Structural chemistry nitrates

A number of X-ray crystal determinations have made the principles of lanthanide cryptate structural chemistry fairly clear. In [La(N03)2(2,2,2-cryptate)][La(N03)6] (Figure 8), the La3+ ion is 12-coordinated with two bidentate nitrate ions coordinating in two of the three spaces between the cryptate chains the third space is thus too compressed to be occupied also.508 [Sm(N03)(2,2,2-cryptate)][Sm(N03)5(H20)] shows only one such space occupied511 and the structure of [Eu(C104)2,2,2-cryptate](C104)2MeCN is similar to the samarium cryptate.512,513 Intemuclear distances in these complexes are shown in Table 10. 

Borates are far more complex in their structural chemistry than carbonates and nitrates, and for that reason are discussed separately later ( 11.02, 11.03). Here, however, we may remark that many orthoborates of composition JB03 contain discrete B033 ions with the same regular configuration as the C032 and N03 ions and with a B-0 distance of 1 37 A. 

Bakke et al. (1982) have shown how montmorillonite catalyses chlorination and nitration of toluene nitration leads to 56 % para and 41 % ortho derivative compared to approximately 40 % para and 60 % ortho derivatives in the absence of the catalyst. Montmorillonite clays have an acidity comparable to nitric acid / sulphuric acid mixtures and the use of iron-exchanged material (Clayfen) gives a remarkable improvement in the para, ortho ratio in the nitration of phenols. The nitration of estrones, which is relevant in making various estrogenic drugs, can be improved in a remarkable way by using molecular engineered layer structures (MELS), while a reduction in the cost by a factor of six has been indicated. With a Clayfen type catalyst, it seems possible to manipulate the para, ortho ratio drastically for a variety of substrates and this should be useful in the manufacture of fine chemicals. In principle, such catalysts may approach biomimetic chemistry our ability to predict selectivity is very limited. 

The monovalent Co chemistry of amines is sparse. No structurally characterized example of low-valent Co complexed exclusively to amines is known. At low potentials and in non-aqueous solutions, Co1 amines have been identified electrochemically, but usually in the presence of co-ligands that stabilize the reduced complex. At low potential, the putative monovalent [Co(cyclam)]+ (cyclam = 1,4,8,11-tetraazacyclotetradecane) in NaOH solution catalyzes the reduction of both nitrate and nitrite to give mixtures of hydroxylamine and ammonia.100 Mixed N-donor systems bearing 7r-acceptor imine ligands in addition to amines are well known, but these examples are discussed separately in Section 6.1.2.1.3. 

Nitration and Aromatic Reactivity (CUP, 1971). ingold, c. k. Structure and Mechanism in Organic Chemistry (Bell, 2nd Edition, 1969). 

It is the purpose of the series to review the field of organic nitro chemistry in its broadest sense by including structurally related classes of compounds such as nitroamines, nitrates, nitrones, and nitrile oxides. It is intended that the contributors, who are active investigators in various facets of the field, will provide a concise presentation of recent advances that have generated a renaissance in nitro chemistry research. 

Alfassi, Z. B S. Padmaja, P. Neta, and R. E. Huie, Rate Constants for Reactions of NO, Radicals with Organic Compounds in Water and Acetonitrile, J. Phys. Chem., 97, 3780-3782 (1993). Allen, H. C., J. M. Laux, R. Vogt, B. J. Finlayson-Pitts, and J. C. Hemminger, Water-Induced Reorganization of Ultrathin Nitrate Films on NaCI—Implications for the Tropospheric Chemistry of Sea Salt Particles, J. Phys. Chem., 100, 6371-6375 (1996). Allen, H. C., D. E. Gragson, and G. L. Richmond, Molecular Structure and Adsorption of Dimethyl Sulfoxide at the Surface of Aqueous Solutions, J. Phys. Chem. B, 103, 660-666 (1999). Anthony, S. E R. T. Tisdale, R. S. Disselkamp, and M. A. Tolbert, FTIR Studies of Low Temperature Sulfuric Acid Aerosols, Geophys. Res. Lett., 22, 1105-1108 (1995). 

As an aromatic system, (1), shows important synthetic and mechanistic nistic uitro group chemistry. See also Nitration. The ex]xrriiueiilal conditions employed usually determine the product structure. 

Meyer, C., Levin, J.M., Roussel, J.M. Rouze, P. (1991). Mutational and structural analysis of the nitrate reductase haem domain of Nicotiana plumbaginifolia. Journal of Biological Chemistry 266, 20561-6. 

Figure 5.13 X-ray crystal structure of the HHH isomer of [Co2 (5.36)3]4+ binding nitrate (the nitrate anion and metal centres are shown as large spheres) (b) partial HNMR spectra of [Co2(5.36)3]4+ as the perchlorate salt (top) and after N03 addition (bottom) (reproduced by permission of The Royal Society of Chemistry).

This section is mainly anecdotal in nature and a reference work such as Chemistry of Explosives [31] should be consulted for fuller information. The story of modern explosives can be said to have started with the accidental discovery of nitrocellulose by Christian Schoenbein in 1846, when his wife s apron, with which he wiped up a spilled mixture of acids, exploded and vanished in a puff of smoke. The significance of nitration is evident in the structures of classical explosives shown in Fig. 16. 

The double nitrates Mg3M2(N03)12, 24 H20 can be recrystallized in strong nitric acid and serve to separate the lighter lanthanides M = La, Pr, Nd and Sm (where Ce has been removed after oxidation to the quadrivalent state). Judd noted 109) that the fine-structure of the absorption band belonging to each /-level of M(III) was so peculiar that it looked as if the chromophore was icosahedral with N = 12 (which is almost unheard about, outside boron chemistry). The crystal structure 110) of the cubic crystals confirmed entirely Judd s proposal, it is indeed [Mg(OH2)6]3 ... 

Quinoline forms part of quinine (structure at the head of this chapter) and isoquinoline forms the central skeleton of the isoquinoline alkaloids, which we will discuss at some length in Chapter 51. In this chapter we need not say much about quinoline because it behaves rather as you would expect—its chemistry is a mixture of that of benzene and pyridine. Electrophilic substitution favours the benzene ring and nucleophilic substitution favours the pyridine ring. So nitration of quinoline gives two products—the 5-nitroquinolines and the 8-nitroquinolines—in about equal quantities (though you will realize that the reaction really occurs on protonated quinoline. 

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