4.2.1 Alcohols Flashcards
Alcohols volatility
Relatively low due to their ability to form hydrogen bonds between alcohol molecules
General formula for alcohols
CnH2n+1OH
Alcohol solubility
Smaller (up to 3 carbons) are soluble as they can form hydrogen bonds with water
Longer the hydrocarbon chain the less soluble the alcohol
Uses of alcohols
Ethanol: alcoholic drinks, solvent in the form of methylated spirits
Methanol: petrol additive to improve combustion and is important as a feedstock in the production of organic chemicals
Types of alcohols
Primary
Secondary
Tertiary
Primary alcohols
Where 1 carbon is attached to the carbon adjoining the oxygen
Secondary alcohols
Where 2 carbons are attached to the carbon adjoining the oxygen
Tertiary alcohols
Where 3 carbons are attached to the carbon adjoining the oxygen
Complete combustion of alcohols
In excess oxygen
Will produce carbon dioxide and water
Oxidizing agent for alcohols
Potassium dichromate 6
K2Cr2O7
Partial oxidation of primary alcohols
Primary alcohol-> aldehyde
Reagent: potassium dichromate 6, warm gently and distil
Observation: orange dichromate ion (Cr2O7 2-) reduces to the green (Cr3+) ion
Write aldehyde as CHO on end
How can you maximize the yield collected in distillation
Approximation of boiling point of desired aldehyde and not higher
Full oxidation of primary alcohols
Reaction: primary alcohol-> carboxylic acid
Reagent: potassium dichromate 6 and dilute sulfuric acid
Conditions: use excess of dichromate and heat under reflux, distil off product after reaction has finished
And observations are same: orange to green
NEEDS TWO OXIDISING AGENTS
What shouldn’t you do in reflux
Seal the end of the condenser
Build up of gas pressure could cause apparatus to explode
What are added to reflux apparatus
Anti-bumping granules added to flask in both distillation and reflux to prevent vigorous, uneven boiling by making small bubbles form instead of large bubbles
Oxidation of secondary alcohols
Secondary alcohol -> ketone Reagent: potassium dichromate 6 solution and dilute sulfuric acid Conditions: heat under reflux Observations: orange to green No further oxidation
Oxidation of tertiary alcohols
Can’t be oxidised by potassium dichromate 6
No hydrogen atom blonde does to the carbon with the OH group
Reaction of alcohols with dehydrating agents
Alcohol -> alkene
Reagents: conc sulfuric or phosphoric acid
Conditions: warm under reflux
Role of reagent: dehydrating agent/ catalyst
Type of reaction: acid catalysts elimination
Dehydration reaction
Removal of a water molecule from a molecule
When can some secondary and tertiary alcohols form more than one product
When double bond forms between different carbon atoms
Substitution reactions of alcohols to form haloalkanes
Mixture of halide ions with conc acid NaCl + H2SO4 can be used for substituting a halogen onto an alcohol
Reaction: alcohol -> haloalkane
Reagents: conc sulfuric acid and sodium halide
