摘要:

AbstractThe rate of the reaction CH2I2+ HI ⇆ CH3I + I2has been followed spectrophotometrically from 201.0 to 311.2°. The rate constant for the reaction fits the equation, log (k1/M−1sec−1) = 11.45 ± 0.18 ‐ (15.11 ± 0.44)/θ. This value, combined with the assumption thatE2= 0 ± 1 kcal/mole, leads to ΔH f298°(CH2I, g) = 55.0 ± 1.6 kcal/mole andDH 298°(HCH2I) = 103.8 ± 1.6 kcal/mole.The kinetics of the disproportionation, 2 CH3I ⇆ CH4+ CH2I2were studied at 331° and are compat

ISSN:0538-8066    

DOI:10.1002/kin.550010302

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe gas phase, nitric oxide catalyzed positional isomerization of 3‐methylene‐1,5,5‐trimethylcyclohexene (MTC) into 1,3,5,5‐tetramethyl‐1,3‐cyclohexadiene (TECD) has been studied for temperatures ranging between 296° and 425°C. The major reaction was first order with respect to nitric oxide and to MTC.The major side product, mesitylene, usually amounted to less than 10% of the TECD isomer formed. Only at high temperatures and large conversions has up to 20% been observed.Conditioned pyrex or quartz vessels coated with KCl have been used. The nitric oxide catalyzed isomerization is apparently a homogeneous process, as demonstrated by the insensitivity of the observed rate constants towards a 15‐fold increase in the surface to volume ratio of the reaction vessels. However, a residual, presumably heterogeneous, thermal isomerization of the starting material could not be eliminated. Good mass balances were obtained for both NO and hydrocarbons.After correcting for the thermally induced conversion the observed rate constants for the nitric oxide catalyzed isomerization yield logk1(1 mole−1sec−1) = (10.7 ± 0.2) – (37.3 ± 0.9)/θ where θ is 2.303 × 10−3RT (kcal mole−1). Plotting logk1versus the ratio of the starting materials (MTC/NO)0it was found that for temperatures ≥ 365°C the rate constants were systematically too high.Using extrapolated values for the higher temperature range yields the more reliable corrected Arrhenius equation logk 1corr= 8.6 – 31.7/θ. The reaction mechanism is outlined and the implications with respect to the stabilization energy generated in the MTCċ radical intermediate and the activation energy of the backreaction MTCċ + HNO are discussed.Using for the activation energyE−1of the backreaction (Rċ + HNO) a literature value of 9.2 ± 0.9 kcal mole−1reported for the cyclohexadiene1,3system, this yields 23.4 ± 2 kcal mole−1for the stabilization energy in the methylenecyclohexenyl radical, which is to be compared with the corresponding values for the allyl (10.2 ± 1.4), methallyl (12.6 ± 1) pentadienyl (15.4 ± 1) and cyclohexadienyl (24.6 ± 0.7) radicals.The pre‐exponential factor agrees well with the value of (8.4 ± 0.2) reported by Shaw and co‐workers for the similar reaction of NO with 1,3‐cyclohexadiene. It is noteworthy that HNO, acting as sole hydrogen donor in the system, is surprisingly stable under the reaction conditions used. Nitrous oxide, HCN, H2O and N2are observed in the product mixture of ex

ISSN:0538-8066    

DOI:10.1002/kin.550010303

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe kinetics of the photoinitiated reductions of methyl iodide and carbon tetrachloride by tri‐n‐butylgermanium hydride in cyclohexane at 25°C have been studied and absolute rate constants have been measured. Rate constants for the combination of CH3ċ and CCl3ċ radicals are equal within experimental error and are also equal to the values found for the self‐reactions of most non‐polymeric radicals in low viscosity solvents, i.e. ∼1–3 × 109M−1sec−1.Rate constants for hydrogen atom abstraction by CH3ċ and CCl3ċ radicals are both ∼1−2 × 105M−1sec−1. Tri‐n‐butyltin hydride is about 10–20 times as good a hydrogen donor to alkyl radicals as is tri‐n‐butylgermanium hydride.The strength of the germanium–hydrogen bond,D(n‐Bu3Ge–H)

ISSN:0538-8066    

DOI:10.1002/kin.550010304

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe kinetics of the thermally and radiation initiated chain reaction between trichloroethylene and cyclopentane to produce 1,1‐dichlorovinylcyclopentane and hydrogen chloride have been investigated in the temperature range 250–360°C at high pressure in the gas phase. The rate governing step in the chain is (k3= 3.3 × 109exp −(4800/RT) cc mole−1sec−1). The rate of the unimolecular decomposition of trichloroethylene is 1.4 × 1014exp −(61

ISSN:0538-8066    

DOI:10.1002/kin.550010305

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe following Arrhenius parameters have been determined for the hydrogen‐abstraction reactions: R + (CH3)4Si → RH + (CH3)3SiCH3TextRTemp. (°K)E(kcal/mole)LogA(mole−1cc sec−1)Logk(400°K) (mole−1cc sec−1)CF3330–4337.23 ± 0.0911.90 ± 0.057.95CH3396–47610.23 ± 0.3611.55 ± 0.185.68CD3396–49610.36 ± 0.1211.84 ± 0.066.20C2H5423–52211.40 ± 0.4811.88 ± 0.225.68The activation energies are in keeping with the strengths of the bonds formed during the reaction. By comparison with the activation energies for the analogous reactions of neopentane it is estimated thatD((CH3)3SiCH2H) ≃ 97 kcal/mole.TheAfactors for the above series of reactions fall within the range predicted by transition‐state theory for this type of process and the validity of previous results of Kerr, Slat

ISSN:0538-8066    

DOI:10.1002/kin.550010306

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550010307

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550010308

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550010301

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY