Methanimine as a sink in the HCN and HNC solid state hydrogenation network

Open Access

Table A.1

Reaction energetic descriptors and comparison to the literature.

Label	Reaction	∆U_rx	∆U^†	∆U^† Other Works	T_c (K)
H-addition reactions

R1	HCN + H^• → H₂CN^•	-90.3	28.4	20.1^a, 30.5^b, 63.6^c, 28.3^d, 26.7^f	182
R2-cis	HCN + H^• → cis-HC^•NH	-60.5	33.9	37.3^a, 53.5^b	261
R2-trans	HCN + H^• → trans-HC^•NH	-78.5	41.7	74.4^c	280
R3	HNC + H^• → C^•NH₂	-43.7	55.9	55.6^a, 80.3^c	296
R4-cis	HNC + H^• → cis-HC^•NH	-111.4	8.2	8.1^a	111
R4-trans	HNC + H^• → trans-HC^•NH	-110.7	12.5	17.6^c	100
R5	H₂CN^• + H^• → H₂CNH	-406.4*	BL	BL^a
R6	H₂CN^• + H^• → ³[H₃CN:]	-145.8	13.5	9.0^a	156
R7	C^•NH₂ + H^• → ¹[HC:NH₂]	-383.9*	BL	BL^a
R8-cis	cis-HC^•NH + H^• → H₂CNH	-450.8*	BL	BL^a
R8-trans	trans-HC^•NH + H^• → H₂CNH	-445.1*	BL
R9-cis	cis-HC^•NH + H^• → ¹[HC:NH₂]	-328.7*	BL	BL^a
R9-trans	trans-HC^•NH + H^• → ¹[HC:NH₂]	-325.4*	BL
R10	³[H₃CN:] + H^• → H₃CN^•H	-385.1*	BL	BL^a
R11	H₂CNH + H^• → H₂CN^•H₂	-145.9	22.9	19.4^a, 25.5^b, 12.7^e, 17.7^f	186
R12	H₂CNH + H^• → H₃CN^•H	-128.8	16.0	15.1^a, 19.2^b	171
R13	¹[HC:NH₂] + H^• → H₂C^•NH₂	-270.1	4.0	N/A^a	96
R14	¹[HC:NH₂] + H^• → HC^•NH₃	-56.9	66.6	101.9	328
R15	H₃CN^•H + H^• → CH₃NH₂	-446.7*	BL	BL^a
R16	H₂C^•NH₂ + H^• → CH₃NH₂	-426.4*	BL	BL^a

H-abstraction and H₂-addition reactions

R17	H₂CN^• + H^• → HCN + H₂	-328.9	BL	BL^a
R18	C^•NH₂ + H^• → HNC + H₂	-383.8*	BL	BL^a
R19-cis	cis-HC^•NH + H^• → HCN + H₂	-367.7	BL	BL^a
R19-trans	trans-HC^•NH + H^• → HCN + H₂	-351.1	2.2		162
R20-cis	cis-HC^•NH + H^• → HNC + H₂	-335.8*	BL	BL^a
R20-trans	trans-HC^•NH + H^• → HNC + H₂	-320.7*	BL
R21	³[H₃CN:] + H^• → H₂CN^• + H₂	-279.6	6.7	BL^a	135
R22-cis	H₂CNH + H^• → cis-HC^•NH + H₂	-33.9	24.8	45.0^a	340
R22-trans	trans-HC^•NH + H₂ → H₂CNH + H^•	-24.7	36.6		371
R23	H₂CNH + H^• → H₂CN^• + H₂	-54.0	29.4		406
R24-cis	¹[HC:NH₂] + H^• → cis-HC^•NH + H₂	-138.5	28.3	22.7^a	349
R24-trans	¹[HC:NH₂] + H^• → trans-HC^•NH + H₂	-140.7	14.7	22.7^a	349
R25	¹[HC:NH₂] + H^• → C^•NH₂ + H₂	-68.1**	8.8**	3.5^a	177
R26	H₃CN^•H + H^• → ³[H₃CN:] + H₂	-73.0	15.6	12.9^a	356
R27	H₃CN^•H + H^• → H₂CNH + H₂	-301.7	4.8	1.8^a	129
R28	H₂C^•NH₂ + H^• → ¹[HC:NH₂] + H₂	-154.4*	BL	N/A^a
R29	H₂C^•NH₂ + H^• → H₂CNH + H₂	-273.5	BL	N/A^a
R30	HC^•NH₃ + H^• → ¹[HC:NH₂] + H₂	-373.6	BL
R31	HC^•NH₃ + H^• → ³[:CNH₃] + H₂	-52.7**	6.6**		57
R32	CH₃NH₂ + H^• → H₂C^•NH₂ + H₂	-67.3, -38.1	9.9, 30.2	37.3^a, 33.4^e	125, 337
R33	CH₃NH₂ + H^• → H₃CN^•H + H₂	-14.3	48.0	44.8^a, 39.7^e	414
R34	¹[HC:NH₂] + H₂ → CH₃NH₂^†	-231.7	102.6		270

Water-assisted H-transfer and isomerization reactions

R35	HNC $\overset{w H t}{\to}$ $Mathematical equation: $\overset{\mathrm{wHt}}{\rightarrow}$$ HCN	-32.4, -33.7	35.1, 73.6	49.6^h	221, 149
R36	trans-HC^•NH $\overset{w H t}{\to}$ $Mathematical equation: $\overset{\mathrm{wHt}}{\rightarrow}$$ H₂CN^•	-32.9	83.7
R37-isom	cis-HC^•NH $\overset{i s o m}{\to}$ $Mathematical equation: $\overset{\mathrm{isom}}{\rightarrow}$$ trans-HC^•NH	-9.6	23.9		136
R37-wHt	cis-HC^•NH $\overset{w H t}{\to}$ $Mathematical equation: $\overset{\mathrm{wHt}}{\rightarrow}$$ trans-HC^•NH	-22.6	65.5		196
R38	C^•NH₂ $\overset{w H t}{\to}$ $Mathematical equation: $\overset{\mathrm{wHt}}{\rightarrow}$$ trans-HC^•NH	-47.1	30.8	88.8^a	52
R39	¹[HC:NH₂] $\overset{w H t}{\to}$ $Mathematical equation: $\overset{\mathrm{wHt}}{\rightarrow}$$ H₂CNH	-106.1	4.9	22.7^a, 14.0^g	187
R40	H₃CN^•H $\overset{w H t}{\to}$ $Mathematical equation: $\overset{\mathrm{wHt}}{\rightarrow}$$ H₂C^•NH₂	-21.5	69.3		100
R41	HC^•NH₃ $\overset{w H t}{\to}$ $Mathematical equation: $\overset{\mathrm{wHt}}{\rightarrow}$$ H₂C^•NH₂	-209.3	BL	BL^a

^a Molpeceres et al. (2024) (ice), ^b Woon (2002) (gas), ^c Talbi & Ellinger (1996), ^d Majumdar et al. (2018) (gas), ^e Joshi & Lee (2022) (gas), ^f de Jesus et al. (2021) (gas), ^g Ferrero et al. (2024) (ice), ^h Baiano et al. (2022).

^*Calculated with respect to the asymptote, omitting ZPE corrections.

^**Calculated with ωB97m-D3(BJ)/ma-def2-TZVP due to unrealistic ZPE correction at M062X-D3(0).

^†The reaction does not stop at H₂CNH₂ + H, but it directly evolves to methylamine over a very high barrier.

Reaction R32 appears twice in the table because two different binding configurations of the reactants were identified, leading to distinct activation barriers (see Sect. 4).

Reaction R35 is also listed twice, corresponding to water-assisted H-transfer (wHt) mechanisms involving three or two water molecules, respectively.

The reactions ³[:CNH₃] + H^• → HC^•NH₃ and HC^•NH₃ $\overset{w H t}{\to}$ $Mathematical equation: $\overset{\mathrm{wHt}}{\rightarrow}$$ H₂C^•NH₂ (R42 and R43) are not included in this table, as they ultimately lead to H₂C^•NH₂ after direct optimization of HC^•NH3 in our model.

Notes. Summary of the reactions considered in this work and their energetics. Each reaction is assigned a label (R1, R2,...) that is used throughout the text. Energy units are in kJ mol⁻¹. ∆U_rx and ∆U_‡ are the reaction and activation energies of each reaction, T_c is the tunneling crossover temperature. BL stands for barrier-less and N/A for “not an answer.”

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.