Alcohol

  • Created by: Hindleyc
  • Created on: 19-05-18 17:13
What uses to alcohols have?
scientific, medicinal and industrial
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What is ethanol?
An alcohol produced using different methods and can be used as a biofuel
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General formula of alcohol?
CnH2n+1OH
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Suffix of alcohol?
-ol
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What is other fg needs suffix ending?
Use prefix hydroxy
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Bond angles in H-C-H and C-C-O? Shape? BP? what do the bp do?
109.5. Tetrahedral. 4 bp. Repel to a position of minimum repulsion.
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Bond angle in H-O-C? shape? BP and LP? what repels more? what do this do?
104.5. Bent line. 2bp and 2 lp. LP repel more than BP. Reduces bond angle
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What is the first type of alcohol?
Primary. 1 carbon is attached to carbon adjoining the oxygen
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What is the second type of alcohol?
Secondary. 2 Carbon attached to carbon adjoining the oxygen
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3rd type of alcohol?
Tertiary. 3 carbon attached to carbon adjoining the oxygen
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How are alcohols produced?
Hydration and fermentation
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Alcohols industrially produced?
Hydration of alkenes in presence of acid catalyst
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How does it work?
Reacted in water in presence of an acid catalyst
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What is hydration?
Addition of water to a molecule
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What are the conditions?
High temp- 660k. High pressure- 6000-7000kPa. Acid catalyst
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What is the acid catalyst?
Concentrated H3PO4 in silica pellets
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Why is It called a catalyst?
Gives H+ but produced at end so is a catalyst
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Why in silica pellets?
Would mix if liquid and react with water
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Advantages of hydration?
No waste products so high atom economy. Faster reaction. Purer product. Continuous process (cheaper man power)
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Disadvantages of hydration?
High technology equipment needed- expensive initial cost. Ethene non-renewable resource (more £ when raw materials run out. High energy costs for pumping to produce high pressure
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What is the reagent?
Ethene from cracking of fractions from distilled crude oil
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reaction?
Electrons from double bond in ethene go to H+ (from conc H3PO4) forming carbocation then lone pair electrons from water on O goes to +ve carbon bonding to it leaving O with +ve charge. E- from oh bond to oxygen making ethanol and H+
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How else is ethanol produced industrially?
Fermentation of glucose
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Eqn
Glucose= Ethanol+ Carbon dioxide. C6H12O6=2C2H5OH+2CO2
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Conditions?
Yeast. No air. Temp 30-40
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Type of reaction? optimum temp?
Fermentation. 38
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What happens at lower temps? what happens at higher temps?
Reaction too slow. Yeast dies and enzymes denatures
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Why no air?
Presence of air can cause extra reactions to occur- oxidises ethanol= ethanoic acid
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ADV
Sugar= renewable resource. Production uses low level technology/ cheap equipment
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DIS
Batch process- slow and gives high production costs . Ethanol made not pure and needs purifying by fractional distillation- then used as biofuel. Depletes land used for growing food crops
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What is a biofuel?
Fuel produced from plants
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What is carob neutral?
Activity that has no net annual carbon (gg) emissions to the atmosphere
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What is ethanol produced from fermentation?
A biofuel
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Why is it argued that ethanol produced from this method is carbon neutral?
Any co2 given off when burnt would have been extracted from the air by photosynthesis when the plant grew therefore no net co2 emissions into atmosphere.
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EQN for removal of co2 by p/s
6CO2+6H20= C6H12O6+6O2 Therefore 6 CO2 molecules removed
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EQN for production of CO2 by fermentation and combustion
C6H12O6=2C2H5OH+2CO2 Therefore 2 molecules emitted. 2C2H5OH+6O2=4CO2+6H20 Therefore 4 molecules when combusted
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So?
6 molecules absorbed and 6 molecules released so no net contribution of co2 to atmosphere
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What doesn't this take into account?
Energy needed to water plants, fractionally distill ethanol from mixture or process fuel and transport.
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What does this mean?
If energy for this comes from fossil fuels then ethanol produced is not carbon neutral.
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Volatility?
Relatively Low
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BP?
High due to their ability to form H bonds between alcohol molecules
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What is the reaction of alcohols with dehydrating agents?
Alcohol to alkene
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What are the reagents?
Concentrated sulphuric or phosphoric acid
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What are the conditions ?
Warm under reflux
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Role of reagent?
Dehydrating agent/ catalyst
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Type of reaction
Acid catalysed Elimination
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What Is a dehydration reaction?
Removal of a H2O molecule from a molecule
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Propan-1-ol goes to
Propene+h2o
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What can some secondary and tertiary alcohols give?
More than 1 product when the double bond forms between different carbon atoms
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EG what can butan-2-ol form
Both alkenes- but-2-ene and but-1-ene but more but-2-ene would be formed
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What could but-2-ene also exist as
E-Z isomer
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What does producing alkenes from alcohols provide a possible route to ?
Polymers without using monomer derived from oil (addition polymers)
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Mechanism for acid catalysed elimination
arrow from Lone pair of electrons on O atom to H+
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Where is the H+ from?
Concentrated H3PO4/H2SO4
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What next?
Oxygen now has positive charge and electrons from C-O bond move to oxygen
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Then?
The electrons from the C-H bond next to where the water molecule was lost move to the C-C bond forming an Alkene and H+
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Other cards in this set

Card 2

Front

What is ethanol?

Back

An alcohol produced using different methods and can be used as a biofuel

Card 3

Front

General formula of alcohol?

Back

Preview of the front of card 3

Card 4

Front

Suffix of alcohol?

Back

Preview of the front of card 4

Card 5

Front

What is other fg needs suffix ending?

Back

Preview of the front of card 5
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