Alcohols

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  • Created by: lridgeway
  • Created on: 20-06-18 20:37
What is the general formula for an alcohol?
CnH2n+1OH
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Do they have a high or low boiling point and why?
High due to the fact they can hydrogen bond
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What factors change the boiling point?
Molecular size due to increases electrons which increase van der waals. Branching will decrease due to less surface area contact and less van der waals
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What is a primary alcohol?
The carbon the OH is attached to has only one other carbon attached
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What is a secondary alcohol?
The carbon the OH is attached to has two other carbon atoms attached
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What is a tertiary alcohol?
The carbon the OH is attached to has three other carbon atoms attached
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What is the equation for the complete combustion of ethanol?
C2H5OH + 3O2 -> 2CO2 +3H2O
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What is the equation for the incomplete combustion of ethanol?
C2H5OH + 2O2 -> 2CO + 3H2O
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What do methylated spirts contain and why?
Ethanol but also small amounts of methanol and purple dye to stop people drinking it
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What is oxidation of alcohols?
Adding oxygen/ removing hydrogen
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What does oxidation of primary alcohols make?
An aldehyde (remove H) and then on further oxidation a carboxylic acid (adding oxygen)
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What is the oxidising agent for oxidation of alcohols?
Acidified potassium dichromate (K2Cr2O7) (acidified by H2SO4)
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What does oxidation of secondary alcohols make?
Ketone
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What does oxidation of tertiary alcohols make?
Nothing they don’t oxidise as the carbon carbon bonds are too strong to break
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How do you get an aldehyde from a primary alcohol?
Use limited potassium dichromate and distill straight away
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How do you get a carboxlyic acid from a primary alcohol?
Excess potassium dichromate and reflux
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Write the equation for the oxidation of ethanol to ethanal
CH3CH2OH + [O] -> CH3CHO + H2O
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Write the equation for the oxidation of ethanol to carboxlyic acid
CH3CH2OH + 2[O] -> CH3COOH + H2O
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How do you make an alkene from an alcohol?
Dehydration reaction
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Write the equation for the dehydration of an alcohol?
CH3CH2OH -> CH2CH2 + H2O
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Write the equation for the formation of alcohol from an alkene?
CH2CH2 + H2O -> CH3CH2OH
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What must be present for the alcohol/alkene reaction to occur?
Acid catalyst (concentrated phosphoric acid)
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What happens when unsymmetrical alcohols are dehydrated?
You end up with more than one product depending on where double bond forms
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Write the equation for the fermentation of glucose to form ethanol?
C6H12O6 —> 2CH3CH2OH + 2CO2
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What must be present for the fermentation to work?
Yeast catalyst
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What conditions are present for fermentation?
Anaerobic
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What are the advantages of making ethanol from ethene?
1 step, pure product, 100% atom economy, larger volume and fast reaction
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What are the disadvantages of making ethanol from ethene?
Non renewable and only 5% yield but can recycle ethene
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What are the advantages of making ethanol by fermentation?
Renewable
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What are the disadvantages of making ethanol by fermentation?
Batch process, impure product (distillation needed), 2 step process, food/fuel conflict over land, N2 atomosphere (so no ethanoic acid), 30% yield as yeast killed at this ethanol conc and 30-42 degrees condition (slow reaction)
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What does the term carbon neutral mean?
No net release of carbon dioxide
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Which process of making ethanol is said to be carbon neutral?
Fermentation
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In which reaction(s) is CO2 absorbed in this process?
Photosynthesis
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In which reaction(s) is CO2 released in this process?
Fermentation and combustion
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Name one method for testing aldehydes and ketones and state the outcome
Tolled reagent test and it produces a silver mirror with aldehyde
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Name the other method for testing aldehydes and ketones and state the outcome
Fehling’s solution (copper (||) sulfate) which is blue turns brick red with an aldehyde
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Name a method for testing alcohols and state it’s outcome
Add a small amount of acidified potassium dichromate and gently heat. The colour will turn from green to orange with primary and secondary alcohols.
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Name a method for testing carboxylic acids and state the outcome
Add solid sodium carbonate and it it fizzes and produces carbon dioxide it is a carboxylic acid (will work for all acids though)
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Other cards in this set

Card 2

Front

Do they have a high or low boiling point and why?

Back

High due to the fact they can hydrogen bond

Card 3

Front

What factors change the boiling point?

Back

Preview of the front of card 3

Card 4

Front

What is a primary alcohol?

Back

Preview of the front of card 4

Card 5

Front

What is a secondary alcohol?

Back

Preview of the front of card 5
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