N-Alkane indices

The CPI, a measure of biologically synthesized n-alkanes, indicates the relative contributions of M-alkanes from natural (CP1>1) compared to anthropogenic (petroleum and industrial pollution, CP1< 1)... 

Bond contraction also happens in liquid skins and gaseous molecules. For instances, bonds at methanol skin contracts by 4.5 % but the hydrogen bond expands by 5.9 % at water surface at room temperature [49]. The spacing between the first and the second atomic layers of liquid Sn, Hg, Ga, and In contracts by 10 % [50]. Phase change occurs at the droplet smface of n-alkane indicates the formation of a monolayer thick solid solution of the oil phase [51]. Bond contraction at liquid skin results in the surface strain and smface stress that drives and sustains liquid drop and gas-bubble formation. X-ray crystallography revealed that a Cr-Cr bond length contracts by 31.5 % from the bulk value of 0.255 to 0.174 nm for a Cr2 anion protected by three bidentate amidinate ligands [52] and 0.175 nm [53] for a neutral Cr2 complex. 

The large dataset of partition coefficients (or activity coefficients at infinite dilution) published in the literature may be used to present a general behaviour of solutes in ionic liquids. The values of activity coefficients at infinite dilution () for the -alkanes increase with an increase in carbon number. In most ionic liquids, the high y" values observed with n-alkanes indicate their low solubility in ionic liquids. The values of n-alkanes are higher than the values obtained with cyclohexane, alkenes, alkynes and aromatics. Introduction of a double or triple bond in the n-alkanes decreases the values. 

Fig. 9.77 Plot of log crystallization rate against nucleation temperature function for coherent unimolecular nucleation for the n-alkanes indicated. Symbols as in Figure 9.75.(280)...

Nepeta (Lamiaceae) is a genus of perennial or annual herbs found in Asia, Europe and North Africa. About 250 species of Nepeta are reported of which, 67 species are present in Iran. Some species of this genus are important medicinal plants and their extracts have been used for medicinal purposes. Aerial parts of Nepeta sintenisii Bornm. was subjected to hydrodistillation and the chemical composition of isolated essential oil has been analyzed by GC/MS method for first time. Identification of components of the volatile oil was based on retention indices relative to n-alkanes and computer matching with the Wiley275.L library, as well as by comparison of the fragmentation patterns of the mass spectra with those reported in the literature. 

For n-alkanes, n-alcohols, 1-chloroalkanes, n-ethers, and chloroethenes, the carbon chain length influences the reactivity, and the clear linear correlations indicate that the attack mechanism of these pollutants by OH or Cl radicals occurs via the same pathway. However, such correlations do not hold true for aromatics, ketones, and aldehydes, for reasons discussed in our previous paper [3]. We also estimated missing values of kci by analogy for ethylbenzene, we take kci = 1.5e-10 cm molecule S, greater than that for m-xylene, but smaller than the 2.0e-10 cm molecule- s-i value for very reactive compoxmds. Also we estimate a similar value for butyraldehyde kci = le-10 cm molecule- s-, only 10% larger than kci of acetaldehyde to remain consistent with the equivalent koH value. 

In n-octane/aqueous systems at 27°C, TRS 10-80 has been shown to form a surfactant-rich third phase, or a thin film of liquid crystals (see Figure 1), with a sharp interfacial tension minimum of about 5x10 mN/m at 15 g/L NaCI concentration f131. Similarly, in this study the bitumen/aqueous tension behavior of TRS 10-80 and Sun Tech IV appeared not to be related to monolayer coverage at the interface (as in the case of Enordet C16 18) but rather was indicative of a surfactant-rich third phase between oil and water. The higher values for minimum interfacial tension observed for a heavy oil compared to a pure n-alkane were probably due to natural surfactants in the crude oil which somewhat hindered the formation of the surfactant-rich phase. This hypothesis needs to be tested, but the effect is not unlike that of the addition of SDS (which does not form liquid crystals) in partially solubilizing the third phase formed by TRS 10-80 or Aerosol OT at the alkane/brine interface Til.121. 

Lageveen et al. [41] showed that the monomer composition of aliphatic saturated poly(3HAMCL) produced by P. oleovorans is depended on the type of n-alkane used. It appeared that the n-alkanes were degraded by the subsequent removal of C2-units and it was therefore proposed that the /1-oxidation pathway was involved in poly(3HAMCL) biosynthesis. Preusting et al. [42] confirmed these results but also showed that with hexane as substrate some 3-hydroxyoctanoate and 3-hydroxydecanoate were produced, indicating that additional pathways were involved in poly(3HAMCL) biosynthesis (Table 1). 

Figure 10. Calculated order parameters of the CH2 groups of isolated molecules of linear alkanes with chain length N as indicated, starting from the centre of the molecule towards its end. The ranking number along the chain is indicated by the letter t. MC simulations by Rabinovich and co-workers [74—76]. Copyright (1997) by Elsevier...

For propane, n-pentane and n-hexane the differential heats of adsorption over FER dropped more rapidly, right after 1 molecule was adsorbed per Bronsted acid site. Similar results were obtained with TON. In contrast, with MOR and FAU the drop in the differential heats of adsorption for n-alkanes occurred at lower coverages, indicating that only a certain fraction of the Bronsted acid sites were accessible to the adsorbing alkane probe molecules. With MFI the drop did not occur until 2 molecules of n-alkane were adsorbed per Bronsted acid site, suggesting perhaps a higher stoichiometry of about two n-alkanes per Bronsted acid site. In the cases of i-butane and i-pentane the drop occurred around one alkane per Bronsted acid site. Finally, n-butane adsorption isotherms measured over TON framework type catalysts having three different A1 contents (Si/Al2 = 90, 104, 128) showed Henry coefficients to increase with increase in the A1 content [5], Based... 

Kovats indices (/-values) are based on the retention time of an analyte compared to retention times of the series of n-alkanes. For a particular GC phase, /-values are very reproducible from one column or from one GC to another. However, they are slightly affected by GC programming conditions. n-Alkanes have most affinity for non-polar phases and tend to elute more quickly from polar phases. In contrast, a polar analyte will elute more slowly from a polar phase and thus relative to the n-alkanes, its retention time and thus its /-value will increase as the polarity of the... 

The compound has four degrees of unsaturation (if it were a substituted alkane, its formula would be C,Hn,N), which indicates the presence of a phenyl ring, (A) dissolves in HCI and therefore is an amine. Since (A) releases with HONO, it is a 1° amine. Since (A) is optically active, it has a chiral C. The —NH cannot be on the ring since the two remaining C s cannot be positioned to give a chiral C. The —NH must be on the side chain. The compound is C H5CH(NH2)CH,. 

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