摘要:

AbstractStable nitroxide radicals andESRtechniques have been used to investigate rotational and translational motions of molecules in the liquid state. It is found that for hydrocarbons and molecules with low polarity the rotational frequencies are about an order of magnitude faster than translational encounters. Arrhenius parameters are reported for the rates of both types of processes. A scheme is given for the relation of these motions to radical recombination in solution and also to reactions requiring activation energy. The consequences of this scheme are examined.Such important properties as hydrodynamic fluidity, thermal conductivity, processes of extraction and solution, occurring in the liquid phase as well as at the interface are determined by mobility of particles in the liquid. The problem of molecular mobility is of essential significance for the kinetics of chemical and chemico‐physical processes in the liquid phase.Application of bothESRtechniques and stable nitroxide radicals for kinetic studies of molecular motions in liquids and the correlation between molecular mobility and the kinetic parameters of liquid‐phase radical reactions have been studied in the present pa

ISSN:0538-8066    

DOI:10.1002/kin.550010402

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractArrhenius parameters have been determined for the hydrogen‐abstraction reactions: R + SiHCl3+ RH + SiCl3TextRTemp (°K)E(kcal/mole)LogA(mole−1cc sec−1)Logk(400°K) (mole−1cc sec−1)CF3323–4615.98 ± 0.0611.77 ± 0.038.50CH3333–4434.30 ± 0.0810.83 ± 0.044.48C2H5314–4135.32 ± 0.0711.54 ± 0.048.63The trend in activation energiesE CH 3

ISSN:0538-8066    

DOI:10.1002/kin.550010403

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe kinetics and mechanism of the reaction between iodine and dimethyl ether (DME) have been studied spectrophotometrically from 515–630°K over the pressure ranges, I23.8–18.9 torr and DME 39.6–592 torr in a static system. The rate‐determining step is,wherek1is given by log (k1/M−1sec−1) = 11.5 ± 0.3 – 23.2 ± 0.7/θ, with θ = 2.303RTin kcal/mole. The ratiok2/k−1,is given by log (k2/k−1) = −0.05 ± 0.19 + (0.9 ± 0.45)/θ, whence the carbon‐hydrogen bond dissociation energy,DH° (HCH2OCH3) = 93.3 ± 1 kcal/mole. From this, ΔH°f(CH2OCH3) = −2.8 kcal andDH°(CH3OCH2) = 9.1 kcal/mole.Some nmr and uv spectral f

ISSN:0538-8066    

DOI:10.1002/kin.550010404

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractIn the presence of elementary iodine, isobutyl iodide (2‐methyl‐1‐iodopropane) undergoes isotopic exchange and also decomposes with production of additional iodine. Both reactions are approximately first order in isobutyl iodide and half order in iodine molecules. In degassed hexachlorobutadiene at 160°, the rate constants for exchange and decomposition are 7.5 × 10−6and 11.4 × 10−6(liter/mole)1/2sec−1, respectively. The decomposition is probably initiated by iodine atom abstraction of a β hydrogen atom, but comparison with rates for related compounds indicates that this hydrogen abstraction does not contribute significantly to the mechan

ISSN:0538-8066    

DOI:10.1002/kin.550010405

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe activating effects of a number of unsaturated groups and a cyclopropyl group have been evaluated in a solvent free system by determining the absolute rate constants, and energies and entropies of activation in the vapor phase pyrolysis of secondary and tertiary esters of the type RC(R′CH3) OAc where R′ = H or CH3and R =c‐Pr,i‐Pr, CH3, CH2CH, CH2CHCH2, C6H5; the cyclopropyl showed only a moderate activating effect. The results are in contrast to the very significant activating effect of a cyclopropyl group in solvolysis of cyclopropylcarbinyl derivatives. Apparently marked activation by this group occurs only when a highly developed positive center forms adjacent to it. The lack of marked activation by the cyclopropyl group supports a mechanism for ester pyrolysis which involves a modest, but detectable, charge separation in the transition state [2] but questions a mechanism in which an intimate ion‐pair was

ISSN:0538-8066    

DOI:10.1002/kin.550010406

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe photolysis of pentafluoroacetone has been investigated in the 3130 Å region, from room temperature to 360°C. The ΦCOvaries from 0.7 to 0.9 over this range, and the decomposition is represented by CF2HCOCF3→ CF2H + CO + CF3. The disproportionation/combination ratio for CF3and CF2H (→ CF3H + CF2) radicals is found to be 0.09. Arrhenius parameters for hydrogen atom abstraction from the ketone are log10A= 12.7 (units are mole−1cc sec−1) andE= 14.3 kcal mole−1for CF2H, and log10A= 12.1 andE= 11.8, for CF3radicals. At low pressures HF elimination reactions are observed from the vibrationally excited fluoroethanes, C2F5H* and C2F4H2*, formed in the system. A rough estimate of the activation energy for the process C2F5H → C2F4+ HF of 60–65 kc

ISSN:0538-8066    

DOI:10.1002/kin.550010407

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550010401

出版商:John Wiley&Sons, Inc.    

年代:1969

数据来源: WILEY