Surface catalyzed isomerization of (CH,),O to CH3CH0 occurs in a small, Pyrex reactor containing 15 or 230 Torr (CH,),O at temperatures in the range 339.2 "C to 461.4 "C. Ro(CH3CHO), the initial rate of formation of CH3CH0, depends on the number of successive pyrolyses and on the evacuation time between pyrolyses, which is not true of the initial rates of formation of Hz, CO, CH,, CH,CO, and C2H6. Ro(CH3CHO) also depends on the reactor S / V and on pretreatment of the reactor with product gases, particularly H,. The reproducible and limiting values of Ro(CH3CHO) are independent of the (CH,),O pressures used. Above 385 "C these initial rates exhibit an Arrhenius temperature dependence while below 385 "C they pass through a maximum.Analysis of the Langmuir-Hinshelwood, low surface coverage mechanism shows that the T > 385 "C isomerization is partially or totally controlled by C H 3 C H 0 desorption and that -AH:,,;,,, < (55 i 10)kcal mol-I, for CH,CHO on this surface. E, = 57 kcal mol-I for the homogeneous first order deconlposition of (CH,),O, in the 15 Torr pyrolysis at temperatures in the range 374.0 to 406.7 "C, and any vibrationally excited CH,CHO, formed in the gas phase at this pressure (and possibly even at 230 Torr), dissociates into chain initiating radicals. L'analyse du recouvrenlent faible de la surface selon Langmuir et Hinshelwood ~nontre que I'isomCrisation pour T > 385 "C est partielle~nent ou totalenlent contr61Ce par la dksorption de CH,CHO et que -AH.,,, < (55 i 10) kcal mol-' pour CH3CH0 sur cette surface.La d6composition honiogene du premier ordre de (CH2),0 a un E:, = 57 kcal mol-I dans la pyrolyse sous 15 Torr et a des temperatures de 374.0 a 406.7 "C; le n~ethanal formC en phase gazeuse et vibration-

The reaction between active nitrogen and acetylene was studied in a low-pressure flow reactor using a leak to a mass spectrometer as the analytical device and varying reaction time from a few to 45 ms. In mixtures in which the initial ratio of acetylene to atomic nitrogen is larger than unity a comparatively slow reaction takes place whose main products are cyanogen, hydrogen and cyanoacetylene. The reaction is accelerated by rising pressure and temperature. The proposed rate determining steps are C 2 H 2 + N K1 ⇆ K-1 C 2 H 2 N*, C 2 H 2 N*+ N 2 → K2 C 2 H 2 N+ N 2 with K 1 = 1·1X 10 -12(+-0·12) exp (-2000(±400)/ RT ) cm 3 molecule -1 s -1 and k -1 = 4x10 -s T e s -1 , if k 2 is taken to be the collisional frequency. The radical C 2 H 2 N is found to react competitively with nitrogen atoms and with acetylene to form the end products. At low (≤ 0·5) initial acetylene to atomio nitrogen ratios a much faster reaction occurs which is accompanied by chemiluminescence of CH and CN radicals and whose main products are hydrogen cyanide, cyanogen and hydrogen. Simultaneously, a rapid recombination of nitrogen atoms takes place, as many as 20 atoms reacting per molecule of acetylene consumed. This rapid reaction has a negative temperature coefficient. It is suggested that this is a chain reaction started by metastable nitrogen molecules ( A 3 Σ + u ) nitrogen atoms which react with acetylene to form hydrogen cyanide and cyanide radicals. The latter cause the recombination of nitrogen atoms by the chain reactions CN + N + N 2 → NCN + N 2 NCN+N → N* 2 + CN, with 3 x 10-30 <k 6 < 2 x 10 -29 cm 6 molecule -2 s -1 . These chains are broken by recombination of cyanide radicals and by the reactions of CN and NCN radicals with acetylene. Cyanogen also causes a catalytic recombination of nitrogen atoms. Ammonia added to acetylene-active nitrogen mixtures suppresses the rapid reaction but has no effect on the slow reaction in richer mixtures.

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