing carries them away. Soaps (fatty acid salts) react with Ca2+/Mg2+ in hard water to give insoluble salts (scum), whereas synthetic detergents (sulfonates/sulfates) remain soluble and work in hard water.
Soaps/detergents are amphiphilic: hydrophobic tails solubilize oils/grease and hydrophilic heads interact with water to form micelles that emulsify and remove dirt; soaps form scum with hard-water Ca2+/Mg2+, detergents do not.
Diabetic-safe sweeteners provide sweetness with little or no effect on blood glucose. Common choices: saccharin (100–500× sweeter than sugar), aspartame (approx. 200×), sucralose (derived from sucrose, heat-stable), acesulfame-K, and steviol glycosides (stevia). Choice depends on heat stability and personal tolerance (e.g., aspartame is not suitable for baking at high temperatures).
Artificial/non-nutritive sweeteners such as saccharin, aspartame, sucralose, acesulfame-K, and natural noncaloric sweeteners like stevia are used for diabetics.
Narcotic drugs (opioids) are substances that depress the CNS, relieve severe pain, induce drowsiness and can cause dependence and addiction; examples: opium, morphine, heroin, codeine. Non-narcotic drugs include analgesics and other therapeutics that do not produce opioid-type dependence: e.g., aspirin, paracetamol (acetaminophen), NSAIDs like ibuprofen, and many antibiotics and antihypertensives. Classification is based on pharmacological action and addiction potential.
Narcotics are addictive drugs that produce sleep and relieve pain (e.g., morphine, heroin, codeine). Non-narcotic drugs provide pain relief or other effects without narcotic-type addiction (e.g., aspirin, paracetamol, ibuprofen).
Antifertility drugs are chemical agents used to prevent pregnancy by inhibiting ovulation, fertilization, implantation or by terminating early pregnancy. Examples: (1) Oral contraceptives — combined estrogen (ethinylestradiol) and progestin (norethindrone) pills; (2) Progestin-only ('mini-pill'); (3) Emergency contraceptives (high-dose levonorgestrel); (4) Abortifacient mifepristone (RU-486) which blocks progesterone receptors and causes termination of early pregnancy.
Antifertility drugs prevent conception or terminate early pregnancy: combined oral contraceptives (ethinylestradiol + norethindrone), progestin-only pills, and abortifacients like mifepristone (RU-486).
Copolymers are produced by polymerizing a mixture of two (or more) different monomers. Depending on how monomer units are arranged, copolymers are classified as random, alternating, block or graft. Copolymerization allows tuning of physical and chemical properties (e.g., toughness, heat resistance). Examples: styrene–butadiene rubber (SBR) used in tyres, ABS used in engineering plastics, ethylene–vinyl acetate (EVA).
A copolymer is a polymer made from two or more different monomers; types include random, alternating, block and graft copolymers. Example: SBR (styrene–butadiene rubber), ABS (acrylonitrile–butadiene–styrene).
Biodegradable polymers undergo enzymatic or microbial degradation in the environment or composting conditions yielding non-harmful products (CO2, H2O, biomass). They reduce persistent plastic waste. Examples: poly(lactic acid) (PLA) made from lactic acid, polyhydroxyalkanoates (PHAs) like PHB produced by bacteria, modified starch or cellulose derivatives and some protein-based polymers. Applications include packaging, disposable cutlery and medical implants (where controlled bioresorption is needed).
Biodegradable polymers are polymers that can be broken down by microorganisms into water, CO2 and biomass. Examples: polylactic acid (PLA), polyhydroxybutyrate (PHB), starch-based plastics, cellulose.
Terylene (PET) is formed by step-growth esterification/polycondensation between ethylene glycol and terephthalic acid (or via dimethyl terephthalate): (1) Direct esterification: \(n\,HOCH_2CH_2OH + n\,HOOC–C_6H_4–COOH \xrightarrow{heat, catalyst} [–OCH_2CH_2O–CO–C_6H_4–CO–]_n + 2n\,H_2O\). (2) Alternatively via transesterification of dimethyl terephthalate releasing MeOH. The polymer is then melt-condensed to high molecular weight. Catalysts and vacuum removal of small molecules drive the reaction to high conversion.
Terylene (polyethylene terephthalate, PET) is prepared by condensation polymerization of ethylene glycol and terephthalic acid (or transesterification of dimethyl terephthalate) producing ester linkages: n HO–CH2CH2–OH + n HOOC–C6H4–COOH → [–OCH2CH2O–CO–C6H4–CO–]n + 2n H2O.
Natural rubber (poly(1,4-cis-isoprene)) is soft and sticky; vulcanization introduces cross-links between polymer chains by reacting double bonds with sulfur. Heating rubber with sulfur (and accelerators) forms sulfur bridges (C–S–C and S–S) at allylic positions, converting the material into tougher, more elastic and thermally stable vulcanized rubber. The degree of cross-linking controls hardness and elasticity (e.g., more sulfur → harder rubber).
Vulcanization is the process of cross-linking natural rubber (polyisoprene) chains with sulfur to form S–S and C–S bridges, improving elasticity, strength and heat resistance; typically heating rubber with sulfur and accelerators.
a) Bakelite — cross-linked thermosetting phenol–formaldehyde resin (three-dimensional network). b) Nylon-6,6 — linear condensation polymer (long linear chains with interchain hydrogen bonding). c) LDPE (low-density polyethylene) — branched polymer (many side chains → lower density). d) HDPE (high-density polyethylene) — largely linear polymer (few branches → high crystallinity and density).