One can predict by which mechanism a reaction will occur, Sn2 or Sn1, by the substrate's order( i.e. primary, secondary, or tertiary carbon) and by the strength of the nucleophile. How can I tell if a nucleophile is strong or weak? For instance, one problem showed methanol combining with cyclohexyl bromide. I thought the methoxide would be a strong nucleophile but it was in fact weak and went through the Sn1 mechanism instead of Sn2. How could I tell if it is strong or weak. Thanks.