Alkanes characterization

For petroleum fractions or similar systems the treatment of phase equilibria will now be discussed briefly. The basic principles are the same as those outlined for polymer systems without recourse to segment-molar quantities. For petroleum fractions the phase-equilibrium problem of importance is the so-called flash calculation that is analogous to the calculation of coexistence curves for a polydisperse polymer solution and in the simplest case a single distribution function is required. For example, the system may contain many alkanes characterized by their normal boiling-point temperatures Tb that in this work will be denoted by x. At moderate pressures the equilibrium condition is given by the continuous thermodynamics form of Raoult s law ... 

Cycloalkanes are alkanes that contain a ring of three or more carbons They are fre quently encountered m organic chemistry and are characterized by the molecular formula C H2 Some examples include... 

The classes of hydrocarbons are alkanes, alkenes, alkynes, and arenes Alkanes are hydrocarbons in which all of the bonds are single bonds and are characterized by the molecular formula C H2 +2... 

Cyclic hydrocarbons can contain more than one ring Spirocyclic hydro carbons are characterized by the presence of a single carbon that is com mon to two rings Bicyclic alkanes contain two rings that share two or more atoms... 

Methyl ketones such as 2 butanone m Figure 17 18 are characterized by sharp singlets near 8 2 for the protons of CH3C=0 Similarly the deshieldmg effect of the carbonyl causes the protons of CH2C=0 to appear at lower field (8 2 4) fhan m a CH2 group of an alkane... 

With concern to the high internal mobility of the molecules in the high temperature solid state phase, some parallelism to n-alkanes can be stated. In the pseudohexagonal (rotator) phase the latter are also characterized by fast molecular motions. For discrimination and according to Pfitzer 14) and Dale 13) in the following the term pseudorotator phase is used for the mobil crystalline state of cyclic molecules. 

The effective carbon number neff is helpful in characterizing surfactants with an inner functional group. Surfactants with isomeric structures can be compared by means of the hydrophobicity index / [69], which indicates the influence of the effective length of the alkane chain on cM ... 

To characterize heteroanalogous alkanesulfonates in which one or more carbon atoms of the alkane chain are replaced by, for example, oxygen, sulfur, or nitrogen, methylene group equivalent values ME are useful ... 

As the number of carbon atoms in the alkane increases, so does the number of possible stractural isomers. Thousands of different alkanes exist, because there are no limits on the length of the carbon chain. Regardless of the number of the chain length, alkanes have tetrahedral geometry around all of their carbon atoms. The structure of decane, Cio H22, shown in Figure 9-15. illustrates this feature. Notice that the carbon backbone of decane has a zigzag pattern because of the 109.5° bond angles that characterize the tetrahedron. 

Craft DL, KM Madduri, M Eshoo, CR Wilson (2003) Identification and characterization of the CYP52 family of Candida tropicalis ATCC 20336, important for the conversion of fatty acids and alkanes to a,(o-dicarboxylic acids. Appl Environ Microbiol 69 5983-5991. 

Maeng JH, Y Sakai, Y Tani, N Kato (1996) isolation and characterization of a novel oxygenase that catalyzes the first step of -alkane oxidation in Acinetobacter sp. strain M-1. J Bacteriol 178 3695-3700. 

Janssen DB, J Gerritse, J Brackman, C Kalk, D Jager, B Witholt (1988) Purification and characterization of a bacterial dehalogenase with activity towards halogenated alkanes, alcohols and ethers. Eur J Biochem 171 67-72. 

A CRO may also allow for the in-house introduction of specialized lipophilic scales by transferring routine measurements. While the octanol-water scale is widely applied, it may be advantageous to utilize alternative scales for specific QSAR models. Solvent systems such as alkane or chloroform and biomimetic stationary phases on HPLC columns have both been advocated. Seydel [65] recently reviewed the suitabihty of various systems to describe partitioning into membranes. Through several examples, he concludes that drug-membrane interaction as it relates to transport, distribution and efficacy cannot be well characterized by partition coefficients in bulk solvents alone, including octanol. However, octanol-water partition coefficients will persist in valuable databases and decades of QSAR studies. 

The surfactants described or characterized for waterflooding are summarized in Table 16-2. Conunercial alkene sulfonates are a mixture of alkene sulfonate, hydroxy alkane sulfonate, and olefin disulfonate [211]. 

The solvent triangle classification method of Snyder Is the most cosDBon approach to solvent characterization used by chromatographers (510,517). The solvent polarity index, P, and solvent selectivity factors, X), which characterize the relative importemce of orientation and proton donor/acceptor interactions to the total polarity, were based on Rohrscbneider s compilation of experimental gas-liquid distribution constants for a number of test solutes in 75 common, volatile solvents. Snyder chose the solutes nitromethane, ethanol and dloxane as probes for a solvent s capacity for orientation, proton acceptor and proton donor capacity, respectively. The influence of solute molecular size, solute/solvent dispersion interactions, and solute/solvent induction interactions as a result of solvent polarizability were subtracted from the experimental distribution constants first multiplying the experimental distribution constant by the solvent molar volume and thm referencing this quantity to the value calculated for a hypothetical n-alkane with a molar volume identical to the test solute. Each value was then corrected empirically to give a value of zero for the polar distribution constant of the test solutes for saturated hydrocarbon solvents. These residual, values were supposed to arise from inductive and... 

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