Alcohols and EthersAH Chemistry Unit 3(b)

Alcohols

Physical properties• When comparing the boiling point of

ethanol with an alkane, which alkane would you compare it with?

• Which would have the higher boiling point?

• Why?

• Alcohols exhibit hydrogen bonding.

• As a result, they exhibit higher boiling points than (most) other organic compounds of similar molecular mass.

• Which is more soluble in water: ethanol or hexan-1-ol?

• Why?

• The lower alcohols are miscible with water but as their chain length increases their solubility in water decreases.

Preparation of alcohols• There are 2 principle methods for

producing alcohols in industry. What are they?

1. Acid-catalysed hydration of alkenes (electrophilic addition)

2. Nucleophilic substitution of halogenoalkanes

Reactions of alcohols• With metals

– produces alkoxides• Dehydration

– produces alkenes• With carboxylic acids

– produces esters, slowly• With acid chlorides

– produces esters, more vigorously

Acid chlorides

Carboxylic acids can be converted into acid chlorides by reaction with:

– Thionyl chloride– Phosphorus(III) chloride– Phosphorus(v) chloride

Producing esters• Use full structural formulae to illustrate

how ethyl propanoate can be produced from an alcohol and an acid chloride.

• What type of reaction is this?

Ethers

General formula

Uses• Solvents

• Reasons:– Dissolve many organic compounds– Volatile (so removed easily by distillation)

Preparation of ethers• Q: How can you prepare an ether in the

lab?

• A: Reaction of a halogenoalkane with a metal alkoxide.

• Q: What type of reaction is this?

• A: Nucleophilic substitution

Naming ethers

Methoxymethane

Methoxyethane

Ethoxypropane

Naming Ethers• Name the longest continuous chain e.g.

pentane

• Name the alkoxy group by removing “yl” from the substituent name and adding “oxy” e.g. propyl becomes propoxy

• Add the appropriate number in front of the substituent if the ether is branched e.g. 3

• Name a halogenoalkane and metal alkoxide combination you could use to prepare ethoxybutane.

• Name a halogenoalkane and metal alkoxide combination you could use to prepare 2-ethoxybutane.

• Name the ether produced by reacting 1-chloropropane with sodium ethoxide.

Physical properties – mp / bp• How do the melting and boiling points

of ethers compare to alcohols?

• Why?

Physical properties - solubility• Why are ethers of low molecular mass

soluble in water?

Chemical properties• Flammable

• Form peroxides on exposure to air / light (these are unstable and explosive) e.g. ethoxyethane peroxide