NEET UG Organic Chemistry Syllabus

What is Wurtz reaction used for?

Preparation of symmetrical alkanes by reacting alkyl halides with sodium metal in dry ether: 2 R-X + 2Na -> R-R + 2NaX.

What product forms when benzene reacts with a mixture of conc. HNO3 and conc. H2SO4, and what is the electrophile?

Nitrobenzene is formed (electrophilic substitution). The attacking electrophile is the nitronium ion, NO2+.

Differentiate between ortho/para-directing and meta-directing groups in benzene.

o/p-directing (mostly activating): -OH, -NH2, -OR, -CH3, halogens (deactivating but o/p-directing). m-directing (deactivating): -NO2, -CN, -COOH, -CHO, -SO3H.

What is the general formula and reactivity order of alkyl halides toward nucleophilic substitution by SN2?

General formula CnH2n+1X. SN2 reactivity order: CH3X > 1deg > 2deg > 3deg (decreases with increasing steric hindrance).

What is the Finkelstein reaction?

Conversion of an alkyl chloride or bromide into an alkyl iodide by treatment with NaI in dry acetone: R-Cl + NaI -> R-I + NaCl. NaCl/NaBr precipitates out, driving the reaction forward.

What is the Swarts reaction?

Preparation of alkyl fluorides by heating an alkyl chloride/bromide with a metallic fluoride such as AgF, Hg2F2, CoF2 or SbF3: R-X + AgF -> R-F + AgX.

Why are haloarenes less reactive than haloalkanes towards nucleophilic substitution?

Due to resonance (partial double-bond character of C-X bond), sp2 hybridization of carbon (shorter, stronger bond), and instability of the phenyl cation; also repulsion between nucleophile and electron-rich ring.

What is the ozone hole and which compounds are mainly responsible for its depletion?

Thinning of the stratospheric ozone layer, mainly caused by chlorofluorocarbons (CFCs/freons). Cl free radicals released by UV catalytically destroy ozone (O3).

What is the principle of Green Chemistry?

Designing chemical processes that reduce or eliminate the use and generation of hazardous substances, using safer solvents/reagents, atom economy, and renewable feedstocks to minimize environmental pollution.

What causes BOD (Biochemical Oxygen Demand) to increase and what does high BOD indicate?

BOD increases with high amounts of biodegradable organic matter (e.g., sewage). High BOD indicates heavily polluted water with low dissolved oxygen. Clean water has BOD < 5 ppm; polluted water has BOD > 17 ppm.

How are alcohols classified as primary, secondary and tertiary?

Based on the carbon bearing the -OH group: primary (1deg) -OH on a carbon attached to one other carbon, secondary (2deg) on a carbon attached to two carbons, tertiary (3deg) on a carbon attached to three carbons.

What is Lucas test and what does it distinguish?

Reaction of alcohols with Lucas reagent (conc. HCl + anhydrous ZnCl2). 3deg alcohol: turbidity immediately; 2deg: turbidity in ~5 min; 1deg: no turbidity at room temperature. Distinguishes 1deg, 2deg, 3deg alcohols.

What is Williamson's ether synthesis?

Preparation of symmetrical and unsymmetrical ethers by reacting an alkyl halide with sodium alkoxide (SN2): R-O-Na+ + R'-X -> R-O-R' + NaX. Best with primary alkyl halides.

Why is phenol acidic and more acidic than aliphatic alcohols?

Phenol is acidic because the phenoxide ion formed after losing H+ is resonance-stabilized (negative charge delocalized into the ring). Alcohols' alkoxide ions are not resonance-stabilized, so phenol is more acidic.

What is the Kolbe's reaction (Kolbe-Schmitt reaction)?

Sodium phenoxide is treated with CO2 under pressure followed by acidification to give salicylic acid (2-hydroxybenzoic acid). It is an electrophilic substitution at the ortho position.

What is Reimer-Tiemann reaction?

Treatment of phenol with chloroform (CHCl3) and aqueous NaOH followed by hydrolysis introduces a -CHO group at the ortho position, forming salicylaldehyde (2-hydroxybenzaldehyde). Electrophile is dichlorocarbene (:CCl2).

Why are aldehydes more reactive than ketones toward nucleophilic addition?

Aldehydes are more reactive due to (i) less steric hindrance (only one alkyl/H group) and (ii) less +I electron-donating effect, leaving the carbonyl carbon more electrophilic (more positive).

What is the Tollens' test and what does a positive result indicate?

Heating with Tollens' reagent (ammoniacal silver nitrate) gives a silver mirror. Positive result indicates an aldehyde (or other easily oxidizable group); ketones do not respond.

What is Fehling's test and which aldehyde does NOT respond to it?

Aldehydes reduce Fehling's solution (alkaline cupric complex) to give a brick-red precipitate of Cu2O. Aromatic aldehydes (e.g., benzaldehyde) do NOT respond to Fehling's test.

State the relative acidic strength order: carboxylic acid, phenol, alcohol, water.

Carboxylic acid > phenol > water > alcohol. Carboxylic acids are strongest because the carboxylate ion is stabilized by resonance with two equivalent oxygen atoms.

What is the Aldol condensation reaction?

Aldehydes/ketones containing alpha-hydrogen react in the presence of dilute base to form a beta-hydroxy aldehyde/ketone (aldol), which on heating loses water to give an alpha,beta-unsaturated carbonyl compound.

What is the Cannizzaro reaction?

Aldehydes lacking alpha-hydrogen (e.g., HCHO, benzaldehyde) undergo self-redox disproportionation with concentrated alkali: one molecule is oxidized to a carboxylate salt and another reduced to an alcohol.

What is the Clemmensen reduction?

Reduction of the carbonyl group (C=O) of aldehydes/ketones to -CH2- (methylene) using zinc amalgam (Zn-Hg) and concentrated HCl. Used for acid-stable compounds.

What is the Wolff-Kishner reduction?

Reduction of aldehydes/ketones (C=O to CH2) using hydrazine (NH2-NH2) followed by heating with a strong base (KOH/NaOH) in ethylene glycol. Used for base-stable compounds.

What is the Hell-Volhard-Zelinsky (HVZ) reaction?

Alpha-halogenation of carboxylic acids containing alpha-H using Cl2/Br2 in the presence of red phosphorus, forming alpha-halo carboxylic acids.

What is the Etard reaction?

Oxidation of toluene with chromyl chloride (CrO2Cl2) gives a chromium complex that on hydrolysis yields benzaldehyde.

How are amines classified as primary, secondary and tertiary?

Based on the number of carbon atoms (alkyl/aryl groups) attached to nitrogen: primary R-NH2 (one), secondary R2NH (two), tertiary R3N (three).

Arrange the basic strength of amines in aqueous solution (ethyl-substituted).

In aqueous (water) solution: 2deg > 1deg > 3deg > NH3, i.e., (C2H5)2NH > C2H5NH2 > (C2H5)3N > NH3 (a balance of +I effect, solvation and steric factors).

What is the carbylamine reaction and what does it test for?

Primary amines (1deg) react with chloroform and alcoholic KOH to give foul-smelling isocyanides (carbylamines): R-NH2 + CHCl3 + 3KOH -> R-NC + 3KCl + 3H2O. It is a test for primary amines only.

What is the Hinsberg's test used for?

To distinguish 1deg, 2deg, and 3deg amines using benzenesulfonyl chloride: 1deg amine gives a product soluble in alkali; 2deg gives a product insoluble in alkali; 3deg amine does not react.

What are diazonium salts and the Sandmeyer reaction?

Diazonium salts (Ar-N2+ X-) form from primary aromatic amines + HNO2/HCl at 0-5degC. Sandmeyer reaction: replacing the diazonium group with Cl, Br or CN using cuprous halides/CuCN (e.g., Ar-N2+Cl- + CuCl -> Ar-Cl + N2).

What are the four classes of biomolecules and their building blocks?

Carbohydrates (monosaccharides), proteins (amino acids), nucleic acids (nucleotides), and lipids (fatty acids + glycerol).

Differentiate between a reducing and non-reducing sugar; give one example of each.

Reducing sugars have a free aldehyde/ketone group and reduce Tollens'/Fehling's (e.g., glucose, fructose, maltose, lactose). Non-reducing sugars have no free anomeric carbon (e.g., sucrose, which has both anomeric carbons glycosidically linked).

What is a peptide bond and what is the difference between essential and non-essential amino acids?

A peptide bond is the amide (-CO-NH-) linkage between the -COOH of one amino acid and the -NH2 of another. Essential amino acids cannot be synthesized by the body and must come from diet; non-essential ones are synthesized in the body.

Differentiate between addition and condensation polymers with examples.

Addition (chain-growth) polymers form by repeated addition of unsaturated monomers with no by-product (e.g., polythene, PVC, Teflon). Condensation (step-growth) polymers form by repeated condensation with elimination of small molecules like water (e.g., nylon-6,6, terylene, bakelite).

Classify drugs as antacids, antihistamines and antibiotics with one example each.

Antacids neutralize stomach acidity (e.g., ranitidine, Mg(OH)2). Antihistamines treat allergies by blocking histamine (e.g., cetirizine, terfenadine). Antibiotics kill/inhibit microbes (e.g., penicillin, chloramphenicol).