Branched chains hydrocarbons

Branched-chain hydrocarbons may contain tertiary CH groups. The group frequencies for this CH unit are not as well defined as those of CH3 and CH2 groups and are generally weak since the number of tertiary CH groups is usually much less than that of CH3 

TABLE 5-V. Characteristic Group Frequencies for Branched-Chain Hydrocarbons 

CH3 asymmetric stretch CH3 symmetric stretch CH2 asymmetric stretch CH2 symmetric stretch CH3 asymmetric scissors CH3 symmetric scissors CH2 symmetric scissors CH stretch CH bend 

All these group frequencies have medium to strong intensity if the vibrational group is present in the molecule in equivalent numbers to other groups. All of them are listed in Table 5-V. 

CH3 Groups Adjacent to Atoms Other Than Saturated Carbon 

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Reforming (Section 2 16) Step in oil refining in which the pro portion of aromatic and branched chain hydrocarbons in petroleum is increased so as to improve the octane rating of gasoline... 

Part A of Table 1.5 shows all the acyclic C4-C6 and some of the Cg hydrocarbons. A general trend is discernible in the data. Branched-chain hydrocarbons are more stable than straight-chain hydrocarbons. For example, A/fj for -octane is —49.82 kcal/mol, whereas the most highly branched isomer possible, 2,2,3,3-tetramethylbutane, is the most stable of the octanes, with of —53.99 kcal/mol. Similar trends are observed in the other series. 

Paraffins are straight or branched chain hydrocarbons having the chemical formula C ii2 +2- The name of each member ends with ane examples are propane, isopentane, and normal heptane (Figure 2-1). 

Toxicity, Similar to NG Uses. This substance, as well as other aliphatic compds such as nitroisobutylglycol dinitrate, comprising a branched chain hydrocarbon to which one nitro and two nitrate groups are attached, has been proposed by Bergeim (Ref... 

The names of branched-chain hydrocarbons and hydrocarbon derivatives are based on the name of the longest continuous carbon chain in the molecule (which may not be shown in a horizontal line). 

The Fischer-Tropsch synthesis, which may be broadly defined as the reductive polymerization of carbon monoxide, can be schematically represented as shown in Eq. (1). The CHO products in Eq. (1) are any organic molecules containing carbon, hydrogen, and oxygen which are stable under the reaction conditions employed in the synthesis. With most heterogeneous catalysts the primary products of the reaction are straight-chain alkanes, while the secondary products include branched-chain hydrocarbons, alkenes, alcohols, aldehydes, and carboxylic acids. The distribution of the various products depends on both the type of catalyst and the reaction conditions employed (4). 

HC Unibon [Hydrocracking] A version of the hydrocracking process for simultaneously hydrogenating and cracking various liquid petroleum fractions to form branched-chain hydrocarbon mixtures of lower molecular weight. The catalyst is dual-functional, typically silica and alumina with a base metal, in a fixed bed. Developed by UOP. By 1988,46 licenses had been granted. Currently offered under the name Unicracking. 

Hysomer [Hydroisomerization] A process for converting -pentane and -hexane into branched-chain hydrocarbons. Operated in the vapor phase, in the presence of hydrogen, in... 

Nurex A process for extracting C8 - C30 linear hydrocarbons from petroleum fractions, using their ability to form urea inclusion complexes. Branched-chain hydrocarbons do not form such complexes. Developed by the Nippon Mining Company, Japan, and operated until 1979. 

The conversion of a chemical with a given molecular formula to another compound with the same molecular formula but a different molecular structure, such as from a straight-chain to a branched-chain hydrocarbon or an alicyclic to an aromatic hydrocarbon. Examples include the isomerization of ethylene oxide to acetaldehyde (both C2H40) and butane to isobutane (both C4H10). 

The petroleum-based oils contain hundreds to thousands of hydrocarbon compounds, including a substantial fraction of nitrogen- and sulfur-containing compounds. The hydrocarbons are mainly mixtures of snaight- and branched-chain hydrocarbons (alkanes), cycloalkanes, and aromatic hydrocarbons. Polynuclear aromatic hydrocarbons, alkyl polynuclear aromatic hydrocarbons, and metals are important components of motor oils and crankcase oils, with the used oils... 

Alkylation in the petroleum industry, a process by which an olefin (e.g., ethylene) is combined with a branched-chain hydrocarbon (e.g., isobutane) alkylation may be accomplished as a thermal or a catalytic reaction. 

Sulfuric acid alkylation an alkylation process in which olefins (C3, C4, and C5) combine with isobutane in the presence of a catalyst (sulfuric acid) to form branched-chain hydrocarbons used especially in gasoline blending stock. 

Alkanes are straight-chained or even branch-chained hydrocarbon molecules made up of methyl groups having the formula CnH2n+2i such as butane, isobutane, and pentane. 

Alkylation, In petrochemicals, any reaction involving the thermal or catalytic addition of an olefin to a branch-chain hydrocarbon or aromatic hydrocarbon. The most notable example in petrochemicals is the addition of ethylene or propylene to benzene to produce ethylbenzene or isopropyl benzene (cumene). Other examples include the production of detergent alkylates. 

Isomerization, A process used to convert straight-chain to branch-chain hydrocarbons as in a butane isomerization plant. 

The windows to the channels thus form a three-dimensional sieve with mesh widths between about 300 and 1000 pm, thus the well-known name molecular sieve for these crystalline aluminosilicates. Zeolites thus have large internal surface areas and high sorption capacities for molecules small enough to pass through the window into the cavities. They can be used to separate mixtures such as straight-chain and branched-chain hydrocarbons. 

Zeolite A (Ca form), when loaded with platinum, has been found to be a good catalyst for the oxidation of hydrocarbon mixtures. However, if the mixture contains branched-chain hydrocarbons, these do not react. Suggest a possible reason. 

FIG. 1.25 Shape selectivity of a zeolite cage. The cage allows (a) straight-chain hydrocarbons to snake their way into the pores while (b) preventing branched-chain hydrocarbons from entry. (Adapted from Ball 1994.)... 

The continuous chain hydrocarbons are known as normal hydrocarbons, and the prefix n- is usually attached to the name. The branched-chain hydrocarbons may have the prefix iso- attached to the name. Usually the prefix iso- is reserved for substances with two methyl groups attached to carbon atoms at the end of an otherwise straight chain. In a straight chain, each carbon atom is connected to no more than two other carbon atoms. The prefix neo- denotes three methyl groups on a carbon atom at the end of a chain. For example, the isomers of pentane are illustrated below. 

Branched-chain substituent groups are given appropriate names by a simple extension of the system used for branched-chain hydrocarbons. The longest chain of the substituent is numbered starting with the carbon attached directly to the parent hydrocarbon chain. Parentheses separate the numbering of the substituent from the main hydrocarbon chain. 

The possibility of having branched-chain hydrocarbons that are structural isomers of the continuous-chain hydrocarbons begins with butane (n = 4). The HJPAC rules for the systematic naming of these hydrocarbons follow. 

The results obtained indicate that for n-alkanes and for Cs-C7 cycloalkanes most radicals arise by the loss of a hydrogen atom from the parent molecule. Although some C-C bond rupture occurs in the lower hydrocarbons, its importance decreases with increasing molecular weight. More extensive C-C bond rupture was observed in branched chain hydrocarbons. 

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