FTIR STUDIES OF THE NO3 INITIATED DEGRADATION OF BUT-2-YNE - MECHANISM AND RATE-CONSTANT DETERMINATION

The products and mechanism of the gas-phase reaction of NO3 radicals w ith but-2-yne in purified air have been investigated by FTIR spectrosc opy. The experiments were carried out at 298 +/- 3 K and 760 +/- 5 Tor r in a 250 1 stainless-steel reactor in which NO3 was generated by the thermal dissociation of N2O5. Experiments with (NO3)-N-15 were also p erformed. Products include butadione, peroxyacetyl nitrate, ketene and acetic acid. Ketene was observed to react further with NO3 and this r eaction was also investigated. The rate constants for the NO3 reaction with but-2-yne and ketene were determined by the relative-rate method as 7.0 +/- 0.8 and 10.6 +/- 1.3 x 10(-14) cm(3) molecule(-1) s(-1), r espectively, using (E)-but-2-ene as a reference. Reaction mechanisms f or the but-2-yne and the ketene degradations are proposed.