Alcohols and Ethers AH 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? Acid-catalysed hydration of alkenes (electrophilic addition) Nucleophilic substitution of halogenoalkanes

Reactions of alcohols With metals Dehydration With carboxylic acids 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 Methoxyethane Methoxymethane 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 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