Compounds structure characteristics

More recently, Dearth and Hites (1991b) measured the half-lives of depuration of 14 different chlordane components (e.g., c/s- and /rans-chlordane and cis- and trans- nonachlor) and metabolites (e.g., heptachlor epoxide, oxychlordane) from the fat of rats fed chlordane in the diet for 28 days. Half-lives ranged from 5.92 days (c/s-chlordane) to 54.1 days (nonachlor III) and were apparently related to the metabolism rate of the various compounds. Structural characteristics associated with slowed depuration included an increasing number of chlorines on ring 1, the chlorine on Cl existing in an endo- (compared with an exo-) configuration, and the presence of two chlorines on C2. In mice treated once or every other day for 29 days, the whole body content of cis- and frans-chlordane remained at very low levels the content of cis- and frans-nonachlor and oxychlordane continued to increase with continued treatment (Hirasawa and Takizawa 1989). The investigators concluded that the chlordane isomers were readily metabolized, but that the nonachlor isomers were not. Oxychlordane, a metabolic intermediate of both chlordane isomers, is very slowly metabolized and tends to persist. 

Structural characteristics of compounds with X Me = 8 are collected in Table 17. Na3NbF8 and Na3TaF8 compounds that form similar crystal structure [77], The structure of Na3TaF8 was determined by Hoard et al. [136], by means of X-ray diffraction of a single crystal. Na3TaF8 is composed of sodium cations and isolated complex ions TaF83, in an Archimedean antiprism configuration, as shown in Fig. 23. 

Most of the M3MeOF6 type compounds belong to the highest symmetry class, except for Na3NbOF6. The main structural characteristics of the M3MeOF6 type compounds are collected in Table 20. 

Among the different families of tantalum and niobium complex fluorides and oxyfluorides, the family of compounds with an X Me ratio equal to 6 is the largest. Table 22 presents the main structural characteristics of hexafluoroniobates and hexafluorotantalates. All known cases of niobium- and tantalum-containing formulary analogs have the same crystal structure type, at least at ambient temperature. 

Dioxytetrafluoroniobates (-tantalates) of alkali metals for the general M3Me02F4 type also belong to the family characterized by X Me=6. Structural characteristics of the compounds are collected in Table 26. 

Table 28 presents structural characteristics of compounds with X Me ratios between 6 and 5 (5.67, 5.5, 5.33, 5.25). According to data provided by Kaidalova et al. [197], MsNbsC Fu type compounds contain one molecule of water to form M5Nb303Fi4-H20, where M = K, Rb, Cs, NH4. Cell parameters for both anhydrous compounds [115] and crystal-hydrates [197] were, nevertheless, found to be identical. Table 28 includes only anhydrous compound compositions because IR absorption spectra of the above compounds display no bands that refer to vibrations of the water molecule... 

Table 28. Structural characteristics of compounds with X Me ratios between 6 and 5.

Table 32. Structural characteristics of M Ta OsFf, compounds (M = NH4, K, Rb) and Cs7TasOnF2i, with 4 < X Me<5 (all compounds have orthorhombic syngony).

Table 36 presents structural characteristics of oxyfluoride compounds with X Me < 3. 

Table 38. Structural characteristics of MeX2 type compounds.

In Figure 13.2, the intensity of the ion at m/z 170 represents a molecular ion of an aromatic compound. The characteristic losses from the molecular ion (M - 1, M - 28, and M - 29) suggest an aromatic aldehyde, phenol, or aryl ether. The molecular formula of Ci2H 0O is suggested by the molecular ion at m/z 170, which can be either a biphenyl ether or a phenylphenol. The simplest test to confirm the structure is to prepare a TMS derivative, even though m/z 11 strongly indicates the diaryl ether. 

The breast cancer resistance protein (BCRP) belongs to the G-branch of the ABC-transporter family (ABCG2). In contrast to most other ABC-proteins, BCRP consists of only one transmembrane domain (TDM) with one nucleotide binding fold (NBF) at its C-terminus. Because of this structural characteristic BCRP as well as other ABC-transporters with only one TMD are termed half transporters. To achieve functional activity these transporters have to form hetero- or homodimers. BCRP is involved in the multidrug resistance of certain tumors and transports endogenous compounds like cholesterol and steroid hormones. 

Synthetic food colorants are chemically synthesized compounds that have a large variety of structures. The structures (Figure 7.3.1) and main properties of some of these pigments are presented below. Depending on their structural characteristics, synthetic pigments used as food colorants can be classified as follows ... 

Molecular structure has been shown to influence absorption. By examining the structural characteristics of drugs that were in use, certain common characteristics of well-absorbed molecules were identified, commonly referred to as the rule of five. Some investigators have used this as a basis for characterizing the drug-likeness of a lead chemical. Other factors also come into play including receptor activity, metabolism profile and for CNS-active compounds, an ability to cross the blood-brain barrier. 

These results thus show that whereas the flashpoint was only moderately influenced by the compound structure (their chemical functionality but especially their atomic composition and vapour), autoignition temperatures seem to be closely linked to the structural factors that affect the chain. So additivity rules for estimation of AIT should be sought. Every time a chemical or physical property is highly influenced by the structure, chemists tried to establish rules that enable one to reduce a molecule to characteristic groups for which the contribution to the value of this property is known. This was done for instance by Kinney for boiling points and Benson2 for thermochemical properties. 

Comparative Evaluation of Related Compounds. Structural studies are incomplete, but NMR and gas chromatographic - mass spectroscopic analysis of a component (fraction 7) isolated by HPLC indicated biphenyl characteristics (30). In an attempt to evaluate the cytolytic effect of compounds with similar structure, 4-hydroxybiphenol and 2-hydroxybiphenol were tested for lytic effects on P. brevis. Bioassays of 2- and 4-hydroxybiphenol indicated that both compounds were cytolytic to P. brevis (31). 

LC-MSn, generally requires some background information on the nature of the solutes. Compared with GC-MS with EI/CI, LC-MS does not offer the same identification possibilities, because of the different ionisation mechanisms. Nevertheless, LC-MS has become an invaluable tool to selectively quantify solutes, and to confirm structures or to elucidate structural characteristics. A drawback of LC-MS is that measurable organic compounds are very limited compared with compounds separable by LC alone. LC-MS places considerable constraints... 

The above compounds contain both cyclic and acyclic P—C—N—B fragments. Complexes formed at the first stage of the reaction undergo a series of successive transformations depending on the electronic and structural characteristics of the substituents and the presence of a mobile hydrogen at heteroatoms. 

These structurally diverse compounds exhibit a range of biological activities in vitro that may explain their potential health-promoting properties, including antioxidant and anti-inflammatory effects and the induction of apoptosis (Hooper and others 2008). Most of the recent interest in flavonoids as health-promoting compounds is related to their powerful antioxidant properties. The criteria to establish the antioxidant capacity of these compounds is based on several structural characteristics that include (a) the presence of o-dihydroxyl substituents in the B-ring (b) a double bond between positions 2 and 3 and (c) hydroxyl groups in positions 3 and 5. 

From the wide variety of emerging pollutants of industrial origin that could be considered here, bisphenol A (BPA) and phthalate esters (PE) are of especial relevance not only because of the high volumes produced and their widespread use, but also because of their demonstrated toxicity, particularly as endocrine disrupters. Both of them have been included in the final report of the European Commission toward the establishment of a priority list of endocrine disrupter chemicals, EDCs [3], and have been rated as of high risk of exposure for human and wildlife populations. Because of their structural characteristics these compounds cannot be included in any of the groups described above, so they will be described in this section (see Fig. 10). 

TSI. The liquid is converted into a vapour jet and small droplets are generated with the help of a heated vapouriser tube. A buffer dissolved in the eluent assists the ionisation process through the formation of adduct ions, which are produced via statistical charging of individual droplets. Due to the softness of the procedure, no structurally characteristic fragments, which could aid identification of unknown compounds, are formed. 

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