hw_11

•Calculate the k(rate constant) in different temperature for the following reaction and plot of ln(k) versus 1000/T then compare with the experimental values.

reaction ： method：

CH₄ +OH^․→ H₂O + CH₃^․MP2/aug-cc-pVTZ

NH₃ +OH^․→ H₂O + NH₂^․CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ

Calculation rate constant(k) K_B=1.38066E-23 h=6.62608E-34 Kº=4.0625E+3

k=(1.38066E-23*T/6.62608E-34)*24465/6.02214E+23*EXP(-(barrier*4184)/8.31451*T))

Step3:

Compare the differences by using the different Electronic Energies from MP2/aug-cc-pVTZ、CCSDT/aug-cc-pVTZ//MP2/aug-cc-pVTZ

Result

CH₄ +OH^․→ H₂O + CH₃^․

^{barrier heigh}

temp.	MP2/aug-cc-pVTZ	CCSDT/aug-cc-pVTZ//MP2/aug-cc-pVTZ
273K	11.1	9.3
298.15K	11.6	9.8
600K	17.3	15.6

ln(K) unit:kcal/mole

temp.	MP2/aug-cc-pvTZ	CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ	exp.
273K	-35.7	-32.4	-33.2
298.15K	-34.7	-31.7	-32.7
600K	-29.0	-27.5	-29.9

NH₃ +OH^․→ H₂O + NH₂^․

barrier heigh

temp.	MP2/aug-cc-pVTZ	CCSDT/aug-cc-pVTZ//MP2/aug-cc-pVTZ
273K	12.3	8.6
298.15K	12.9	9.2
600K	20.4	16.7

ln(K) unit:kcal/mole

temp.	MP2/aug-cc-pvTZ	CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ	exp.
273K	-38.0	-31.1	-30.1
298.15K	-37.1	-30.7	-29.4
600K	-31.6	-28.5	-29.2

Arrhenius plot

1000

ref.:Sasha Madronich,William Felder Direct measurements of the rate coefficient for the reaction OH+CH4 → CH3+H2O over 300-1500 K 1985,703-713

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