Providing evaluated kinetic data on the web since 1999. |

# IUPAC Subcommittee on Gas Kinetic Data Evaluation

Website: http://www.iupac-kinetic.ch.cam.ac.uk/ See website for latest evaluated
data. Datasheets can be downloaded for personal use only and must not be
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This datasheet last evaluated: 2004-03-09 ; last change in preferred values: 2001-07-16 ; last peer-reviewed publication: 2004-03-09

HO_{2}^{}NO_{2}^{} + M | → | HO_{2}^{} + NO_{2}^{} + M | | (1) | |
Δ *H*^{ο}
= 100.5
kJ mol^{-1} |
---|

### Rate Coefficient Data: Low-pressure rate coefficients

*Absolute Rate Coefficients*

Rate Coefficient (k_{0})
/
| Temperature
/
| Reference | Techniques and Comments |
---|

s^{-1} | Kelvin | | |

1.5$\times $10${}^{-20}$ [N${}_{2}$] | 298 | Cox and Patrick, 1979 | (a) |

5.2$\times $10${}^{-6}exp[-(10014\pm 250)/T]$ [N${}_{2}$] | 261–295 | Graham et al., 1978 | (b) |

1.3$\times $10${}^{-20}$ [N${}_{2}$] | 298 | | |

4.1$\times $10${}^{-5}exp[-(10645\pm 260)/T]$ [N${}_{2}$] | 261–307 | Zabel, 1995 | (c) |

1.2$\times $10${}^{-20}$ [N${}_{2}$] | 298 | | |

### Comments

**(a)** Derived from measurements of the reverse reaction. Conversion of the data to the dissociation reaction of HO${}_{2}$NO${}_{2}$ using the equilibrium constant ${K}_{c}$ = 1.68$\times $10${}^{28}$ exp($-$11977/$T)$ cm${}^{3}$ molecule${}^{-1}$ from Uselman et al. (1978) and comparison with earlier dissociation data.

**(b)** FTIR study in a 5800 L chamber. Measurements were made at 1.3–9.3 mbar (1–7 Torr) of N${}_{2}$. At higher pressures ($\ge $9.3 mbar), deviations from low pressure behavior were observed.

**(c)** FTIR study in a 420 L chamber. The pressure range was 14–1027 mbar (10–772 Torr). The falloff curve was evaluated with ${F}_{c}$ = 0.5.

### Preferred Values

$\begin{array}{}\frac{{k}_{0}}{s^{-1}}=\{\begin{array}{ccc}1.3E-20\mathrm{N\_2\left[{N}_{2}\right]}& \text{if}& T=298\\ 4.1E-5e^{\frac{\mathrm{PlusMinus}(-10650, 500, T)}{}}\mathrm{N\_2\left[{N}_{2}\right]}& \text{if}& 260\le T\le 300\end{array}\\ \end{array}$*Comments on Preferred Values*

The preferred values are from the study of Zabel (1995), and are in close agreement with those from Graham et al. (1978). The data from Zabel (1995) provide the most consistent picture of all RO${}_{2}$NO${}_{2}$ dissociation reactions. Falloff curves are constructed with ${F}_{c}$ = 0.5.

### Rate Coefficient Data: High-pressure rate coefficients

*Absolute Rate Coefficients*

Rate Coefficient (k_{
∞
})
/
| Temperature
/
| Reference | Techniques and Comments |
---|

s^{-1} | Kelvin | | |

$>$0.018 | 278 | Graham et al., 1978 | (a) |

5.7$\times $10${}^{15}exp(-11170/T)$ | 261–307 | Zabel, 1995 | (b) |

0.30 | 298 | | |

### Comments

**(a)** See comment (b) for ${k}_{0}$. This is a lower limit since a linear Lindemann-Hinshelwood evaluation of the falloff curve was made for the pressure range 0.013–1.01 bar (10–760 Torr) of N${}_{2}$.

**(b)** See comment (c) for ${k}_{0}$.

### Preferred Values

$\begin{array}{}\frac{{k}_{\infty}}{s^{-1}}=\{\begin{array}{ccc}0.25& \text{if}& T=298\\ 4.8E15e^{\frac{\mathrm{PlusMinus}(-11170, 500, T)}{}}& \text{if}& 260\le T\le 300\end{array}\\ \end{array}$*Comments on Preferred Values*

See Comments on Preferred Values for ${k}_{0}$. The data from Zabel (1995) were re-evaluated with ${F}_{c}$ = 0.6 such as used for the falloff curves of the reverse reaction HO${}_{2}$ + NO${}_{2}$ + M $\to $ HO${}_{2}$NO${}_{2}$ + M and because ${F}_{c}$ is identical for the forward and backward reaction. Since the measurements from Zabel (1995) were made close to the low pressure limit, only the extrapolation to ${k}_{\infty}$ is noticeably influenced by the change of the used ${F}_{c}$.

### References

Cox, R. A. and Patrick, K.
, Int. J. Chem. Kinet.
, **11**
, 635
, 1979.
Graham, R. A., Winer, A. M. and Pitts Jr., J. N.
, Chem. Phys. Lett., 51, 215 (1977); J. Chem. Phys., 68, 4505
, 1978.
Uselman, W. M., Levine, S. Z., Chan, W. H., Calvert, J. G. and Shaw, J. H.
, Chem. Phys. Lett.
, **58**
, 437
, 1978.
Zabel, F.
, Z. Phys. Chem.
, **188**
, 119
, 1995.