Reactions of alkyl radicals. Part 1.—Methyl radical photosensitized decomposition of ethyl formate

1962 ◽  
Vol 58 (0) ◽  
pp. 676-684 ◽  
Author(s):  
J. C. J. Thynne
Keyword(s):  
Ethyl Formate ◽  
Methyl Radical ◽  
Alkyl Radicals

Ultraviolet Photodissociation of Gas-Phase Alcohols, Amines, and Nitroalkanes

1996 ◽  
Vol 50 (5) ◽  
pp. 608-613 ◽  
Author(s):  
Philip L. Ross ◽  
Scott E. Van Bramer ◽  
Murray V. Johnston
Keyword(s):  
Vacuum Ultraviolet ◽  
Large Species ◽  
Methyl Radical ◽  
Alkyl Radicals ◽  
Bond Dissociation ◽  
Free Jet ◽  
Flight Mass Spectrometry ◽  
Collisional Cooling ◽  
193 Nm ◽  
Substituted Alkanes

The 193-nm photochemistry of alcohols, amines, and nitroalkanes in the C3-C6 size range is presented. The photolysis products are photoionized with coherent vacuum ultraviolet radiation and analyzed by time-of-flight mass spectrometry. For alcohols and amines, C-C bond dissociation competes with dissociations involving the heteroatom (C-O, O-H, C-N, N-H). Dissociation of the α(C-C) bond is preferred over other locations. Dissociation of a C-C bond is suppressed when a methyl radical would be produced. This behavior is similar to that observed for other substituted alkanes. Nitroalkanes exhibit both C-N and N-O bond dissociation pathways. Their low bond energies cause a substantial amount of internal energy to be partitioned among the primary photodissociation products. Under collision-free conditions, the alkyl radicals produced from these molecules undergo extensive secondary fragmentation. If the photodissociation step is performed in a free jet expansion, collisional cooling stabilizes the primary products and allows large species, such as intact pentyl and hexyl radicals, to be detected.

scholarly journals The polymerization of olefines induced by free radicals

1941 ◽  
Vol 179 (977) ◽  
pp. 169-193 ◽  
Keyword(s):  
Methyl Radical ◽  
Reaction Cycle ◽  
Alkyl Radicals ◽  
Successive Addition ◽  
Rate Of Polymerization ◽  
Alternative Processes ◽  
Complex Polymer ◽  
Ethyl Radicals ◽  
Kinetics Of ◽  
Polymerization Chain

The rate of photolysis of the simple aldehydes at 300° is in general reduced by ethylene, propylene or iso -butylene, and many molecules of the olefine may undergo an induced polymerization for each quantum of light absorbed by the aldehyde. A similar polymerization is induced by photolysis of ketones. The kinetics of these interdependent processes have been investigated by combining pressure measurements with chemical analysis at each stage, the rates of olefine polymerization and of aldehyde photolysis being independently determined. The experimental results accord with a mechanism in which large radicals are built up by the successive addition of olefine molecules to the primary radicals from the photolysis of the aldehyde or ketone. When the polymer radicals contain approximately three olefine molecules they undergo one of two alternative processes, either breaking down by regeneration of a methyl radical which begins a new polymerization chain, or giving inactive products. The former ‘transfer process’ explains how the chain length of the reaction may be large, yet the molecular weight of the product comparatively small. Certain differences between acetaldehyde and propionic aldehyde are explained by the fact that the ethyl radicals from the latter may regenerate in the course of the reaction cycle m ethyl radicals o f slightly greater reactivity. A quantitative comparison o f the various reactions shows that on ascending the series of alkyl radicals their reactivity towards both aldehydes and olefines diminishes only slowly. On ascending the olefine series, how ­ ever, the rate of polymerization rapidly decreases. This depends not upon a lowered efficiency of reaction of the primary radicals with the olefines, but rather upon a greater tendency of the more complex polymer radicals to be transformed into products which do not continue the reaction cycle.

scholarly journals Selective deoxygenative alkylation of alcohols via photocatalytic domino radical fragmentations

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hong-Mei Guo ◽  
Xuesong Wu
Keyword(s):  
High Reactivity ◽  
Methyl Radical ◽  
Primary Alcohols ◽  
Homolytic Cleavage ◽  
One Pot ◽  
Alkyl Radicals ◽  
Tertiary Alcohols ◽  
Mild Conditions ◽  
Radical Generation ◽  
Selective Formation

AbstractThe delivery of alkyl radicals through photocatalytic deoxygenation of primary alcohols under mild conditions is a so far unmet challenge. In this report, we present a one-pot strategy for deoxygenative Giese reaction of alcohols with electron-deficient alkenes, by using xanthate salts as alcohol-activating groups for radical generation under visible-light photoredox conditions in the presence of triphenylphosphine. The convenient generation of xanthate salts and high reactivity of sequential C–S/C–O bond homolytic cleavage enable efficient deoxygenation of primary, secondary and tertiary alcohols with diverse functionality and structure to generate the corresponding alkyl radicals, including methyl radical. Moreover, chemoselective radical monodeoxygenation of diols is achieved via selective formation of xanthate salts.

H2O2-Promoted Alkylation of Quinoxalin-2(1H) ones with Styrenes and Dimethyl sulfoxide

Synlett ◽  
2021 ◽  
Author(s):  
Xiaoyang Zhong ◽  
Hua Yao ◽  
BIngqing Wang ◽  
Yan Zhaohua ◽  
Feng Xiong ◽  
...  
Keyword(s):  
Dimethyl Sulfoxide ◽  
Methyl Radical ◽  
Alkyl Radicals ◽  
Simple Protocol

A H2O2-mediated quinoxaline-2(1H)-ones hydrocarbylation reaction has been reported. The reaction is achieved through the difunctionalization of styrene. In this transformation, methyl radical resulting from dimethyl sulfoxide firstly attacks styrenes to provide alkyl radicals which then undergo alkylation at the C3 position of quinoxalin-2(1H)-one. A green, convenient, and simple protocol for the synthesis of 3-alkylquinoxalin-2(1H)-ones was provided.

Copper Catalyzed sp3 C-H α-Acetylation

2019 ◽  
Author(s):  
Otome Okoromoba ◽  
Eun Sil Jang ◽  
Claire McMullin ◽  
Thomas Cundari ◽  
Timothy H. Warren
Keyword(s):  
Natural Products ◽  
Dft Studies ◽  
Alkyl Radicals ◽  
Important Chemical ◽  
Alkyl Electrophiles ◽  
Synthetic Intermediates ◽  
Alkylation Reactions

<p>α-substituted ketones are important chemical targets as synthetic intermediates as well as functionalities in in natural products and pharmaceuticals. We report the sp<sup>3</sup> C-H α-acetylation of sp<sup>3</sup> C-H substrates R-H with arylmethyl ketones ArC(O)Me to provide α-alkylated ketones ArC(O)CH<sub>2</sub>R at RT with <sup>t</sup>BuOO<sup>t</sup>Bu as oxidant via copper(I) β-diketiminato catalysts. Proceeding via alkyl radicals R•, this method enables α-substitution with bulky substituents without competing elimination that occurs in more traditional alkylation reactions between enolates and alkyl electrophiles. DFT studies suggest the intermediacy of copper(II) enolates [Cu<sup>II</sup>](CH<sub>2</sub>C(O)Ar) that capture alkyl radicals R• to give R-CH<sub>2</sub>C(O)Ar under competing dimerization of the copper(II) enolate to give the 1,4-diketone ArC(O)CH<sub>2</sub>CH<sub>2</sub>C(O)Ar.</p>

Copper Catalyzed sp3 C-H α-Acetylation

2019 ◽  
Author(s):  
Otome Okoromoba ◽  
Eun Sil Jang ◽  
Claire McMullin ◽  
Thomas Cundari ◽  
Timothy H. Warren
Keyword(s):  
Natural Products ◽  
Dft Studies ◽  
Alkyl Radicals ◽  
Important Chemical ◽  
Alkyl Electrophiles ◽  
Synthetic Intermediates ◽  
Alkylation Reactions

<p>α-substituted ketones are important chemical targets as synthetic intermediates as well as functionalities in in natural products and pharmaceuticals. We report the sp<sup>3</sup> C-H α-acetylation of sp<sup>3</sup> C-H substrates R-H with arylmethyl ketones ArC(O)Me to provide α-alkylated ketones ArC(O)CH<sub>2</sub>R at RT with <sup>t</sup>BuOO<sup>t</sup>Bu as oxidant via copper(I) β-diketiminato catalysts. Proceeding via alkyl radicals R•, this method enables α-substitution with bulky substituents without competing elimination that occurs in more traditional alkylation reactions between enolates and alkyl electrophiles. DFT studies suggest the intermediacy of copper(II) enolates [Cu<sup>II</sup>](CH<sub>2</sub>C(O)Ar) that capture alkyl radicals R• to give R-CH<sub>2</sub>C(O)Ar under competing dimerization of the copper(II) enolate to give the 1,4-diketone ArC(O)CH<sub>2</sub>CH<sub>2</sub>C(O)Ar.</p>

Visible-Light Photosensitized Aryl and Alkyl Decarboxylative Carbon-Heteroatom and Carbon-Carbon Bond Formations

2019 ◽  
Author(s):  
Tuhin Patra ◽  
Satobhisha Mukherjee ◽  
Jiajia Ma ◽  
Felix Strieth-Kalthoff ◽  
Frank Glorius
Keyword(s):  
Energy Transfer ◽  
Visible Light ◽  
Alkyl Radical ◽  
General Strategy ◽  
Alkyl Radicals ◽  
Bond Forming ◽  
Radical Trapping ◽  
Carbon Carbon Bond ◽  
Radical Generation ◽  
Trapping Agent

<sub>A general strategy to access both aryl and alkyl radicals by photosensitized decarboxylation of the corresponding carboxylic acids esters has been developed. An energy transfer mediated homolysis of unsymmetrical sigma-bonds for a concerted fragmentation/decarboxylation process is involved. As a result, an independent aryl/alkyl radical generation step enables a series of key C-X and C-C bond forming reactions by simply changing the radical trapping agent.</sub>

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