Alkenes

• The Cahn-Ingold-Prelog priority rules are used to deduce the full IUPAC name
• In the Cahn-Ingold-Prelog rules, an atom with a higher atomic number takes priority.
• Steps to determine the priority groups using the Cahn-Ingold-Prelog rules

  1️⃣ Consider the groups attached to the left-hand carbon of the C=C bond

  2️⃣ Consider the groups attached to the right-hand carbon of the C=C bond

  3️⃣ Determine the higher priority groups on each carbon

  4️⃣ Check if the higher priority groups are on the same side of the C=C bond

  5️⃣ Assign the Z or E isomer
• If the higher priority groups are on the same side of the C=C bond, it is the Z-isomer.
• Match the type of reaction with its description:

  Addition reaction ↔️ A small molecule is added across the C=C bond

  Electrophilic addition ↔️ Reaction with an electron pair acceptor
• Electrophiles are attracted to the high electron density of the C=C bond in alkenes.
• A curly arrow shows the movement of a pair of electrons.
• What is the observation when bromine reacts with ethene?

  Orange to colourless
• In the reaction of bromine with ethene, bromine acts as the electrophile.
• Bromine is used to test for the presence of a C=C group in a molecule.
• Hydrogen halides (HX) react with alkenes via electrophilic addition.
• What are the two possible products when propene reacts with hydrogen chloride?

  1-chloropropane and 2-chloropropane
• In hydrogen halides, the hydrogen atom is always δ+ due to the permanent dipole.
• When ethene reacts with concentrated sulfuric acid, the product is ethane hydrogensulfate.
• What is the definition of hydrolysis?

  The breaking of a bond using water
• The hydration of alkenes to form alcohols requires steam and a phosphoric acid catalyst.
• Order the stability of carbocations from most stable to least stable

  1️⃣ Tertiary (3°)

  2️⃣ Secondary (2°)

  3️⃣ Primary (1°)
• Unsymmetric alkenes produce two different organic products upon electrophilic addition.
• In the addition of HBr to propene, which carbocation is more stable?

  2° carbocation
• The major product in electrophilic addition to unsymmetrical alkenes is formed via the more stable carbocation.