Primary alkyl halide are those in which halogen is attached to that carbon which is attached to only one other carbon. Primary alkyl halides usually undergo [tex]S_N2[/tex] (bimolecular nucleophilic substitution) mechanism (in which nucleophiles attack from the backward direction) and rarely [tex]E2[/tex] (bimolecular elimination) mechanisms.
1-bromo-2-methylpropane (isobutyl bromide), [tex](CH_3)_2CHCH_2Br[/tex] is a primary alkyl halide which on reacting with strong base, both products are formed from [tex]S_N2[/tex] and [tex]E2[/tex] mechanism. As methoxide ion is a good nucleophile formed from the strong base methanol. The reaction is shown in the image.
The products formed are 1-methoxy-2-methylpropane (from [tex]S_N2[/tex] mechanism) and 2-methylpropene (from [tex]E2[/tex] mechanism).
