đŸ”´đŸ”¸2.7 -Alcohols And Carboxylic Acids Flashcards
Define alcohol
A homologous series containing -OH as the functional group
Define fermentation
An enzyme catalysed reaction that converts sugars to ethanol
How is alcohol produced on a large scale? (2)
- Hydration of ethane
2. Fermentation
How is ethane produced on a large scale in the hydration of ethene
By cracking hydrocarbons produced from petroleum, reacting with steam to produce ethanol
Ch2=Ch2(g) + H2O(g) —<> CH3CH2OH(g)
đŸ”ºH = -45 (Exothermic)
What conditions are used in the hydration of ethene?
Compromise temperature of 300degrees, pressure of 60-70 atmospheres and a catalyst of phosphoric acid
What happens to the ethene not converted in the hydration of ethene
Only 5% converted and the remaining is recycled back to the reaction chamber
Basic description of fermentation
Dissolving sugar in water, adding yeast and leaving in warm place
(Process where sugars are converted to ethanol)
Why is yeast essential for fermentation?
It contain enzymes that catalyse the reaction :: C6H12O6 —> 2C2H5OH + 2CO2
C6H12O6 —> 2C2H5OH + 2CO2
How is ethanol separated?
Co2 is gas :: escapes :: 2C2H5OH remaining
Ethanol has boiling point of 80 degrees and :: to separate use fractional distillation
Why is fractional distillation rather than distillation needed to separate ethanol in fermentation?
Boiling temperatures of ethanol (80) and water (100) are quite close together
Define biofuel
A fuel that has been produced using a biological source
What are the two main forms of biofuel
Why can they be used as fuels?
Bioethanol and biodiesel
Can be used as fuels since both burn exothermically
How is bioethanol obtained?
From sugars in plants by fermentation
How is biodiesel obtained?
From the oils and fats present in the seeds of some plants
Name 3 advantages of using biofuels
- Renewable (grown and produced by animal waste)
- Carbon neutral (as plants use CO2 for photosynthesis, then produce CO2 when burnt) :: less overall greenhouse gases
- Economic and political security (countries that don’t have fossil fuels are less dependent on changes in price and availability)
Name disadvantages of biofuels
1) land use (land can’t be used to produce food + forests cleared for biofuel production)
2) resource use (needs large quantities of water and fertilisers to grow :: causes water pollution)
3) not carbon neutral as use Co2 to build/run factories for biofuel production
What forms when an alcohol is dehydrated?
Show an example equation
Dehydrated to form alkenes
E.g CH3CH2CH2OH —> CH3CH=CH2 + H2O
What are most commonly used to dehydrate alcohols
Concentrated sulphuric acid or heated aluminium oxide
Why is the dehydration of alcohol an elimination?
A double bond is produced by the removal of OH from one carbon atom and H from adjacent atom
Define classification of alcohols
Classification into primary, secondary or tertiary according to their structures
What is a primary alcohol
Occurs when the -OH is joined to a carbon that is itself joined to not more than one other carbon atom e.g methanol or propan-1-ol (check book if unsure)
What is a secondary alcohol
occurs when the -OH is joined to a carbon that is itself joined to two other carbon atom
E.g Propan-2-ol
What is a tertiary alcohol
occurs when the -OH is joined to a carbon that is itself joined to 3 other carbon atoms
E.g 2-methyl butan-2-ol
(Check on pg 155 if unsure)
What can be used to oxidase alcohols
How is this carried out?
Acidified potassium dichromate (VI)
Carried out by heating the alcohol with a mixture of aqueous potassium dichromate(VI) and sulphuric acid
