Saturated Hydrocarbons and their Derivatives

Saturated hydrocarbons are generally transparent down to 170 m/x and are therefore suitable for use as solvents. The transitions in paraffins and some of their simple derivatives were discussed earlier in Chapter 3. Simple paraffins exhibit bands due to o- a transitions (CH4 Amax 125 m/x C2H Amax 135 mu) which occur just prior to the sharp Rydberg bands caused by the ionization of the molecules. Quite often it is difficult to distinguish bands due to a - y transitions from the ionization bands. The derivatives of the saturated hydrocarbons containing atoms with unshared pairs of electrons 

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As in the alkanes, it is possible for carbon atoms to align themselves in different orders to form isomers. Not only is it possible for the carbon atoms to form branches which produce isomers, but it is also possible for the double bond to be situated between different carbon atoms in different compounds. This different position of the double bond also results in different structural formulas, which, of course, are isomers. Just as in the alkanes, isomers of the alkenes have different properties. The unsaturated hydrocarbons and their derivatives are more active chemically than the saturated hydrocarbons and their derivatives. 

These methods appear rather simple, yet they were the starting point of a long evolution. Gilles Klopman, whose research interests at Case-Western Reserve University later turned to modeling bioactive molecules, was the first to use Sandorfy s methods. Kenichi Fukui made extensive use of them in his well-known work on the structures and reactions of saturated hydrocarbons and their derivatives. Fukui added his frontier orbital considerations. Around 1959 the milieu of developments in quantum chemistry contributed to inspire William N. Lipscomb to conceive the extended Hiickel method, which was subsequently implemented by Lawrence L. Lohr and Roald Hoffmann.83 Soon thereafter, John Pople and his coworkers introduced self-consistent field methods based on the zero-differential overlap approximation.815... 

Studies of chain reactions of hydrobromination [119-121] and hali-dization [122, 123] of ethylene and chlorination of various saturated hydrocarbons and their derivatives [124-128] confirmed the existence of the low-temperature limit of the rate constant. The pattern of chain growth under hydrobromination of ethylene after y-irradiation-induced HBr decomposition is as follows ... 

In Group 14 (IV), carbon serves as a Lewis base in a few of its compounds. In general, saturated ahphatic and aromatic hydrocarbons are stable in the presence of BF, whereas unsaturated ahphatic hydrocarbons, such as propjdene or acetylene, are polymerized. However, some hydrocarbons and their derivatives have been reported to form adducts with BF. Typical examples of adducts with unsaturated hydrocarbons are 1 1 adducts with tetracene and 3,4-benzopyrene (39), and 1 2 BF adducts with a-carotene and lycopene (40). 

Classical organic chemistry provides a wide variety of potential analytes for electron ionization, the only limitation being that the analyte should be accessible to evaporation or sublimation without significant thermal decomposition. These requirements are usually met by saturated and unsaturated aliphatic and aromatic hydrocarbons and their derivatives such as halides, ethers, acids, esters, amines, amides etc. Heterocycles generally yield useful El spectra, and flavones, steroids, terpenes and comparable compounds can successfully be analyzed by El, too. Therefore, El represents the standard method for such kind of samples. 

C. Sandorfy, Can. J. Chem., 33,1337 (1955). LCAO MO Calculations on Saturated Hydrocarbons and Their Substituted Derivatives. 

The selectivity of the separation process in GC can be increased by the formation of inclusion compounds. Maczek and Phillips [139] used lri-r -thymotide, which forms inclusion compounds. They found that in a column containing tri-r -thymotide, unbranched saturated hydrocarbons and their halogen derivatives are retained longer than branched saturated hydrocarbons and secondary and tertiary alcohols. They also found... 

Unsaturated cyclic hydrocarbons, aromatic hydrocarbons and their derivatives, and polycyclic hydrocarbons give a very sensitive reaction with sulfuric acid and formaldehyde, in which deeply colored resinous substances are formed. In this manner as little as 0.1% of benzene in solvent mixtures can be detected. Saturated hydrocarbons, unsaturated aliphatic hydrocarbons, and cyclic saturated hydrocarbons do not give this reaction. 

Sandorfy C (1955) LCAO MO calculations on saturated hydrocarbons and their substituted derivatives. Can J Chem 33 1337... 

Chakactkrisation of Unsaturatkd Aliphatic Hydrocarbons Unlike the saturated hydrocarbons, unsaturated aliphatic hydrocarbons are soluble in concentrated sulphuric acid and exhibit characteristic reactions with dUute potassium permanganate solution and with bromine. Nevertheless, no satisfactory derivatives have yet been developed for these hydrocarbons, and their characterisation must therefore be based upon a determination of their physical properties (boiling point, density and refractive index). The physical properties of a number of selected unsaturated hydrocarbons are collected in Table 111,11. 

Other compounds, containing sulphur or nitrogen, may be present in some oils (like onion, garlic).Investigations on the solubility of pure essential-oil components in carbon dioxide showed that the separation of terpene hydrocarbons and oxygenated derivatives by fractionated extraction is difficult, since their solubility behaviours and vapour pressures are almost the same. Saturating the CO2 with water as modifier can increase the differences in solubility [78],... 

Fatty acids are hydrocarbon chains of various lengths and degrees of unsaturahon that terminate with a carboxylic acid group. The fatty acid chains in membranes usually contain between 14 and 24 carbon atoms they may be saturated or unsaturated. Short chain length and unsaturahon enhance the fluidity of fatty acids and their derivatives by lowering the melting temperature. 

The basic structure, a hydrophobic hydrocarbon chain with a hydrophilic polar group at one end, endows fatty acids and their derivatives with distinctive properties, reflected in both their food and industrial use. Saturated fatty acids have a straight hydrocarbon chain. A trans-Aoablt bond is accommodated with httle change in shape, but a cis bond introduces a pronounced bend in the chain (Fig. 1). 

A well-known phase which is used as a reference, since it is the only one that is perfectly defined, is squalane, which on the McReynolds scale has a polarity of zero (cf Section 2.10.3). This saturated hydrocarbon (C3oHg2) is derived from squalene, a terpenoid natural extract from shark s liver (also present in the sebum of the skin). On this stationary phase, which can be used between 20 and 120 °C (following either deposition or impregnation), the compounds are eluted in increasing order of their boiling temperatures, the retention time being inversely proportional to the analyte vapour pressure. Diverse bonded phases based upon polyalkylsiloxanes, almost apolar, can be used as a replacement for squalane. 

Fatty acids and their derivatives. Fatty acids are characterized by the presence of a carboxylic acid function attached to a hydrocarbon chain. Because the biosynthesis of fatty acids involves the combination of a series of two-carbon fragments, the comnon fatty acids are unbranched chains with even numbers of carbon atoms. Many are saturated, but biochemical interest centers principally around the unsaturated fatty acids containing up to five double bonds. Comnon unsaturated acids have their double... 

Data on the relative basicity of a number of aromatic hydrocarbons and their alkyl derivatives were obtained by the Dutch researchers They measured the coefficients of hydrocarbon distribution between an inert solvent (n-hexane) and liquid hydrogen fluoride, containing additives of inorganic fluorides or saturated with BFj. The protonation of aromatic hydrocarbons in HF is described by the equation ... 

Low bioavailability of hydrocarbon pollutants can limit the biodegradation by indigenous micro-communities in soils. CDs enhance desorption of the nonpolar contaminants from the solid surface and transfer them to the water-phase biofilms, where the hydrocarbon-degrading microbes work. Therefore, this special character of CDs and their derivatives can be used for enhanced removal of hydrocarbon contaminants from soil [92]. This is so-called CD-enhanced pump and treat technology for the removal of dense, non-aqueous phase liquid from the saturated soil. For example, HP- -CD solution was added into the source zone... 

HDO reactions have received less attention than HDS and HDN because organic oxygen compounds are present in low concentrations in petroleum. HDO consists of the removal of the O-atom from hydrocarbons and its conversion to water (H2O). O-compounds are found as phenols, naphthol, furan, and their derivatives [31]. As in HDS and HDN, the reactivity of O-compounds decreases with molecular weight It has been reported that HDO proceeds preferably through partial saturation of the aromatic rings rather than through direct hydroge-nolysis [24],... 

The test is run only on liquid unknowns. Saturated hydrocarbons, fluori-nated and chlorinated saturated hydrocarbons, and aromatic hydrocarbons and their halogenated derivatives all give violet solutions. All other species give a positive test (brown solution). 

Concentrated Sulfuric Acid. Saturated hydrocarbons, halogenated saturated hydrocarbons, simple aromatic hydrocarbons, and their halogenated derivatives are insoluble in cold concentrated sulfuric acid. 

Minisci and Fontana [14] have recently offeree an alternative e. planation in which an Fe species (of undefined origin) reacts with TBHP in the Fenton manner to generate a t.-buto.xide radical, which then reacts with the hydrocaibon to make a carbon radical, which then reacts with the anion attached to Fe and so makes the derivative and reforms Fe. Certain of the recorded facts do not agree with this interpretation [15] and further work is needed. However whichever interpretation of the facts is correct, we do have a very efficient method for turning saturated hydrocarbons into their monochloro derivatives. 

All the information available on reactions of atomic hydrogen with saturated hydrocarbon molecules and their derivatives suggest that the dominant reaction here is the abstraction of a hydrogen atom from the molecule of the initial hydrocarbon (dehydrogenation) to form a hydrogen molecule and a radical R H + RH H2 + R- The activation energy for this process seldom exceeds 40 kJ. 

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