Aminomethyl radical

Although Otsu et al. [12] have studied the BPO-DMA system by electron spin resonance (ESR) technique and trapped the aminomethyl radical, there is still a lack of direct proof of the above second step, particularly concerning the behavior of the aminium radical salt. We [13] have proposed the aminium radical salt with purple color through this reaction of DMT with CCI4 in the presence of O2 following the displacement reaction as ... 

This aminium radical salt in aqueous solution in the form of solvated radical salt is very stable and will not polymerize acrylonitrile even with CeHsCOONa to form the corresponding benzoate. Therefore, we believe that in the nucleophilic displacement, there must be some intermediate step, such as intimate ion pair and cyclic transition state, which will then proceed the deprotonation to form the active aminium radical ion [14], as shown in Scheme 1. The presence of the above aminomethyl radical has also been verified [15] through ultraviolet (UV) analysis of this polymer formed such as PAN or PMMA with the characteristic band as the end group. 

The spin adducts of free radicals and MNP or DMPO were observed by means of an ESR spectrometer. The data of hyperfine splitting constants were compiled in Tables 9 and 10 [40-42,44,45]. ESR studies on the initial free radicals revealed that the monoalkylamino radical RHN-, dialkylamino radical R2N-, and aminomethyl radical -CH2N< or aminoethylidene radical >N( CHCH3) were obtained from the corresponding primary, secondary, and cyclic tertiary amine. In case of a tertiary diamine such as TMEDA, formation of... 

Thus, an aminium radical from primary or secondary amine will at last form an amino radical instead of an aminomethyl radical. This amino radical will then serve as the only active radical species to initiate the vinyl polymerization. 

The high-molecular weight was assigned to the PMMA grafted to the copolymer chains and the low-molecular weight to the PMMA initiated by the MMA radical (II). However, only one molecular weight distribution peak was observed for the PMMA initiated by the latter system, i.e., in combination with BP, which implies that only aminomethyl radicals are capable of initiating the polymerization. 

Hug GL, Bonifacic M, Asmus K-D, Armstrong DA (2000a) Fast decarboxylation of aliphatic amino adds induced by 4-carboxybenzophenone triplets in aqueous solutions. A nanosecond laser flash photolysis study. J Phys Chem B 104 6674-6682 Hug GL, Carmichael I, Fessenden RW (2000b) Direct EPR observation of the aminomethyl radical during the radiolysis of glycine. J Chem Soc Perkin Trans 2 907-908 Hunter EPL, DesrosiersMF, Simic MG (1989) The effect of oxygen, antioxidants and superoxide radical on tyrosine phenoxyl radical dimerization. Free Rad Biol Med 6 581-585 Ito O (1992) Flash photolysis study for reversible addition reactions of thiyl radicals with olefins and acetylenes. Trends Phys Chem 3 245-266... 

The first step in the formation of the dihydrofullerenes is electron transfer and proton loss. The C02 loss from carboxyl radicals is well known [233], The so-formed aminomethyl radical then adds to C6o- The final step is the abstraction of hydrogen from the environment (Scheme 23). 

Ammonia is formed in a yield about equal to hydrogen. Part of it may have the amino radical (reaction 60) identified by flash photolysis (229,230), as precursor, but other routes to ammonia are probably more important (reactions 65-68). The combination of the methylamlno radical [6] with the aminomethyl radical [7] leads to [8]. The structure of [8] resembles that of the hemiacetals which are known to be unstable so that [8] is involved in the equilibrium 67. An alternative route (reaction 68), which gives rise to ammonia and an alkylideneimine such as [10],... 

S02-extrusion affords the electrophilic radical 49 (Scheme 10). Intramolecular homolytic substitution eventually gives tetrahydronaphthalene 50 (92%). Beckwith showed that the A-(o-bromophenyl)amide 51 can be transformed into the corresponding oxindole 54 (70%) at high temperatures using BusSnH via tandem radical translocation of the initially formed aryl radical 52 to form 53 with subsequent intramolecular homolytic substitution [77]. The nucleophilic a-aminomethyl radical 55 reacted in a tandem addition/homolytic aromatic substitution reaction via radical 56 to tetrahydroquinoline 57 [78]. Radical 55 can either be prepared by oxida-... 

However, the same interaction— hyperconjugation— is present in the parent amine, as revealed by spectroscopic features of the C—H bond (see Section 1.1.8). Recent direct measurements have been made for (CH3)3N and (CH3CH2)3N, as well as the pyrrolidine and piperidine, among others. The results obtained are shown below. The recommended value for the RSE for the aminomethyl radical is 13 1 kcal/mol. Similar results were obtained using G2(MP2) calculations with isodesmic reactions. Pyrrolidine, the five-membered cyclic amine, has a slightly larger RSE because there is some relief of eclipsing interactions in the radical. 

In 1982, Ohga and Mariano first reported the photoallylation of iminium salts. The photoreaction of iminium salts with allyl-trimethylsilane in acetonitrile affords allylated compounds via the addition of an allyl radical to an a-aminomethyl radical. Allyl radicals are produced via the cleavage of C-Si bonds of allylsilane radical cations and the a-aminomethyl radicals are generated by one-electron reduction of iminium salts as shown in Scheme 4. 

CHP were heated in acetonitrile at 100°C in a sealed NMR tube, the formation of 12b was clearly indicated by the appearance of a sharp singlet at 55 ppm. Proof of the formation of 12b was provided by the addition of an authentic sample to the reaction mixture after partial thermolysis, leading to an increase in intensity for all appropriate NMR signals. We suggest that is formed by addition of CHP to the formaldehyde N-methylanilinium ion, generated from a-aminomethyl radical 1 one-electron oxidation. 

Derivatives With Cumene Hydroperoxide. Oxazolidine Formation Via Addition of a-Aminomethyl Radicals to Formaldehyde," J. Org. Chem., 1483 (1983). 

The reaction of substituted aminomethyl radicals with benzoyl, acetyl or cyclohexanesulfonylacetyl peroxides involves at least partially the free radical process of Scheme 26 (Horner and Schwenk, 1944 Homer and Betzel, 1953 Horner and Anders, 1962 Walling and Indictor, 1958 Hrabak and Lokaj, 1970). The same products are also formed by the ionic Polonovski-type reaction involving the intermediate PhN(Me)202CPh PhCOJ which decomposes to PhN(Me)CH202CPh via PhI (Me)(02CPh)CH2. ... 

The radiolytic oxidation of glycine anion by OH was studied by pulse radiolysis CWTR EPR. Both aminomethyl radicals CH2NH2 and H2N-CH-CO2-, with a yield of 29% for -CHjNHj and 53% for H2N-CH-C02 , were identified. No EPR lines attributable to the aminyl radical HN-CH2-CO2 were directly detected. However, clear evidence for the presence of the aminyl radical was obtained in spin trapping experiments. The implications of the results of Hug et al are discussed in the context of the recently proposed scheme for the oxidation of glycine anions by Bonifacic et al (cf. also Section 2.2.1.5). 

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