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Table 3

Summary of reactions review.

Reactions ΔE α β γ F0 g Reference
kJ mol−1
He + + C2 N2 → CN + + CN + He −437 8 × 10−10 0 0 3 0 Rate constant from Raksit & Bohme (1984)
→ CCN+ + N + He −470 8 × 10−10 0 0 3 0
He+ + CNCN → CN+ + CN + He −522 1.6 × 10−10 −0.4 0 3 0 By comparison with He+ + NCCN taking into account the
→ CNC+ + N + He −695 1.6 × 10−10 −0.4 0 3 0 dipolar moment of CNCN
H+ + C2 N2 → H + C2 N −22 4.0 × 10−9 0 0 3 0 Similar to H+ + molecule without dipolar moment,
IE(NCCN) = 13.37 eV
H+ + CNCN → H + CNCN+ −65 0 Similar to H+ + molecule with dipolar moment
→ H + C2 N −99 1.0 × 10−8 −0.4 0 3 0 We avoid introducing CNCN+ which will react quickly
→ NCN+ + CH +380 0 with H2 leading to the same final products that C2N
→ CH+ + NCN +154 0
H + NC3 N → HCN + C2 N +15 0 NC3N has a triplet ground state so it will react quickly
→ HNC + C2 N +67 0 with atoms and radicals. The two unpaired electrons are
→ CN + HCCN +108 0 localized on central C atom and on terminal N atoms:
N ≡C −∙C = C = N∙↔∙N = C = ∙C −C ≡N
→ CH + C2 N2 +105 0 The ∙ represents the lonely electron and show the reactive sites
C+ + C2 N2 → CNC+ + CN −65 1.0 × 10−9 0 0 3 0 Charge exchange is endothermic. Rate constant similar
→ CCN+ + CN +77 0 to C+ + C2H2, close to capture rate
C+ + CNCN → CNC+ + CN −149 2.0 × 10−9 −0.4 0 3 0 Charge exchange is endothermic. Rate constant similar to
→ CCN+ + CN −8 0 C+ + HCN, close to capture rate with temperature
dependency from charge-dipole interaction
C + C2 N2 → NC3 N + hν −435 2.0 × 10−14 −1.5 0 10 0 The results from Safrany & Jaster (1968b,a) and Whyte & Phillips (1983)
→ C3 + N2 −294 0 are complex, the products assumed for this reaction, CN + CCN, being
→ CN + CCN +98 0 widely endothermic. We have performed theoretical calculations
→ N + C3 N +157 0 (see appendix). We propose that the experimental observations are
→ C2 + NCN +266 0 due to 3-body NC3N formation. In interstellar molecular clouds
the pressure is too low for 3-body reactions but radiative association
may play a role. The radiative association rate constant is
calculated using our ρ-association model (Hebrard et al. 2013)
C + CNCN → C + C2 N2 −84 1.0 × 10−10 0 0 3 0 See text and appendix
C + NC3 N → CN + C3 N −142 2.0 × 10−10 0 0 3 0 NC3N has a triplet ground state so it will react quickly with atoms and
radicals. The two unpaired electrons are localized on central C atom
and on terminal N atoms: N ≡C −∙C = C = N∙↔∙N = C = ∙C −C ≡N
CH + C2 N2 → C2 N + HCN −81 2.0 × 10−10 0 0 3 0 There is very likely no barrier for this reaction considering the very high
→ HCCN + CN +20 0 0 0 0 0 reactivity of the CH radical
→ C3 H + N2 −177 0 0 0 0 0
CN + HNC → C2 N2 + H −103 2.0 × 10−10 0 0 4 0 See Petrie & Osamura (2004)
CN + HCNH+ → HC2 N + H +11 "0" The reaction is endothermic and show a barrier of 52 kJ mol−1
at M06-2X/AVTZ level (see Table G.1)
N + C2 N2 → C2 N2 + H "0" Very large barriers for N addition on the nitrogen (91 kJ mol−1) or on the
carbon atoms (63 kJ mol−1) (M06-2X/AVTZ calculations). The rate
constant value in Safrany & Jaster (1968c) is likely due to the presence
of N (Michael 1980; Dutuit et al. 2013)
N + CNCN → C2 N2 + H "0" The most favourable attack on final carbon atom shows a large barrier for N
addition (32 kJ mol−1) (M06-2X/AVTZ calculations)
N + C3 N → C + C2 N2 −157 6.0 × 10−11 0 0 3 0 Theoretical calculations. Important NCCN formation pathway
→ C + CNCN −72 1.0 × 10−11 0 0 3 0 in dense molecular clouds
→ CN + C2 N −43 2.0 × 10−11 0 0 3 0
→ C3 + N2 −333 0 0 0 3 0
N + NC3 N → CN + C2 N2 −299 4.0 × 10−11 0 0 3 0 NC3N has a triplet ground state so it will react quickly with atoms and radicals
→ N2 + C3 N −337 4.0 × 10−11 0 0 3 0 The two unpaired electrons are localized on central C atom and on
terminal N atomes N ≡C −∙C = C = N∙↔∙N = C = ∙C −C ≡N
C2 N + H → HC2 N + H2 −215 2.8 × 10−9 0 0 1.2 0 See Anicich (2003).
C2 N + HCO+ → HC2 N + CO −67 1.7 × 10−9 0 0 2 0 By comparison with NCCN + H considering the
H/ HCO+ masses difference
CNCN + H → HCNCN+ + H2 −240 0 By comparison with NCCN + H taking into account the low dipole moment
→ HNCNC+ + H2 −256 0 of CNCN. We do not introduce HC2N isomers as their DR will leads to
→ HC2 N2 + + H2 2.8 × 10−9 −0.3 0 2 0 similar products with our statistical calculations
CNCN + HCO+ → HCNCN+ + CO −92 0 We do not introduce HC2N isomers as their DR will leads to similar products
→ HNCNC+ + CO −109 0 with our statistical calculations
→ HC2 N + CO 1.6 × 10−9 −0.3 0 2 0
C2 N + H2 → HNCCN+ + H −200 0 Anicich (2003)
→ HC2 N + H 9.0 × 10−10 0 0 1.4 0
CNCN+ + H2 → HNCNC+ + H −190 0 Same as C2N + H2. We do not introduce HC2N isomers
→ HC2 N + H 9.0 × 10−10 0 0 2 0 as their DR will leads to similar products with our statistical calculations
HC2 N + e− → H + C2 N2 −668 1.7 × 10−7 NCCN/CNCN branching calculated using statistical theory, as well
→ H +CNCN −583 1.0 × 10−8 as HNC/HCN ratio.
→ HCN +CN −616 1.0 × 10−7
→ HNC +CN −564 1.0 × 10−7
→ H + CN +CN −93 0
HC3 NH+ + e− → HC3 N + H −568 6.0 × 10−7 −0.58 0 3 0 The global rate constant and the 52% of HC3N isomers formation and
→ HNC3 + H −369 1.4 × 10−7 −0.58 0 3 0 48% of HCN isomers formation is from
→ H + HCNCC −250 1.0 × 10−8 −0.58 0 3 0 Geppert et al. (2004); Vigren et al. (2012) using also Osamura et al. (1999)
→ H + HCCNC −473 3.0 × 10−8 −0.58 0 3 0 The relative HC3N/HNC3/HCNCC/HCCNC and HCN/HNC
→ C2 H + HCN −377 3.6 × 10−7 −0.58 0 3 0 branching ratios are arbitrary
→ C2 H + HNC −345 3.6 × 10−7 −0.58 0 3 0
→ C3 N + H + H +29 0 −0.58 0 3 0

Notes. Definition of α, β, γ, F0, g can been found in Wakelam et al. (2012, 2010): , T is the temperature and ranges between 10 and 300 K except for some cases (noted).

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