Nitrate radical reaction with ethers

It is likely that as further anhydrous nitrates are prepared, further examples of such behavior will be found. Certain ruthenium nitrates also give nitrite on hydrolysis (28). All metal nitrates which by their covalent bonding can release NO2 radicals during reaction need not necessarily give nitrite on hydrolysis the latter is a complicated process which involves the coordination chemistry of the metal. For example, copper nitrate gives only nitrate ions in aqueous solution, but its reactions with ethers are at present interpreted on a free-radical basis. 

Only a few examples exist for the intermolecular trapping of allyl radicals with alkenes68,69. The reaction of a-carbonyl allyl radical 28 with silyl enol ether 29 occurs exclusively at the less substituted allylic terminus to form, after oxidation with ceric ammonium nitrate (CAN) and desilylation of the adduct radical, product 30 (equation 14). Formation of terminal addition products with /ram-con figuration has been observed for reaction of 28 with other enol ethers as well. 

Meldrum s acid, like other 1,3-dicarboxyl compounds, was amenable to radical reactions at C-5. The radical reaction between Meldrum s acid benzyl alkyl ethers mediated by InCl3/Cu(OTf)2 has been reported to proceed regioselectively at the benzylic position of the ether moiety (Scheme 35) <2006AGE1949>. Radical reaction of Meldrum s acid and alkenes was carried out with 2equiv of ceric ammonium nitrate (CAN) to give the a-carboxy-lactones which were subsequently subjected to decarboxylative methylenation affording the a-methylene lactones in 35-50% yield (Scheme 35) <2006SL1523>. 

Langer, S., E. Ljungstrom, I. Wangberg, T. J. Wallington, and O. J. Nielsen, Atmospheric Chemistry of Di-fert-butyl Ether—Rates and Products of the Reactions with Chlorine Atoms, Hydroxyl Radicals, and Nitrate Radicals, Int. J. Chem. Kinet, 28, 299-306 (1996). 

Bases, Neutral Salts.— As a base it forms salts, in which form the diazo compound is obtained by diazotization, and which though also unstable has been isolated in small quantities and the composition and properties determined. Of the three salts, the sulphate, chloride and nitrate, the first is the most stable and the last is the least stable. They are colorless crystalline neutral compounds soluble in water, difficultly soluble in alcohol and insoluble in ether. After being prepared by the ordinary diazo reaction, with sodium nitrite in cold acid water solution, they may be precipitated in crystalline form by the addition of alcohol and ether. If the diazotization is effected in alcohol solution by means of amyl nitrite or ethyl nitrite the crystals of the diazonium salt separate at once. These salts of diazo benzene all show true salt characteristics, e.g., they lower the freezing point of solutions. The diazo radical, (CeHs—N2—) is thus basic toward strong acids, and the hydroxide, the non-isolated hypothetical diazo benzene, CeHs—N2—OH, is the free base. It may be considered as the simplest aromatic diazo compound and the mother substance of all other members of the class. 

The reaction of NO3 with unsaturated ethers proceeds by addition to the >C=C< double bond. Both steric and inductive effects are known to influence the reactivity of NO3 with unsaturated alcohols, e.g. 2-methyl-3-butene-2-ol is slightly less reactive than 1-butene. Unsaturated ethers are more reactive than unsaturated alcohols towards NO3. Comparison of the measured rate constants shows that, similar to the reaction with O3, the presence of the carbonyl group decreases the reactivity of NO3 toward the >C=C< double bond. The reaction of NO3 with unsaturated oxygenates proceeds by addition to either one of the carbon atoms of >C=C< double bond, preferentially to the most substituted radical. In the presence of NOx, the reaction may ultimately lead to organic nitrates among the first generation products. 

The rate data for reaction of NO3 with aliphatic esters show that the presence of the ester group in an organic molecule has little influence on the reactivity compared to the parent alkane. The reactivity trends exhibited by the nitrate radical for reactions with alcohols, ethers and esters are similar to those shown for the analogous reactions of hydroxyl radicals. The major products identified from the NO3 radical-initiated oxidation of alcohols, ethers and esters under atmospheric conditions were esters, carbonyls and alkyl nitrates. Similar products arise from the reactions of OH radicals with these molecules under atmospheric conditions. 

In the second series of experiments, the products from the photo-oxidation of diethyl ether, carried out in a Teflon bag reactor at ppm and ppb levels, have been determined by withdrawing vapour samples and monitoring by gas chromatography, HPLC and by chemiluminescence analysis. The major reaction products which have been measured are ethyl formate, ethyl acetate, acetaldehyde, formaldehyde, PAN, methyl nitrate and ethyl nitrate. The products observed arise from the decomposition reactions of the 1-ethoxyethoxy radical and from its reaction with oxygen. The data enable the establishment of a quantitative mechanism for the photo-oxidative reaction. In addition the rate of conversion of NO to NO2, determined by chemiluminescence analysis, shows that for each molecule of ether reacted only one molecule of NO is converted to NO2. In further end-product analyses experiments, the OH radical initiated photo-oxidation of n-hexane or the photolyses of 2- or 3-hexyl nitrites were studied to examine the... 

A number of esters [10], ethers [11, 12] and alcohols [13] were investigated with respect to reactivity with nitrate radicals. Both absolute and relative rate methods were employed. Rate coefficients for the reaction of NO3 are given in Table 1. The rate coefficients for aliphatic esters may be predicted from available group reactivity factors for alkanes provided that formate carbonyl hydrogen atoms are treated as primary hydrogen atoms. The rate coefficients with temperature dependence for ethers and alcohols are valid between 268 to 363 K. 

ScarfogUero, M., B. Picquet-Varrault, J. Salce, R. Durand-Jolibois, and J.-F. Doussin (2006), Kinetic and mechanistic study of the gas-phase reactions of a series of vinyl ethers with the nitrate radical, J. Phys. Chem. A., 110, 11074—11081. 

Nitrated fluoro compounds are synthesized by electrophilic (NOz+), radical (NO2 ), or nucleophilic (NO2-) methods Indirect nitration routes can suppress the side reactions associated with severe reaction conditions and some nitration reagents Novel fluoronitro compounds, unobtainable by direct nitration, can also be pre pared For example, the nitration of (2-fluoro-2,2-dinitroethoxy)acetaldoxime followed by oxidation of the nitroso intermediate with hydrogen peroxide yields 2-fluoro-2,2-dinitioethyl 2,2-dinitroethyl ether [f] (equation 1)... 

Nitration of fluoroolefins can be achieved by several methods. Widely studied thermal reaction of N204 with fluoroolefins has a radical mechanism, although the low temperature reaction of nitrogen dioxide with polyfluorinated vinyl ethers proceeds as electrophilic addition of nitrosonium nitrate NO+ N02 across the C=C bond [6] ... 

Thiochroman-4-ones are converted to thiochromones by conversion to their trifropropylsilyl enol ethers and dehydrogenation with ceric ammonium nitrate. It is proposed that the reaction proceeds via a radical cation which undergoes desilylation. (l-Elimination from the cation generated by single-electron transfer completes the sequence (Scheme 206) <1995TL3985>. 

The paper discusses two types of reaction involving metal complexes, and it is postulated that each proceeds by an initial free-radical step. In reactions between metal carbonyls and N2O4—NO2 mixtures, the nature of the product depends upon the phase in which the reaction is carried out. In the liquid phase, where the predominant equilibrium is N204 N0+ + NO3-, metal nitrates or carbonyl nitrates are formed in the gas phase, where the equilibrium is N2O4 2NO2/ nitrites or their derivatives are produced. Reactions of Mn2(CO) o Fe(CO)5, Co2(CO)3, and Ni(CO)4 are discussed. Anhydrous metal nitrates in which the nitrate group is covalently bonded to the metal have enhanced reactivity. This is believed to result from the dissociation M—O—N02 M—O + NO2 This can explain the solution properties of beryllium nitrates, and the vigorous (even explosive) reaction of anhydrous copper nitrate with diethyl ether. 

Alternatively, 5-allyl-2(5/f)-furanones can be obtained from TMSOF and allylic acetates using lithium perchlorate in ether. 5-Propargyl-2(5//)-furanones are prepared by coupling with bex-acarbonyldicobalt complexes of propargylium cations (eq 5). Reaction of the intermediate complex with cerium(TV) ammonium nitrate removes the cobalt Fluoroalkylation is acbieved by using bis(fluoroalkanoyl) peroxides in 1,1,2-tricbloro-1,2,2-trifluoroethane (Freon 113) (eq 6). This process is believed to involve combination of a fluoroalkyl radical with the furan-derived radical cation. 

Applications of Crown Ethers.—Crown ethers have been found to form molecular complexes with bromine that can be used as reagents in bromination reactions, e.g. of alkenes. The crown-halogen interaction seems not to be encapsulation but rather to be the formation of a polymeric structure. The complexes of nitro-nium tetrafluoroborate (NO2BF4) with various crown ethers, for example the 1 1 complex with 18-crown-6, have been reported to be selective nitrating agents. A new rapid synthesis of alkylseleno- and alkyltelluro-arenes from arenediazon-ium tetrafluoroborates and dialkyl diselenides or ditellurides employs KOAc and 18-crown-6 as a phase-transfer catalyst a radical mechanism has been suggested. Fluorine-19 n.m.r. evidence has been presented to show that KF forms... 

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