Some functional groups react more readily than others. For example, an aldehyde is more reactive than a ketone towards nucleophilic addition. In a molecule containing both an aldehyde and a ketone, you must choose conditions that react with the aldehyde selectively. Many Chemsheets problems are designed to test exactly this type of selectivity.
| Conversion | Reagents & Conditions | |------------|------------------------| | Alkene → Alkane | H₂, Ni/Pt/Pd catalyst, 150°C | | Alkene → Dihaloalkane | Br₂ (or Cl₂), room temp, no UV | | Alkene → Halohydrin | Br₂ / H₂O (or Cl₂ / H₂O) | | Alkene → Diol | Cold dilute KMnO₄ or OsO₄ | | Haloalkane → Alcohol | NaOH(aq) or KOH(aq), heat under reflux | | Haloalkane → Nitrile | KCN in ethanol/water, heat under reflux | | Haloalkane → Amine | Excess NH₃ in ethanol, heat in sealed tube | | Haloalkane → Alkene | NaOH or KOH in ethanol, heat | | Alcohol → Aldehyde | K₂Cr₂O₇ / H₂SO₄, distil immediately | | Alcohol → Carboxylic acid | K₂Cr₂O₇ / H₂SO₄, heat under reflux | | Aldehyde → Carboxylic acid | K₂Cr₂O₇ / H₂SO₄, heat; or Tollens’ reagent | | Aldehyde → Primary alcohol | NaBH₄ (or LiAlH₄) in water/ethanol; or H₂ / Ni | | Ketone → Secondary alcohol | NaBH₄ or LiAlH₄ | | Carboxylic acid → Ester | Alcohol + conc. H₂SO₄, heat | | Ester → Carboxylic acid + alcohol | Dilute H₂SO₄ or dilute NaOH, heat (hydrolysis) | | Benzene → Nitrobenzene | Conc. HNO₃ + conc. H₂SO₄, 50°C | | Nitrobenzene → Phenylamine | Sn / conc. HCl, then NaOH(aq); or H₂ / Ni | | Phenol derivative from benzene | Via sulfonation / nitration / halogenation |
in ethanol/water, reflux). Crucial for increasing the carbon chain length. Nucleophilic substitution (excess ethanolic NH3cap N cap H sub 3 , heated in a sealed tube). To Alkene: Elimination (ethanolic NaOHcap N a cap O cap H KOHcap K cap O cap H 3. Alcohols, Carbonyls, and Carboxylic Acids Primary Alcohol to Aldehyde: Partial oxidation (acidified K2Cr2O7cap K sub 2 cap C r sub 2 cap O sub 7 , distill immediately). Chemsheets Organic Synthesis Problems Answers
The eureka moment arrived when Emma realized that the sequence of reactions corresponded to a specific set of answers. The group quickly filled in the blanks, and the synthesis problems yielded their secrets.
Step-by-Step Strategy for Solving Chemsheets Synthesis Problems Some functional groups react more readily than others
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Knowing that "Acidified Potassium Dichromate" is the "how," while "Heat under Reflux" is the "environment." Many Chemsheets problems are designed to test exactly
| Starting Material | Target | Reagents & Conditions (Chemsheets standard) | |------------------|--------|-----------------------------------------------| | Ethene | Ethane | H2 , Ni or Pt , 150°C | | Ethane | Bromoethane | Br2 , UV light (free radical substitution) | | Bromoethane | Ethanol | NaOH(aq) , heat under reflux | | Ethanol | Ethene | Conc. H2SO4 , 170°C (elimination) | | Ethene | 1,2-dibromoethane | Br2 in inert solvent (e.g., CCl4 ), room temp | | Benzene | Bromobenzene | Br2 + FeBr3 catalyst, room temp | | Bromobenzene | Benzoic acid | 1. Mg, dry ether (Grignard). 2. CO2 . 3. H3O+ | | Phenol | 2,4,6-tribromophenol | Br2(aq) , room temp (no catalyst needed) |
At the A2 level, students must also consider the three‑dimensional arrangement of atoms (stereochemistry) and which position on a molecule reacts (regiochemistry). These considerations turn a simple reaction map into a detailed puzzle.
The Royal Society of Chemistry’s Synthesis Explorer is one interactive tool that allows students to “plan synthetic routes and study key organic chemistry reactions interactively,” choosing from a wide range of starting compounds and seeing the possible pathways to a target molecule. Using such tools alongside Chemsheets worksheets can reinforce the connections between reactions.
Chemsheets tasks excel because they do not just ask you to memorize facts; they train you to think like a synthetic chemist. To solve these problems efficiently, you must shift your mindset from forward-memorization to analytical deduction. The Power of Retrosynthetic Analysis