SN1 and SN2 reactions

[mays8014]

HI!

When I'm given a reaction, and need to determine whether it undergoes Sn1 or Sn2, I almost always get it wrong. Is there an easy way to figure these ones out?

[mcat_premed3832]

Here is a flow chart (ignore E1, E2 because alkene chemistry is no longer part of the new MCAT): http://www.brynmawr.edu/Acads/Chem/mnerzsto/SN2vsE2_flowchart.htm

Here are 3D representations: www.colby.edu/chemistry/OChem/DEMOS/Substitution.html