IONS, particularly \[A{{G}^{+}}\] catalyse \[{{S}_{N}}1\] reaction because of the presence of empty ORBITAL.\[C{{H}_{3}}C{{H}_{2}}Br+A{{g}^{+}}\rightleftharpoons {{[C{{H}_{3}}C{{H}_{2}}\CDOT \cdot \cdot X\cdot \cdot \cdot Ag]}^{+}}\] \[\xrightarrow[(-AgX)]{slow}C{{H}_{3}}CH_{2}^{+}\xrightarrow[from\,{{H}_{2}}O]{O{{H}^{-}}}C{{H}_{3}}C{{H}_{2}}OH\]