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Electrophilic Addition (ethene School)
Ethene + Br2: the C=C attacks Br2, a bromonium / stepwise school picture, product 1,2-dibromoethane. Br2 water decolourises (orange to colourless) — the alkene test. HBr adds (Markovnikov named: H to the carbon that already has more H, if unsymmetric). H2 / Ni: hydrogenation to alkane (named). Steam / acid: ethanol from ethene (industrial name, not a plant). Meaning: the double bond is a nucleophi
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Electrophilic Addition (ethene School)
What is it?
Ethene + Br2: the C=C attacks Br2, a bromonium / stepwise school picture, product 1,2-dibromoethane. Br2 water decolourises (orange to colourless) — the alkene test. HBr adds (Markovnikov named: H to the carbon that already has more H, if unsymmetric). H2 / Ni: hydrogenation to alkane (named). Steam / acid: ethanol from ethene (industrial name, not a plant). Meaning: the double bond is a nucleophilic cloud; the reagent is the electrophile. Electrophile attacks pi bond; carbocation intermediate then nucleophile adds — Markovnikov for HX. Show curly arrows on addition mechanisms; Markovnikov reasoning must precede the product structure.
In simple words
- Ethene + Br2: the C=C attacks Br2, a bromonium / stepwise school picture, product 1,2-dibromoethane.
- 1. Br2 AND H2: Organic solvent or water: still addition.
- 2. HBr AND STEAM: Unsymmetric alkene: two possible products; major follows Markovnikov named.
- Exam reminder: Exam Br2 test: alkene decolourises Br2 water addition across C=C alkane does not (no C=C)
Important terms
ELECTROPHILIC ADDITION (ETHENE SCHOOL): Ethene + Br2: the C=C attacks Br2, a bromonium / stepwise school picture, product 1,2-dibromoethane.
1. Br2 AND H2: Organic solvent or water: still addition.
2. HBr AND STEAM: Unsymmetric alkene: two possible products; major follows Markovnikov named.
What you should learn
- Explain electrophilic addition (ethene school) in simple chemical language.
- Connect 1. br2 and h2 with 2. hbr and steam using equations, observations, or trends where needed.
- Answer a short Federal Board question with the correct terms and a clear reason.
Examples
- Orange -> colourless
- H2 / Ni named
- Count: one Br2 per C=C
Br2 AND H2
Organic solvent or water: still addition. Ni, Pt, or Pd named as hydrogenation catalysts (names). Vegetable-oil hardening named as a slogan, not a factory SOP. Ethene + Br2 -> 1,2-dibromoethane; + H2O (catalyst) -> ethanol industrial route named.
HBr AND STEAM
Unsymmetric alkene: two possible products; major follows Markovnikov named. Ethene + H2O (acid) -> ethanol named. Cold dilute KMnO4: diol, purple fade (named mild ox). Mechanism arrows: pi electrons attack E+, then Nu- attacks carbocation.
Recommended for Class 11
Full school-level explanation
Ethene + Br2: the C=C attacks Br2, a bromonium / stepwise school picture, product 1,2-dibromoethane. Br2 water decolourises (orange to colourless) — the alkene test. HBr adds (Markovnikov named: H to the carbon that already has more H, if unsymmetric). H2 / Ni: hydrogenation to alkane (named). Steam / acid: ethanol from ethene (industrial name, not a plant). Meaning: the double bond is a nucleophilic cloud; the reagent is the electrophile. Electrophile attacks pi bond; carbocation intermediate then nucleophile adds — Markovnikov for HX. Show curly arrows on addition mechanisms; Markovnikov reasoning must precede the product structure.
Test, then unsymmetric add:
WHAT — ELECTROPHILIC ADDITION (ETHENE SCHOOL)
Ethene + Br2: the C=C attacks Br2, a bromonium / stepwise school picture, product 1,2-dibromoethane. Br2 water decolourises (orange to colourless) — the alkene test. HBr adds (Markovnikov named: H to the carbon that already has more H, if unsymmetric). H2 / Ni: hydrogenation to alkane (named). Steam / acid: ethanol from ethene (industrial name, not a plant). Meaning: the double bond is a nucleophilic cloud; the reagent is the electrophile. Electrophile attacks pi bond; carbocation intermediate then nucleophile adds — Markovnikov for HX. Show curly arrows on addition mechanisms; Markovnikov reasoning must precede the product structure.
WHY — Why this topic matters
ELECTROPHILIC ADDITION (ETHENE SCHOOL) 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
Br2 AND H2: Organic solvent or water: still addition. Ni, Pt, or Pd named as hydrogenation catalysts (names). Vegetable-oil hardening named as a slogan, not a factory SOP. Ethene + Br2 -> 1,2-dibromoethane; + H2O (catalyst) -> ethanol industrial route named. Examples: Orange -> colourless; H2 / Ni named; Count: one Br2 per C=C. HBr AND STEAM: Unsymmetric alkene: two possible products; major follows Markovnikov named. Ethene + H2O (acid) -> ethanol named. Cold dilute KMnO4: diol, purple fade (named mild ox). Mechanism arrows: pi electrons attack E+, then Nu- attacks carbocation. Examples: Propene + HBr named; Ethene hydration named; KMnO4 diol named. Exam Br2 test: alkene decolourises Br2 water addition across C=C alkane does not (no C=C)
Br2 AND H2
Organic solvent or water: still addition. Ni, Pt, or Pd named as hydrogenation catalysts (names). Vegetable-oil hardening named as a slogan, not a factory SOP. Ethene + Br2 -> 1,2-dibromoethane; + H2O (catalyst) -> ethanol industrial route named.
Remember
- decolourise Br2
Examples
- Orange -> colourless
- H2 / Ni named
- Count: one Br2 per C=C
HBr AND STEAM
Unsymmetric alkene: two possible products; major follows Markovnikov named. Ethene + H2O (acid) -> ethanol named. Cold dilute KMnO4: diol, purple fade (named mild ox). Mechanism arrows: pi electrons attack E+, then Nu- attacks carbocation.
Remember
- H to richer H carbon
Examples
- Propene + HBr named
- Ethene hydration named
- KMnO4 diol named
Remember
- C=C attacks E+
- Br2 water test
- orange disappears
- school only
- decolourise Br2
- H to richer H carbon
- C=C attacks E+
- Br2 water test
How the ideas connect
Exam Br2 test: alkene decolourises Br2 water addition across C=C alkane does not (no C=C)
Deeper understanding
Go beyond memorising Electrophilic Addition (ethene School). Connect the definition to reasons, relationships, exceptions, and exam wording.
How the ideas connect
Exam Br2 test: alkene decolourises Br2 water addition across C=C alkane does not (no C=C)
Common mistakes
Exam focus
Core Idea
1. Br2 AND H2
2. HBr AND STEAM
Exam Example
Exam focus
Quick revision
- C=C attacks E+
- Br2 water test
- orange disappears
- school only
- ELECTROPHILIC ADDITION (ETHENE SCHOOL): Ethene + Br2: the C=C attacks Br2, a bromonium / stepwise school picture, product 1,2-dibromoethane.
- 1. Br2 AND H2: Organic solvent or water: still addition.
School addition. No industrial hydration-plant design.
For long answers on Electrophilic Addition (ethene School): define clearly → explain the main parts → give one example → state one exam caution.
Exam Focus
Exam Focus
Important points
- C=C attacks E+
- Br2 water test
- orange disappears
- school only
Important formulas
- C=C attacks E+
- Br2 water test
- orange disappears
Common exam traps
- Do not confuse 1. Br2 AND H2 with 2. HBr AND STEAM; state the difference before giving an example.
- Writing only “C=C attacks E+” is not enough. Explain what it means in a complete sentence.
Long question structure
Definition → key parts → example → exam caution
Common Mistakes
Common Mistakes
- Mistake
Do not confuse 1. Br2 AND H2 with 2. HBr AND STEAM; state the difference before giving an example.
- Mistake
Writing only “C=C attacks E+” is not enough. Explain what it means in a complete sentence.
- Mistake
School addition. No industrial hydration-plant design.
- Mistake
School addition. No industrial hydration-plant design.
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
C=C attacks E+
Br2 water test
orange disappears
school only
Ethene + Br2: the C=C attacks Br2, a bromonium / stepwise school picture, product 1,2-dibromoethane. Br2 water decolourises (orange to colourless) — the alkene
C=C attacks E+
- Definition
- Ethene + Br2: the C=C attacks Br2, a bromonium / stepwise school picture, product 1,2-dibromoethane. Br2 water decolourises (orange to colourless) — the alkene
- Formula
- C=C attacks E+
- Example
- Orange -> colourless
- Critical warning
- Do not confuse 1. Br2 AND H2 with 2. HBr AND STEAM; state the difference before giving an example.
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Exam Practice
Define
Q1. Define Electrophilic Addition (ethene School).
Explain
Q2. Explain: Br2 AND H2.
Example
Q3. Give one clear example of Electrophilic Addition (ethene School) and say why it fits.
Mistake
Q4. State one common mistake students make about Electrophilic Addition (ethene School).
Exam note
Q5. Write a short exam note on Electrophilic Addition (ethene School): definition, two points, one example.
Sources & References
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.