4.1.3 - Alkenes

• What is cis-trans isomerism?

  A type of E/Z isomerism with same substituents
• According to CIP priority rules, where are the highest priority substituents in cis isomers?

  On the same side of the double bond
• How do trans isomers differ from cis isomers according to CIP rules?

  They have highest priority substituents on opposite sides
• What is a covalent bond?

  A strong bond formed by shared electrons
• What causes the shape of a molecule according to electron pair repulsion?

  Electron pairs position as far apart as possible
• What shape do carbon atoms in alkanes adopt?

  Trigonal planar shape
• What is the bond angle in a trigonal planar shape?

  120°
• What is an electrophile?

  An electron pair acceptor
• What occurs during electrophilic addition?

  A π bond breaks and new σ bonds form
• What is E/Z isomerism caused by?

  Restricted rotation of π bonds
• What must be attached to each carbon atom of the C=C group for E/Z isomerism?

  Two different groups
• How do Z isomers differ from E isomers according to CIP rules?

  Z isomers have highest priority on the same side
• What is heterolytic fission?

  One atom receives both electrons from a bond
• What is a hydrocarbon?

  A compound with carbon and hydrogen only
• What does Markownikoff's Rule predict?

  The major product of an addition reaction
• How does H attach according to Markownikoff's Rule?

  To the less substituted carbon
• What is a monomer?

  A small molecule forming polymers
• What does photodegradable mean?

  Can be broken down by light
• What is a polymer?

  A large molecule made from small units
• What is a primary carbocation?

  Carbon with positive charge attached to one alkyl group
• Why is a primary carbocation the least stable?

  It has the least alkyl groups attached
• What is a repeat unit in a polymer?

  A structure that appears repeatedly in a polymer
• What is a secondary carbocation?

  Carbon with positive charge attached to two alkyl groups
• How does the stability of a secondary carbocation compare to a primary carbocation?

  More stable than primary, less than tertiary
• What is a tertiary carbocation?

  Carbon with positive charge attached to three alkyl groups
• Why is a tertiary carbocation the most stable?

  It has the most alkyl groups attached
• What is a σ-bond?

  A covalent bond formed by head-on overlap
• What is a π-bond?

  A covalent bond formed by sideways overlap
• Why are alkenes more reactive than alkanes?

  Alkenes have low bond enthalpy π-bonds
• What is addition polymerisation?

  Formation of a long chain molecule from monomers
• What is an addition reaction?

  A reaction where molecules combine to form one product
• What is an alkene?

  An organic compound with a C=C double bond
• What does biodegradable mean?

  Can be decomposed by living organisms
• What is bond enthalpy?

  Energy required to break one mole of bonds
• How do actual bond enthalpies differ from average bond enthalpies?

  Actual values may vary in different molecules
• What are the Cahn-Ingold-Prelog (CIP) priority rules?

  Rules to identify E or Z stereoisomers
• How do atoms with higher atomic numbers relate to CIP rules?

  They have higher priority in isomer identification
• What determines if a stereoisomer is E or Z?

  Position of highest priority substituents
• What is a catalyst?

  A substance that increases reaction rate
• What are stereoisomers?

  Compounds with same formula, different arrangements