Ethene Reactions Flashcards
(10 cards)
Q: What happens when ethylene undergoes hydrogenation? Include catalyst and conditions.
Catalyst:
Ni, Pd, or Pt (metal catalysts)
Conditions:
High pressure + heat 🌡️
Mechanism:
Syn addition → both H atoms add to the same side of the double bond
Why it matters:
Used in the conversion of unsaturated fats to saturated fats, like in margarine production 🧈💪
Q: Predict the product of HBr addition to ethylene. Explain the mechanism and Markovnikov’s rule.
⚡ Electrophilic Addition of HBr to Ethene
Reaction:
CH₂=CH₂+ HBr ⟶ CH₃CH₂Br
Mechanism:
H⁺ from HBr attacks the double bond, forming a carbocation
Br⁻ quickly attacks the carbocation
➡️ Electrophilic addition ftw ⚡
Markovnikov’s Rule:
H adds to the carbon with more H atoms (less substituted one)
📝 Here it doesn’t matter much—ethene is symmetrical
Carbocation Stability:
Forms a primary carbocation
💡 Not very stable, but no worries here—symmetry makes it chill ✨
Q: How is ethanol synthesized from ethylene? Describe the catalyst and carbocation role.
Reaction:
CH₂=CH₂ + H₂O →(H₂SO₄)→ CH₃CH₂OH
Catalyst:
Concentrated H₂SO₄ (sulfuric acid)
Conditions:
Warm & dilute acid environment 🌡️💧
Mechanism:
Protonation of the double bond by H⁺ → forms carbocation
Water (H₂O) acts as a nucleophile → attacks the carbocation
Deprotonation → ethanol is formed 🧪✨
Q: What product forms when ethylene reacts with bromine? Explain the mechanism and stereochemistry.
Q: What product forms when ethylene reacts with bromine?
Reaction:
CH₂=CH₂ + Br₂ → CH₂Br–CH₂Br
Conditions: Room temp, in CCl₄
Mechanism: Electrophilic addition via bromonium ion
Stereochemistry: Anti-addition (Br atoms go on opposite sides)
Why it matters: Decolorizes bromine water = test for double bonds
Q: What happens when ethylene reacts with Br₂ + H₂O?
Reaction:
CH₂=CH₂ + Br₂ + H₂O → CH₂OH–CH₂Br
Mechanism: Bromonium ion → water attacks more substituted carbon
Stereochemistry: Anti-addition
Regioselectivity: Follows Markovnikov (OH to more substituted C)
Q: What products form when ethylene undergoes ozonolysis?
Reaction:
CH₂=CH₂ + RCO₃H → CH₂OCH₂ (epoxide)
Catalyst: Peracid (e.g., mCPBA)
Conditions: Mild (room temp)
Stereochemistry: Syn addition (both atoms same side)
Q: How is ethylene oxide synthesized from ethylene?
Reaction:
CH₂=CH₂ + RCO₃H → CH₂OCH₂ (epoxide)
Catalyst: Peracid (e.g., mCPBA)
Conditions: Mild (room temp)
Stereochemistry: Syn addition (both atoms same side)
Q: How is polyethylene synthesized from ethylene? Describe the catalyst.
Reaction:
nCH₂=CH₂ → (CH₂–CH₂)ₙ
Catalyst:
Radical initiators → LDPE
Ziegler-Natta → HDPE
Conditions:
High pressure → LDPE
Low pressure → HDPE
Q: Draw the mechanism for hydrohalogenation (e.g., HBr + ethylene).
Protonation of double bond → carbocation.
Bromide ion attacks carbocation.
Carbocation Stability: Ethylene forms a primary carbocation (less stable, but reaction proceeds due to simplicity).
Q: What is Markovnikov’s rule? Give an example.
Rule: “H goes to the carbon with more H” — the rich get richer!
Example:
CH₃–CH=CH₂ + HBr → CH₃–CHBr–CH₃
(Br goes to more substituted carbon)
