Aggregation of hydrocarbon

Figure 5.5 The hydrophobic effect. Aggregation of hydrocarbon molecules in water reduces the number of molecules with restricted motion...

Fig. 4. Schematic phospholipid membrane cross-section composed of double aggregates of hydrocarbons and oxygen polyhedra. Glycerol is presented schematically the PC -residues have been omitted. The molecular dimensions are based on the Na+0 octahedron (after Matheja and Degens48))...

Liu, H. Q., Ruckenstein, E. (1999). Aggregation of hydrocarbons in dilute aqueous solutions. Journal of Physical Chemistry, B, 102, 1005-1012. 

Kitamura T., Takahashi Y., Yamanaka T., Uchida K. Luminescence associated with the molecular aggregation of hydrocarbons doped in amorphous silica glasses. J. T.iimin. 1991 48/49 373-376... 

The methodology for preparation of hydrocarbon-soluble, dilithium initiators is generally based on the reaction of an aromatic divinyl precursor with two moles of butyUithium. Unfortunately, because of the tendency of organ olithium chain ends in hydrocarbon solution to associate and form electron-deficient dimeric, tetrameric, or hexameric aggregates (see Table 2) (33,38,44,67), attempts to prepare dilithium initiators in hydrocarbon media have generally resulted in the formation of insoluble, three-dimensionally associated species (34,66,68—72). These precipitates are not effective initiators because of their heterogeneous initiation reactions with monomers which tend to result in broader molecular weight distributions > 1.1)... 

Soot. Emitted smoke from clean (ash-free) fuels consists of unoxidized and aggregated particles of soot, sometimes referred to as carbon though it is actually a hydrocarbon. Typically, the particles are of submicrometer size and are initially formed by pyrolysis or partial oxidation of hydrocarbons in very rich but hot regions of hydrocarbon flames conditions that cause smoke will usually also tend to produce unbumed hydrocarbons with thek potential contribution to smog formation. Both maybe objectionable, though for different reasons, at concentrations equivalent to only 0.01—0.1% of the initial fuel. Although thek effect on combustion efficiency would be negligible at these levels, it is nevertheless important to reduce such emissions. 

The degree of aggregation of polystyryl alkali salts in hydrocarbons, as well as the reactivity of their respective unassociated pairs, decrease along the series Li +, Na+, K +, Cs+ (Ref.Il, pp. 20 21). For example, the propagation constant of the lithium pair in benzene at 25 °C is estimated to be greater than 100 M "1 sec- while those of K +, Rb+, and Cs+ were determined as 47, 24, and 18 M-1 sec-1, respectively. Such a gradation contrasts with that of the reactivities of tight pairs in ethereal solvents,... 

Figure 6.5. Experiments involving mimics of sporopollenin (the principal component of spore walls] demonstrate that patterns very similar, if not identical to those of natural spores and pollen, can be produced from mixtures containing colloidal particles. All scales refer to bar in (a. (a Spore-like structures of polystyrene particles and particle aggregates formed around a droplet of hydrocarbon. Scale = 10 p.m. (b A broken structure like that shown in (a. Scale =...

Hydrocarbon oxidation produces polar oxygen-containing compounds. These compounds tend to associate in nonpolar hydrocarbon and form some aggregates. The formation of such a microheterogeneous polar system can influence the rate and mechanism of oxidation [20]. The study of hydrocarbon oxidation in the systems with reversed micelles has its special... 

Surfactants that form micelles have also been shown to accelerate the formation of nitrosamlnes from amines and nitrite (33.) A rate enhancement of up to 80 0-fold was observed for the nitrosation of dihexylamine by nitrite in the presence of the cationic surfactant decyltrimethylammonium bromide (DTAB) at pH 3.5. A critical micelle concentration (CMC) of 0.08% of DTAB was required to cause this effect, which was attributed to a micelle with the hydrocarbon chains buried in the interior of the micelle. The positively-charged ends of the micelle would then cause an aggregation of free nitrosatable amine relative to protonated amine and thus lead to rate enhancements. Since surfactants are commonly used in water-based fluids (25-50% lubricating agent or 10-2 0% emulsifier in concentrates), concentrations above the CMC of a micelle-forming surfactant could enhance the formation of nitrosamines. 

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