The kinetics and thermochemistry of S2F10 pyrolysis

✍ Scribed by Sidney W. Benson; Jerry Bott

• Publisher: John Wiley and Sons
• Year: 1969
• Tongue: English
• Weight: 353 KB
• Volume: 1
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550010504

✦ Synopsis

Data on the kinetics of S,F,, pyrolysis, which gives SF, + SF, , have been reinterpreted to give a value for the equilibrium constant of S,FIo SF, + SF, . This, together with statistical estimates of the entropy and heat capacity of S,F,, , can be used to give for this reaction values of AH,.,, = 19.7 f 1.0 kcal/mole and AS, , , , = 47.6 f 2 gibbs/mole.

with step 2 rate-determining. The overall, best first order rate constant is proposed as k,,,, = 1017.42-43.0/e sec-l = K,k, , where 0 = 2.303RT in kcal/mole. Independent measurements of AH; and S" for the SF, radical, permits the evaluation of the equilibrium constant K , = 108.92-'27.'*6)~e l./mole-sec and yields k, = I08.50-15.9/e l./mole-sec. The observed homogeneous catalysis by NO and CHCl = CHCl can be explained in terms of a direct abstraction of F from S,F,, : C + S,F,, -+ CF + S,Fg, followed by S,Fg + SF, + SF, and SF, + CF z SF, + C (C = NO or C,H,Cl,).

* The authors are indebted to R. L. Wilkins for making the calculations.

t Wilmshurst and Bernstein estimate these three frequences as 37, 57, and 89 cm-l on the basis of guessed force constants. This assignment, however, gives values for So(S2Flo) which are much too high relative to additivity estimates (S. W. Benson, Thermochemical Kinefics [4]) from comparable species. O n the basis of additivity rules, we have assigned the mean values of 200 cm-l.