Molecule that contains the leaving group a carbon

Molecule that contains the leaving group a carbon must be sp 3 If a carbon is tertiary, then SN 1, E 1, or E 2 is possible. If a carbon is secondary, then SN 1, SN 2, E 1, or E 2 is possible. If a carbon is primary, then SN 2 is possible. E 2 is also possible if the base is very bulky like KOt. Bu. If a carbon is methyl, then only SN 2 is possible. Special cases do exist due to resonance or steric factors, here are some possibilities SN 2 is VERY UNLIKELY due to steric hindrance SN 1 or SN 2 due to resonance

Molecule that does not contain the leaving group E 1 SN 2 Cl- H 2 SO 4 Ts. OH H 2 O H 3 PO 4 Strong Acid Non-nucleophilic ROH RSH E 2 RSi. Pr. OHOMe. O- Br. I- Strong Base Weak Base Moderate Base Weak Nucleophile Strong Nucleophile Hindered Nucleophile Strong Base Weak Base Strong Nucleophile In case of tie, think right. SN 2 SN 1, SN 2, E 1, E 2 SN 1 SN 2 is to the right of SN 1

FLOW CHART FOR SN 1/SN 2/E 1/E 2 No Is there a good leaving group? No Is the alpha carbon sp 3? No Is the alpha C tertiary? No Is the alpha C secondary? Nonnucleophilic acid like sulfuric acid, phosphoric acid, or tosic acid Yes E 1 No No Reaction Yes E 2 No Yes SN 2 No Nonnucleophilic acid like sulfuric acid, phosphoric acid, or tosic acid No Non basic nucleophile like ROH, N 3 -, I-, Br- Cl- No Good nucleophile present like RS-, N 3 -, I-, Br- Cl- No Yes Is KOt. Bu or other very hindered base present? Yes E 2 Is the alpha C methyl? No Yes Is there a strong base present? Yes Proton Acid Base Reaction Is the alpha C primary? Yes Is there a strong or moderate base present, such as RO- or NH 3 or NC-? Yes Is there a strong or moderate base present, ie RO- or NH 3? Yes No SN 1/SN 2/E 1 E 2 is possible but rare No Reaction Yes No No Is there strong acid present to make one? Yes E 1 Yes Good nucleophile present like RS-, N 3 -, I-, Br-, Cl-, including strong bases like RO- and deprotonated terminal acetylenes No No Reaction SN 1 No No Is a weak nucleophile like water or an alcohol present ? Yes SN 1 Yes