PR - CI12.2 Alkenes

• Have a C=C double bond
• Unsaturated hydrocarbons
• With ending -ene eg. ethene
• BP increases with chain length
• General formula - CnH2n
• Can get cycloalkenes which are dienes eg. penta-1,3-diene

Shapes of Alkenes

• Flat molecule with bond angles of 120 degrees
• Tetrahedral arrangement around non-double bonded C
• Planar arrangement around C=C

Chemical Reactions

• 4 electrons around the C=C give a higher than normal density of electrons (-ve charge)
• +ve ions are attracted to the C=C and can accept a pair…