Secondary alkyl:
Secondary alkyl halides can go through both SN2 and E2 reactions to provide mixture halides of products. Though, the substitution product predominates if a polar aprotic solvent is employed and nucleophile is a weak base. The Elimination will predominate if a strong base is employed as the nucleophile in a polar, protic solvent. In this case, bulky bases are not that much crucial and the use of ethoxide in ethanol will give more elimination product as compared to the substitution product. Rising the temperature of the reaction favors E2 elimination over SN2 substitution as described above.
If weakly basic or nonbasic nucleophiles are employed in protic solvents, elimination and substitution may take place by the SN1 and E1 mechanisms to provide mixtures.