Nitrate, structure

Polyvinyl nitrate [Structure (2.6)], originally thought to be a replacement for NC (at least partly), had been explored by a number of groups [1-3] who concluded that the propellants based on PVN (on replacement of NC by PVN) have the properties comparable heat of explosion and burning rate, decreased tensile strength, increased elongation and pressure exponent (n) and hence PVN is not acceptable as a replacement of NC [4]. 

Sadeghipour M, Terreux R, Phipps J. 2005. Flavonoids and tyrosine nitration Structure-activity relationship correlation with enthalpy of formation. Toxicol in Vitro 19 155-165. 

Thus, ascribing infrared bands to monodentate nitrates on the assumption that the metal atom adopts its usual coordination number is somewhat tenuous in the present absence of clear-cut examples of monodentate nitrate structures. Despite the fact that about 30% of the coordinated-nitrate compounds in the literature are suspected from infrared studies to contain monodentate nitrate, a significant portion may on structural analysis be found to possess bidentate nitrate if the ratio of structures in Table II is at all representative. 

We first searched for a nitrate-aluminum bound acetyl nitrate structure as proposed by Prins and coworkers. Prins and coworkers have used chemical anisotropy broadening arguments in their N NMR results to claim that the NO2 moiety is bound to the aluminum site. " We, however, were unsuccessful in finding such a species with our All-03 acid site model. As mentioned previously, A1 sites 1 and 2 are not as flexible as A1 sites 3-9. Thus, stable nitrate coordination with All would not be expected. More of an interaction between the nitrate moiety of the acetyl nitrate and A1 sites 3-9 may be possible because these sites participate in octahedral coordination because of their flexibility, which we are currently pursuing." Prins and coworkers have noted that ZSM-5 also exhibits similar broadening, but octahedral aluminum coordination occurs negligibly in ZSM-5. Thus, there appears to be more than one way to explain the broadening they observed. We show that chemical... 

Arsenic dissolves in concentrated nitric acid forming arsenicfV) acid, H3ASO4, but in dilute nitric acid and concentrated sulphuric acid the main product is the arsenic(III) acid, HjAsOj. The more metallic element, antimony, dissolves to form the (III) oxide Sb O, with moderately concentrated nitric acid, but the (V) oxide Sb205 (structure unknown) with the more concentrated acid. Bismuth, however, forms the salt bismulh(lll) nitrate Bi(N03)3. 5H,0. 

Dinitrogeri pentoxide is the anhydride of nitric acid and is prepared by removing water from pure nitric acid by means of phosphorus (V) oxide. It is a crystalline solid having the ionic structure of (N02) (N03) , nitronium nitrate (the nitronium ion is mentioned later). It decomposes above 273 K, thus ... 

The chemical properties of nitric acid require us to consider the structure first. The vapour of pure nitric acid (i.e. anhydrous) is probably composed of molecules of hydrogen nitrate , which structurally is a resonance hybrid of such forms as ... 

Hydrated nitrates, and anhydrous nitrates of very electropositive metals (for example Na, K), contain the ion NOJ which has the structure ... 

There is increasing evidence that the ionisation of the organic indicators of the same type, and previously thought to behave similarly, depends to some degree on their specific structures, thereby diminishing the generality of the derived scales of acidity. In the present case, the assumption that nitric acid behaves like organic indicators must be open to doubt. However, the and /fp scales are so different, and the correspondence of the acidity-dependence of nitration with so much better than with Hg, that the effectiveness of the nitronium ion is firmly established. The relationship between rates of nitration and was subsequently shown to hold up to about 82 % sulphuric acid for nitrobenzene, />-chloronitrobenzene, phenyltrimethylammonium ion, and p-tolyltrimethylammonium ion, and for various other compounds. ... 

There is evidence for the existence of structures of this kind, and for their importance in electrophilic substitution in general, and in nitration in particular. Because of the way in which the electrophile is attached to the ring they are called cr-complexes. 

If, on the other hand, the encounter pair were an oriented structure, positional selectivity could be retained for a different reason and in a different quantitative sense. Thus, a monosubstituted benzene derivative in which the substituent was sufficiently powerfully activating would react with the electrophile to give three different encounter pairs two of these would more readily proceed to the substitution products than to the starting materials, whilst the third might more readily break up than go to products. In the limit the first two would be giving substitution at the encounter rate and, in the absence of steric effects, products in the statistical ratio whilst the third would not. If we consider particular cases, there is nothing in the rather inadequate data available to discourage the view that, for example, in the cases of toluene or phenol, which in sulphuric acid are nitrated at or near the encounter rate, the... 

It is the purpose of this and the following chapter to report the quantitative data concerning the relationship of structure to orientation and reactivity in aromatic nitration. Where data obtained by modern analytical methods are available they are usually quoted in preference to the results of older work. Many of the papers containing the latter are, however, noted in the brief discussion which is given of interpretations of the results. 

The isomer proportions for the nitration of the chlorotoluenes, to be expected from the additivity principle, have been calculated from the partial rate factors for the nitration of toluene and chlorobenzene and compared with experimental results for nitration with nitric acid at o °C. The calculated values are indicated in brackets beside the experimental values on the following structural formulae. In general, it can be... 

Mercuric halides, silver nitrate, and copper nitrates form stable complexes with bis-2.2 -thiazolylazo compounds (1591). for which the X-ray structure is not yet known. 

Three equally stable Lewis structures are possible for nitrate ion The negative charge in nitrate is shared equally by all three oxygens... 

Nitrate ion is stabilized by electron delocalization which we can represent m terms of resonance between three equivalent Lewis structures... 

Write the structure of the principal organic product obtained on nitration of each of the following... 

With iodine in carbon tetrachloride, 4-methylpyrazole affords a deep-red oil for which the structure (266) has been proposed. Nitric acid, silver nitrate and iodine together convert pyrazole into 1,3,4-triiodopyrazole (267 = R" = I, = H). The fV-iodopyrazoles are... 

As Olah et al. have reported (81JOC2706), iV-nltropyrazole in the presence of Lewis or Brpnsted acid catalysts is an effective nitrating agent for aromatic substrates. The greater lability of the N—NO2 bond in iV-nltropyrazole compared with aliphatic nltramines was discussed on the basis of its molecular structure as determined by X-ray crystallography. 

Nitration of a series of methyl-1,2-benzisoxazoles was studied by Tahkar and Bhawal using fuming nitric acid and sulfuric acid in acetic acid at 100 °C. 3-Methyl-1,2-benzisoxazole gave a mixture of 5-nitro- and 5,7-dinitro-3-methyl-l,2-benzisoxazole, with the 5-nitro isomer predominant. The product obtained from 3,5-dimethyl-1,2-benzisoxazole was the 4-nitro derivative and not the 7-nitro compound as proposed by Lindemann (26LA(449)63). The synthesis of the 7-nitro compound by an alternative method was used as structural proof. Two products were obtained from 3,6-dimethyl-l,2-benzisoxazole and these were the 5-nitro and 5,7-dinitro derivatives. 3,7-Dimethyl-l,2-benzisoxazole was converted into the 5-nitro derivative (Scheme 25) (77lJC(B)l06l). 

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