Differentiate between addition and elimination reaction
Answers
Answer:
Elimination and addition reactions differ on how they affect the structure of the molecule.
Elimination reactions will take place if a strong base is present, the reagents are in a protic solvent, and heat is used (although not necessary). A strong base such as hydroxide (HO-), alkoxide (RO-), or amide (H2N-) will do the job nicely. For a molecule to undergo an elimination reaction, a good leaving group must be bonded to the alpha carbon and on the adjacent beta carbon a hydrogen (beta hydrogen). The change in the molecular structure occurs when the base deprotonates the beta carbon, forcing the beta carbon to bond to the alpha carbon. The leaving group will happily leave seeing that it is resonance stabilized or a huge atom (I, Br). You start with an alkane (C-C) and end with an alkene (C=C).
Addition reactions are the complete opposite. You start with an alkene/alkyne and end with a product that has one less bond between the carbons. Take catalytic hydrogenation for example, in order for a reaction to take place there must be a metal catalyst (Ni, Pd, or Pt) and high pressure hydrogen gas. Both reagents must be present for the reaction to occur. The mechanism behind the reaction can get complicated, but in essence the pi bonds between the carbons will bond hydrogens via sigma bonds until the carbon is saturated. You start with an alkene (C=C) and end with an alkane (C-C).
Explanation: