Use of the SADDLE technique to locate a transition state

Optimize the geometry of the reactant(s).
Using the same atoms in the same sequence, optimize the geometry of the products.
To save time, run a LOCATE-TS calculation to move the reactants and products nearer to each other. A typical example would be LOCATE-TS=(C:10,10;)
Run a SADDLE calculation using either the reactant(s) and product(s) or the "first" and "second" geometries from the LOCATE-TS job.
For neatness, format the data-set as follows:
```
GEO_DAT="text" +
GEO_REF="text" +
SADDLE plus other keywords
```
Most calculations end because "both reactants and products are on the same side of the transition state" If this happens, examine the output and find a geometry with a large COSINE. Anything over about 0.7 is good. The smaller the value of "DISTANCE A - B" the better, anything below about 0.2 should be okay. Use that geometry to start a transition state refinement calculation and IRC run.

Animation of reaction	ZIP file	Description
CH₃I + F(-) ⇔I(-) + CH₃F	CH₃I + F(-)	S_N2 reaction in aqueous media

CH₃CHCH₃ ⇔ CH₃CH₂CH₂	CH₃CHCH₃	Hydrogen atom migration

CH₃COOH + CH₃CH₂OH ⇔ CH₃COOCH₂CH₃ + H₂O	Ester	Ester hydrolysis in aqueous media

1,5-hexadiene ⇔ 1,5-hexadiene	Cope	1,5 Hexadiene Cope re-arrangement

CH₃-CHOH=CH₂ ⇔ CH₃-CO-CH₃	Keto-Enol	Acetone keto - enol tautomerization


isochorismic acid t⇔ pyruvic plus salicylic acids	Isochorismic acid	Retro-ene elimination
[HCO-CH-CH₃]^- + [C₅H₅N-CH₃]⁺⇔ HCO-CH=CH₂ + C₅H₆N-CH₃	SADDLE for Hydride transfer	Hydride transfer from a methyl group on propionaldehyde anion to the para or C₄ carbon on the pyridinium cation. This reaction, although interesting, was particularly difficult to model.
Butane plus butyl ⇔ butyl plus butane	Butane + butyl	A narcissistic reaction in which a hydrogen atom migrates from a n-butane molecule to a n-butyl radical