ELECTROPHILLIC ADDITION

• WHY DO ALKENES EXHIBIT E/Z ISOMERISM?

  restriction of rotation in pi bond
• TEST FOR ALKENE?

  bromine water
• WHAT RESULT WILL BE OBTAINED IF ALKENES ARE PRESENT WHILE USING BROMINE WATER?

  reddish-brown -> colourless
• WHAT ARE MORE REACTIVE ALKENES OR ALKANES?

  alkenes
• BOND ENTHALPY OF C-C BOND?

  347 kJ/mol
• PREDICTED BOND ENTHALPY OF C=C BOND?

  694 kJ/mol (347 x 2)
• ACTUAL BOND ENTHALPY OF C=C BOND?

  612 kJ/mol
• BOND ENTHALPY REQUIRED FOR A PI BOND TO UNDERGO FISSION?

  265 kJ/mol (612-347)
• WHAT TYPE OF BOND IS WEAKER PI OR SIGMA BOND?

  pi
• WHAT IS THE MAIN REACTION OF ALKENES?

  electrophilic addition reaction
• WHAT DO ELECTROPHILES DO?

  accept electron pair
• WHAT ARE ELECTROPHILES ATTRACTED TO?

  high electron density (C=C bond)
• EXAMPLES OF TYPES OF ELECTROPHILES?

  positive ions, regions of partial charges, included in partial charges
• EXAMPLES OF ELECTROPHILES?

  Br2, HBr, NO2+, H2O
• WHAT HAPPENS WHEN AN ELECTROPHILE REACTS WITH AN UNSYMMETRICAL ALKENE?

  mix of products formed
• WHAT PRODUCT IS THE MAJOR PRODUCT IN ELECTROPHILIC ADDITION REACTIONS?

  more stable compounds (primary < secondary < tertiary)
• WHAT ARE ALKYL GROUPS?


  alkanes with one lost H atom
• WHAT CAN ALKYL GROUPS BE REPLACED WITH?

  R
• GENERAL FORMULA OF ALKYL GROUPS?

  CnH2n+1
• WHAT ARE PRIMARY CARBOCATIONS?

  one alkyl group attached to positive carbon
• WHAT ARE SECONDARY CARBOCATIONS?

  two alkyl groups attached to positive carbon
• WHAT ARE TERTIARY CARBOCATIONS?

  three alkyl groups attached to positive carbon
• HOW DOES STABILITY CHANGE WITH CARBOCATIONS?

  increases down (primary -> secondary -> tertiary)
• EFFECT OF INCREASING STABILITY WITH CARBOCATIONS NAME?

  positive inductive effect
• POSITIVE INDUCTIVE EFFECT?

  alkyl groups contain greater higher electron density than H atoms
• CONDITIONS OF ELECTROPHILIC ADDITION REACTIONS?

  concentrated H2SO4, cold (room temperature)
• HOW IS H2SO4 WRITTEN IN ELECTROPHILIC ADDITION REACTIONS?

  H & O-SO2-OH