Hydrocarbons carbon

In the United States butadiene was prepared initially from ethanol and later by cracking four-carbon hydrocarbon streams (see Butadiene). In Germany butadiene was prepared from acetylene via the following steps acetylene — acetaldehyde — 3-hydroxybutyraldehyde — 1,3-butanediol — ... 

Natural gas is a mixture of low molecular weight compounds of hydrogen and carbon (hydrocarbons) found in underground fields of sandstone or other porous rock. This gas escapes to the surface of the earth when the field is tapped by drilling. 

Molar entropies increase as the size and complexity of the molecule increases. Compare, for example, the standard molar entropies of the three two-carbon hydrocarbons ... 

These reactions do not occur at lower temperatures because of activation energy barriers and because H2 becomes the dominant form of hydrogen. Aromatic species are produced initially from acetylene via Diels-Alder type processes, in which a two-carbon and a four-carbon hydrocarbon condense into an aromatic species. Once PAHs are synthesized, they may continue to grow to form carbonaceous small grains. 

Hydrocarbon bond saturation and cyclization also play roles in water solubility. Figure 6.7 shows that, among the six-carbon hydrocarbons, the various forms of hexane, C6H14, have the lowest solubility, and the hexenes and cyclohexane with the formula C6H12 have three times the solubility. Fewer hydrogen atoms consistently lead to higher solubilities, and benzene has one hundred times the water solubility of normal and iso-hexanes. 

Turpentine, the pleasantly smelling piney solvent, gets its name from the Greek word for the tree from which turpentine was distilled. As a solvent, turpentine has medical uses to treat wounds, to combat lice infestation and as an inhalant (the well-known Vick s vapom rub used to contain turpentine). Turpentine is a mixture of 10 carbon hydrocarbons (C,o), and the composition varies depending on the tree species (usually a pine or balsam) from which it has been distilled. It was recognised that a family of Cjo terpenes... 

Benzene s molecular formula is C6H6, but it does not behave like hexane, hexene, or any of their isomers. One would expect it to be similar to these other six-carbon hydrocarbons in its properties. Table 4 provides a comparison between benzene, hexane and 1-hexene. The table shows that there are major differences between benzene and the straight-chain hydrocarbons of die same carbon content. Hexene s ignition temperature is very near to hexane s. The flash point difference is not great, however, there are significant differences in melting points. The explanation for these differences is structure which in the case of benzene is a cyclical form with alternating double bonds. 

Ethyl alcohol, also called ethanol, absolute alcohol, or grain alcohol, is a clear, colorless, flammable liquid with a pleasant odor. It is associated primarily with alcoholic beverages, but it has numerous uses in the chemical industry. The word alcohol is derived from the Arabic word al kuhul, which was a fine powder of the element antimony used as a cosmetic. In Medieval times, the word al kuhul came to be associated with the distilled products known as alcohols. The hydroxyl group, -OH, bonded to a carbon, characterizes alcohols. Ethyl is derived from the root of the two-carbon hydrocarbon ethane. 

The longest continuous carbon chain carrying the OH group is a six-carbon unit. The prefix for a six-carbon hydrocarbon is hex-. 

There are two major routes to hydrocarbon production via gas phase ion-molecule reactions. These routes can be labeled C+ or C insertion (see Herbst, Adams, and Smith 1983, 1984) and condensation (see Mitchell and Huntress 1979, Walmsley et al. 1979, Winnewisser 1981, or Schiff and Bohme 1979). The insertion route for two-carbon hydrocarbons proceeds by reactions such as the following (Herbst, Adams, and Smith 1983, 1984) ... 

What effect do shocks have on the gas phase synthesis of complex interstellar molecules This question has been investigated at least for hydrocarbons through six carbon atoms in complexity by Mitchell (1983, 1984). He has found that if a shock passes through a dense cloud where much of the carbon is already in the form of carbon monoxide, complex hydrocarbons are not formed in high abundance. However, if a shock passes through a diffuse cloud, of density approximately 103 cm-3, where much of the cosmic abundance of carbon is in the form of C+ and to a lesser extent C, a different scenario is present. As the shock cools, the C+ and C, which remain in appreciable abundance for up to 10s yrs after the shock passage, react via many of the reactions discussed above as well as others to produce a rich hydrocarbon chemistry. The net effect is that large abundances of hydrocarbons build up as the cloud cools and eventually reaches a gas density of 3 x 104 cm-3. Do these results bear any relation to the results obtained from ambient gas phase models In both types of calculations, hydrocarbon chemistry appears to require the presence of C+ and/or C both to synthesize one-carbon hydrocarbons such as methane and then, via insertion reactions, to produce more complex hydrocarbon species. Condensation reactions do not appear to be sufficient. 

The //-alkanes usually range in chain length from 21 to 31 or 33 carbons. Hydrocarbons with fewer than 20 carbons commonly occur as pheromones, defensive compounds and intermediates to pheromones and defensive compounds, but their volatility makes them unsuited to function as cuticular components, n-Alkanes have been found on almost every insect species analyzed, and can range from less than one percent of the total hydrocarbons, as in tsetse flies (Nelson and Carlson, 1986 Nelson et al., 1988) to almost all of the hydrocarbon fraction, as in the adult tenebrionid beetle, Eurychora sp. (Lockey, 1985). Depending upon the species, they can consist of essentially only one major component, such as n-pentacosane in the American cockroach, Periplaneta americana (Jackson, 1972) to a series of //-alkanes, such as the series from C23 to C33 in the housefly, Musca domes-tica (Nelson et al., 1981), with trace amounts to C37 (Mpuru et al., 2001). In all cases, the odd-numbered alkanes predominate, due to their formation from mostly two carbon units followed by a decarboxylation (Blomquist, Chapter 3, this book). Small amounts of even-numbered carbon chain //-alkanes often occur, and presumably arise from chain initiation with a propionyl-CoA rather than an acetyl-CoA. Occasionally, gas chromatographic analyses reveal similar amounts of even-numbered chain //-alkanes and odd-numbered chain components. This is a red flag that the samples must be checked for contamination. 

Terpenes are plant-derived natural products constructed of multiples of the five-carbon hydrocarbon isoprene. 

Another means of classification depends on the type of bonding that exists between carbons. Hydrocarbons which contain only carbon-to-carbon single bonds are called alkanes. These are also referred to as saturated molecules. Hydrocarbons containing at least one carbon-to-carbon double bond are called alkenes, and those compounds with at least one carbon-to-carbon triple bond are called alkynes. These are compounds that are referred to as unsaturated molecules. Finally, a class of cyclic hydrocarbons that contain a closed loop (sextet) of electrons are called aromatic (see Chapter 14 in your text for further details). Table 28.1 distinguishes between the families of hydrocarbons. 

This name is derived from the five carbon hydrocarbon, pentane.)... 

Before you design your Chemistry Newsletter at the end of Unit 1, consider that fuels are composed of compounds containing hydrogen and carbon (hydrocarbons). What kind of reaction have you seen in this section that involves those kinds of compounds What type of warning would you expect to see on a container of lawnmower fuel How is the warning related to the types of reaction that involve hydrocarbons ... 

Saturated four-carbon hydrocarbons (butanes) occur in natural petroleum products such as crude oil and the heavy vapors in wet natural gas. The saturated C4s are also produced from other hydrocarbons during the various petroleum refining processes. The butylenes— unsaturated C4s—do not occur in nature, but are derived from butanes or other hydrocarbons either deliberately or as by-products. The complex interrelationships of C4 hydrocarbons, including their production and use, are described in Fig. 10.27. 

The spectrum of products which can be derived from the four-carbon hydrocarbons is shown in Fig. 10.28. Several of these can also... 

Smiley191 has measured gas-liquid retention volumes to obtain values for the activity coefficients at infinite dilution for eight different five-carbon hydrocarbons in NMA. The activity coefficients were determined at 40, 70, and 100 °C and, from the temperature dependence, values for the partial molar heats of solution were calculated. Frost and Bittrich192) have reported limiting activity coefficients of benzene and cyclohexane in NMA at 25 and 50 °C. 

The redox conditions in the environment will determine which carbon species are thermodynamically stable carbon dioxide under oxidative conditions, and elementary carbon and hydrocarbons under reductive conditions. The oxidation state of organic substances is always between these two thermodynamically stable species. Since these organic substances are thermodynamically not stable, they are driven to transform to carbon dioxide or to elementary carbon/hydrocarbons, which processes, however, are limited by kinetic barriers. 

Carbon Hydrocarbons l> Polar fraction Metals HH Water... 

Instead of considering it as a derivative of methane it is considered as a derivative of propane because three carbons is the longest straight chain of carbon atoms present, and the three carbon hydrocarbon is propane. It is then methyl propane in which the methyl is linked to carbon atom number two. Its name is written as follows 2-methyl propane. 

The aldehyde derived from the next higher hydrocarbon of the ethylene series, viz., the four carbon hydrocarbon, butene, is known as crotonic aldehyde because on oxidation it yields an acid known as crotonic acid. As there are two isomeric butenes due to the position of the double bond there will likewise be possible two isomeric aldehydes or butenals. 

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