6 2:
Red ball represents the incoming hydroxide ion and green ball represents
the outgoing halide ion
In the year 1937,
Edward Davies Hughes
and Sir Christopher
Ingold 
proposed 
mechanism for an SN2a
reaction The solid wedge represents the bond coming out of the paper, dashed line going down the
paper and a straight line representing bond in the plane of the paper Rationalised 2023-24
172
Chemistry
single step and no intermediate is formed