Alkane normal

A means for normalizing retention times by comparing a solute s retention time with those for normal alkanes. 

Kovat s retention index for a normal alkane is 100 times the number of carbons thus... 

The following data were collected for a series of normal alkanes using a stationary phase of Carbowax 20M. 

Wax usually refers to a substance that is a plastic solid at ambient temperature and that, on being subjected to moderately elevated temperatures, becomes a low viscosity hquid. Because it is plastic, wax usually deforms under pressure without the appHcation of heat. The chemical composition of waxes is complex all of the products have relatively wide molecular weight profiles, with the functionaUty ranging from products that contain mainly normal alkanes to those that are mixtures of hydrocarbons and reactive functional species. 

A paraffin wax is a petroleum wax consisting principally of normal alkanes. MicrocrystalHne wax is a petroleum wax containing substantial proportions of branched and cycHc saturated hydrocarbons, in addition to normal alkanes. SernimicrocrystaUine wax contains more branched and cycHc compounds than paraffin wax, but less than microcrystalHne. A classification system based on the refractive index of the wax and its congealing point as... 

Paraffin wax is macrocrystalline, britde, and is composed of 40—90 wt % normal alkanes, with the remainder C g—isoalkanes and cycloalkanes. Paraffin wax has Httle affinity for oil content fully refined paraffin has less than 1 wt % cmde scale, 1—2 wt %, and slack [64742-61-6] above 2 wt %. Within these classes, the melting point of the wax determines the actual grade, with a range of about 46—71°C. Typical properties of petroleum waxes are listed in Table 3. 

Figure 4.12 continued) (c) An expansion of the inset region from (b), with the normal alkanes shown as (a-e). Other unidentified components (f-i) are presented to locate specific peaks for comparison purposes, (d) A light gas oil analysed under the same conditions as for the cycle oil, showing the same expanded region. In this case, the oil has not been ti eated in the same manner as the cycle oil, so it retains the components that were absent from the cycle oil. Peaks (a-i) are the same as those seen in (c). 

Branched-chain alkanes, also known as isoparaffins or isoalkanes, are possible when n > 4. The prefix iso is used when two methyl groups are attached to a terminal carbon atom of an otherwise straight chain and the prefix neo when three methyl groups are attached in that manner. Branched-chain alkanes are sometimes regarded as normal alkanes with attached substituent alkyl groups. An example is... 

Paraffins (Alkanes). These saturated aliphatic hydrocarbons include normal alkanes as well as branched alkanes (isoalkanes), represented by the formula The... 

Normal alkanes (n-alkanes, n-paraffms) are straight-chain hydrocarbons having no branches. Branched alkanes are saturated hydrocarbons with an alkyl substituent or a side branch from the main chain. A branched... 

Compounds like butane and pentane, whose carbons are all connected in a row, are called straight-chain alkanes, or normal alkanes. Compounds like 2-methylpropane (isobutane), 2-methylbutane, and 2,2-dimethylpropane, whose carbon chains branch, are called branched-chain alkanes. The difference between the two is that you can draw a line connecting all the carbons of a straight-chain alkane without retracing your path or lifting your pencil from... 

Hydrogens on carbon next to an ether oxygen are shifted downfield from the normal alkane resonance and show U-f NMR absorptions in the region 3.4 to 4.5 8. This downfield shift is clearly seen in the spectrum of dipropyl ether shown in Figure 18.4. 

Normal alkane (Section 3.2) A straight-chain alkane, as opposed to a branched alkane. Normal alkanes are denoted by the suffix n. as in //-C4H10 (//-butane). 

Using the data given in the last column of Table 18-111, plot the heat released per carbon atom against the number of carbon atoms for the normal alkanes. Consider the significance of this plot in terms of the molecular structures of these compounds. 

Normal alkanes or fatty acid methyl esters are generally used as the standard homologous compounds. The column separation number is dependent on the nature of the stationary phase, the column length, column temperature, and carrier gas flow rate [42-44]. Referring to Figure 1.2, at a sufficiently high capacity factor value either n, N, or SN provides a reasonable value for comparing... 

A more general reaction between kojic acid and aldehydes is a trimolecu-lar condensation discovered by Barham and Reed." By a process of elimination, they arrived at the conclusion that C6 of kojic acid was most probably the point of attack two molecules of kojic acid reacted with one molecule of the aldehyde, with the elimination of one molecule of water, giving a product of structure LXXV. Such compounds were prepared from kojic acid and the following aldehydes the normal alkanals from formaldehyde to heptanal, benzaldehyde, cinnamaldehyde, hydrocinnamaldehyde, 2-furaldehyde, and acrolein. The compound derived from kojic acid and benzaldehyde (LXXV, R = phenyl) was also obtained by treating LXXII (R = phenyl) with hot, aqueous sodium carbonate.92... 

Jonsson, J. A., Vejrosta, J., Novak, J. (1982) Air/water partition coefficients for normal alkanes (n-pentane to n-nonane). Fluid Phase Equil. 9, 279-286. 

Kudchadker, A.P., Zwolinski, B.J. (1966) Vapor pressures and boiling points of normal alkanes, C21 to C100. J. Chem. Eng. Data 11, 253-255. 

Tsonopoulos, C. (1999) Thermodynamic analysis of the mutual solubilities of normal alkanes and water. Fluid Phase Equil. 156, 21-33. 

Tsonopoulos, C. (1999) Thermodynamic analysis of the mutual solubilities of normal alkanes and water. Fluid Phase Equil. 156, 21-33. Tsonopoulos, C., Prausnitz, J.M. (1971) Activity coefficients of aromatic solutes in dilute aqueous solutions. I EC Fundum. 10, 593-600. 

Rao and Singh32 calculated relative solvation free energies for normal alkanes, tetra-alkylmethanes, amines and aromatic compounds using AMBER 3.1. Each system was solvated with 216 TIP3P water molecules. The atomic charges were uniformly scaled down by a factor of 0.87 to correct the overestimation of dipole moment by 6-31G basis set. During the perturbation runs, the periodic boundary conditions were applied only for solute-solvent and solvent-solvent interactions with a non-bonded interaction cutoff of 8.5 A. All solute-solute non-bonded interactions were included. Electrostatic decoupling was applied where electrostatic run was completed in 21 windows. Each window included 1 ps of equilibration and 1 ps of data... 

Molecular fossils have been successfully identified in younger Precambrian rocks and linked to certain classes of biological source material. In organic analyses of ancient sediments the cleaned, pulverized rocks are treated with organic solvents to extract a soluble fraction containing the less complex and more easily identifiable compounds. However, this fraction is more subject to contamination since it is not locked within the rock matrix. Normal alkanes have been identified in extracts of the 3 billion year old Fig Tree Shale. These alkanes have a probable biological origin in cellular lipids. The odd and even-numbered alkanes are evenly distributed, a characteristic of alkanes from ancient rocks. It is uncertain, however, whether these compounds were present at the time of deposition or derived from a later source [24]. 

Recently, researchers have detected 2,5-dimethylfuran and 2-methylfuran and normal alkanes in kerogen of the 2.7 x 109 year old Belingwe, Rhodesia stromatolites, by the method of pyrolysis/ GC/MS [26]. They concluded that although furans could probably be derived from many compounds, their probable origin is in bacterial and algal sugars, and that the alkanes are either products of decarboxylation of fatty acids or unaltered constituents of ancient organisms. 

Hexane is contained in a variety of products commonly used in household settings. Given its volatility, this creates possibilities for exposures from inhalation as well as by dermal contact and ingestion. In a study of over 1,000 common household products, -hexanc was detected in 101 products, about the same detection rate as for BTEX compounds (e g., benzene, toluene, xylene or ethylbenzene) and other normal alkanes. -Hexane was detected in more than 10% of the items sampled in the following product categories automotive products oils, greases and lubricants and adhesive-related products (Sack et al. 1992). 

Rather large kH/kD isotope ratios (29) have been reported in model studies of dehydrocyclization using deuterated vs. normal alkanes, particularly when one considers the high temperatures being used, but the origin of these effects is difficult to sort out. In contrast to catalytic dehydrocyclization reactions, the dehydrocyclization reactions of the observable p-H-bridged cyclodecyl cations are much more amenable to mechanistic studies, albeit difficult because of the low temperatures involved. Examination of the dehydrocyclization transition... 

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