Alcohols
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What do all alcohols contain?
O-H bond
What are the names and structural formula of the first four alcohols?
• Methanol - CH₃OH • Ethanol - CH₃CH₂OH • Propanol - CH₃CH₂CH₂OH • Butanol - CH₃CH₂CH₂CH₂OH • The displayed formula of ethanol is shown in the image for reference • These are the structural formulae, the molecular formula for ethanol, for example, is C₂H₅OH. Note how you still leave OH in as it is the functional group
What are the three ways that ethanol can be oxidised?
• Complete Combustion • Microbial oxidation • Heating with potassium dichromate(VI) in dilute sulfuric acid
What is the balanced symbol equation for the complete combustion of ethanol in air?
C₂H₅OH + 3O₂ –> 3H₂O + 2CO₂
How is ethanol oxidised through microbial oxidation?
• Bacteria in the air use atmospheric oxygen to oxidise the ethanol and create ethanoic acid and water • Symbol equation: C₂H₅OH + O₂ –> CH₃COOH + H₂O This is what happens if you leave wine out for too long. It will taste vinegary due to the ethanoic acid formed
How is ethanol oxidised using potassium dichromate (VI)?
• Ethanol is heated with potassium dichromate in dilute sulfuric acid • The potassium dichromate acts as an oxidising agent which oxidises the ethanol, producing ethanoic acid and water • Symbol equation: C₂H₅OH + [O] –> CH₃COOH + H₂O • The [O] just means the oxidising agent, as other things could be used • Other products will be produced, but it will depend on the oxidising agent used
What are the two ways in which ethanol can be manufactured?
• Hydration of ethene • Fermentation
What are the conditions necessary for the reaction which manufactures ethanol through the hydration of ethene?
• 60-70 atm • 300 degrees celsius • Presence of solid phosphoric acid (H₃PO₄) catalyst
How is ethanol manufactured through the hydration of ethene?
• Ethene is reacted with steam in the presence of a phosphoric acid (H₃PO₄) catalyst under the correct conditions • Then, the ethanol and remaining ethene and water are seperated through fractional distilliation • Symbol equation: C₂H₄ + H₂O –> C₂H₅OH • It is steam because the reaction happens at 300 degrees, but at the seperation stage, the remaining steam is water because the temperature is lower again • This is less favourable due to how it comes from non-renewable crude oil resources
How is ethanol manufactured through fermentation?
• Yeast is added with glucose to water, and left for a few days in the absence of oxygen and at 30 degrees celcius • The yeast respire anaerobically using the glucose to produce ethanol and carbon dioxide • It must be without oxygen for anaerobic respiration to occur, and 30 degrees celcius is the optimal temperature for the enzymes in yeast which break down the sugar to function • Symbol equation: C₆H₁₂O₆ (+ yeast enzymes) –> 2CO₂ + C₂H₅OH • It is literally just the equation for anaerobic respiration in plants • This is good as it is from renewable resources