Branched hydrocarbon molecules

The best way to learn to name branched hydrocarbon molecules is to apply the rules to an example molecule ... 

An endless variety of hydrocarbon molecules can be constructed. Each molecule will have different physical and chemical properties. For example, gasoline is made of hydrocarbon molecules having from five to ten carbon atoms. When smaller-chain hydrocarbon molecules and branched hydrocarbon molecules are added to the gasoline, a car engine works more smoothly. Each hydrocarbon molecule has unique properties and a unique structure. We can consider a hydrocarbon molecule as a microsculpture having a unique shape. We will examine shape further and understand the relationship between shape and branched and cyclic hydrocarbon molecules. (See Figure 5.2.)... 

The separated hydrocarbon fraction is then analyzed by capillary column gas chromatography, which simultaneously separates the mixture of hydrocarbons into its components and measures how much of each compound is present. Individual n-alkanes can usually be identified by their relative retention times in gas chromatograms, although sometimes branched hydrocarbon molecules will share the same retention time as an n-alkane. For this reason, positive identification of biomarker hydrocarbons require the combination of gas chromatography and mass spectrometry using verified mass spectra. 

Chemical Properties and Reactivity. LLDPE is a saturated branched hydrocarbon. The most reactive parts of LLDPE molecules are the tertiary CH bonds in branches and the double bonds at chain ends. Although LLDPE is nonreactive with both inorganic and organic acids, it can form sulfo-compounds in concentrated solutions of H2SO4 (>70%) at elevated temperatures and can also be nitrated with concentrated HNO. LLDPE is also stable in alkaline and salt solutions. At room temperature, LLDPE resins are not soluble in any known solvent (except for those fractions with the highest branching contents) at temperatures above 80—100°C, however, the resins can be dissolved in various aromatic, aUphatic, and halogenated hydrocarbons such as xylenes, tetralin, decalin, and chlorobenzenes. 

Alkylation in petroleum processing produces larger hydrocarbon molecules in the gasoline range from smaller molecules. The products are branched hydrocarbons having high octane ratings. 

The effective cross-section of an /z-alkane molecule is smaller than 5 A the effective cross-section of branched, cyclic, or aromatic hydrocarbon molecules is larger than 5 A. Therefore only n-alkanes are adsorbed by a 5-A zeolite all other types of hydrocarbons are excluded. The adsorbed n-alkanes can be recovered by different methods and are subsequently available in a pure form, for further processing. 

It has been suggested [18] that the greater tendency for long-chain hydrocarbons to knock as compared to smaller and branched chain molecules may be a result of this internal, isomerization branching mechanism. 

Alkyl groups a group of carbon and hydrogen atoms that branch from the main carbon chain or ring in a hydrocarbon molecule. The simplest alkyl group, a methyl group, is a carbon atom attached to three hydrogen atoms. 

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. 

Aliphatic hydrocarbon molecules, normally called hydrocarbons, are divided into several major groups. Their molecules are mostly formed as straight or branched chains that form three major subgroups ... 

The molecular formulas just shown for 10 alkane hydrocarbon molecules represent the proportions of carbon to hydrogen in each molecule. These formulas do not reveal much about their structures, but rather indicate the proportions of each element in their molecules. Each molecule may have several different structures while still having the same formula. Molecules with different structures but the same formulas are called isomers. For example, n-butane is formed in a straight chain, but in an isomer of butane, the CH branches off in the middle of the straight chain. Another example is ethane, whose isomeric structure can be depicted as H,C H,C-CH,. The name for the normal structure sometimes uses n in front of the name. 

Small-pore zeolites can accommodate linear chain molecules, such as straightchain hydrocarbons and primary alcohols and amines, but not branched chain molecules. As discussed in the previous section, the port size can be enlarged to about 500 pm in diameter by replacing sodium ions with calcium ions. 

The conclusions which one draws in consideration of the above facts are that both the physical and chemical properties of hydrocarbon molecules are largely a function of the electron distribution. The structural elements which play a prominent role in this distribution are chain length, chain branching, methyl groups, double bonds, and benzene nuclei. 

The form of the isotherms of the mixtures is largely independent of the cation distribution within the cage, i.e., whether the cation-poor or cation-rich model is used. This result is somewhat surprising, especially in view of the different adsorbate structures predicted by single-component isotherms (118-120). Only nonpolar adsorbates were considered in this study and the insensitivity to cation arrangement may well change if one component possesses a permanent dipole. These simulations were based on simple spherical molecules, but the competition for pore space as it depends on size, shape, and polarizability may be extended to other adsorbates. Indeed, Santilli et al. (129) observed experimentally that a branched hydrocarbon adsorbs in preference to a linear one at low loading. 

When every carbon atom in a hydrocarbon except the two terminal ones is bonded to only two other carbon atoms, the molecule is called a straight-chain hydrocarbon. (Do not take this name literally, for, as the w-pentane structures in Figure 12.1 show, this is a straight-chain hydrocarbon despite the zigzag nature of the drawings representing it.) When at least one carbon atom in a hydrocarbon is bonded to either three or four carbon atoms, the molecule is a branched hydrocarbon. Both wo-pentane and /w-pentane are branched hydrocarbons. 

Construct a kinetic sculpture depicting an organic molecule such as methane or a longer, branched hydrocarbon. Use Styrofoam balls for atoms and springs or toothpicks for bonds between atoms. Color the Styrofoam balls to represent atom types. Find a way to show atomic vibrations and molecular rotations and translations. Your kinetic sculpture should be in constant motion. 

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