Sir, How can I predict whether a reaction will undergo an SN2 mechanism or E2 mechanism?

hi,

the E2 mechanism is analogous to the Sn2 . and both competes . usually  in most of the cases we get both the substituition as well as elimination product . the ratio of E : S varies , which depends upon certain factors

 normally all nuclephiles are base . but when we have good nucleophiles Sn2 is favoured . &when we have strong bases E2 is favoured.

it also depends upon how acidic the H , which is attatched to the adjacent C , is.

if it is more acidic than obviously we will get a favoured  Ellimination product.