N-Alkanes chain length

Figure 3. Glass capillary gas chromatogram (high resolution) of saturated hydrocarbons from Stomach contents of cod near the Argo Merchant oil slick, which is virtually identical to saturated hydrocarbons in Argo Merchant cargo oil. Numerals denote n-alkane chain length (55).

Fig. 2. Total ion chromatograms for the sandstone sample (CN409, Subu-1,142.95 m) showing (a) the distribution of aliphatic hydrocarbons and (b) the distribution of aromatic hydrocarbons. Numbers refer to n-alkane chain length. Pr, pristane Ph, phytane DMNs, dimethylnaphthalenes TMNs, trimethylnaphthalenes MFl, methylfluorene P, phenanthrene MPs, methylphenanthrenes and DMPs, dimethy Iphenanthrenes.

Figure 2. (a) Melt densities of -alkanes as a funetion of carbon number at 443 K experimental data (open triangles from (Harmandaris et al. 2002) [8], erosses from (Dee et al. 1992) [5], open square from NIST database [19] and stars from (Daubert 2003) [4], and MD predietions (filled points) (b) NPT MD predictions for the mean squared end-to-end distanee divided by the mean squared radius of gyration as a function of n-alkane chain length at 473 K and 3.4 MPa. 

Gao et al. used [bmim][BFJ to prepare nonaqueous [bmim][BFJ-benzene-TX-100 [26] and [bmim][BFJ-cyclohexane-TX-100 [30] microemulsions. Tliey reported the phase behavior of IL-oil microemulsion and found physicochemical properties similar to those of water-oil microemulsions [26]. The microstructure was investigated by SANS [28], electron microscopy [30], DLS, UV-Vis, FTIR, and H-NMR spectroscopy [26]. An in-depth phase diagram study of EAN-n-alkane-CiEj surfactant systems was reported by Atkin and Warr, where the influence of the n-alkane chain length and of the surfactant structure on the efficiency was highlighted [29]. 

LEB 84b] Lebert A., Richon D., Study of the influence of solute (n-alcohols and n-alkanes) chain length on their retention by purified olive oil . Journal of Food Science, vol. 49, no. 5, pp. 1301-1304,1984. 

The H- and N-isoforms of Ras support the first (isoprenoid) hydrophobic modification by additional thioester formation with palmitoylic acids [18]. At physiological temperature (37°C) the dissociation of doubly modified lipo-peptides with an isoprenyl thioether and a palmitoyl thioester is very slow and characterized by half-times in the order of 50 h. Here, the relative effect of the carboxymethylation is significantly reduced. Palmitoyl groups with their C16 alkane chain length contribute more efficiently to membrane anchoring than the farnesyl modification. 

Rgure 3.8. Volume fraction of n-alkane at the onset of flocculation as a function of n-aUcane chain length (C H2 +2). The continuous phase is made of a mixture of n-aUcane, dodecane, and SMO (1 wt%). Glycerol droplets (5% in volume) have a diameter of 0.38 pm. T = 65°C. (Adapted from [13].)... 

Fig. 4 also shows a shallow maximum in activity for an alkane chain length of 6 to 7 carbon atoms. As secondary carbon atoms are more reactive than primary ones, the activity is expected to increase with chain length. To explain the maximum, the diffusivity of the n-alkanes should decrease with chain length. 

Fig. 6. Regioselectivity in the ketone fraction expressed as standarized molar ratios of C2/C3 and C2/(C4+C5). Corrections are made so as to have an equal number of C2 and (C4 + C5) positions in the n-alkane chain, irrespective of its chain length. Conditions are the same as in Fig. 4.

In Table 10.2 we list the observed and calculated frequencies for the TAMs of the -alkanes (n = 5 to 12). They are gathered onto the common plot shown in Fig. 10.11. It is seen that the shorter alkanes have their upper frequency band-heads (frequency variation is very similar to that observed for the ( OLAM)max in the INS spectra of the same samples. It is a consequence of the finite length of the alkanes and the failure of the idealised wavevectors as descriptions of the atomic displacements in short alkanes. The longer the alkane the more nearly it is approximated by the idealised wavevector and the less its dynamics... 

Oxidation of cyclohexane with Oj can be described by a series of elementary reactions similar to the ones for n-butane. In this case, however, the hydrocarbon contains no primary hydrogens and three times as many secondary hydrogens as the acyclic alkane. Chain lengths are, therefore, longer and reaction products less numerous. Cyclohexyl hydroperoxide and cyclohexanol are the major propagation products while cyclohexanone and cyclohexanol are formed in termination ... 

Figure 12.3.27 Cyclic voltammograms for the reduction of a,o)-9,9 -dianthrylalkanes (i.e., An-(CH2) -An, where An = anthracene) in 1 1 benzene acetonitrile containing 0.1 Mtetra-n-butylammonium perchlorate at a Pt electrode. As alkane chain length, n n 0, 2, 4, 6), lengthens, the voltammograms show a decreasing repulsive interaction. [From K. Itaya, A. J. Bard, and M. Szwarc, Z. PhysiL Chem. N. F., 112, 1 (1978), with permission.]...

The Mo-alkyl mean bond dissociation enthalpies decrease with the increase of the n-alkyl chain length, in a way closely resembling the D(C-H) trend in the alkanes. The results suggest that, in the absence of important steric effects, further increases of the chain length will not significantly affect the Mo-alkyl bond dissociation enthalpy. 

Deuterium NMR spectroscopy has been employed to probe the interaction between perdeuteriated n-alkanes and host molecules such as liquid crystals, urea crystals, lipid bilayers or zeolites. In general, the temperature-dependent quadrupolar splitting of the deuterium signals is interpreted in terms of conformation and ordering of the alkane chains. For lipid bilayers these studies are of interest in connection with the anaesthetic properties of alkanes. Phospatidylcholine bilayer membranes were chosen as a model. The solubilities of n-alkanes as determined by NMR were found to be dependent on both the membrane- and alkane-chain length ". The complex signal patterns which show the dynamic processes of perdeuteriated hexane in a multilayer is reproduced in Figure 3 ... 

Wudl and Heeger et al. prepared the self-dopable polymers poly(n-(3 -thienyl)alkanesulfonic acids) (P3TASH) and their sodium salts with alkane chain lengths ranging from 2 to 4 [127-129]. In an extension of this study, Ikenoue et al. found that poly(3-(3 -thienyl)propanesulfonic acid) (P3TPSH), which was obtained by exchanging the sodium ions in poly(sodium-3-(3 -thienyl)propanesulfonate) (P3TPSH) with protons... 

In this work, the diffusion of three light components, namely H2, CO and H2O, to heavy n-alkanes and mixtures of n-alkanes at elevated temperatures and pressures was examined using MD simulations. Accurate atomistic force fields were used to model n-alkane chains and light component molecules. The force field for the n-alkanes was initially vahdated against experimental density values for different chain lengths and was shown to be very accurate. 

Figure 3 The length of the largest short chain n-alkane which is immiscible with a given long chain n-alkane. The length of the long chain alkane ranges from 75 up to 9,000 carbon atoms.

Recently, the photochemical attachment of n-alkanes with 8,19, 20, 21, 24, and 28 carbon atoms and 1-eicosene to pyrene has been investigated. The dependence of attachment selectivity (based on the degree of retention of the pyrenyl aromatic system in the products and the fraction of them in which attachment is at the 1-position of the -alkane and the 1-position of pyrene) and efficiency (based on the relative yields of attached products when irradiations were performed under conditions of constant flux) on solvent phase, pyrene concentration, radiation wavelength (above and below 300 nm), and alkane chain length was explored. Without exception, attachment was more efficient and selection was greater in the solid than in the liquid phases of the alkanes. Also, the efficiency decreased significantly when initial pyrene concentrations were > 10" M. Reactions in the sohd state of solid -alkanes with >21 carbon atoms yielded l-(n-alkyl)pyrenes almost exclusively when the radiation wavelength was >300 nm. This behavior was attributed, in part, to the location of the pyrene molecules at the interfaces between alkane lamellae. 

The molecular ions decrease in intensity with increasing chain length but are still detectable at C40. In contrast to branched alkanes, the loss of a methyl group is not favored for n-alkanes. Usually the... 

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. 

If the diamond lattice itself is used for the mapping of the PE chains, each internal bead represents a methylene unit, the step length is the C-C bond length, and CxH2x 2 is represented by x beads. Typical bulk densities for n-alkane melts, which are in the range 0.7-0.8 g/cm3, are achieved with occupancy of 16-19 % of the sites on this lattice. 

Second, some organisms are able to incorporate longer pendent chains yielding another class of PHA medium chain length PHA, poly(HAMCL). Poly (HAmcl) is specifically accumulated by fluorescent pseudomonads. When aliphatic hydrocarbons like n-alkane, n-alkanoate, or n-alkanol serve as feedstocks for Pseudomonas oleovorans the resulting PHA is a random copolymer... 

---