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VOl. 75
COMMUNICATIONS TO THE EDITOR
FMN.6 FAD-X is an intermediate in this process stream contains traces of nitrogen. Also nitrosyl and under relatively mild conditions, such as ex- chloride could be contaminated with nitric oxide or posure of FAD spots to ammonia vapor before nitrogen dioxide, and ozone would rapidly convert paper chromatography, a quantitative conversion either of these to nitrogen pentoxide. Therefore we to FAD-X may be effected. deliberately added small amounts of nitrogen pentTreatment of FMN-X with intestinal phospha- oxide to the ozone stream to examine the effect of a tase (Armour) yields a product which is chromato- probable impurity. A fast homogeneous reaction graphically identical with riboflavin, thus excluding set in with the stoichiometry of Eq. 1. With a riboflavinyl g l ~ c o s i d e . ~ Microbiological assays,* large excess of ozone, the reaction in the presence kindly performed by Dr. E. E. Snell, have shown of nitrogen pentoxide was found to be one-half that F-ID-X contains riboflavin and not lyxo- order in nitrosyl chloride. By correcting for this flavin .9,10 dependence on nitrosyl chloride, rates were found The above evidence supports the hypothesis that to be one-half order in ozone, and all runs from start FAD-X is a flavin dinucleotide, isomeric with FAD, to finish were one-half order in each of the two rebut having a cyclic phosphate structure. It can- actants. When the log of these rate constants was not be stated a t present whether FAD-X occurs plotted against the log of the catalyst concentration, itaturally or is produced artificially during the the slope was very nearly one-half, indicating oneisolation of FL4D. half order dependence on nitrogen pentoxide. Thus the empirical rate expression was (7) L. G. Whithy, Nature, 166, 47!J (1950). (8) E. E. Snell and F. M. Strong, Ensymologia, 6, 186 (1939). (9) E . S. Pallares and H . M. Garza, Arch. Biochsm., 22, 63 (1949). (IO) G. A. Emerson and K. Folkers, THISJOURNAL, 73, 2398 (1951).
-d[NOCl]/dt = k[NOCl]'/~[Oa]'/~[NzOj] '/z (2)
The following mechanism is proposed for this reaction
DEPARTMENT OF BIOCHEMISTRY F.M. HUENNEKENS UNIVERSITYOF WASHINGTON SEATTLE 5, WASHINGTON THEINSTITUTE FOR ENZYME RESEARCH 11. R. SANADI UNIVERSITYOF WISCONSIN E. DIMANT A . I. SCHEPARTZ MADISON 5 , WISCONSIN RECEIVED JUNE6, 1953
ki
I\T*o,----f
KO2
+ NO,
kz
+ NO3 +NzOs NOz + +NO3 f XOC1 + NO8 +NOzCl + KO, NO2
k3
0 2
0 3
k4
THE MECHANISM OF THE REACTION BETWEEN OZONE AND NITROSYL CHLORIDE
Sir: Schumacher and Sprengerl produced nitryl chloride by the reaction of ozone with nitrosyl chloride which they described as "rapid and complete"
+
+
By making the steady-state assumption for nitrogen dioxide and Nos, the rate expression exactly derived from the mechanism is
-d[NoC1l
dt
=
(yyz
[NOCl]'/9[03]'/z[N106]1/~ (3)
which agrees with the observed rate function. The values of k l / k z and kBare known,4 and by subThis reaction is an interesting analog of the reac- stituting the values and the observed rate into tion between nitrogen dioxide and ozone,2 and also Eq. (3) we find kd to be 0 . i X lo* cc. rnole-'sec.-' it has an additional feature of interest in that it a t 40'. If the pre-exponential factor is about 1 O I 2 involves a forbidden electronic t r a n ~ i t i o n . ~By cc. mole-'sec.-', the energy of activation of kd is following nitrosyl chloride by its absorption of the about 6 kcal. 405 mp Hg line, we have followed this "rapid" It is interesting to notice that while Eq. (1) reaction in a meter-long Pyrex tube by the same involves a forbidden electronic transition, no step method used with nitrogen dioxide and ozone.2 in the proposed mechanism is forbidden. In the Our preliminary results were erratic, irreproducible, work of Schumacher and Sprenger there must cerand partially heterogeneous. There was an induc- tainly have been some unsuspected nitrogen penttion period, followed by an increase in rate which oxide present. With initially pure reactants our went through a maximum and fell to zero as the work indicated heterogeneous catalysis for the reactants were consumed. We went to great equilibrium 2NOC1 iS 2 N 0 C1, followed by lengths to remove all impurities from the reactants rapid reaction of nitric oxide and ozone to produce and used a cell with smaller surface to volume ratio. nitrogen pentoxide, which then catalyzes reaction Under these conditions the reaction appeared to (1). cease altogether. \Ye finally concluded that the This work was supported by the Office of Naval reaction as written above does not occur a t all. Research, Contract N6 onr 25131, Project NR 051 Ozone produced by an electric discharge con- 246. tains traces of nitrogen pentoxide if the oxygen CHEMISTRY DEPARTMENT HAROLD S. JOHNSTON SOCl
0 3
=
NOeCl
0 2
(1)
+
(I) H. J. Schumacher and G. Sprenger 2. anorg. Chem., 182, 139 (1929).
(2) H. S.Johnston and D. M. Yost, J . Chem. Phys., 17, 386 (1949). (3) G. Herzberg, "Spectra of Diatomic Molecules," D. Van Nostrand Co., Inc., N e w Tork, S . y . , 1050, p. 47%.
STANFORD UNIVERSITY FREDERICK LEIGHTON, JR. STANFORD, CALIFORNIA RECEIVED JUNE 22, 1953 (4) H. S.Johnston, THISJ O U R N A L , 1 3 , 4542 (1961).
