Bis nitroxide

PPH in the presence of III (or its bis-nitroxide) we have found that the doubly grafted species V is generated in much larger quantities (23.) ... 

Weber et al. have developed pulsed electron double resonance (PELDOR) at S-band, and used it to probe the dipolar and exchange interactions in the bis-nitroxides 13 - 16, where in the ester-bridged compounds the exchange interactions are diminished relative to the acetylene-bridged compounds, whilst maintaining a similar separation.10 They also demonstrate distance measurements by this technique. 

Oxidation of the four N atoms in N1 leads to trinitroxide NOl and tetranitroxide N02. By comparison with spectra of the bis(nitroxide) radical cation, NOS, it could be concluded that in N02 +, a radical cation comprising all four NO moieties is formed. This can be anticipated from the EPR spectrum (narrow, g factor = 2.0061) and the substantially lower oxidation potential of N02 (1.37 V versus Ag/AgCl) in comparison to NOl and NOS (1.65 V versus Ag/AgCl, both). moreover, a characteristic absorption at 1020nm was found for N02. ... 

Thus, the Pyrex-filtered irradiation of an acetonitrile solution of 2,3-diazabicy-clo[2.2.1]hept-2-ene 1 (R, R, R, R = H) in a Rayonet photoreactor in the presence of nitr-oxide and with benzophenone employed as a triplet photosensitizer gave bicyclo[2.1. Ojpentane (4) in 40% yield and the two bis-nitroxide adducts cis- and trans-5 in 21 and 39% yields, respectively, based on 60% conversion. Separately generated bicyclo[2.1.Ojpentane was shown to be unreactive towards the nitroxide under the conditions of the photolysis furthermore no reaction occurred in the absence of light. However, these bis-nitroxide photoadducts were also produced, albeit to a smaller extent, when the reaction was carried out in the absence of benzophenone, implying that the nitroxide itself may act as a sensitizer. This triplet cyclopenta-1,3-diyl diradical has also been generated in the gas phase. ... 

The publications dealing with the mechanism of copolymerization of trifluoronitrosomethane with tetrafluoroethylene and the cross-linking of trifluoronitrosomethane-tetrafluoroethylene-hexafluorobuta-l, 3-diene copolymers with the new bis-nitroxide 0-N(CF3)CF2-CF2-N(CF3)-0-deserve further space here, on the grounds of long-standing academic and industrial interest, respectively. 

U.v. irradiation of perfliioro-AUV -difluoropipeiazine in the presence of oxyeen and/or silica yields a wax which changes into a purple liquid believed to contain the bis-nitroxide... 

CF, N 0 PCls O N(CFs) CFj CF,. Further work is in progress. tit is not necessary to isolate the bis-hydroxylamine prior to the oxidation stage. On one occasion a volatile yellow liquid was produced in the oxidation step, and this exploded violently when attempts were made to separate it from the bis-nitroxide removal of chloride ion from the hydrolysate as silver chloride eliminates this problem. 

Conti et aV have studied the bis-nitroxide fulleropyrrolidine 6 by CW and time-resolved (TR-)EPR. The CW spectrum of 6 in toluene solution reveals that the exchange between the nitroxides expressed as J/g is temperature dependent from ca. 2 mT at 350 K to ca. 3.5 mT at 250 K. More importantly, an excited S = 2 state is observed by TR-EPR upon photoexcitation. This is a rare example of spin states of higher than triplet multiplicity being observed by TR-EPR. 

Table 6 Structure of monomers and nitroxides employed in the synthesis of linear ABA triblock copolymers by NMP from difunctional alkoxyamines or bis-nitroxides... 

A stable nitroxide such as 2,2,6,6-tetramethylpiperidine-l-oxyl (TEMPO) was originally used as the initiator, which helped to maintain the equilibrium between dormant and active chains during the propagation step. This ensures the formation of polymers with narrow MW distributions. However, the main disadvantage of using TEMPO is that it requires a high polymerisation temperature (>120 °C). Subsequently, numerous nitroxides derivatives (acyclic, cyclic (5,6,7,8-membered ring), aromatic), bis-nitroxides and... 

Bis(trifluoromethyl)nitroxide displaces the dimethylamino-group from tris(dimethylamino)phosphine to form (59). 

Chakraborty and Scott have reported the detection of N-OH groups in the photo-oxidation of methylcyclohexane containing a bis-piperidine or a nitroxide, based on their observation of an IR absorption at 2765 cm-1(13). However we have found the )>N-0H absorption to occur at 3 60 cm 1 (ll) in 1-hydroxyl-2,2,6,6-tetramethylpiperidines which throws some doubt on their IR detection of >N0H. 

An early example of an application of ENDOR to extract hyperfine couplings from a very complex, poorly resolved ESR spectrum is that of Allendoefer and Englemann19 who studied a solution of bis(p-methoxyphenyl)nitroxide and obtained the results shown in Table 2.4. The figures in parentheses indicate the level of precision. 

Amino-3-methylisoxazole, 1502 2-Amino-4-methyloxazole, 1500 5-Amino-3-methylthio-l,2,4-oxadiazole, 1192 Ammonium A-nitrosophenylaminooxide, 2399 2-Aza-l,3-dioxolanium perchlorate, 0898 Azoformaldoxime, 0815 Bis(l-benzo[d]triazolyl) carbonate, 3598 Bis(l-benzo[d]triazolyl) oxalate, 3629 Bis(trifluoromethyl) nitroxide, 0638 2-/er/-Buty 1-3 -phenyloxaziridine, 3406 Calcium bis(O-hydroxylamide). 3930 Calcium hydroxide O-hydroxylamide, 3929... 

The treatment of C q with an excess of bis(trifluoromethyl)nitroxide [(CF3)2NO radicals] leads to multiple additions with an average of 18 (Cp3)2NO groups bound to the fuUerene sphere (Scheme 6.16) [74]. The reaction has been carried out in a glass tube equipped with a Teflon valve. The resulting light brown solid decomposes above 158 °C. 

Early publications on [VO(/3-diketonato)2] have been reviewed.355 More recently, complexes with benzoyl m-nitroacetanilide, benzoyl acetanilide545 and l,l -(l,3-phenylene)-bis(butane-1,3-dione546 have been synthesized. Other [VO(/S-dik)2] adducts have been isolated, for example [VO(acac)2] adducts with a series of pyridine N-oxides547 and several pyridine carboxamides, 48 and [VO(bzac)2] adducts with pyridine, methylamine, isoquinoline and 4-picoline.549 Equilibrium constants of 1 1 and 2 1 adducts of pyrazine with [VO(tfacac)2] have been determined (equation 38).550 In the 2 1 complex, the pyrazine bridge between two equatorial sites of adjacent vanadium atoms promotes a weak exchange interaction. The nitroxide radical 2,2,6,6-tetramethylpiperidinyl N-oxide also forms an adduct with [VO(hfacac)2] in which there is a strong interaction between the electrons on the metal and nitroxide.551... 

Bis(trifluoromethyl) nitroxide abstracts aldehydic hydrogen atoms from perfluorobenzaldehyde with great case, to give the ( [bis(trifluoromethyl)amino]oxyjcarbonyl)arene in almost quantitative yields.188 The reaction has also been extended to other classes of compounds (vide infra).189... 

V,/V-Bis(trifluoromethyl)hydroxylamine (5) is oxidized with potassium permanganate in acetic acid to an interesting free-radical compound, bis(trifluoromethyl)nitroxid-A7-yl(6), a pink-violet gas which condenses to a deep brown-violet liquid.246 Various oxidizing agents are effective in the oxidation of 5 to the corresponding nitroxyl 6.247 The best appears to be cerium(IV) salts either in the solid state or in aqueous acid solution.247 Efficient oxidation processes have been developed using aqueous potassium persulfate solutions, or electrochemical oxidation with cerium(III) nitrate and sodium nitrate in dilute nitric acid.247... 

See Platinum hexafluoride Bis(trifluoromethyl) nitroxide See other N—O COMPOUNDS... 

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