What the board asks
We went through the ISC board papers, question by question, and matched each question to a topic. Here is what was asked, how often, and what was never asked.
Chemistry: 384 topics in the 2027 syllabus, across 10 units. The board has asked 252 of them at least once. 132 were never asked in the papers we checked.
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C6 Haloalkanes and Haloarenes
All the topics in Chemistry: Haloalkanes and Haloarenes
Asked topics first, the most asked at the top. Tap a topic to see what to write, the result, the years, and the real board questions.
38 topics shown
| # | Topic | Type | Marks | Times asked | Last asked | Status |
|---|---|---|---|---|---|---|
| 1 | Two or three step conversions within haloalkanes and haloarenesPlan and write each step with reagent and condition over the arrow for conversions such as benzene to biphenyl, propene to 1-bromopropane, chloroethane to n-butane, ethanol to iodoform, chloroform or iodoform to acetylene. | Conversion | 1 | 4 papers | Specimen 2027 | Asked |
| 2 | Chlorobenzene to phenol and aniline: conditionsWrite the balanced equation with exact conditions for chlorobenzene with NaOH at 623 K and 300 atm then acid (Dow's process) and with NH3 and Cu2O at 475 K and 60 atm, naming the product. | Reaction | 1 | 4 papers | 2026 | Asked |
| 3 | Wurtz-Fittig and Fittig reactionsWrite the balanced equations for a haloarene with a haloalkane and sodium in dry ether (Wurtz-Fittig, alkylbenzene) and for two haloarene molecules with sodium (Fittig, biphenyl), naming the products. | Reaction | 1 | 4 papers | 2025 improvement | Asked |
| 4 | Chloroform properties: phosgene, storage, silver powder, nitric acidWrite equations for chloroform with O2 in light (phosgene), phosgene with ethanol (ethyl carbonate), chloroform with silver powder (acetylene), with HNO3 (chloropicrin) and with a primary amine and KOH (carbylamine), and state how it is stored. | Reaction | 1 | 3 papers | 2026 | Asked |
| 5 | Iodoform: preparation from ethanol or acetone, and propertiesWrite the balanced equation for ethanol (or acetone) with I2 and NaOH (or Na2CO3) giving yellow iodoform, and the reaction of iodoform with silver powder giving acetylene, plus its use as an antiseptic. | Reaction | 1 | 3 papers | 2026 | Asked |
| 6 | KCN vs AgCN and KNO2 vs AgNO2: ambident nucleophilesWrite the equations for a haloalkane with alcoholic KCN and with AgCN, and with KNO2 and AgNO2, and give the IUPAC (and common) name of each product. | Reaction | 1 | 2 papers | Specimen 2027 | Asked |
| 7 | Wurtz reaction: haloalkane with sodium in dry etherWrite the balanced equation for two molecules of a haloalkane with sodium in dry ether, name the alkane with double the carbons, and use it in a conversion such as chloroethane to n-butane. | Reaction | 1 | 2 papers | Specimen 2027 | Asked |
| 8 | Finkelstein and Swarts reactions: halide exchangeWrite the equation for each named reaction with reagent and solvent (NaI in dry acetone; AgF, Hg2F2, CoF2 or SbF3), name the product, and say what drives the Finkelstein reaction forward. | Reaction | 1 | 2 papers | 2025 | Asked |
| 9 | SN1 vs SN2: mechanism, rate law and stereochemistryDraw the SN2 one-step mechanism with backside attack, transition state and inversion, and the SN1 two-step mechanism through a carbocation with racemisation; write each rate law and state which halides (1, 2, 3) follow which path and why. | Mechanism | 3 | 2 papers | 2025 | Asked |
| 10 | Case study: ambident nucleophiles give different productsFrom a short story about two reagents on one alkyl halide, write both equations, name both products, and explain in two lines that CN- (or NO2-) is ambident: the ionic KCN attacks through C, the covalent AgCN through N, and only the nitrile hydrolyses to the acid. | Give reason | 3 | 1 paper | Specimen 2027 | Asked |
| 11 | Chlorination, nitration, sulphonation of chlorobenzene with mechanismWrite the equation for each reaction with reagents and conditions giving the ortho and para products (para major), and draw the mechanism: formation of the electrophile, attack to form the arenium ion, loss of H+. | Mechanism | 2 | 1 paper | 2026 | Asked |
| 12 | Alcohol to haloalkane with PX3, PCl5 and SOCl2Write the balanced equation for an alcohol with PCl3 (or PBr3/PI3 made in situ), PCl5 and SOCl2 (pyridine), and say why SOCl2 is the preferred reagent. | Reaction | 1 | 1 paper | 2025 improvement | Asked |
| 13 | Identify haloalkane isomers from rate or mechanism cluesFrom a description of rate behaviour (rate depends on [RX] only, or on [RX] and [OH-]) or stereochemical result, decide SN1 or SN2, then draw and name the matching isomer of the given formula. | Give reason | 2 | 1 paper | 2025 | Asked |
| 14 | Haloarene by electrophilic halogenation with a Lewis acidWrite the equation for benzene with Cl2 (or Br2) and anhydrous FeCl3 (or FeBr3) in the dark, show how the Lewis acid makes the electrophile Cl+, and judge statements about the role of FeCl3. | Reaction | 1 | 1 paper | 2025 | Asked |
| 15 | Chiral carbon, enantiomers and racemic mixture in haloalkanesMark the asymmetric carbon(s) in a given haloalkane, say whether it is optically active, draw the pair of enantiomers, and define racemic mixture, retention and inversion; judge assertion-reason items on chirality. | Structure or name | 1 | 1 paper | 2023 | Asked |
| 16 | Haloalkane with NaOH, water, NaI, NH3 and aminesWrite the balanced equation for a given haloalkane with aqueous NaOH/KOH, water, NaI, alcoholic NH3, a primary amine and a secondary amine, with conditions, and name each product. | Reaction | 1 | 1 paper | 2023 | Asked |
| 17 | Alkene + HX: Markovnikov addition and peroxide effect with HBrWrite the addition of HX to a given alkene, choose the Markovnikov product, and for HBr with organic peroxide write the anti-Markovnikov product, naming each product. | Reaction | 1 | 1 paper | 2020 | Asked |
| 18 | Chloroform from ethanol or acetone with bleaching powderWrite the steps (bleaching powder gives Cl2 and Ca(OH)2, oxidation and chlorination to chloral or trichloroacetone, hydrolysis by Ca(OH)2) with balanced equations, and name it as a haloform reaction. | Reaction | 1 | 1 paper | 2020 | Asked |
| 19 | Dehydrohalogenation with alcoholic KOH and Saytzeff's ruleWrite the equation for a haloalkane with alcoholic KOH on heating, state Saytzeff's rule, and pick the major and minor alkenes for an unsymmetrical halide. | Reaction | 1 | 1 paper | 2019 | Asked |
| 20 | Classify halogen compounds: 1, 2, 3, allylic, benzylic, vinylic, arylGive the general formula CnH2n+1X, then label each given compound as primary, secondary or tertiary haloalkane, allylic, benzylic, vinylic or aryl halide, or as mono-, di- (gem/vic) or tri-halo, with the structural reason. | Statement | 1 | never | Never asked | |
| 21 | Common and IUPAC names of mono, di and tri-halo compoundsWrite the common name and the IUPAC name for each given structure (or draw the structure from a name), numbering the chain so the halogen gets the lowest locant and listing substituents alphabetically. | Structure or name | 1 | never | Never asked | |
| 22 | Nature of C-X bond in haloalkanes: polarity and reactivityExplain in two or three lines that the C-X bond is polar (C delta+, X delta-) so the carbon is attacked by nucleophiles, and use bond length and bond enthalpy to give the reactivity order of R-I, R-Br, R-Cl, R-F. | Give reason | 1 | never | Never asked | |
| 23 | Haloalkane from alkane and halogen (free radical substitution)Write the equation for an alkane with Cl2 or Br2 in UV light or heat, name the product, and state that a mixture of mono and polyhalo products forms so the method is poor for pure samples. | Reaction | 1 | never | Never asked | |
| 24 | Hunsdiecker reaction: silver salt of fatty acid with bromineWrite the equation for the silver salt of a carboxylic acid with Br2 in CCl4 on heating, name the bromoalkane, and note it has one carbon less than the acid. | Reaction | 1 | never | Never asked | |
| 25 | Haloalkanes: state, boiling point and solubility order with reasonsArrange given haloalkanes in order of boiling point (or state, density, solubility) and give the reason: size of halogen and van der Waals forces, branching lowering surface area, and no hydrogen bonding with water. | Comparison | 1 | never | Never asked | |
| 26 | Order of reactivity of halides towards SN1 or SN2Arrange a given set of halides (1, 2, 3, allylic, benzylic, different X) in order of SN1 or SN2 reactivity and give the one-line reason for each step. | Comparison | 1 | never | Never asked | |
| 27 | Haloalkane with silver salt of fatty acid and with LiAlH4Write the equation for a haloalkane with the silver salt of a carboxylic acid (ester formed) and with lithium aluminium hydride (alkane formed), and name the products. | Reaction | 1 | never | Never asked | |
| 28 | Grignard reagent from haloalkane or haloarene and magnesiumWrite the equation for a haloalkane or bromobenzene with Mg in dry ether, name the Grignard reagent, and say why moisture must be kept out (with the equation of its reaction with water). | Reaction | 1 | never | Never asked | |
| 29 | Structures of freons and DDTDraw or write the structure and full name of freon-11, freon-12 and DDT (p,p'-dichlorodiphenyltrichloroethane). | Structure or name | 1 | never | Never asked | |
| 30 | Uses and environmental effects of polyhalogen compoundsFor each named compound give one use and one harmful or environmental effect in a line each (ozone depletion by freons and CCl4, DDT persistence and biomagnification, chloroform and phosgene toxicity). | Statement | 1 | never | Never asked | |
| 31 | Give reasons: haloarenes resist nucleophilic substitutionGive the reasons in one or two lines each: resonance gives the C-X bond partial double bond character, sp2 carbon makes it shorter and stronger, the phenyl cation is unstable, and electron-rich ring repels the nucleophile; compare with haloalkanes. | Give reason | 1 | never | Never asked | |
| 32 | Sandmeyer and Gattermann reactions to make haloarenesWrite the equations from benzene diazonium chloride with CuCl/HCl or CuBr/HBr (Sandmeyer) and with Cu powder and HCl or HBr (Gattermann), naming the haloarene, and the diazotisation step from aniline if asked. | Reaction | 1 | never | Never asked | |
| 33 | Haloarenes: melting point of para isomer and other propertiesCompare melting and boiling points of o-, m- and p-dichlorobenzene (or other isomers) and give the reason: the symmetrical para isomer packs better in the crystal; state solubility and state of haloarenes. | Comparison | 1 | never | Never asked | |
| 34 | Give reasons: halogen is ortho-para directing yet deactivatingExplain with resonance structures that the lone pair of X raises electron density at ortho and para positions, and that the -I effect lowers overall ring reactivity, so substitution is slower than in benzene but goes ortho/para. | Give reason | 2 | never | Never asked | |
| 35 | Nucleophilic substitution in haloarenes: mechanism and nitro effectDraw the addition-elimination mechanism (attack of OH- at the C-Cl carbon, resonance-stabilised carbanion, loss of Cl-) and explain why -NO2 at ortho or para positions makes the reaction easy while meta has little effect. | Mechanism | 2 | never | Never asked | |
| 36 | Reduction of chlorobenzene to benzeneWrite the equation for chlorobenzene with nascent hydrogen from Ni-Al alloy and NaOH (or H2 with Pd) giving benzene. | Reaction | 1 | never | Never asked | |
| 37 | Identify A, B, C in a halo compound chainFollow a reaction chain (for example C2H5Br with KCN then hydrolysis, or chlorobenzene with NaOH then acid) and write the structure and name of each lettered compound, with the equation if asked. | Conversion | 2 | never | Never asked | |
| 38 | Distinguish halo compounds by a chemical testName the test and the observation for each compound, for example ethyl chloride vs chlorobenzene (warm with aqueous NaOH, acidify with HNO3, add AgNO3: white AgCl only from ethyl chloride) or chloroform vs carbon tetrachloride (carbylamine test). | Tell apart (test) | 1 | never | Not in syllabus |
This list was made from the 2027 syllabus and checked with 9 board papers, including the 2027 specimen paper. It is not yet checked with the textbook.
The 10 topics Chemistry papers ask most
Counted on the board papers from 2018 to the 2027 specimen paper, which every unit has been checked against.
- 1.IUPAC names of coordination compounds from formulaC5 Coordination Compounds · asked 8 times since 2018
- 2.Faraday's first law: mass, charge, current or timeC2 Electrochemistry · asked 7 times since 2018
- 3.Give reasons: transition metal ions are coloured, some colourlessC4 d- and f-Block Elements · asked 7 times since 2018
- 4.Alcohols from Grignard reagent: 1, 2, 3 degreeC7 Alcohols, Phenols and Ethers · asked 7 times since 2018
- 5.Williamson's synthesis of ethersC7 Alcohols, Phenols and Ethers · asked 7 times since 2018
- 6.Identify A, B, C, D in a given reagent chainC8 Aldehydes, Ketones and Carboxylic Acids · asked 7 times since 2018
- 7.Identify compounds from formula and test results (case problem)C8 Aldehydes, Ketones and Carboxylic Acids · asked 7 times since 2018
- 8.Identify A, B, C: amide, Hoffmann and amine-test chainsC9 Organic Compounds containing Nitrogen · asked 7 times since 2018
- 9.Gibbs energy and maximum work from cell emfC2 Electrochemistry · asked 6 times since 2018
- 10.Coordination number and oxidation state of the central metalC5 Coordination Compounds · asked 6 times since 2018