Chemistry notes

INTRODUCTION
• A chemical reaction is the transformation of one chemical substanc
collection of chemical substances into another
• A chemical reaction involves making new chemical bonds and
breaking old chemical bonds
• A chemical reaction can be assessed on the basis of
(a) The type of reaction
(b) The mechanism of the reaction

,MECHANISM OF A CHEMICAL
REACTION
• A reaction mechanism is an overall description of how a reaction
occurs
• It describes in details exactly what occurs at each stage of a chemic
transformation
➢Which bonds are broken
➢Which bonds are formed
• It involves a detailed explanation of the electron movement in the
course of chemical reactions
• It must account for all reactants used and all products formed

,MECHANISM OF A CHEMICAL
REACTION CONT’D
• A reaction mechanism is a reasonable, stepwise illustration of how
electrons in the bonds of the reactants of a reaction are reorganized
into its products under a given set of reaction conditions
• Bond breaking and bonding are involved in an organic reaction

, THE BREAKING OF BONDS
❖BOND FISSION
o TYPES: (i) Homolytic Fission (Homolysis) (ii) Heterolytic Fission
(Heterolysis)
o Homolytic Fission
➢If the bond breaks in such a way that each of the two departing atom
goes away with one of the bonding pair of electrons to form free
radicals