alkenes

• sigma bond definition 


  when 2 orbitals overlap in a straight line giving a high charge density

  this means that there is strong electrostatic attraction between the nuclei and the bonding pair
• what is a pi bond

  when orbitals overlap sideways

  electron density is spread out meaning the electrostatic attraction is weak
• types of carbon bond

  C-C sigma bond

  C=C sigma and pi bond
• C=C bond is less than twice as strong as C-C bond
• why is a double bond weaker than a single bond

  a double bond contains a pi bond which is a weaker bond

  this is because the electrons are spread out in a larger area
• a C=C bon restricts rotation so the p orbital overlaps
• cis 


  same group are on the same side of a double bond
• trans 


  groups are on opposite sides
• E/Z only occurs 


  if there is a C=C bond

  each C is bonded to a different atom or group
• E 


  atom or groups are on opposite sides
• Z 


  atoms or groups on the same side
• what are the CIP rules

  atoms which have a larger atomic number are given higher priority

  cis/trans for same group

  E/Z for different groups