Branched-chain Hydrocarbons Research Articles

Mass-spectrometric method of determination of straight- and branched-chain paraffinic hydrocarbons in petroleum fractions

Mass-spectrometric method of determination of straight- and branched-chain paraffinic hydrocarbons in petroleum fractions

Submillimetre and far i.r. studies of normal and branched chain hydrocarbons

Complete far i.r. spectra of normal and branched chain hydrocarbons in solid and liquid phases are reported. In conunon with most other materials these systems exhibit a broad low frequency absorption which is sensitive to the chain structure and length. It is apparent that there is no single explanation of the total absorption in the whole frequency region and the various molecular processes responsible exhibit a combination of resonant and relaxation characteristics. The most important components are Debye rotational relaxation of terminal groups, collisional polarization of molecular chain units, intermolecular (lattice) vibrational modes (both fundamentals and multiphonon combinations) and intramolecular ‘vibrational’ modes of the hydrocarbon skeleton.

Gamma Radiolysis of Branched Chain Hydrocarbons: 2,2,4-Trimethylpentane and 2,2,5-Trimethylhexane

The gamma radiolysis of liquid 2,2,4-trimethylpentane and 2,2,5-trimethylhexane at room temperature was investigated under vacuum, at different doses. The effect of some additives and impurities (iodine, diphenilpicrylhydrazyl, oxygen and water) was also investigated. The fragmentation products, some of the recombination products, and the alkyl iodides formed by reaction of the primary radicals with the scavenger iodine were identified and measured. The yield (G) of formation of the products and the yield (G) of rupture of the different bonds of the molecules were calculated and correlated with the molecular structure.

Unsaponifiable matter of crude and processed coconut oil.

AbstractCoconut oil samples were taken prior to and during processing. Hydrocarbons, alcohols and sterols were separated from unsaponifiable matter (UNS) by column chromatography (c.c.) on Florisil and characterised by gas‐liquid chromatography (g.l.c.) Hydrocarbons ranged from the C‐17 to C‐32 straight chain homologs and squalene. Small amounts of iso‐ and/or anteiso and branched chain hydrocarbons were found. Straight chain, iso‐ and/or anteiso‐aliphatic alcohols, and four triterpenoid alcohols were identified. The UNS contained cycloartenol, α‐ and β‐amyrin and 24‐methylenecyloartenol. Campesterol, stigmasterol and β‐sitosterol were found, with the latter comprising as much as 69.0% of the total sterol fraction. Some minor changes were noted in relative distribution of certain components at various stages in oil processing.

Hydrocarbons from males, females, and larvae of pecan weevil:Curculio caryae (Horn)

As part of a program to identify as many as possible of the components of the pecan weevil, Curculio caryae (Horn), the hydrocarbons from males, females, and larvae were isolated by solvent extraction and column chromatography and subjected to gas lipuid chromatography-mass spectrometry analysis. n-Alkanes from C14-C32 in the larvae and unsaturated and branched chain hydrocarbons from C20-C32 in males and females were found. There are no significant differences between the hydrocarbons of the male and female pecan weevils.

Heat of immersion studies on carbon formed from polyvinylidene chloride

A heat of immersion study has been conducted on a highly microporous polyvinylidene chloride (PVDC) carbon. The effect of chain length on the heat of immersion has been investigated for a series of n-alkanes and n-alkanols. By measuring the heat of immersion of the carbon in hexane, as a function of precoverage with hexane, it has been demonstrated that the heat of immersion is a direct measure of the net heat of adsorption. The surface of the carbon appeared to be reasonably uniform with a net heat of adsorption of 10.25 kcal · mole −1. Using a series of branched chain hydrocarbons, as molecular probes, it was observed that the carbon had an almost uniform pore size with entrances between 5 Å and 6 Å in width.

The organic geochemistry of torbanite precursors

The generally accepted hypothesis of the composition of torbanite precursors has been shown to be incorrect. Contrary to previous thinking, the monomers largely responsible for coorongite, and torbanite, are not fatty acids or branched chain hydrocarbons but straight chain alkadienes arising from the green form of the alga. The rubbery deposit of the orange form of the alga is composed of polymerised botryococcenes.

Mobilities and Ranges of Electrons in Liquids: Effect of Molecular Structure in C5–C12 Alkanes

X-radiolysis free ion yields and electron mobilities were measured in a series of branched chain hydrocarbons at several temperatures. The numbers listed after the following compounds are the temperature (K), Gfi, most probable penetration range of the secondary electrons (Å) and thermal electron mobility (cm2/V s): 2,2-dimethylpropane (neopentane), 294, 1.09, 213, 50; 2,2,3,3-tetramethylbutane, 379, 0.80, 130, –; 2,2,4,4-tetramethylpentane, 295, 0.83, 158, 24; 2,2,5,5-tetramethylhexane, 293, 0.67, 138, 12; 2,2,6,6-tetramethylheptane, 293, 0.47, 113, –; 2,2,7,7-tetramethyloctane, 383, 0.58, 100, –; 2,2,3,3-tetramethylpentane, 295, 0.42, 102, 5.2; cyclohexane, 294, 0.16, 67, 0.45. The difference between the activation energies of the reactions[Formula: see text]and[Formula: see text]is (E15–E14) ≈ (2 to 3)RT for twenty two different hydrocarbons, including olefins and benzene. The rate of energy loss by epithermal electrons in liquid hydrocarbons increases with increasing anisotropy of polarizability of the molecules or groups; the range of the electron interaction in a given molecule appears to be about two C—C bonds in series (groups up to neopentyl in size). There is a correlation between the mobilities of thermal electrons in liquids and the penetration ranges of the secondary electrons in the liquids. The electron mobility in a liquid alkane appears to be limited by inelastic scattering. The inelastic scattering cross sections for both thermal (< 0.1 eV) and epithermal (~ 1 eV) electrons in liquid alkanes are affected in similar ways by the anisotropy of polarizability of the molecules. In both instances the scattering apparently involves rotational (librational) excitation of the medium.

Degradation and mineralization of petroleum by two bacteria isolated from coastal waters.

AbstractWithin the framework of a study on the oil biodegradation potential of the sea the ability of a Flavobacterium sp. and Brevibacterium sp. to metabolize a paraffinic crude oil and a chemically defined hydrocarbon mixture was investigated. Major components of the crude oil were identified by combination gas chromatography and mass spectrometry. The rate and extent of total hydrocarbon biodegradation was measured. In addition, CO2 evolution from the crude oil was continuously monitored in a shaker‐mounted gas train arrangement. Degradation started after a 2 to 4 day lag period, and reached its maximum within two weeks. At this time up to 60% of the crude oil and 75% of the model hydrocarbon mixture, each added at the level of 1 ml per 100 ml artificial sea water, were degraded. Mineralization(conversion to CO2) was slightly lower due to formation of products and bacterial cell material. n‐Paraffins were preferentially degraded as compared to branched chain hydrocarbons. Biodegradation of n‐paraffins in the range of C12 to C20 was simultaneous; no diauxie effects were observed.

Molecular sieve properties of the carbonaceous products prepared by chemical dehydrohalogenation of polyvinylidene chloride

The molecular sieve properties of the carbonaceous products prepared by chemical dehydrohalogenation of polyvinylidene chloride (hereafter referred to as “carbons”) have been investigated by a heat of immersion study, using the immersional liquid as a molecular probe. Dehydrohalogenation reaction time has been found to play an important role in the carbons' molecular sieve properties. Characterization of the carbons by low temperature nitrogen adsorption was found in some cases to be limited by activated diffusion so the study was supplemented by measuring the adsorption of carbon dioxide at –78 and 0°C. A marked transition was observed in the molecular sieve properties as reaction time during dehydrohalogenation was varied. This was clearly illustrated by a sudden drop in surface area, as measured by low temperature nitrogen adsorption, when entrance into the pores by nitrogen is prevented by an activated diffusion mechanism. The carbons prepared using a small reaction time are shown to have 4–5 A molecular sieve properties which can separate straight and branched chain hydrocarbons. Carbons prepared by longer reaction periods were found to have 3 A molecular sieve properties. These carbons have also been contrasted to the properties of carbons prepared by pyrolysing polyvinylidene chloride.

The activation of saturated hydrocarbons by transition-metal complexes in solution. Part III. Use of photoelectron spectra of halogen-substituted hydrocarbons and hydrocarbons containing quaternary carbon atoms to interpret the nature of platinum(II)-catalysed hydrogen–deuterium exchange

Representative fluoro-, chloro-, bromo-, and iodo-substituted alkanes and aromatic compounds, and two branched-chain hydrocarbons that contain an ethyl group adjacent to a quaternary carbon atom, have been studied both by photoelectron spectroscopy and in hydrogen–deuterium exchange reactions catalysed by PtCl42– in 50 mol % acetic [2H1]acid–deuterium oxide. For the halogen-substituted compounds, H–D exchange occurs in those molecules for which the first ionisation potential in the photoelectron spectrum is associated with a molecular orbital centered on carbon–hydrogen bonds. For these compounds, an exponential relationship exists between the rate constant for exchange and this potential. When the first ionisation potential is associated with electrons of the halogen atom, then displacement of the halogen occurs. For the branched-chain hydrocarbons, the rate constant for exchange in the ethyl group correlates with the rate constants for the linear alkanes, provided an ionisation potential attributable to electrons of the ethyl group is used.

Composition of the Unsaturated Hydrocarbons of the Millipede Graphidostreptus Tumuliporus (Karsch) (Diplopoda: Spirostreptida)

Upon fractionation on silicagel impregnated with silver nitrate the total hydrocarbons from males and females of the millipede Graphidostreptus tumuliporus (Karsch) were separated into four fractions, viz., on an average 10% alkanes, 38% alk-1-enes, 46% alkadienes and 6% alkatrienes with traces of squalene. The alk-1-enes and also the alkadienes and alkatrienes contain one terminal double bond (vinyl group, - CH=CH 2 ), while the remaining internal double bonds appear to be of the cis-type. Apart from straight-chain homologues with chain lengths up to 38 carbon atoms several series of homologous branched-chain hydrocarbons are present in all fractions. The complete composition of all fractions is given, based on gas-liquid chromatography and infrared and nuclear magnetic resonance spectrometry. Most of the hydrocarbons isolated from Graphidostreptus possess a structure which is not known from other organisms. Especially the cis-cyclopropane-alk-1-enes with a chain length of 25 to 35 carbon atoms are intriguing, since these structures were present in only the females (15% of the alk-1-enes), suggesting a relationship with the unusual cyclopropane fatty acids that have been isolated from only this sex, too. Except for these cyclopropane hydrocarbons only quantitative differences exist between the hydrocarbon compositions of male and female G. tumuliporus.

Studies of the combustion of branched-chain hydrocarbons

The cool-flame oxidation of both 3-ethylpentane and 3-methylpentane has been studied in the temperature range 250°–410°C. The results show that, with these two branched-chain hydrocarbons, the principal chain-propagating cycle involves alkylperoxy radical isomerization, followed by decomposition of the resulting hydroperoxyalkyl radicals; evidence is presented for the first time that ethyl group shifts can occur during the breakdown of the latter radicals. The “alkene-hydroperoxy radical addition” route appears to play only a minor role, even at 403°C. It is also shown that the higher the octane number of a hydrocarbon fuel the more likely it is to lead to β -scission products. Since many of these products are lower molecular weight alkenes, this result is very relevant to the problem of pollution from vehicle exhausts, since alkenes may react photochemically to form smog.

Hydrocarbon pollution of edible shellfish by an oil spill

A spill of 650,000 to 700,000 l of No. 2 fuel oil has contaminated the coastal areas of Buzzards Bay, Massachusetts (USA). Gas chromatography demonstrates the presence of this oil in the sediments of the affected area. Two months after the accident, essentially unchanged oil is still being released from the sediments. The presence of the same pollutant is demonstrated in whole oysters Crassostrea virginica and in the adductor muscle of the scallop Aequipecten irradians. A presumably biochemical modification leads to a gradual depletion of the straight chain and, to a lesser extent, of branched chain hydrocarbons. This does not result in detoxification, as the more toxic aromatic hydrocarbons are retained in the organisms several months after the accident. Scallops from an uncontaminated area contain hydrocarbons in lesser amounts and of very different molecular weight and type distribution; they are accountable entirely from biological sources.

Metabolism of Long-Chain Fatty Acids in the Rumen

Publisher Summary This chapter discusses the metabolism of long-chain fatty acids in the rumen. The studies described in the chapter reveal the importance of veterinary problems in stimulating new interest in biochemical processes that might improve foods of animal origin and, thus, human nutrition. They have contributed to one of the most interesting areas of biochemical studies: the molecular basis of evolution. They have allowed the discovery of living biochemical fossils and have helped to elucidate the mechanisms of branched fatty acid biosynthesis and unsaturated fatty acid biohydrogenation. Studies on the origin of petroleum in association with studies on biological evolution show that branched-chain hydrocarbon structures derive from the corresponding fatty acid molecules. In fatty acid biohydrogenation, the enzyme responsible for the disappearance of a π bond probably represents a vestige, whose deep biological meaning is now hidden in the rumen, of the mechanisms of energy transformations of primitive organisms, when there was no oxygen in the atmosphere, at the beginning of life on earth.

Lipid Composition of Rat Liver Plasma Membranes

Rat liver plasma membranes were isolated by discontinuous sucrose gradient centrifugation. The purity of membrane preparations was checked by electron microscopy and enzyme assays. A new glycolipid, tentatively called the S-lipid, is proposed as a marker to indicate the purity of plasma membranes. It is present in most subcellular particulates (mitochondria, microsomes, lysosomes, etc.) but is absent from plasma membranes. The plasma membrane lipids represent 39.8% of the total dry weight of the membranes. Plasma membrane total lipid contains 39% neutral lipids of which free cholesterol (18.1%) and free fatty acids (7.9%) are the major components. These are present in somewhat lower amounts (4.0 and 1.3%, respectively) in lipid extracts from whole liver homogenate. The phospholipids constitute 55.4% of membrane total lipids. The phospholipid fraction is composed mainly of phosphatidylcholine (19.3% of the total lipids), phosphatidylethanolamine (10.3%), and sphingomyelin (9.8%). The minor constituents are phosphatidylserine, phosphatidylinositol, phosphatidylglycerol, phosphatidic acid, and lysophosphatidylcholine. The phospholipids of the plasma membranes, compared with those of the entire liver, have considerably higher amounts of sphingomyelin and phosphatidylserine (both about 3-fold). In the membranes, about 5.6% of the total lipids are glycolipids and lipids that are unaccounted for. Compared with the liver, the membranes, according to gas-liquid chromatographic analyses of the total lipid fatty acids and hydrocarbons, show a tendency to accumulate the longer chain fatty acids and hydrocarbons. The membranes also contain relatively higher amounts of saturated fatty acids and much less branched chain hydrocarbons.

Analysis of Natural Soiles. III.

By means of gas chromatography using 0.75% Silicone SE-30 Gas Chrom P, 80100 mesh, glass column and Apiezon L capillary column, hydrocarbons were separated into straight and branched chain hydrocarbons, of which carbonnumber are from C14 to C41 and are mainly C22C31. Waxes were separated into straight and branched chain waxes, of which carbon number are from C24 to C42 and are mainly C36 by 1.5 % Silicone OV-17 Chromosorb W, 6080 mesh, glass column gas chromatography.

Thermodynamics of proton ionization in dilute aqueous solution. Part XI. pK, ΔH°, and ΔS° values for proton ionization from protonated amines at 25°

A calorimetric study has been made of proton ionization from 69 protonated amines in aqueous solution at 25°. The resulting ΔH° values were combined with pK values to calculate ΔS° values. pK Values were obtained from the literature for 51 compounds and new values were determined for 18 compounds. A compilation of pK, ΔH°, and ΔS° values from the present study and the literature is given for proton ionization from 169 protonated amines. The effect of hydrocarbon chain length and branching on ΔH° and ΔS° values for proton ionization from primary and secondary aliphatic protonated amines is described by simple linear equations. Proton ionization for protonated amines was not found to follow the linear relation between ΔG° and ΔS° predicted by the Bjerrum theory of electrostatics. The changes in the ΔH° and ΔS° values from the first to the second step of ionization for 37 protonated diamines have been examined by using the Bjerrum and Kirkwood–Westheimer theories of electrostatic interactions in aqueous solution. A deviation identical to that previously found for dicarboxylic acids was found between the results derived from the experimental data and those predicted by the Kirkwood-Westheimer theory. Possible reasons for this deviation are discussed.

Natural Gas: Oil's Principal Competitor: ABSTRACT

Petroleum gases and liquids, often occurring together, are found in the same types of traps by the same exploratory methods and are exploited and produced in the same manner. Moreover, all crude oil contains some natural gas, but nearly 75% of all natural gases are not associated with crude oil in the reservoir. The two phases of petroleum are highly competitive. There are important differences in the physics and chemistry of natural gases and crude oil. Natural gases are a mixture of various organic compounds, usually accompanied by smaller amounts of inorganic elements and compounds. Natural gases of commerce are petroleum natural gases, although helium and hydrogen sulfide--also natural gases--may be valuable components. Even carbon dioxide, also a natural gas, finds markets. Physically, natural gases are highly mobile, difficult to contain, and are soluble in both crude oil and water, particularly under pressure. Chemically, there are marked differences between petroleum natural gases and crude oil. Methane is the simplest, most ubiquitous and principal component of petroleum natural gases. It is often accompanied by much smaller quantities of heavier hydrocarbons. Natural gases are alkanes: paraffinic, saturated, straight chain hydrocarbons. The division between petroleum natural gases and the somewhat more complex, heavier alkanes occurring with them as vapors, is between propane and butane. Butane and heavier paraffinic hydrocarbons can be found both as normal, saturated straight chain or as isomers: saturated, branched chain hydrocarbon compounds. The substantial chemical differences between the simple compounds of petroleum gases and the far more complex crude oils suggest somewhat differ nt modes of origin. An early and multiple origin for methane seems probable, inasmuch as substantial quantities are found in youngest Holocene sediments in swamps and glacial drift, and it is present as part of the atmosphere of several of the planets. The vastly different physical and chemical characteristics of petroleum gases and crude oil have a great bearing on economics of exploring for, developing and producing them. The phenomenal growth in production of natural gas and in its use as a form of primary energy has been a major factor in the declining growth in the need for crude oil. The two substances are directly competitive for space heating, for domestic uses, and for generation of electricity. Liquefied petroleum gases (natural gasolines) and lease condensate have further supplanted crude oil. Production of petroleum natural gases, wet, increased from 4,423 trillion BTU in 1945 to 20,121 trillion BTU in 1967, and in 1967 amounted to 36.4% (excluding lease condensate) of production of primary energy, compared to 32.6% fo crude oil (including lease condensate). Moreover, according to Winger et al., dry natural gas yields less than 4¢ of every dollar of income from a representative group of companies, the financial characteristics of which have been studied for years by the Chase Manhattan Bank. Although natural gas liquids and lease condensate add somewhat to this amount, natural gas is a much less attractive exploration objective than crude oil. Most natural gases have been found as a result of the search for crude oil. Under present economic conditions, natural gases alone are not attractive exploration objectives in most areas of the United States. Hence, as demand has continued to accelerate, drilling of gas wells has declined sharply, and ratio of annual production to annual additions to reserves has declined to a dangerous point. Unless this trend is reversed, the next few years may see a shortage of available natural gases--although none exists in nature--simply because of lack of incentive to search for and develop natural gases in the quantities which will be needed. End_of_Article - Last_Page 2209------------

Hydrogenolysis of saturated hydrocarbons on a nickel catalyst: II. Selectivity of hydrogenolytic cleavage of some aliphatic and alicyclic hydrocarbons and their reactivity

The hydrogenolysis of octane, decane, isooctane, neohexane, and some alicyclic hydrocarbons, like alkylcyclopentanes, alkylcycloheptanes, and dialkylcyclohexanes, in the gaseous phase on a nickel catalyst containing 8% (wt) Al 2O 3 was studied at 220 °C under atmospheric pressure of hydrogen. In the hydrogenolysis of these hydrocarbons the predominant reaction was successive degradation to methane and a hydrocarbon containing one carbon atom less than the starting hydrocarbon. In the case of isoparaffins, only the methyl groups bonded to secondary or tertiary carbon atoms and not those from quarternary carbon atoms were split off. With dialkylcyclohexanes the alkyl groups were successively removed. The cleavage of the cyclohexane ring did not take place under the reaction conditions. The splitting of CC bonds in the side chains of alkylcyclopentanes and alkylcycloheptanes was accompanied by hydrogenolytic opening of the ring. The reactivity of branched-chain hydrocarbons was higher than that of corresponding hydrocarbons containing a straight chain. The high stability of the cyclohexane ring and the higher reactivity of alkylcyclohexanes than that of other alkylcyclanes is explained by the formation and electronic effect of a surface complex of quasiaromatic nature. The differences in the reactivity of hydrocarbons are discussed in terms of the participation of electronic and steric effects.