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Find the transition state and calculate the barrier height (ΔV^≠) for the following reaction.
reaction：HNC → HCN
methods : MP2/aug-cc-pVTZ、MP2/6-31+G**

 

	RCH(Å)	RCN(Å)	AHCN(degree)
MP2/aug-cc-pVTZ	1.17	1.19	74
MP2/6-31+G**	1.17	1.20	74

 

ΔV^≠=E(TS)-E(HNC)

 

MP2/aug-cc-Pvtz
	E(Hartree)	ΔV≠(Hartree)	ΔV≠(kcal/mol)
HCN	-93.25975	0.05482	34.4
HNC	-93.23130
TS	-93.17648

 

MP2/6-31+G**
	E(Hartree)	ΔV≠(Hartree)	ΔV≠(kcal/mol)
HCN	-93.17212	0.05605	35.2
HNC	-93.14306
TS	-93.08701

 

 

 

Calculate the k(rate constant) in different temperatures (at least 3 different temperatures) for the following reaction and plot of ln(k) versus 1000/T then compare with the experimental values. 

reaction：CH4 +OH․→ H2O + CH3․                              reaction：CD4 +OH․→ H2O(1 H will replace by D) + CD3․

methods : MP2/aug-cc-pVTZ、MP2/6-31+G**            methods : MP2/aug-cc-pVTZ、MP2/6-31+G** 

k unit : cm3molecule-1s-1

T(K)	k(EXP)	k(MP2/aug-cc-pVTZ)	k(MP2/6-31+G**)		T(K)	k(MP2/aug-cc-pVTZ)	k(MP2/6-31+G**)
298	8.5E-15	1.2E-14	7.9E-15		298	1.6E-15	9.9E-16
500	1.5E-13	5.4E-13	2.2E-13		500	1.1E-13	6.3E-14
700	4.8E-13	2.0E-12	7.6E-13		700	8.2E-13	4.5E-13

T(K)	1000/T	lnk(EXP)	lnk(MP2/aug-cc-pVTZ)	lnk(MP2/6-31+G**)		T(K)	1000/T	lnk(MP2/aug-cc-pVTZ)	lnk(MP2/6-31+G**)
298	3.4	-32.40	-32.08	-32.48		298	3.4	-34.07	-34.55
500	2.0	-29.50	-28.25	-29.14		500	2.0	-29.82	-30.39
700	1.4	-28.37	-26.95	-27.91		700	1.4	-27.83	-28.43

 

KIE=kH/kD

 

KIE	(MP2/aug-cc-pVTZ)	(MP2/6-31+G**)
298	7.32	7.98
500	4.82	3.51
700	2.40	1.68

 

 

 

Conclusions: 1.The rate constant of CD4 is smaller than the rate constant of CH4.

                     2.The calculated results for CD4 have the same trend.

 

 

reference : Madronich, S.;Felder, W.; Direct measurements of the rate coefficient for the reaction OH+CH₄ → CH₃+H₂O over 300-1500 K,Symposium (International) on Combustion,1985(20),703-713