3.5 Alcohols Flashcards
KEY DEFINITION: structural isomers
Compounds with the same molecular formula but a different structural formula
What is a functional group isomer of C4H10O?
Diethyl-ether
What boiling points do alcohols have and why?
• relatively high
• they form hydrogen bonds
Solubility of alcohols:
• alcohols with a low mr are more soluble in water due to H-bonding
What are the conditions for the hydration of alkenes to form alcohols?
• 300*C
• 60 atmospheres
• H3PO4 catalyst
Give 4 commercial uses of ethanol:
• sterilising medical equipment
• solvents (eg computer cleaner)
• alcoholic beverages
• fuel
What are the conditions for fermentation?
• yeast enzymes
• 35*C
• anaerobic
Why does fermentation have to be anaerobic?
• prevents oxidation ~ CH3COOH
When does the fermentation stop?
• when the mixture reaches 15% ethanol
• because high alcohol levels poison the yeast
Compare the processes of hydration of ethene and fermentation:
Hydration of ethene:
• uses crude oil
• pure products
• fast rate of reaction
• needs high energy
• continuous process
• 100% atom economy (only 1 product)
Fermentation:
• uses plants
• impure products
• slow rate of reaction
• needs low energy
• batch process
• 51% atom economy
KEY DEFINITION: biofuel
A fuel derived or produced from renewable biological resources
Disadvantages of using crops to produce fuel:
• land used to grow crops for fuel cannot be used to grow food (ethical dilemma)
• fertilisers often added to soil to increase biofuel crop production
• deforestation to create land for the crops to grow
Products of elimination of alcohols:
Alkene + water + hydrogen ion
Observations when acidified potassium dichromate oxidises alcohols:
Turns from orange to green
Possible oxidation products of primary alcohols:
1 - aldehyde (-CHO)
2 - carboxylic acid (-COOH)
Oxidation product of secondary alcohols:
Ketone (C=O) - bonded to 2 other carbon atoms
Oxidation products of tertiary alcohols:
None - resists oxidation
Method to oxidise primary alcohols:
- acidified potassium dichromate
- immediate distillation: alcohol, acidified potassium dichromate, anti-bumping granules, sulfuric acid
- product will likely be an aldehyde
Method to oxidise to a carboxylic acid:
Reflux: alcohol, acidified potassium dichromate, sulfuric acid, anti-bumping granules
Why is the product likely to be a carboxylic acid?
- vapours continuously condense so react further
- the reaction will go to completion
Method to oxidise secondary alcohols:
Reagents - acidified potassium dichromate, sulfuric acid
Conditions: heat and reflux
Tollen’s reagent general equation:
[Ag(NH3)2]+ + e-»_space;> Ag(s) + 2NH3
Fehling’s solution test:
Active ingredient: Cu2+ ions
Observations: blue solution»_space; brick-red precipitate (Cu2+ has been reduced)
Fehling’s solution general equation:
Cu2+»_space;> Cu2O
