Aniline molecular structure

Figure 29 Some of the molecular structures used to interpret the EPR spectra of poly(aniline) oligomers. The molecules are labelled 1 and 4 in the same fashion as Ref. [149].

Wiener H (1948a) Relation of the physical properties of the isomeric alkanes to molecular structure. Surface tension, specific dispersion, and critical solution temperature in aniline. J. Phys. Chem. 52 1082-1089. 

Some conjugated polymers, such as polythiophene and polyaniline were synthesized already in the last century [8a,b], It is not surprising that, for example, polyaniline has played a major role in research directed toward synthetic metals because it possesses a relatively stable conducting state and it can be easily prepared by oxidation of aniline, even in laboratories without pronounced synthetic expertise (see section 2.6). It is often overlooked, however, that a representation of, for example, polypyrrole or polyaniline by the idealized structures 1 and 2 does not adequately describe reality, since various structural defects can occur (chart 1). Further, there is not just one polypyrrole, instead each sample made by electrochemical oxidation must be considered as a unique sample, the character of which depends intimately on the conditions of the experiment, such as the nature of the counterion or the current density applied (see section 2.5). Therefore, one would not at all argue against a practical synthesis, if the emphasis is on the active physical function and the commercial value of a material, even if this synthesis is quick and dirty . Care must be exercised, however, to reliably define the molecular structure before one proceeds to develop structure-property relationships and to define characteristic electronic features, such as effective conjugation length or polaron width. 

Wiener, H. (1948a). Relationship of Physical Properties of Isomeric Alkanes to Molecular Structure Surface Tension, Specific Dispersion and Critical Solution Temperature in Aniline. J.Phys.Colloid Chem., 52,1082-1089. 

Polymerization mechanisms for polyaniline have been proposed in the literature [45, 46], Figure 2 illustrates some of the basic steps occurring during polymerization of aniline. The oxidation states of PANI, and of polyanilines in general, are indicated by an index for the degree of oxidation (Y). It is in its completely reduced form (leucoemeraldine) when Y = 1, and its completely oxidised form (pemigraniline) is dominant when Y = 0. At Y = 0.5, the 50% intrinsically oxidized polymer (emeraldine) is ambient [49, 50], The molecular structures of the different forms (oxidation states) of PANI are illustrated in Figure 1. 

Penta- and hexasubstituted anilines as well as iV-substituted anilines with large substituents on the amino group may exhibit strong disturbances of their molecular structures due to steric overcrowding and, sometimes, to charge perturbation. 

The crystal and molecular structure was determined of the picrates (174) of aniline (la), its A-Me derivatives, 1,2- (lj), 1,3- (lk) and 1,4-phenylenediamine (11). Except for lj, combining with two picric acid molecules, the rest show 1 1 stoichiometry. The main structural feature is H-bonding of various strengths, with O-N distances from 267 pm for A-methylaniline to 288 pm for lj. The acid proton in these compounds sits on the N atom forming ammonium salts, as shown by the Cl-O bond distances near 125 pm for a picrate anion, rather than 130 to 134 pm for picric acid or its tt-complexes with benzene and PAH. The picrates of N-methylaniline and lk also show jr-stacking to some extent, especially in the latter case266. 

A series of /V-salicylidene-2,6-dialky Ian ilines (84a-84e, 85a-85d, 86a-86d, 87a, 87d, 88a, 88b, 88d, 89a, 89d, 90a, 90b and 90d) has been investigated in order to evaluate the alkyl substituent effects on the crystal packing of molecules and, in turn, their photochromic properties in the solid state178. The alkyl groups, particularly the isopropyl group, at the 2,6-positions of the aniline ring can lead to a nonplanar molecular structure, which is effective for the crystals to exhibit photochromism. 

The phenylimido-bridged dimer [(C5H4CH2GH2GH2N(H)GMe3)Ti(NHPh)(/x-NPh)]2 is obtained by reaction of the Cp-amido complex (C5H4GH2GH2CH2NCMe3)/(NMe2)2 with aniline. Its molecular structure has been determined by X-ray diffraction and reveals a slightly asymmetric Ti(/x-NPh)2Ti core (Scheme 281, Section 4.05.3.4).616... 

Wiener, H. (1948a) Relationship of physical properties of isomeric alkanes to molecular structure surface tension, specific dispersion and critical solution temperature in aniline. /. Phys. Colloid Chem., 52, 1082-1089. 

The conformation about the C-N bond has been studied in cyclic amides (O) [29 a] and enamines (D) [29 b]. Gilli et al. did a similar analysis and expanded the selection of fragments with thioamides (S), amidines (N), and anilines (A) [29 c]. The 90 molecular structures included in the study map a pathway whereby the rotation... 

TLV of 1 ppm in air. The four-digit UN identification number is 1652. The NFPA 704 designation is health 3, flammability 2, and reactivity 1. Nitrobenzene is a nitro hydrocarbon derivative, but it is not very explosive. The primary uses are as a solvent, an ingredient of metal polishes and shoe polishes, and in the manufacture of aniline. The structure and molecular formula are shown Figure 8.29. 

A. Greenberg and T. A. Stevenson, Molecular Structure and Energetics Studies of Organic Molecules (Eds. J. F. Liebman and A. Greenberg), VCH, Deerfield Beach, 1986. See also the discussion in J. F. Liebman and R. M. Pollack, in The Chemistry of Enones, Part I (Eds. S. Patai and Z. Rappoport), Wiley, New York, 1989 wherein the resonance energy of crotonaldehyde was shown to be less than that of piperylene while the rotational barriers are in the reverse order. From Stull, Westmm and Sinke we find the barrier to rotation of the nitro group in nitrobenzene is 25.1 kJmol , to be compared with the rotational barrier of the amino group in aniline of 14.2 kJmol". ... 

Figure 8.6 U V-vis-NIR spectra of solutions of Janus Green B azo dye in NMP (A), and aqueous acidic solution (B), and resonance Raman spectra of Janus Green B azo dye in the solid state obtained at the indicated exciting radiations. The dye molecular structure is also shown. (Reprinted with permission from Macromolecules, Aniline Polymerization into Montmorillonite Clay A Spectroscopic Investigation of the Intercalated Conducting Polymer by G. M. do Nascimento, V. R. L. Constantino, R. Landers and M. L. A. Temperini, 37, 25. Copyright (2004) American Chemical Society)...

Introducing derivatives and copolymers of PANI also results in different ER effect because of different molecular structure and electrical properties, e.g., poly(o-anisidine), poly(anihne-co-o-ethoxy aniline), poly(o-tolu-idine) (POT), substituted PANI (with long alkyl pendants, PDOA), poly(N-methyl aniline) (PNMAn), poly(N-ethyl aniline) (PNEAn), and poly(2-ethyl anihne) (P2EAn) with reduced conductivity [36,37]. 

Alabugin I. V., Manoharan M., Buck M., Clark R. J. (2007). Substituted Anilines The Tng-Of-War between Pyramidalization and Resonance Inside and Outside of Crystal Cavities. Journal of Molecular Structure (THEOCHEM), 813, 21-27. 

Figure 1.3 Loschmidt s molecular structural formulae for benzene (3) and aniline (4).

Alan G. MacDiarmid and his colleagues reported that aniline monomer in an acid aqueous solution (e.g., 1.0 M HCl) could be chemically oxidized by APS to form a green powder with a conductivity as high as 3 S cm, which was latter called the emeraldine salt (ES) form of PANI [46]. PANI is easy to synthesize and at a low cost and has great potential for modification of the molecular structure, and undergoes... 

Since B and B2 were chosen so that all the relevant concentrations can be determined by U V/ vis spectroscopy, the unknowns in Eq. 5.16 are K -b and the activity coefficients. A reasonable assumption is that the activity coefficients for the B2 entities are the same as for the Bi entities in the new solution, becau.se aggregation and non-ideal behavior are related to molecular structure, and both Bi and B2 are anilines. Given this assumption, Eq. 5.16 reduces to Eq. 5.17. Now fCa.B2H- can be determined. The next step is to choose an even weaker aniline base, B3, which requires a higher percent acid for appreciable protonation, but for which the protonation state of B3 and B2 can both be measured in the same acidic solution. This allows calculation of Ka.B,n, and so on. 

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