Amine oxide, structure

In the oxide of trimethylamine, (GH3)3NO, the electron diffraction data of Lister and Sutton show that the NO bond distance is 1 36 A which is approximately the value for a single bond. If the nitrogen were penta valent, the bond would be double and the distance less and evidently, in the amine oxides, structures of the type (GH3)3N—O, make a large contribution. In nitrosyl chloride and nitrosyl bromide the NO bond length is decreased, from i ii to 1 14 A, which suggests that the bond is a hybrid of the structures... 

Like amine oxide elimination, selenoxide eliminations normally favor formation of the E-isomer in acyclic structures. In cyclic systems the stereochemical requirements of the cyclic TS govern the product composition. Section B of Scheme 6.21 gives some examples of selenoxide eliminations. 

The effects on the dynamics of photo-injected electrons where not systematically studied, despite scattered reports on the influence of amines, which induce surface deprotonation, and lower surface charge with a resulting negative shift in band edge position and an increase in the open circuit potential, Voc [103], The opposite effect is induced by Li+ ions, which intercalate in the oxide structure. Guanidinium ions increase Voc when used as counterions in place of Li+. Other adsorbing molecules that influence both Voc and short circuit current are polycar-boxylic acids, phosphonic acids, chenodeoxycholate and 4-guanidinobutyric acid. 

With Increased proton character, the H has a tendency to hydrogen bond. Below pH 7.5, the appearance of the cationic form has a marked condensing effect In association with unionized amine oxide and results In the production of elongated structures replacing progressively the small and spherical micelles of LDAO In the nonlonlc form. Below pH 4.5, the elongated structures are progressively converted Into low viscosity, small spherical micelles made of LDAOH. 

Binda, C., Mattevi, A. and Edmondson, D.E. (2002) Structure-function relationships in flavoenzyme-dependent amine oxidations. A comparison of polyamine oxidase and monoamine oxidase. The Journal of Biological Chemistry, 277, 23973-2397(>. 

The oxidation by amine oxides provides a basis for selection among non-equivalent groups on boron. In acyclic organoboranes, the order of reaction is tertiary > secondary > primary. In cyclic boranes, stereoelectronic factors dominate. With 9-BBN derivatives, for example, preferential migration of a C—B bond which is part of the bicylic ring structure occurs. 

In a previous publication ( ), results were presented on the micellar properties of binary mixtures of surfactant solutions consisting of alkyldimethylamine oxide (C12 to Cig alkyl chains) and sodium dodecyl sulfate. It was reported that upon mixing, striking alteration in physical properties was observed, most notably in the viscosity, surface tension, and bulk pH values. These changes were attributed to 1) formation of elongated structures, 2) protonation of amine oxide molecules, and 3) adsorption of hydronium ions on the mixed micelle surface. In addition, possible solubilisation of a less soluble 1 1 complex, form between the protonated amine oxide and the long chain sulfate was also considered. 

This interpretation is confirmed by the solution behaviour of CisDAO/SDS mixtures. Solutions of these two components have been shown to be turbid and birefrlngent, and the addition of SDS to C18DA0 results in the production of filament-like structures and an increase in the bulk pH value, suggesting the formation of a new species between protonated CieDAO and SDS, which is also responsible for the surface tension lowering ( 1.) The increase in bulk pH value is then a consequence of the consumption of hydrogen ions in the production of cationic amine oxide, and the protonated amine oxide and the long chain sulfate precipitate out stoichiometrlcally. 

The difference between the behavior of the amine oxides and phosphine oxides can be rationalized in terms of the possibility of back bonding in the latter. Whereas amine oxides are restricted to a single structure containing u dative N—O bond. RjN— 0. the phosphine oxides can have contributions from [Pg.969]

Lindsay Smith JR, Mead LAV. Amine oxidation. Part VII. The effect of structure on the reactivity of alkyl tertiary amines toward alkaline potassium hexacyanoferrate(III). Chem Soc Perkin II 1973 206-210. 

Hadzi, D., Hydrogen bonding in some adducts of oxygen bases with acids. Part I. Infrared spectra and structure of crystalline adducts of some phosphine, arsine, and amine oxides, and sulphoxides with strong acids, J. Chem. Soc., 5128, 1962. 

As noted previously, the formation of approximately tetrahedral bonds to nitrogen occurs principally in ammonium cations (R,N+), amine oxides (R3N+—O"), and Lewis add-base adducts (e.g., R3N+—B X3). In the amine oxides and these adducts, the bonds must have considerable polarity in the amine oxides, for instance, N — O donation cannot be effectively counterbalanced by any back-donation to N. In accord with this, the stability of amine oxides decreases as the R3N basidty decreases, since the ability of N to donate to O is the major factor. Similarly, R3N —> BX3 complexes have stabilities that are roughly parallel to R3N basicity for given BX3. When R is fluorine, basicity is minimal and F3N —> BX3 compounds are unknown. It is, therefore, curious that F3NO is an isolable compound. Evidently the extreme electronegativity of fluorine coupled with the availability otpir electrons on oxygen allows the structures in (9-V) to contribute to stability. 

The compound is not a typical amine oxide, R3NO, since the short N—O bond of 1.159 A indicates a high degree of double bond character. It is best described as a resonance hybrid of ONF2F structures this is consistent with the rather long polar N—F bonds, 1.432 A. 

The consequences of vacant d orbitals are also evident on comparing the amine oxides, R3NO, with R3PO or R3AsO. In the V-oxide the electronic structure can be represented by the single canonical structure R3N+—O-, whereas for the others the bonds to oxygen have multiple character and are represented as resonance hybrids ... 

When the alcohol is secondary, the possibility for kinetic resolution exists if the titanium tartrate complex is ctqxiUe of catalyzing the enantioselective oxidation of the amine to an amine oxide (or other oxidation product). The use of the standard asymmetric epoxidation complex, i.e. Ti2(tartrate)2, to achieve such an enantioselective oxidation was unsuccessful. However, modification of the complex so that the stoichiometry lies between Ti2(tartrate)i and Ti2(tartrate)i.s leads to very successful kinetic resolutions of p-hydroxyamines. A representative example is shown in equation (13). " The oxidation and kinetic resolution of more than 20 secondary p-hydroxyamines provi s an indication of the scope of the reaction and of some structural limitations to good kinetic resolution. These results also show a consistent correlation of absolute configuration of the resolved hydroxyamine with the configuration of tartrate used in the catalyst. This correlation is as shown in equation (13), where use of (+)-DIPT results in oxidation of the (5)-P-hydroxyamine and leaves unoxidized the (/ )-enantiomer. 

Among the available methods for introducing an unsaturated carbon-carbon bond into organic molecules, selenoxide elimination reaction has been shown to be quite useful because of its simple procedure and its characteristic regioselec-tivity. Jones et al., who discovered the first selenoxide elimination, proposed an intramolecular mechanism entailing a five-membered ring structure to explain its syn nature [11]. This proposition was shown to be correct by Sharpless et al. who applied the method that was utilized by Cram to determine the stereochemistry of elimination in amine oxides [12]. Thus, the oxidation of erythro-selenide afforded only Z-olefin and that of f/zreo-selenide gave only -olefin (Scheme 4). 

It is not possible to draw a Lewis structure of an amine oxide having only neutral atoms. 

---