ChemistryChapter 21: Organic Synthesis
Worked School Routes (allowed Set)
Ethene to ethanol: steam / acid catalyst named.
Learning objectives
- Explain worked school routes (allowed set) in simple chemical language.
- Connect 1. c2 menu with 2. c3 menu using equations, observations, or trends where needed.
- Answer a short Federal Board question with the correct terms and a clear reason.
Definition
Ethene to ethanol: steam / acid catalyst named. Ethanol to ethene: conc H2SO4 heat. Ethanol to ethanal: distil dichromate. Ethanol to ethanoic: reflux dichromate. Ethanol to chloroethane: PCl5 named. Bromoethane to ethanol: aq KOH. Bromoethane to ethene: alc KOH. Propene to propan-2-ol: H2O/H+ or Markovnikov from HBr then aq KOH. That is the allowed menu. Example: ethene -> bromoethane -> ethanol -> ethanoic acid — each step named reagent. Count carbons after each synthetic step; silent carbon loss is the most common multi-step mistake.
Important terms
- WORKED SCHOOL ROUTES (ALLOWED SET)
- Ethene to ethanol: steam / acid catalyst named.
- 1. C2 MENU
- Ethene hub.
- 2. C3 MENU
- Propene -> 2-bromopropane (HBr) -> propan-2-ol (aq KOH).
Overview
Two carbons, then three:
C2 Menu
Ethene hub. Ethanol hub. Ethanoic and ethanal as ox. Chloroethane as sub. All named above. Stick to two or three steps as exam usually limits.
Examples Hydrate · Oxidise · PCl5 named
C3 Menu
Propene -> 2-bromopropane (HBr) -> propan-2-ol (aq KOH). Or direct hydration. Propan-2-ol -> propanone (dichromate). Iodoform on the ketone. Balance economy: fewer steps often better if reagents allowed.
Examples 2-bromopropane · Propanone · CHI3 yes
WHAT — WORKED SCHOOL ROUTES (ALLOWED SET)
Ethene to ethanol: steam / acid catalyst named. Ethanol to ethene: conc H2SO4 heat. Ethanol to ethanal: distil dichromate. Ethanol to ethanoic: reflux dichromate. Ethanol to chloroethane: PCl5 named. Bromoethane to ethanol: aq KOH. Bromoethane to ethene: alc KOH. Propene to propan-2-ol: H2O/H+ or Markovnikov from HBr then aq KOH. That is the allowed menu. Example: ethene -> bromoethane -> ethanol -> ethanoic acid — each step named reagent. Count carbons after each synthetic step; silent carbon loss is the most common multi-step mistake.
WHY — Why this topic matters
WORKED SCHOOL ROUTES (ALLOWED SET) is an independent FBISE learning unit because students must use its definitions, conditions, equations, or trends separately in explanations and calculations.
HOW — How it works
C2 MENU: Ethene hub. Ethanol hub. Ethanoic and ethanal as ox. Chloroethane as sub. All named above. Stick to two or three steps as exam usually limits. Examples: Hydrate; Oxidise; PCl5 named. C3 MENU: Propene -> 2-bromopropane (HBr) -> propan-2-ol (aq KOH). Or direct hydration. Propan-2-ol -> propanone (dichromate). Iodoform on the ketone. Balance economy: fewer steps often better if reagents allowed. Examples: 2-bromopropane; Propanone; CHI3 yes. Worked: propene to propanone. hydrate (or HBr then aq KOH) to propan-2-ol acidified dichromate to propanone secondary alcohol path
Worked example
- propene to propanone.
- hydrate (or HBr then aq KOH) to propan-2-ol
- acidified dichromate to propanone
- secondary alcohol path
In simple words
Syllabus menu only. No extra steps, no drugs, no explosives.
Key points
- copy the named arrow
- do not add extra reagents
- C2 stays C2
- Markovnikov
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Worked School Routes (allowed Set)
Sticky Notes · Quick Revision
Core Idea
- Ethene to ethanol: steam / acid catalyst named. Ethanol to ethene: conc H2SO4 heat. Ethanol to ethanal: distil dichromate. Ethanol to ethanoic: reflux dichromate. Ethanol to chloroethane: PCl5 named. Bromoethane to ethanol: aq KOH. Bromoethane to ethene: alc KOH. Propene to propan-2-ol: H2O/H+ or Markovnikov from HBr then aq KOH. That is the allowed menu. Example: ethene -> bromoethane -> ethanol -> ethanoic acid — each step named reagent. Count carbons after each synthetic step; silent carbon loss is the most common multi-step mistake.
1. C2 MENU
- Ethene hub. Ethanol hub. Ethanoic and ethanal as ox. Chloroethane as sub. All named above. Stick to two or three steps as exam usually limits.
- Hydrate
- Oxidise
- PCl5 named
2. C3 MENU
- Propene -> 2-bromopropane (HBr) -> propan-2-ol (aq KOH). Or direct hydration. Propan-2-ol -> propanone (dichromate). Iodoform on the ketone. Balance economy: fewer steps often better if reagents allowed.
- 2-bromopropane
- Propanone
- CHI3 yes
Exam Example
- Worked: propene to propanone.
- hydrate (or HBr then aq KOH) to propan-2-ol
- acidified dichromate to propanone
- secondary alcohol path
Common Misconceptions
- Do not confuse 1. C2 MENU with 2. C3 MENU; state the difference before giving an example.
- Writing only “copy the named arrow” is not enough. Explain what it means in a complete sentence.
FBISE Exam Check
- Explain worked school routes (allowed set), compare its two main parts, and include the correct chemical evidence.
- Syllabus menu only. No extra steps, no drugs, no explosives.
60-second revision
- Ethene to ethanol: steam / acid catalyst named.
- 1. C2 MENU: Ethene hub.
- 2. C3 MENU: Propene -> 2-bromopropane (HBr) -> propan-2-ol (aq KOH).
- Exam reminder: Worked: propene to propanone.
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