4.4 Alcohols

• What do alcohols contain at least one of?

  Hydroxy (-OH) group
• What is the general formula of alcohols?

  C$n$H$2n+$$1$OH
• How can alcohols be prepared?

  By a wide range of chemical reactions
• What type of bonding occurs in alcohols?

  Hydrogen bonding
• What elements must hydrogen be attached to for hydrogen bonding?

  Fluorine, oxygen, or nitrogen
• What causes hydrogen atoms in alcohols to be slightly positive?

  Electrons are pulled towards electronegative oxygen
• What intermolecular forces are present in alkanes?

  Temporary induced dipole-dipole forces
• Why do alcohols have higher boiling points than alkanes?

  Hydrogen bonds are stronger than induced dipoles
• What is the boiling point of propane?

  -42 °C
• What is the boiling point of propanol?

  97 °C
• How do boiling points of alcohols change with carbon chain length?

  Boiling points increase with more carbon atoms
• Why does solubility of alcohols in water decrease with longer chains?

  Hydrocarbon chains disrupt hydrogen bonds in water
• What are primary alcohols?

  Alcohols with -OH group attached to one carbon
• What are secondary alcohols?

  Alcohols with -OH group attached to two carbons
• What are tertiary alcohols?

  Alcohols with -OH group attached to three carbons

  
• What do primary alcohols oxidize to form?

  Aldehydes
• What do secondary alcohols oxidize to form?

  Ketones

  
• What do tertiary alcohols undergo?

  They do not undergo oxidation
• What are common oxidizing agents for alcohols?

  Acidified K$2Cr2O7$ and KMnO$4$
• What color change occurs with acidified potassium dichromate when oxidizing alcohols?

  Orange to green

  
• What color change occurs with acidified potassium manganate when oxidizing alcohols?

  Purple to colorless
• How is an aldehyde distilled during oxidation?

  It has a lower boiling point than alcohol
• What happens if an aldehyde is not distilled off during oxidation?

  It can be oxidized to a carboxylic acid
• What happens to ketones during oxidation?

  They cannot be further oxidized
• What is dehydration in the context of alcohols?

  Formation of alkenes by removing water

  
• What small molecule is eliminated during dehydration of alcohols?

  Water
• What catalyst is used for dehydration of alcohols?

  Aluminium oxide or concentrated acids

  
• What is formed when ethanol undergoes dehydration?

  Ethene gas

  
• What occurs in the substitution reaction of alcohols?

  Hydroxy group is replaced by a halogen
• What is the result of substituting an alcohol with HX?

  Formation of haloalkanes
• What is an alternative method to produce bromoalkanes?

  Using phosphorus tribromide (PBr$3$)
• What happens when PBr$3$ is added to ethanol?


  It reacts vigorously to form bromoethane
• What is the hydrolysis reaction of PBr$3$?


  PBr$3$ reacts with water to produce HBr
• What are the properties of alcohols?

  • Contain hydroxy (-OH) group
  • Exhibit hydrogen bonding
  • Higher boiling points than alkanes
  • Solubility decreases with longer chains
• What are the classifications of alcohols?

  • Primary alcohols: -OH attached to one carbon
  • Secondary alcohols: -OH attached to two carbons
  • Tertiary alcohols: -OH attached to three carbons

  
• What are the reactions of alcohols?

  • Combustion: forms CO$2$ and water
  • Oxidation: forms aldehydes, ketones, or carboxylic acids
  • Dehydration: forms alkenes
  • Substitution: forms haloalkanes
• What are the oxidizing agents for alcohols?

  • Acidified potassium dichromate (K$2Cr2O7$)
  • Acidified potassium manganate (KMnO$4$)
• What are the color changes of oxidizing agents during alcohol oxidation?

  • K$2Cr2O7$: orange to green
  • KMnO$4$: purple to colorless
• What are the mechanisms of alcohol reactions?

  • Aldehyde formation: distillation after oxidation
  • Ketone formation: no need for immediate distillation
  • Dehydration: water is eliminated to form alkenes

  
• What are the methods for substitution reactions of alcohols?

  • Reacting with HX
  • Using phosphorus tribromide (PBr$3$)