•Find the transition state and calculate the barrier height for CH3F + F− → CH3F + F− with following model.

Model: Gas/Microsolvation/Continuum Model ( PCM, sovlent=Water )

Method: MP2/aug-cc-pVDZ

 

SN2

Gas phase	EB.O.(kcal/mol)	Microsolvation	EB.O.(kcal/mol)	Continuum model	EB.O.(kcal/mol)
CH3F	-87485.6	CH3F	-87485.6	CH3F	-87487.8
F-	-62541.3	F-+H2O	-110422.6	F-	-62624.8
TS	-150029.1	TS	-197899.5	TS	-150092.7
Barrier height	ΔEB.O.(kcal/mol)		ΔEB.O.(kcal/mol)		ΔEB.O.(kcal/mol)
	-2.1		8.7		20.0

 

-->According to the results, as the number of water molecules increases, the barrier height becomes larger.

 

Gas:

Microsolvation: 反應物(右)-因為水是加在F^-

Continuum Model: 把水分子看成是一種連續而沒有結構的介質

(Continuum model :溶質分子的電荷分布極化了溶劑分子，此極化作用產生了一個電場稱為 Reaction Field，此電場與溶質分子的電荷分布作用進一步降低了溶質分子的能量)

(溶劑效應是因為溶劑被極化，產生了一個電場稱為 Reaction Field，溶質電子結構會被電場影響)

 

log檔

Microsolvation

Contiuummodel

GAS

 

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Continuum model's input:   

SCRF， 其中 R 代表 Reaction Field