𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Absolute Rate Constants for the Addition of Benzyl (PhĊH2) and Cumyl (PhĊMe2) Radicals to Alkenes in Solution

✍ Scribed by Manfred Walbiner; Jie Qiang Wu; Hanns Fischer

Publisher
John Wiley and Sons
Year
1995
Tongue
German
Weight
792 KB
Volume
78
Category
Article
ISSN
0018-019X

No coin nor oath required. For personal study only.

✦ Synopsis

Absolute rate constants and thzir temperature dependence were determined by time-resolved electron spin resonance for the addition of the radicals PhcH, and PhcMe, to a variety of alkenes in toluene solution. To vinyl monomers CH,=CXY, PhCH, adds at the unsubstituted C-atom with rate constants ranging from 14 M-Is-' (ethoxyethene) to 6.7. lo3 M-'s-' (Cvinylpyridine) at 296 K, and the frequency factors are in the narrow range of log ( A /M-'s-') = 8.6 & 0.3, whereat$ the activation energy varies with the substituents from ca. 51 kJ/mol to en. 26 kJ/mol. The rate constants and the activation energies increase both with increasing exothermicity of the reaction and with increasing electron affinity of the alkenes and are mainly controlled by the reaction enthalpy, but are markedly influenced also by nucleophilic polar effects for electron-deficient substrates. For 1,2-disubstituted and trisubstituted alkenes, the rate c'mstants are affected by additional steric substituent effects. To acrylate and styrenes, PhcMe, adds with rate constants similar to those of PhcH,, and the reactivity is controlled by the same factors. A comparison with relative-rate data shows that reaction enthalpy and polar effects also dominate the copolymerization behavior of the styrene propagation radical. ' ) b, (E)-Alkene.

Standard deviation in units of the last digit is given in brackets.

📜 SIMILAR VOLUMES

The Addition of tert-Butyl (Me3Ċ) and (t
The Addition of tert-Butyl (Me3Ċ) and (tert-Butoxy)carbonylmethyl (Me3CO2CĊH2) radicals to alkynes in solution studied by ESR spectroscopy
✍ Herbert Rubin; Hanns Fischer 📂 Article 📅 1996 🏛 John Wiley and Sons 🌐 German ⚖ 686 KB

All arrangements and procedures for steady-state and time-resolved ESR were as described in [4]. The radicals Me,C and Me3C02CCH, were generated by photolysis of the corresponding disubstituted ketones. These undergo type-I cleavage from a short-lived triplet state followed by a fast decarbonylation

Absolute rate constants for the addition
Absolute rate constants for the addition of hydroxymethyl radicals to alkenes in methanol solution
✍ J. Q. Wu; H. Fischer 📂 Article 📅 1995 🏛 John Wiley and Sons 🌐 English ⚖ 753 KB

Absolute rate constants and their temperature dependencies were determined for the addition of hydroxymethyl radicals ( C H 2 0 H ) to 20 monoor 1,l-disubstituted alkenes (CH2 = C X Y ) in methanol by time-resolved electron spin resonance spectroscopy. With the alkene substituents the rate constants

Rate constants for the addition of the 2
Rate constants for the addition of the 2-hydroxy-2-propyl radical to alkenes in solution
✍ K. Héberger; H. Fischer 📂 Article 📅 1993 🏛 John Wiley and Sons 🌐 English ⚖ 432 KB 👁 1 views

Absolute rate constants for the addition of the 2-hydroxy-2-propyl radical to 18 substituted alkenes (CH2 = C X Y ) were determined at (296 -+ 1) Kin 2-propanol by time-resolved electronspin-resonance spectroscopy. With alkene substitution the rate constants vary by more than 6 orders of magnitude.

Rate constants for the addition of the 2
Rate constants for the addition of the 2-cyano-2-propyl radical to alkenes in solution
✍ K. Hėberger; H. Fischer 📂 Article 📅 1993 🏛 John Wiley and Sons 🌐 English ⚖ 811 KB

Absolute rate constants for the addition of the 2-cyano-2-propyl radical to 26 alkenes CH2 = CXY at 315 K were determined in solution by time-resolved electron-spin-resonance spectroscopy. They vary with the alkene substituents from 30 M-' s-l to 7'010 M-' s-'. For styrene the temperature dependence