Alcohols and Ethers AH Chemistry Unit 3b Alcohols

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? 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 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 a halogenoalkane and metal alkoxide combination you could use to prepare 2 ethoxybutane. • Name the ether produced by reacting 1 chloropropane with sodium ethoxide.