Producing Alcohols (CIE AS Chemistry)

Revision Note

Philippa Platt

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Production of Alcohols

  • Alcohols are compounds that contain at least one hydroxy (-OH) group
  • The general formula of alcohols is CnH2n+1OH
  • Alcohols can be prepared by a wide range of chemical reactions

Electrophilic addition of alkenes

  • When hot steam is reacted with an alkene, using concentrated phosphoric(VI) acid (H3PO4)as a catalyst, electrophilic addition takes place to form an alcohol

 

The electrophilic addition of ethene using water

Hydroxy Compounds Electrophilic Addition, downloadable AS & A Level Chemistry revision notes

Electrophilic addition of steam to alkenes forms alcohols

Oxidation of alkenes

  • Cold, dilute KMnO4 is a mild oxidising agent and oxidises alkenes
  • The C-C double bond is not fully broken and a diol is formed
    • A diol is a compound with two hydroxy, -OH, groups

 Oxidation of ethene using cold, dilute KMnO4

Hydroxy Compounds Oxidation, downloadable AS & A Level Chemistry revision notes

The oxidation of alkenes using cold, dilute KMnO4 forms a diol

Nucleophilic substitution of halogenoalkanes

  • The halide atom in halogenoalkanes can be substituted when heated with aqueous NaOH in a nucleophilic substitution reaction

 Nucleophilic substitution of bromoethane using NaOH

Hydroxy Compounds Nucleophilic Substitution, downloadable AS & A Level Chemistry revision notes

The nucleophilic substitution of halogenoalkanes using NaOH forms an alcohol

Reduction of aldehyde & ketones

  • Aldehydes and ketones can be reduced by reducing agents such as NaBH4 or LiAlH4 
  • Aldehydes are reduced to primary alcohols
    • The carbon attached to the hydroxy group is bonded to one other alkyl group

  • Ketones are reduced to secondary alcohols
    • The carbon attached to the hydroxy group is bonded to two other alkyl groups

 The reduction of ethanal and propanone

Hydroxy Compounds Reduction, downloadable AS & A Level Chemistry revision notes

The reduction of aldehydes and ketones forms primary and secondary alcohols respectively

Reduction of carboxylic acids

  • Similarly, carboxylic acids are reduced by LiAlH4 to primary alcohols
  • NaBH4 is not used as it is not a strong enough reducing agent for this reaction

 

The reduction of ethanoic acid

ethanoic-acid-reduction-lialh4

The reduction of carboxylic acids forms primary alcohols

Hydrolysis of ester

  • Esters are made by a condensation reaction between an alcohol and a carboxylic acid
  • When an ester is heated with dilute acid or alkali, hydrolysis will take place and the carboxylic acid and alcohol will be reformed

 

Acidic and alkaline hydrolysis of ethyl ethanoate

acidic-and-alkaline-hydrolysis-of-ethyl-ethanoate

The hydrolysis of esters forms alcohols

Alcohol production reactions table

Reaction Type Reagents Conditions  Product
Electrophilic addition Alkene
Steam

Heat 

H3PO4 catalyst

Alcohol
Oxidation Alkenes
Cold, dilute KMnO4
Shaking of reagents Diol
Nucleophilic substitution Halogenoalkanes
Aqueous NaOH
Heat Alcohol
Reduction Aldehydes / ketones LiAlH4 or NaBH4 Primary / secondary alcohol
Reduction Carboxylic acid LiAlH4 Primary alcohol
Hydrolysis Esters

Dilute acid or alkali

Heat

Alcohol

Examiner Tip

The symbol [O] is used to represent oxygen provided by an oxidising agent

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Philippa Platt

Author: Philippa Platt

Expertise: Chemistry

Philippa has worked as a GCSE and A level chemistry teacher and tutor for over thirteen years. She studied chemistry and sport science at Loughborough University graduating in 2007 having also completed her PGCE in science. Throughout her time as a teacher she was incharge of a boarding house for five years and coached many teams in a variety of sports. When not producing resources with the chemistry team, Philippa enjoys being active outside with her young family and is a very keen gardener.