Here is a mini answer key for the most common Chemsheets transformations. Use it to check your work instantly.
| 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) |
This is a common "tricky" question in A-Level synthesis.
Chemsheets organic synthesis problems are a cornerstone of A-Level chemistry revision, challenging students to connect disparate reactions into logical multi-step pathways. Mastering these requires a shift from memorizing individual reagents to understanding "chemical roadmaps." Essential Synthesis Resources Organic Synthesis (1272) Booklet
: This is the primary comprehensive guide used by many students to practice multi-step reactions. Detailed answer guides for Chemsheets 1272
cover common transformations like the 3-step synthesis of paracetamol from phenol. Quick Check Synthesis A (1135)
: A foundational worksheet focused on identifying reaction types and reagents for basic conversions. The official answer key for 1135 provides a clear breakdown of A →right arrow →right arrow →right arrow D pathways. Chemsheets Organic Synthesis Problems Answers
Specialized Worksheets: Chemsheets offers targeted practice for specific categories, such as aromatic (1096), aliphatic (1106), and general synthesis problems (1097), often available through platforms like Scisheets. Strategies for Solving Synthesis Problems
Count the Carbons: Always determine if the carbon chain length changes. Reactions like the addition of KCNcap K cap C cap N
increase the chain, while decarboxylation or specific oxidative cleavages can decrease it.
Work Backwards (Retrosynthesis): If the starting material is unclear, look at the target molecule (Z) and identify its immediate precursor (Y). This "one step back" approach often clarifies which functional group was required to reach the final product.
Identify Functional Groups: Label every group in both the starting and final molecules. Compare them to see which needs to be added, removed, or transformed.
Reaction Mapping: Build a mental or physical "map" of reactions. For example, knowing that an alkene can lead to an alcohol via hydration, which can then be oxidized to a carboxylic acid, allows you to bridge those gaps quickly. Common Synthetic Pathways Starting Material Intermediate Final Product Key Reagents Nitrobenzene Phenylamine 2-bromopropane Propan-2-ol HBrcap H cap B r 2-hydroxypropanenitrile Lactic Acid Target: Halogenoalkane
Chemsheets A2 1272 Organic Synthesis Reactions ... - Studocu
You can download the problem sheets for free from:
Answers: As noted, official answers are teacher-locked. However, many YouTube channels (e.g., MaChemGuy, Allery Chemistry) solve Chemsheets problems step-by-step on video – those are essentially video answer keys.
Problem (Chemsheets A2 1080 style):
Starting from benzene, prepare 4-aminobenzoic acid in 4 steps.
Answer:
Step 1: Benzene → Methylbenzene (toluene) Target: Aldehyde (Primary Alcohol only)
Step 2: Methylbenzene → 4-methylbenzoic acid
Step 3: 4-methylbenzoic acid → 4-nitrobenzoic acid
Step 4: Nitro group → amino group
But target was 4-aminobenzoic acid? This shows why synthesis planning must consider directing groups. A correct 4-aminobenzoic acid route:
Benzene –(HNO₃/H₂SO₄)→ Nitrobenzene –(Sn/HCl)→ Phenylamine –(CH₃Cl, AlCl₃?) No – amino group reacts with AlCl₃. So protect first? Too complex. Chemsheets often expects:
Benzene → Chlorobenzene → 4-nitrochlorobenzene → 4-nitrophenol → 4-aminophenol – not right for 4-aminobenzoic acid.
The actual simple route:
Benzene –(CH₃Cl, AlCl₃)→ Methylbenzene –(KMnO₄)→ Benzoic acid –(HNO₃/H₂SO₄)→ 3-nitrobenzoic acid –(Sn/HCl)→ 3-aminobenzoic acid.
To get 4-aminobenzoic acid, you need to start with aniline and protect –NH₂, or start with benzoic acid and nitrate at 4-position, which is impossible due to meta direction. So Chemsheets sometimes uses “wrong” syntheses to test understanding of limitations.
Thus the correct Chemsheets answer for 4-aminobenzoic acid from benzene is: