7.2. Reactions of Alkenes and Alcohols

• What is the general formula for alkenes?

  C$n$H$2n$
• Why are alkenes considered unsaturated?

  Because they have at least one carbon-carbon double bond
• What are the first four alkenes?

  • Ethene
  • Propene
  • Butene
  • Pentene
• How can unsaturated carbons be represented?

  • Chemical formulae
  • Structural formulae
  • Chemical structure
• What is the functional group of alkenes?

  C=C
• What is a characteristic of alkenes when they burn in air?

  They tend to burn with smoky flames due to incomplete combustion
• What is formed during incomplete combustion of alkenes?

  Carbon or carbon monoxide (CO)
• What happens to the double bond in alkenes during reactions with hydrogen, water, and halogens?

  The double bond is broken to form a single carbon-carbon bond
• What is the product when ethene reacts with bromine (Br$_2$)?


  1,2- dibromoethane

  
• What are the key points about reactions of alkenes with hydrogen, water, and halogens?

  • The C=C bond is broken to form a C-C bond
  • The added compound splits into two groups
  • Each group is added to different carbons in the C=C bond
• What functional group do alcohols contain?

  –OH
• What are the first four alcohols?

  • Methanol
  • Ethanol
  • Propanol
  • Butanol
• What do alcohols produce when they burn in air?

  Carbon dioxide and water
• What happens when alcohols dissolve in water?

  They form a neutral solution with a pH of 7
• What do alcohols produce when they react with sodium?

  Hydrogen and a salt
• What do alcohols react with to form carboxylic acids?

  Oxidising agents
• What are the uses of methanol, ethanol, propanol, and butanol?

  • Methanol: chemical feedstock, anti-freeze, biodiesel
  • Ethanol: main alcohol in drinks, solvent, fuel
  • All four can be used as fuels
• How can ethanol be produced?

  By fermentation of sugar with yeast
• What are the conditions for producing ethanol by fermentation?

  About 35°C, anaerobic, and yeast enzyme catalyst
• What is the equation for the fermentation of sugar to produce ethanol?

  Sugar → ethanol + carbon dioxide
• What is the functional group of carboxylic acids?

  –COOH
• What are the first four carboxylic acids?

  • Methanoic acid
  • Ethanoic acid
  • Propanoic acid
  • Butanoic acid
• How do carboxylic acids react in water?

  They dissolve to produce acidic solutions
• What do carboxylic acids produce when they react with metal carbonates?

  Carbon dioxide, a salt, and water
• What happens when carboxylic acids react with alcohols in the presence of an acid catalyst?

  They produce esters
• What is a characteristic of carboxylic acids in solution?

  They do not ionise completely, making them weak acids
• How does the pH of carboxylic acids compare to strong acids of the same concentration?

  They have a higher pH (less acidic)