Organic Mechanisms (SME)

• What is homolytic fission?

  Breaking a bond to form two radicals

  
• What is heterolytic fission?

  Breaking a bond where one atom takes both electrons

  
• How does heterolytic fission differ from homolytic fission?

  Heterolytic fission forms ions, homolytic forms radicals

  
• What is a nucleophile?

  An electron-rich species that donates electrons
• What does 'nucleophile' mean?

  'Nucleus/positive charge loving'
• What is an electrophile?

  An electron-deficient species that accepts electrons
• What does 'electrophile' mean?

  'Electron/negative charge loving'
• What is an addition reaction?

  Two molecules combine to form a single product
• What is a substitution reaction?

  Replacing an atom or group with another

  
• What is an elimination reaction?

  Removing a small molecule from an organic molecule
• What is a hydrolysis reaction?

  Breaking down a compound by water
• What is a condensation reaction?

  Two molecules join and eliminate small molecules
• What is an oxidation reaction?

  Adding oxygen or removing hydrogen atoms
• What is a reduction reaction?

  Removing oxygen or adding hydrogen atoms
• What does the symbol [O] represent in organic redox reactions?

  One atom of oxygen from an oxidising agent
• What does the symbol [H] represent in organic redox reactions?

  One atom of hydrogen from a reducing agent
• What do curly arrows represent in organic reaction mechanisms?

  Movement of electron pairs
• Where do curly arrows begin and point in a reaction mechanism?

  Start at a bond or lone pair, point to acceptor
• What is a free radical?

  A species with unpaired electrons

  
• What are the three steps of a free radical reaction?

  Initiation, propagation, termination

  
• What occurs during the initiation step of a free radical reaction?

  Breaking a bond using UV light to form radicals

  
• What happens during the propagation step of a free radical reaction?

  Radicals attack reactant molecules to form more radicals

  
• What occurs during the termination step of a free radical reaction?

  Two free radicals react to form a product

  
• What is the mechanism of free radical substitution?

  Initiation, propagation, termination

  
• What is a nucleophilic substitution reaction?

  A nucleophile attacks a carbon with a partial positive charge

  
• Why is a hydroxide ion a better nucleophile than water?

  It has a full formal negative charge

  
• Why do halogenoalkanes undergo nucleophilic substitution reactions?

  Due to the polar C-X bond

  
• What happens in the nucleophilic substitution reaction of bromoethane with aqueous alkali?

  The halogen is replaced by a nucleophile, OH

  
• What is an elimination reaction in organic chemistry?

  A small molecule is removed, forming an alkene
• What occurs during the elimination reaction of bromoethane with ethanolic sodium hydroxide?

  The C-X bond breaks heterolytically, forming an alkene

  
• What is electrophilic addition?

  Two reactants form only one product

  
• Why are alkenes reactive in electrophilic addition reactions?

  The C=C double bond is electron-rich

  
• What happens when alkenes react with hydrogen halides?

  They form halogenoalkanes

  
• What determines the product formed from an asymmetrical alkene in electrophilic addition?

  The stability of the carbocation intermediate

  
• What is the order of stability for carbocations?

  Tertiary > secondary > primary
• Why is the secondary halogenoalkane the major product in electrophilic addition?

  Because a secondary carbocation is more stable