WM - Reaction mechanisms Flashcards

1
Q

Elimination reaction

A

a small group of atoms break away from the larger molecule

the small group is not replaced by anything else

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2
Q

How do you make an alkene from ethanol

A

Make an alkene by eliminating water from an alcohol in a dehydration reaction

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3
Q

Two ways of dehydrating alcohols to form alkenes

A
  1. Ethanol vapour is passed over a hot catalyst of pumice stone or aluminium oxide, Al2O3 - the catalyst provides a large surface area for the reaction.
  2. reflux ethanol with excess concentrated sulfuric acid at 170degreesC.
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4
Q

Dehydrating alcohols - using a catalyst experient

A

ceramic wool is soaked in ethanol, pumice stone or Al2O3 is heated, the alkene gas collects in an inverted cylinder in a water bath

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5
Q

Dehydrating alcohols - reflux experiment

A
  • heat solution in a flask fitted with a vertical Liebig condenser - this causes the solution to continuously boil/eveaporate and then condense back into the flask, giving it time to react
  • heat solution electronically; hot plates, heating mantles.
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6
Q

dehydrating alcohols - reflux reaction

A

DRAW THIS
The conc. sulfuric acid acts as a dehydration agent in the elimination reaction

  1. the hydroxyl group will bond to the H+ ions from the strong acid.
    - the alcohol is protonated, giving the atom a +ve charge
  2. the +vely charged oxygen will pull electrons away from the neighbouring carbon, and water will ‘fall off’
    - creates an unstable carbon intermediate
  3. the carbocation loses H+ and the alkene is formed
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