4.2.1 - Alcohols

What is the general formula of alcohols?

CnH2n+1OH

Why are small alcohols soluble in water?

They form hydrogen bonds with water

Which alcohols are soluble in water?

Alcohols with up to 3 carbons

How does increasing hydrocarbon chain length affect alcohol solubility?

Solubility decreases

Why do alcohols have relatively low volatility?

Hydrogen bonding between alcohol molecules

What intermolecular force exists between alcohol molecules?

Hydrogen bonding

What is methylated spirits mainly composed of?

Ethanol

What is ethanol commonly used as?

A solvent

What is methanol used for in fuels?

Petrol additive

Why is methanol added to petrol?

To improve combustion

What industrial use does methanol have?

Feedstock for organic chemicals

What is a primary alcohol?

Alcohol with one carbon attached to the carbon bonded to OH

What is a secondary alcohol?

Alcohol with two carbons attached to the carbon bonded to OH

What is a tertiary alcohol?

Alcohol with three carbons attached to the carbon bonded to OH

What type of alcohol is propan 1 ol?

Primary

What type of alcohol is propan 2 ol?

Secondary

What type of alcohol is methylpropan 2 ol?

Tertiary

What are the products of complete combustion of alcohols?

Carbon dioxide and water

What conditions are needed for complete combustion of alcohols?

Excess oxygen

What is the equation for complete combustion of ethanol?

CH3CH2OH + 3O2 → 2CO2 + 3H2O

Ethanol + Oxygen → Carbon Dioxide + Water

What oxidising agent is commonly used with alcohols?

Potassium dichromate

What is the formula of potassium dichromate?

K2Cr2O7

What colour change occurs during oxidation with dichromate?

Orange to green

Why does dichromate change from orange to green?

Cr2O7 2− is reduced to Cr3+

What determines the oxidation product of an alcohol?

Whether the alcohol is primary secondary or tertiary and the conditions used

What is partial oxidation of a primary alcohol?

Oxidation to an aldehyde

What reagents are used to oxidise a primary alcohol to an aldehyde?

Potassium dichromate and dilute sulfuric acid

What conditions are used to oxidise a primary alcohol to an aldehyde?

Warm gently and distil

Why is aldehyde distilled off during oxidation?

To prevent further oxidation

What functional group change occurs when a primary alcohol forms an aldehyde?

Alcohol to aldehyde

What suffix do aldehydes use?

Al

Why do aldehydes not need a position number?

The CHO group is always on carbon 1

What is the equation for oxidation of propan 1 ol to propanal?

CH3CH2CH2OH + [O] → CH3CH2CHO + H2O

How should aldehydes be written in condensed formulae?

CHO not COH

What is the simplified oxidising symbol used in equations?

[O]

What is the product of oxidising propan 1 ol partially?

Propanal

What is the purpose of distillation in alcohol oxidation?

Separate the aldehyde from the reaction mixture

Where should the thermometer bulb be placed in distillation?

At the T junction to the condenser

Why is water fed into the condenser from the bottom?

For efficient cooling and to prevent backflow

Why are electric heaters used in organic chemistry?

alcohols are highly flammable

Why can the receiving flask be cooled in ice?

To improve yield of distillate

Why should distillate only be collected at the aldehyde boiling point?

To maximise purity and yield

What is full oxidation of a primary alcohol?

Oxidation to a carboxylic acid

What reagents are used to oxidise a primary alcohol to a carboxylic acid?

Potassium dichromate and dilute sulfuric acid

What conditions are used to oxidise a primary alcohol to a carboxylic acid?

Excess dichromate and reflux

What is the equation for oxidation of propan 1 ol to propanoic acid?

CH3CH2CH2OH + 2[O] → CH3CH2COOH + H2O

What is the product of full oxidation of propan 1 ol?

Propanoic acid

What functional group change occurs when a primary alcohol forms a carboxylic acid?

Alcohol to carboxylic acid

What is reflux?

Heating with a condenser to prevent loss of vapours

Why is reflux used?

To heat organic mixtures for long periods

What does the condenser do during reflux?

Condenses vapours back to liquid

Why must the condenser never be sealed?

Pressure buildup could cause explosion

Why are anti bumping granules added?

To ensure smooth boiling

How do anti bumping granules work?

They form small bubbles instead of large bubbles

What is the oxidation product of a secondary alcohol?

Ketone

What reagents oxidise secondary alcohols?

Potassium dichromate and dilute sulfuric acid

What conditions are used to oxidise secondary alcohols?

Heat under reflux

What is the equation for oxidation of propan 2 ol?

CH3CHOHCH3 + [O] → CH3COCH3 + H2O

What is the product of oxidising propan 2 ol?

Propanone

What suffix do ketones use?

One

When do ketones need a number in their name?

When the chain has 5 or more carbons

Can ketones be further oxidised under these conditions?

No

Why can tertiary alcohols not be oxidised by dichromate?

No hydrogen on the carbon bonded to OH

What is dehydration?

Removal of a water molecule

What is the product of alcohol dehydration?

Alkene

What reagents are used for dehydration?

Concentrated sulfuric acid or phosphoric acid

What conditions are used for dehydration?

Warm under reflux

What is the role of sulfuric or phosphoric acid in dehydration?

Dehydrating agent and catalyst

What type of reaction is alcohol dehydration?

Acid catalysed elimination

What is the equation for dehydration of propan 1 ol?

CH3CH2CH2OH → CH2=CHCH3 + H2O

Can some alcohols form more than one alkene during dehydration?

Yes

Why can butan 2 ol form two alkenes?

Double bond can form in different positions

What alkenes can form from butan 2 ol?

But 1 ene and but 2 ene

Which alkene forms more from butan 2 ol dehydration?

But 2 ene

What stereoisomerism can but 2 ene show?

E Z isomerism

What type of reaction converts alcohols to haloalkanes?

Substitution

What reagents convert alcohols to haloalkanes?

Concentrated sulfuric acid and sodium halide

What is the equation for ethanol reacting with HCl?

CH3CH2OH + HCl → CH3CH2Cl + H2O

What is the equation for sodium chloride reacting with sulfuric acid?

NaCl + H2SO4 → NaHSO4 + HCl

What functional group change occurs when alcohols form haloalkanes?

Alcohol to haloalkane

Can other halogenating compounds be used to make haloalkanes from alcohols?

Yes