Aliphatic Free Radicals Research Articles

Study of the thermal conversions of organic carbon of Huadian oil shale during pyrolysis

The essence of kerogen decomposition in retorting process is organic carbon conversion. FTIR and GC-MS methods were employed in analyzing the conversion process of “kerogen→bitumen” and “bitumen→shale oil” in this paper. To achieve a deeper investigation of thermochemical transformation of organic carbon during the oil shale retorting, a set of physical models of carbon chains were constructed and analyzed using the transition state theory (TST) of quantum chemistry with gauss03 package. According to the results, the main reactions in the transformation of kerogen to bitumen are the re-integration of macromolecular structure and the breakup of oxygen-bridged bonds. Long alkyl chains containing functional groups decompose and transform to shorter alkanes, alkenes and aliphatic free radicals. The rupture of alkanes happens first at the middle position of long carbon chains. Alkyl free radicals further convert to alkanes, alkenes or aromatic rings. The alkanes take the highest content in shale oil.

Kinetics and Reaction Mechanisms of Copper(I) Complexes with Aliphatic Free Radicals in Aqueous Solutions. A Pulse-Radiolysis Study

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics and Reaction Mechanisms of Copper(I) Complexes with Aliphatic Free Radicals in Aqueous Solutions. A Pulse-Radiolysis StudyNadav Navon, Gilad Golub, Haim Cohen, and Dan MeyersteinCite this: Organometallics 1995, 14, 12, 5670–5676Publication Date (Print):December 1, 1995Publication History Published online1 May 2002Published inissue 1 December 1995https://doi.org/10.1021/om00012a037RIGHTS & PERMISSIONSArticle Views291Altmetric-Citations51LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Oxidation of copper(II) bis(glycinate) by methyl free radicals in aqueous solutions. A pulse-radiolysis study

The reaction of {sm bullet}CH{sub 3} free radicals with Cu{sup II}(NH{sub 2}CH{sub 2}CO{sub 2}{sup {minus}}){sub 2} in aqueous solutions was studied. The formation of the unstable intermediate (NH{sub 2}CH{sub 2}CO{sub 2}{sup {minus}}){sub 2}Cu{sup III}-CH{sub 3}(aq) in this reaction was observed. This intermediate decomposes into Cu{sup III}(NH{sub 2}CH{sub 2}CO{sub 2}{sup {minus}}){sub 2}{sup +}(aq) + CH{sub 4}. The formation of Cu{sup III}(NH{sub 2}CH{sub 2}CO{sub 2}{sup {minus}}){sub 2}{sup +}(aq) is not observed, as this complex is short-lived under these conditions and decomposes via ligand oxidation. The {sm bullet}CH{sub 3} free radicals react with the transient complex (NH{sub 2}CH{sub 2}CO{sub 2}{sup {minus}}){sub 2}Cu{sup III}-CH{sub 3}(aq) to form ethane and Cu{sup II}(NH{sub 2}CH{sub 2}CO{sub 2}{sup {minus}}){sub 2}; the specific rate of this reaction approaches the diffusion-controlled limit. The results thus point out that aliphatic free radicals can oxidize copper(II) complexes to copper(III) complexes. The results suggest that the reactions of aliphatic free radicals with copper complexes might cause the reported radiosensitization by copper compounds. 18 refs., 3 figs., 3 tabs.

Metal Induced Decarboxylation of Aliphatic Free Radicals. I. Kinetics of the Reactions of Copper(I) and Copper(II) Ions with the 2‐Methyl‐2‐Carboxylicacid‐Propyl Free Radical in Aqueous Solutions. A Pulse Radiolysis Study

AbstractCH2C(CH3)2CO2H free radicals react with Cu2+aq to form CuIII‐CH2C(CH3)2CO2H2+aq, which probably is rapidly transformed into intermediate I. This intermediate decomposes into Cu+aq + CO2 + CH2=C(CH3)2. This is the first system in which a metal ion induced β‐carboxyl elimination reaction was observed. ·CH2C(CH3)2CO2H free radicals react with CuIII‐CH2C(CH3)2CO2H2+aq to form Cu2+aq and a mixture of (‐CH2C(CH3)2CO2H)2, (CH3)3CCO2H, and HOCH2C(CH3)2CO2H. CH2C(CH3)2CO2H reacts with Cu+aq to form CuII‐CH2C(CH3)2CO2H+aq. The latter intermediate decomposes both via homolysis and by a reaction with Cu2+aq to form 2Cu2+aq + (CH3)3CCO2H. The spectra of the intermediates and the kinetics of reaction are reported.

ChemInform Abstract: Formation and Decomposition of Transient Complexes with a Copper‐Carbon σ‐Bond in the Reaction of Copper(I) Phenanthroline with Aliphatic Free Radicals. A Pulse Radiolysis Study

ChemInform Abstract: Formation and Decomposition of Transient Complexes with a Copper‐Carbon σ‐Bond in the Reaction of Copper(I) Phenanthroline with Aliphatic Free Radicals. A Pulse Radiolysis Study

Formation and decomposition of transient complexes with a copper-carbon .sigma.-bond in the reaction of copper(I) phenanthroline with aliphatic free radicals. A pulse radiolysis study

The oxidation of copper(I) phenanthroline by /center dot/CH/sub 2/CH/sub 2/OH and /center dot/CH/sub 2/C(CH/sub 3/)/sub 2/OH free radicals yields ethylene and 2-methylpropene, respectively. During this process transients with a copper-carbon /sigma/-bond have been observed with an absorbance similar to that of copper(I) phenanthroline in the visible region. Rate constants for the formation of these transients are estimated to be larger than 10/sup 10/ M/sup /minus/1/ s/sup /minus/1/. These intermediates decompose via a /beta/-hydroxyl elimination reaction with specific rate constants of (1.7 /plus minus/ 0.4) /times/ 10/sup 3/ and (1.1 /plus minus/0.3) /times/ 10/sup 4/ s/sup /minus/1/ for /center dot/CH/sub 2/C(CH/sub 3/)/sub 2/OH and /center dot/CH/sub 2/CH/sub 2/OH in the pH range 4-10, respectively. The mechanism of the decomposition is discussed, and a stability constant for the ligation of /center dot/CH/sub 2/C(CH/sub 3/)/sub 2/OH and /center dot/CH/sub 2/CH/sub 2/OH to the cuprous complex is estimated to be larger than 6 /times/ 10/sup 6/ M/sup /minus//. 28 refs., 5 figs., 3 tabs.

Properties of complexes with cobalt–carbon bonds formed by reactions of aliphatic free radicals with nitrilotriacetate–cobalt(II) in aqueous solution. A pulse radiolysis study

The reactions of the aliphatic free radicals ˙R [˙R =˙CH3, ˙CH2OH, ˙CH(CH3)OH, ˙C(CH3)2OH, ˙CH(CH3)OC2H5, ˙CH2CO–2 and CO˙–2] with CoII(nta)(H2O)–2 in aqueous solutions yield the unstable transients (nta)CoIII—R(H2O)– with cobalt–carbon σ bonds. The complexes with ˙R =˙CH3, ˙CH2OH, ˙CH(CH3)OH, ˙C(CH3)2OH and ˙CH(CH3)OC2H5 decompose via homolytic cleavage of the cobalt–carbon bond. The kinetics of reaction of these free radicals with (nta)CoIII—R(H2O)– are reported. The only organic products of the latter reactions are the dimers R—R for ˙R =˙CH3 and ˙CH2OH, whereas a mixture of disproportionation products and dimers is formed for ˙R =˙CH(CH3)OH and ˙C(CH3)2OH. For ˙R =˙CH2OH, ˙CH(CH3)OH and ˙C(CH3)2OH the pKa values for the acidic dissociation of the alcoholic group in the complexes are reported. For ˙R =˙CH2OH the activation parameters for the homolytic dissociation of the cobalt–carbon bond and the acidic dissociation are reported. The ultraviolet–visible spectra of all the transients are reported.

ChemInform Abstract: Carbon‐Carbon Bond Formation in the Reaction of Aliphatic Radicals with Alkylcobaloximes.

AbstractThe alkylaquocobaloximes (I) react with aliphatic free radicals to form compounds such as (III) by highly specific C‐C bond formation with concomitant one‐electron reduction of the metal center to yield (II).

Carbon-carbon bond formation in the reaction of aliphatic radicals with alkylcobaloximes

Benzyl, methyl, ethyl, and isopropylaquocobaloximes, R'Co(dmgH)/sub 2/OH/sub 2/, react with aliphatic free radicals, R/sup ./, forming RR' and Co/sup II/(dmgH)/sub 2/OH/sub 2/. This reaction is quite general for aliphatic radicals, except for R = benzyl. Rate constants with R = /sup ./C(CH/sub 3/)/sub 2/OH and /sup ./CH(CH/sub 3/)OC/sub 2/H/sub 5/ exhibit little sensitivity toward the steric bulk of substituents on the ..cap alpha..-carbon atom of the organocobaloxime. This discounts homolytic displacement by attack at the organic group. It is proposed that the radical addition takes place at the nitrogen end of the N=C bond of the macrocycle cis to the Co-C bond, followed by the reductive elimination of RR'.

True stabilization: the behaviour of lead compounds against the thermal decomposition of polyvinyl chloride

Investigations which have been conducted within the last two decades into the behaviour of basic lead compounds as stabilizers against the thermal dehydrochlorination of polyvinyl chloride are summarized. It is shown that the results can be explained satisfactorily in terms of a free radical dehydrochlorination mechanism and a regenerative exchange process which interferes with the dehydrochlorination. This may be regarded as “true stabilization” in contrast to “hydrogen chloride scavenging”. In true stabilization it is proposed that aliphatic carboxylate groups (such as the stearate ion) react with reservoirs of basic lead compounds (such as white lead) to form relatively mobile salts (such as stearates of lead). Also, it is proposed that these salts take part in exchange reactions with chlorine atoms released by the PVC during free radical decomposition, to give innocuous chlorides of lead and the corresponding aliphatic carboxylate free radicals. Hence the chlorine atoms are trapped and no longer able to propagate dehydrochlorination of the polymer. Further, it is proposed that the aliphatic carboxylate free radicals can esterify PVC chains at sites where prior attack by chlorine atoms has abstracted methylenic hydrogen atoms leaving unpaired electrons. This step eliminates the stimulus for loss of chlorine atoms from the PVC, thereby also interfering with the free radical propagation mechanism. Subsequently, the pendant aliphatic carboxylate groups dissociate from the polymer chains with neighbouring chloromethylenic hydrogen atoms to form the corresponding acids, and leaving the chlorine atoms adjacent to carbon-carbon double bonds in relatively stable vinyl-type positions. The aliphatic carboxylic acids so formed can react with the basic lead compounds reservoir to regenerate mobile salts so that the stabilizing process is therefore continuous and cyclic. It is demonstrated that ionic and unimolecular mechanisms which normally are put forward to explain the behaviour of primary stabilizers in PVC are not satisfactory because they do not account for all observations made with basic lead stabilizing regimes. Other evidence which favours the free radical decomposition and stabilization mechanisms is cited, and a suggestion is made for further work.

Homolytic decomposition of tertiary organochromium(III) complexes and evidence for their decomposition via reactions with aliphatic free radicals. A pulse radiolysis study

Homolytic decomposition of tertiary organochromium(III) complexes and evidence for their decomposition via reactions with aliphatic free radicals. A pulse radiolysis study

Reactions of B12r with aliphatic free radicals: a pulse-radiolysis study

The spectra of the intermediates formed in the reactions of B/sub 12r/ with the free radicals Br/sub 2//sup -/., CO/sub 2//sup -/., .CH/sub 2/C(CH/sub 3/)/sub 2/OH, .C(CH/sub 3/)/sub 2/OH, . CH/sub 2/CHO, and .CH(OH)CH/sub 2/OH are reported. The results indicate that Br/sub 2//sup -/. oxidizes B/sub 12r/ to B/sub 12a/, via an inner-sphere mechanism, and CO/sub 2//sup -/ . reduces B/sub 12r/ to B/sub 12s/. All the aliphatic free radicals studied, .R, react with B/sub 12r/, yielding as the first product a pseudocoenzyme denoted Co/sup III/-R. Co/sup III/-CH/sub 2/C(CH/sub 3/)/sub 2/OH is stable for over a second in the pH range 3 to 10 as is Co/sup III/-CH/sub 2/CHO. The latter compound hydrolyzes in acid solutions to yield B/sub 12a/ and CH/sub 3/CHO. Co/sup III/-C(CH/sub 3/)/sub 2/OH and Co/sup III/-CH(OH)CH/sub 2/OH decompose heterolytically to yield mainly B/sub 12s/; a side reaction that probably yields Co/sup III/-H via a ..beta..-hydride shift is also observed. The kinetics of decomposition of Co/sup III/-CH(OH)CH/sub 2/OH in neutral solutions are reported. No water elimination from the latter intermediate occurs. The reasons for the latter observation are discussed. 6 figures.

Oxidation, reduction, and copper-carbon bond formation in the reactions of copper(II) tetraglycine with pulse radiolytically generated free radicals

The reactions of copper(II) tetraglycine (Cu/sup II/G/sub 4/) with a variety of aliphatic free radicals and with .Br/sub 2//sup -/ and .OH have been investigated by the pulse radiolytic technique. Three types of reaction are observed: (i) oxidation of Cu/sup II/G/sub 4/ to Cu/sup III/G/sub 4/ by .Br/sub 2//sup -/ and .OH; (ii) rapid reduction to copper(I) by .CH/sub 2/OH, .CO/sub 2//sup -/, and (CH/sub 3/)/sub 2/COH; (iii) formation of unstable copper(III)-carbon-bonded intermediates with lifetimes from several milliseconds to several seconds with .CH/sub 2/C(CH/sub 3/)/sub 2/OH, .CH/sub 2/CO/sub 2//sup -/, and .CH/sub 2/C(OH)CH/sub 3/ radicals. Rate constants are reported for formation and decomposition of all intermediates, and the relative instability of neutral Cu/sup III/(H/sub -2/G/sub 4/) compared to Cu/sup III/(H/sub -3/G/sub 4/)/sup -/ is confirmed by direct observation.

Reactions of aliphatic free radicals with copper cations in aqueous solution. Part 2.—Reactions with cupric ions: a pulse radiolysis study

Reactions of Cu2+aq with the aliphatic-free radicals ·CH2CO–2, CH3[graphic omitted]HCO–2, O–2C[graphic omitted]HCH(OH)CO–2, ·CCl3, [graphic omitted]H2CH2OH and ·CH2C(CH3)2OH in aqueous solutions were studied.

Reactions of aliphatic free radicals with copper cations in aqueous solutions. Part 3.—Reactions with cuprous ions: a pulse radiolysis study

Helium-saturated solutions containing copper sulphate and an aliphatic alcohol (methanol, ethanol or propan-2-ol) were pulse irradiated. The kinetics of the reactions thus initiated were followed by the spectrophotometric and conductometric techniques. The results indicate that all three radicals, ·CR1R2OH, react with Cu2+aq to yield Cu+aq+ CR1 R2O + H3O+. ·CH2OH radicals react with Cu+aq according to Cu+aq+·CH2OH ⇄ CuII—CH2OH+, K≈ 5 × 103 dm3 mol–1. The corresponding equilibrium constants for CuII—CH(CH3)OH+ and CuII—C(CH3)2OH+ are too low to be measured and the corresponding intermediates are not observed. Cu+aq reacts with the β radicals, ·CH2CH2OH and ·CH2CH(CH3)OH, according to Cu+aq+·CH2CR1R2OH → CuII—CH2CR1R2OH+. The latter intermediates decompose via acid catalysed reactions to yield Cu2+aq+ H2CCR1R2+ H2O.

Intermediates with copper–carbon bonds formed by the reaction of aliphatic free radicals with a copper–peptide complex in aqueous solutions

The reactions of ·CH2CO2– and ·CH2CMe2OH with a copper–peptide complex in neutral aqueous solutions yield relatively long lived intermediates with copper–carbon σ bonds.

Kinetics of the formation and decomposition of carbon-cobalt(III) bonds in aqueous solutions by the reaction of aliphatic free radicals with a coenzyme B-12r model cobalt(II) complex

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics of the formation and decomposition of carbon-cobalt(III) bonds in aqueous solutions by the reaction of aliphatic free radicals with a coenzyme B-12r model cobalt(II) complexHanoch Elroi and Dan MeyersteinCite this: J. Am. Chem. Soc. 1978, 100, 17, 5540–5548Publication Date (Print):August 1, 1978Publication History Published online1 May 2002Published inissue 1 August 1978https://doi.org/10.1021/ja00485a045RIGHTS & PERMISSIONSArticle Views106Altmetric-Citations37LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Theoretical analysis of long-range hyperfine interactions in aliphatic free radicals. Orgin of the W and anti-W rules

Theoretical analysis of long-range hyperfine interactions in aliphatic free radicals. Orgin of the W and anti-W rules

Decomposition of lauroyl, decanoyl, and octanoyl peroxides in solution

The thermal decomposition from 50 to 250° of lauroyl, decanoyl, and octanoyl peroxides in solution in a high molecular weight hydrocarbon was studied. These peroxides are convenient sources of C-11, C-9, and C-7 straight-chain aliphatic free radicals, whose reactions may be considered as models for the higher molecular weight radicals formed during thermal cracking of polyolefins.The ratio of disproportionation to combination for these radicals is about 0.2, which is very similar to the values obtained for lower alkyl radicals in the gas phase. This ratio appears to be relatively independent of temperature. Intramolecular chain transfer, which results in the isomerization of the radical, occurs at the higher temperatures, and the process has an apparent activation energy of about 2 kcal per mole.The product distribution indicates that at reaction temperatures up to 250° a statistically random distribution of alkyl radicals is never achieved in solution. Since the radicals are formed in pairs, they tend to react with each other rather than with radicals formed from other peroxide molecules. This is demonstrated by the near absence of cross-combination products when two different peroxides are decomposed in the same solution simultaneously at 70°. At 250°, some cross-product is formed but less than one-fifth of the amount expected if the radicals were uniformly distributed in the solution. The activation energy for the formation of cross-product is of the same order as that for diffusion. The significance of these results in terms of the classical picture of "cage reactions" is discussed.

Reactions of halogenoaliphatic acids with free radicals in aqueous solution. Part II. Reactions with aliphatic free radicals

Dehalogenation of halogenoaliphatic compounds by aliphatic free radicals was investigated. The reactivity of the radicals studied followed the sequence BrCH2·CH·OH ≃ ClCH2·CH·OH > (CH3)2C·OH > CH3·CH·OH > CH2·OH CBr2·CO2H > CH3·CBr·CO2H > BrCH·CO2H CH3·CH·CO2H ≃ CH2·CO2H. The last two radicals do not induce any dehalogenation. The reactivity of the substrates toward the radicals increases in the order ClCH2·CH2·OH < ClCH2·CO2H < BrCH2·CO2H < CBr3·CO2H. The results indicate a charge-transfer mechanism in these reactions rather than halogen abstraction.