Pyridine molecular structure

Fig. 1-6). The structure obtained for thiazoie is surprisingly close to an average of the structures of thiophene (169) and 1,3,4-thiadiazole (170) (Fig. 1-7). From a comparison of the molecular structures of thiazoie, thiophene, thiadiazole. and pyridine (171), it appears that around C(4) the bond angles of thiazoie C(4)-H with both adjacent C(4)-N and C(4)-C(5) bonds show a difference of 5.4° that, compared to a difference in C(2)-H of pyridine of 4.2°, is interpreted by L. Nygaard (159) as resulting from an attraction of H(4) by the electron lone pair of nitrogen. 

Acridine is a heterocyclic aromatic compound obtained from coal tar that is used in the synthesis of dyes. The molecular formula of acridine is C13H9N, and its ring system is analogous to that of anthracene except that one CH group has been replaced by N. The two most stable resonance structures of acridine are equivalent to each other, and both contain a pyridine-like structural unit. Write a structural formula for acridine. 

Treatment of UCI4 with the lithium complex obtained from dicyclohexylcar-bodiimide followed by crystallization from pyridine afforded a dinuclear uranium(rV) oxalamidinate complex in the form of dark green crystals in 94% yield (Scheme 191). The same compound could also be obtained by first reducing UCI4 to LiUCli (or UQs+LiCl) followed by reductive dimerization of di(cyclo-hexyl)carbodiimide as shown in Scheme 191. The molecular structure of this first oxalamidinato complex of an actinide element is depicted in Figure 31. ° ... 

Figure 15 Molecular structure of Ph2SnCl(MP) with the atom numbering scheme, (AMP = 2-mercapto pyridine). ...

We have recently investigated X-ray structure of 3-methoxycarbonyl-[l,4,2] diazaphospholo[4,5-a]pyridine as first example of molecular structure determination for [l,4,2]diazaphosphole ring [84], The ester substituent lies strictly in the molecular plane with carbonyl group in the trans orientation with the formal C=P bond. Endocyclic P-N and P-C bonds are averaged between respective single and double bond lengths. 

From 2002 to 2007, Kubiak and Janczak [27-30] and Sun s [31] groups investigated various symmetrical MPcs with pyridine and its derivatives 4-CP and 4-MP as two axial ligands. Six complexes in this series with crystal structures are reported. The crystal structures of MnPc(Py)2 (M = Mg (4), Mn (5), Co (6) or Fe (7)) complexes with axial pyridine ligands are isostructural. Another two compounds [FenPc(4-CP)2] 2(4-CP) (8) and [RunPc(4-MP)2] -2CHC13 (9) have similar molecular structures to 4-7. The central metal ions in these complexes lie at the inversion centres thus, the molecules are centrosymmetric. In the six complexes, the central metal ion and the four Niso atoms of the Pc(2-) ligands lie on a strict plane. The... 

Related to such type of ligands is also the behaviour of the two isomers of the diruthenium(III) complex with the (pentafluoroanilino)pyridinate anion, the molecular structures of which are illustrated in Figure 5.6... 

The effects of exposure of organic solids to particular solvents such as pyridine on their conformational stability can also be Interpreted In terms of the structural features discussed above. How small nucleophilic molecules disrupt Inter- and Intramolecular polar Interactions In coals thereby relaxing the structural matrix and allowing further solvent penetration has been extensively discussed by Peppas (e.g. 11,12), Larsen (1,13) and Marzec (14-16) and their colleagues. Indeed the extent to which exposure to a polar solvent such as pyridine destabilizes a material s molecular structure Is a measure of the extent to which the stability of the material depends on polar Interactions. 

Solvent destabilization of the molecular structure of organic materials can be quantified by simple proton nuclear magnetic resonance ( H NMR) measurements at ambient temperatures. Such measurements have shown that up to 60% of a coal s molecular structure can be destabilized by pyridine and, by the same token, that at least 40% Is Impervious to this solvent (15-18). 

Hydrogen halides give iV-protonation of 2/7-1,2,3-diazaphospholes (molecular structure of a hydrochloride in Table 2) but also add to the P=C bond (see Section 4.22.5.1.2). Hydrolysis opens the P=N bond of l,2,3-diazaphospholo[l,5-a]pyridines <95S173>. 

Problem 11-4. Determine and sketch the nodal structure of the pyridine molecular orbitals. 

A great deal of work has been done on nuclear spin-spin coupling in pyridine derivatives. The variety and scope of this work is illustrated in Table 9, which shows a sample of the results obtained over the last few years, and indicates the type of information available, and the way in which it can be correlated with other facets of molecular structure and interactions. 

The performance of several semi-empirical (modified neglect of diatomic overlap (MNDO), AMI, PM3, and SAMI) and ab initio (Hartree-Fock (FIF) and MP2/6-31G ) methods for determining structural and electronic factors of a series of isothiazolo[5,4-b]pyridines was compared by Martinez-Merino et al. <1996T8947>. They found that most of the semi-empirical methods calculated reasonable molecular structures when compared to the actual X-ray structures (compounds 3-5) (see, for example. Table 1 for selected bond lengths of compound 3). Flowever, the dipole moments were not reproducible using these methods. 

Dyes, Dye Intermediates, and Naphthalene. Several thousand different synthetic dyes are known, having a total worldwide consumption of 298 million kg/yr (see Dyes and dye intermediates). Many dyes contain some form of sulfonate as —S03H, —S03Na, or — SC NH. Acid dyes, solvent dyes, basic dyes, disperse dyes, fiber-reactive dyes, and vat dyes can have one or more sulfonic acid groups incorporated into their molecular structure. The raw materials used for the manufacture of dyes are mainly aromatic hydrocarbons (67—74) and include benzene, toluene, naphthalene, anthracene, pyrene, phenol (qv), pyridine, and carbazole. Anthraquinone sulfonic acid is an important dye intermediate and is prepared by sulfonation of anthraquinone using sulfur trioxide and sulfuric acid. 

Each Cu1 center (gray ball) is bound to an imine and to a pyridine nitrogen atom from each strand and shows a rather distorted tetrahedral coordination geometry. On the other hand, Fig. 2.15, which displays the molecular structure of the [Cun(16)](CF3S03)2 salt, shows that the Cu11 ion prefers to form a mononuclear complex species. 

Fig. 12.35 [Mfpyjtren))2 complexes (a) The py iren ligand N(CH2CH2N=CHC

The 15N chemical shifts as well as the coupling constants Jh.isn in the bases, and related compounds have not been interpreted theoretically. On the other hand, the magnitude of the coupling constants has been predicted from the molecular structure with reasonable accuracy by means of CNDO/2 calculations for pyrimidine, pyridine, or pyra-zole.543 We can expect that a similar prediction of the spin-spin coupling constants may be made for the pyrimidine and purine nucleic acid bases. 

To obtain a unique SMILES notation, computer programs such as the Toolkit include the CANGEN algorithm [1] which performs CANonicalization, resulting in unique enumeration of atoms, and then GENerates the unique SMILES notation for the canonical structure. In the case of pyridine, this is notation (III). Any molecular structure entered in the Toolkit is converted automatically into its unique representation. 

The homoleptic derivatives of Mo and W(VI) are rather scarcely studied. The only structurally characterized complex, W(OMe)5, possesses the molecular structure analogous to those of alkoxide halids, i.e. a dimer built up of two edge-sharing octahedra. The structure of monooxo homometallic derivatives is unknown and their individuality appears questionable. The only dioxocom-plex of molybdenum(V) isolated as pyridin solvate demonstrates the [Ti(OMe)w]-type structure (Table 12.19). 

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