Alcohols Flashcards
What are the bond angles in alcohols?
H-C-H bonds and C-C-O are 109.5
H-O-C bond is 104.5
What is the boiling point of alcohols?
- Relatively low volatility and high bp
Why do alcohols have high BP?
- Ability to form H-bond between alcohol molecules
Why can smaller alcohols dissolve in water?
Can form h-bonds to water molecules
What is the oxidising agent that causes alcohols to oxidise?
Potassium dichromate
Describe the partial oxidation of primary alcohols
Reaction: Primary alcohols to aldehyde
Reagent: potassium dichromate (VI) and dilute sulfuric acid
Conditions: warm gently and distil out the aldehyde as it forms
What is the observation for oxidising alcohols?
Orange dichromate ion reduces to green Cr3+ ion
What are the two ways ethanol can be produced?
- Hydration of ethene
- Fermentation
Describe hydration of ethene?
Reagent: Excess steam
Catalyst: concentrated h3po4
Conditions: high temperature, high pressure (60 atm), excess steam
Mechanism: electrophilic addition
Why is high pressure used in hydration?
- Equilibrium shifts to the right as there are fewer gaseous molecules
- Yield of alcohol increases
What is a biofuel?
A fuel produced from plants
What are the conditions for fermentation?
- Anaerobic
- 37 degrees
- Yeast
Why are anaerobic conditions used for fermentation?
Oxygen from air is kept out to prevent oxidation of ethanol to ethanoic acid
Give an advantage and a disadvantage of carrying fermentation at higher temperatures
Advantage: ethanol is produced at a faster rate
Disadvantage: more energy is used
How is pure ethanol obtained from industrial fermentation?
- Use fractional distillation to separate water and ethanol
- They have different BP
- The BP of water is 100 degrees and ethanol is 78 degrees