11.5 Reaction Mechanisms

When a covalent bond breaks and one of the bonded atoms takes both the electrons from the bond

When the electronegativity difference between the two atoms or compounds is large

When a covalent bond breaks and each of the bonded atoms takes one of the shared pair of electrons from the bond Each atom has an impaired electron

When the electronegativity is similar or the same

An an atom or group of atoms with an unpaired electron Dot next to compound

Movement of a pair of electrons

• must begin at a lone pair electron on an atom OR • must begin from a bond that is about the be broken • should point at a new bond forming (an atom that will share electrons OR • point at atoms taking both electrons from a bond and gaining a lone pair

Draw a half arrow to each atom to show one electron going to each element

Addition reaction - adding more molecules, 2 reactants join to form 1 product Substitution - atom or group of atoms replaced by an atom or group of atoms Elimination - removing a small molecule from a larger one

Homolytic fission

Direct overlap of the s orbitals directly between the bonded atoms

• sigma bonds are the direct overlap of s-orbitals while pi bonds are the sideways overlap of p-orbitals • sigma bonds have electron density between bonded atoms, pi bonds have electron density above and below bonding atoms

Its functional group