Energy release and product ion fragmentation in proton transfer reactions of N₂H⁺ and ArH⁺ with acetone*

Figures & data

Table 1. Average of absolute rate coefficients k_abs of reactions (1)–(5) are compared with calculated collision rate coefficients k_ADO, resulting in the efficiency ϕ = k_abs/k_ADO. Errors correspond to the standard deviation of all measuremts. The energy release of each reaction in eV was calculated as the CCSD/aug-cc-pVDZ level of theory single point energy combined of the MP2/aug-cc-pVDZ structures and zero-point energies.

	Reaction	kabs / 10^−10 cm³ s^−1	kADO / 10^−10 cm³ s^−1	Φ / %	Energy release / eV
	N2H^+ + C3H6O → products	25 ± 2	27.92	90
(1)	N2H^+ + C3H6O → C3H7O^+ + N2	20 ± 1			3.35
(2)	N2H^+ + C3H6O → C2H3O^+ + CH4 + N2	0.6 ± 0.3			2.52
(3)	N2H^+ + C3H6O → C3H5^+ + H2O + N2	1.9 ± 0.5			0.92
(4)	N2H^+ + C3H6O → CH3O^+ + C2H4 + N2	2.7 ± 0.5			0.72
(5’)	CH3O^+ + C3H6O → C3H7O^+ + CH2O	12 ± 0.5	27.32	44	1.05
	ArH^+ + C3H6O → products	24 ± 6	25.05	96
(1)	ArH^+ + C3H6O → C3H7O^+ + Ar	14 ± 4			4.57
(2)	ArH^+ + C3H6O → C2H3O^+ + CH4 + Ar	1.9 ± 1			3.74
(3)	ArH^+ + C3H6O → C3H5^+ + H2O + Ar	2.2 ± 1			2.14
(4)	ArH^+ + C3H6O → CH3O^+ + C2H4 + Ar	6.1 ± 3			1.94
(5’’)	CH3O^+ + C3H6O → C3H7O^+ + CH2O	22 ± 11	27.32	81	1.05

Table 2. Comparison of experimental [18] and calculated proton affinities of argon, nitrogen, and acetone. The calculated values contain MP2/aug-cc-pVDZ, and CCSD/aug-cc-pVDZ optimised values including their respective thermal enthalpy corrections. Furthermore, CCSD/aug-cc-pVDZ single-point energies using MP2/aug-cc-pVDZ optimised structures and thermal enthalpy corrections are listed.

Proton affinity of	exp [18] / eV	MP2/aug-cc-pVDZ / eV	CCSD/aug-cc-pVDZ singlepoint / eV	CCSD/aug-cc-pVDZ / eV
Ar	3.83	3.70	3.79	3.95
N2	5.12	4.93	5.02	5.01
C3H6O	8.42	8.23	8.39	8.41

Figure 1. Reaction kinetics of (a) N₂H⁺ and (b) ArH⁺ with acetone at a backing pressure of 1.9 × 10⁻⁸ mbar and 1.3 × 10⁻⁸ mbar, respectively. For (a) and (b) the first 0.15 and 0.8 s were neglected for the fit, respectively, as thermalisation effects conflict with the pseudo-first order reaction model used for fitting the results.

Figure 2. Reaction profiles of PTR from N₂H⁺ and ArH⁺ to acetone and formation of (a) C₃H₅⁺ with loss of H₂O; (b) CH₂OH⁺ with loss of C₂H₄; (c) C₂H₃O⁺ with loss of CH₄. Structures are calculated at the MP2/augcc-pVDZ level of theory, the energies are calculated using CCSD/aug-cc-pVDZ single-point energies and the zero-point corrections derived from MP2/aug-cc-pVDZ level of theory. The trivial neutrals (Ar or N₂) are not shown after the PTR, but their energies were considered.

E.P.L. Hunter and S.G. Lias, J. Phys. Chem. Ref. Data. 27, 413–656 (1998). doi:10.1063/1.556018 .

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