176. The reactions of alkyl radicals. Part IX. The addition of methyl, ethyl, isopropyl, and t-butyl radicals to acetylene and the isomerization of alkenyl radicals

1962 ◽  
pp. 940 ◽  
Author(s):  
J. A. Garcia Dominguez ◽  
A. F. Trotman-Dickenson
Keyword(s):  
Methyl Ethyl ◽  
Alkyl Radicals

LOCAL STRUCTURE AND METAL–METAL INTERACTION IN SOME Cr(III)-DITHIOPHOSPHONATE COMPOUNDS

2002 ◽  
Vol 16 (10n11) ◽  
pp. 401-407
Author(s):  
O. COZAR ◽  
RODICA MICU-SEMENIUC ◽  
L. DAVID ◽  
I. HAIDUC
Keyword(s):  
Local Structure ◽  
Broad Band ◽  
Octahedral Geometry ◽  
Methyl Ethyl ◽  
Monomeric Species ◽  
Alkyl Radicals ◽  
Chromium Ions ◽  
Polynuclear Species ◽  
Metal Metal ◽  
Strong Exchange

Cr(III)-tris[4-metoxyphenyl-O-alkyl] -dithiophosphonate compounds (alkyl (R) = methyl, ethyl, n-propyl, i-propyl) were prepared and investigated by UV-VIS, IR and EPR spectroscopies. The electronic spectra of these compounds show two bands at 13620–14000 cm -1 (ν1) and 18310–18500 cm -1 (ν2) assigned to 4 A 2g (F) → 4 T 2g (F) and 4 A 2g (F) → 4 T 1g (F) transitions. The valence vibrations of the PS2 group confirm the anizobidentate coordination of dithiophosphonate anions. EPR spectra suggest the superposition of two signals, one with a resolved fine structure typical for isolated Cr(III) ions in a pseudo-octahedral geometry (monomeric species) and a broad band at g eff ≈ 2, characteristic of strong exchange coupled chromium ions (dimeric or polynuclear species). The number of monomeric species increases with the dimension of alkyl radicals because the distance between chromium ions also increases.

Disproportionation and combination reactions of simple alkyl radicals: methyl, ethyl, n-propyl, and isopropyl

1967 ◽  
Vol 45 (20) ◽  
pp. 2327-2333 ◽  
Author(s):  
J. O. Terry ◽  
J. H. Futrell
Keyword(s):  
Free Radicals ◽  
High Intensity ◽  
Room Temperature ◽  
Methyl Ethyl ◽  
High Concentration ◽  
Cross Combination ◽  
Alkyl Radicals ◽  
Competing Reactions

Rates of the possible cross-disproportionation reactions of these radicals relative to their rates of cross-combination, have been measured and are compared with auto-disproportionation-to-combination ratios which were also determined for these radicals. Selected asymmetric azo alkanes RNNR′ and mixtures of symmetric azo alkanes RNNR were used as sources of the desired free radicals. Photolysis under relatively high intensity conditions (ca. 1018 quanta/cm2 s) at room temperature generated the radicals in sufficiently high concentration that competing reactions of abstraction and condensation were negligible. Both the alkene and alkane products of disproportionation reactions were measured to ensure the completeness of the mechanism invoked and to increase the accuracy of the results. Δ(Me, Et) = 0.036 ± 0.003, Δ(Me, Prn) = 0.058 ± 0.004, Δ(Me, Prs) = 0.163 ± 0.005, Δ(Et, Prn) = 0.065 ± 0.005, Δ(Et, Prs) = 0.18 ± 0.008, Δ(Prn, Et) = 0.057 ± 0.005, Δ(Prs, Et) = 0.12 ± 0.01, and Δ(Prn, Prs) = 0.41 ± 0.02 were deduced from the data, where Δ(A, B) refers to the ratio of disproportionation producing the alkane product derived from A to the combination of A with B.

Electron Spin Resonance Studies of the Radiolysis of Aliphatic Amines at 77 °K

1971 ◽  
Vol 49 (11) ◽  
pp. 1869-1879 ◽  
Author(s):  
P. Wardman ◽  
D. R. Smith
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Aliphatic Amines ◽  
Methyl Ethyl ◽  
Alkyl Radicals ◽  
Restricted Rotation ◽  
Parallel Component ◽  
Alkyl Groups ◽  
Spin Resonance ◽  
Butyl Amine

Several frozen aliphatic amines have been γ-irradiated at 77 °K and the electron spin resonance (e.s.r.) spectra of the trapped radicals obtained at 77 °K and on warming. Radiolysis of methyl, ethyl and isopropyl amines produces predominantly alkylamino [Formula: see text] radicals. The proton hyperfine (h.f.) couplings of [Formula: see text] radicals are 10–30% larger than those in the corresponding isoelectronic alkyl radicals and the parallel component of the 14N coupling is about 35 G. Restricted rotation of alkyl groups occurs at 77 °K in some cases. On warming from 77 °K, the [Formula: see text] radicals generally abstract from the solvent or isomerize to produce radicals of the aminoalkyl type (e.g. RĊHNH2). The alkyl proton h.f. splittings of these latter radicals are 20–40% lower than in the corresponding alkyl radicals, and the observed 14N coupling was [Formula: see text] in ĊH2NR2 and [Formula: see text] in (CH3)2ĊNH2 and CH3ĊHNH2. The amino proton couplings in the aminoalkyl radicals were not resolved. Irradiated dimethylamine produces both (CH3)2N and CH2N(CH3) radicals, but (CH3)2N disappears on warming. Only ĊH2N(CH3)2 was observed after irradiation of (CH3)3N at 77 °K. Solid methoxyamine (giving CH3ONH) and tert-butyl-amine were also studied.

The Far Ultraviolet Photolysis of Alkenes: The Use of Hydrogen Sulfide as a Radical Scavenger

1972 ◽  
Vol 50 (15) ◽  
pp. 2391-2399 ◽  
Author(s):  
Guy J. Collin ◽  
Patrick M. Perrin ◽  
Christian M. Gaucher
Keyword(s):  
Hydrogen Sulfide ◽  
The Other ◽  
Radical Scavenger ◽  
Methyl Ethyl ◽  
Hydrogen Atoms ◽  
Radical Species ◽  
Alkyl Radicals ◽  
Vinyl Radicals ◽  
Ultraviolet Photolysis ◽  
Far Ultraviolet

The far u.v. photolysis of cis-2-butene, n-1-pentene, and cis-2-pentene was carried out in the presence of various quantities of hydrogen sulfide. We showed that in these systems, hydrogen atoms add to the double bond and are not scavenged by 5–10% hydrogen sulfide. On the other hand, alkyl radicals such as methyl, ethyl, s-butyl, and s-pentyl react with hydrogen sulfide, and the formation of the corresponding alkanes may be used to measure the absolute yields of the radical species. The same holds true for vinyl radicals. We also report some experiments published elsewhere. In particular, in the case of 1,3-butadiene, identification of the principal radicals is possible; however, measurement of absolute yields becomes more difficult.

Rate constant for chlorine abstraction from CCl4 by the 5-hexenyl radical

1987 ◽  
Vol 65 (2) ◽  
pp. 311-315 ◽  
Author(s):  
Deborah Rae Jewell ◽  
Lukose Mathew ◽  
John Warkentin
Keyword(s):  
Free Radical ◽  
Double Bond ◽  
Chlorine Atom ◽  
Rate Constant ◽  
Methyl Ethyl ◽  
Chain Mechanism ◽  
Secondary Product ◽  
Radical Chain ◽  
Alkyl Radicals ◽  
Primary Products

Cyclization of the 5-hexenyl free radical to the cyclopentylmethyl free radical was used to clock chlorine atom abstraction by 5-hexenyl from carbon tetrachloride in solution. The source of 5-hexenyl radicals was 5-hexenyl[1-hydroxy-1-methyl-ethyl]diazene ((CH3)2C(OH)N=N(CH2)4CH=CH2), which decomposes thermally in CCl4 by a radical chain mechanism to afford chloroform, acetone, nitrogen, 6-chloro-1-hexene, cyclopentylchloromethane, 1-hexene, and methylcyclopentane as primary products. 6-Chloro-1-hexene is converted, in part, to a secondary product, 1,1,1,3,7-pentachloroheptane, by radical chain addition of CC14 to the double bond. The rate constant for chlorine atom abstraction, kCl, was calculated from the product composition and the known rate constant for cyclization of the 5-hexenyl radical. For the temperature range 274–353 K, kCl is given by log (kCl/M−1 s−1) = (8.4 ± 0.3) − (6.2 ± 0.4)/θ where θ = 2.3 RT kcal mol−1, which leads to [Formula: see text]. This value is significantly smaller than recently reported estimates for other primary alkyl radicals.

The Use of Styrenes as Embedding Media for Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 488-489
Author(s):  
Edward D. De-Lamater ◽  
Eric Johnson ◽  
Thad Schoen ◽  
Cecil Whitaker
Keyword(s):  
Electron Microscopy ◽  
Surface Tension ◽  
Ultraviolet Light ◽  
Methyl Ethyl Ketone Peroxide ◽  
Methyl Ethyl ◽  
Styrene Polymerization ◽  
Radical Initiation ◽  
Tertiary Butyl ◽  
Low Viscosity ◽  
Free Radical Initiation

Monomeric styrenes are demonstrated as excellent embedding media for electron microscopy. Monomeric styrene has extremely low viscosity and low surface tension (less than 1) affording extremely rapid penetration into the specimen. Spurr's Medium based on ERL-4206 (J.Ultra. Research 26, 31-43, 1969) is viscous, requiring gradual infiltration with increasing concentrations. Styrenes are soluble in alcohol and acetone thus fitting well into the usual dehydration procedures. Infiltration with styrene may be done directly following complete dehydration without dilution.Monomeric styrenes are usually inhibited from polymerization by a catechol, in this case, tertiary butyl catechol. Styrene polymerization is activated by Methyl Ethyl Ketone peroxide, a liquid, and probably acts by overcoming the inhibition of the catechol, acting as a source of free radical initiation.Polymerization is carried out either by a temperature of 60°C. or under ultraviolet light with wave lengths of 3400-4000 Engstroms; polymerization stops on removal from the ultraviolet light or heat and is therefore controlled by the length of exposure.

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