Hydrocarbon Sources and Properties
Hydrocarbon is an organic compound having hydrogen and carbon in the entire molecule containing one or more single, double or triple bonds in two adjacent carbon atoms. When two or more carbon atoms linking by the single common bond are called saturated hydrocarbons but if the compound containing at least one pair of adjacent carbon atoms liked by multiple bonds are called unsaturated hydrocarbons in chemical science or organic chemistry. The natural crude oil or mineral oils are the main sources of aliphatic and aromatic hydrocarbon like methane, ethane, propane, cycloalkene, etc. Natural gas is another source of hydrocarbons that contain large quantities of gas with undissociated liquid petroleum. When the natural gas does not contain hydrocarbons above ethane are called lean or dry gas and contains the higher hydrocarbons are called rich or wet gases.
Hydrocarbon is almost insoluble in water but rapidity soluble in ethanol and ether. As far when we concern alkanes the attractive forces are only weak Van der Waals forces. Again the dipole moment of all alkanes whether straight or branched-chain will be zero. Zero polarity of these hydrocarbon associated due to balancing the C-H bond by the remaining alkyl group. The position of electromagnetic infrared spectrum region of the CH group in hydrocarbon depends on the carbon atom. Therefore the stretching frequency region of primary carbon > secondary carbon > tertiary carbon.
Hydrocarbon from Liquid Petroleum
Crude petroleum oil of our earth’s environment contains mainly the gases occurring naturally in forms of liquified or the solid dissolved in liquid. The density and composition of crude petroleum oil vary with the locality of occurrence but all saturated with organic compounds mainly liquid hydrocarbon. Therefore, crude petroleum oil contains alkanes, cycloalkenes or naphthenes, and aromatic hydrocarbons. In addition to hydrocarbon, there are also present compounds containing oxygen, nitrogen, sulfur, and crystalline metallic compounds.
Elementary crude petroleum is classified into two types like paraffinic predominate constituents is alkanes or asphaltic predominate constituents is naphthalenes. According to this classification crude oil from Pennsylvania, Iran and Rumania are paraffinic and Baku, Venezuela is asphaltic. But from Texas, Mexico, Oklahoma is intermediate types.
Hydrocarbon from Natural Gas
The terms natural gas used for the total quantity of gas present in liquid petroleum. Therefore, the main component of natural gas varies according to the source. Hence natural gas consists chiefly of the first six alkanes or hydrocarbons. The percentage of alkanes decreases with increasing molecular weight.
Therefore, the hydrocarbon separated from natural gas by fractional distillation under increased pressure and uses in different purposes of our daily life. Oxidation of natural gas under controlled conditions produces a mixture of organic aldehyde, acid, acetone, and alcohol use in the different industries by separated frictional distillation. The mixture of Hydrocarbons like methane, ethane, propane, butane, pentane, and hexane obtained when natural gas heated about the temperature 200-300°C with 1-200 atm pressure in presence of a catalyst.
Structure and Types of Organic Compounds
The valence shell electronic configuration of carbon, 2s2 2px1 2py1 2pz. When the electron from 2s-orbital promotes to vacant 2pz-orbital and hybridization to form four equivalent sp3 hybrid orbitals. Therefore, these four hybridized orbitals of carbon atom mixing with the hydrogen atom to form saturated organic compounds. But for sp2 and sp-hybridization, the carbon atom is not saturated by valency four. Hence these hybridizations form unsaturated organic hydrocarbon. According to the structural dimensions and bonding, organic compounds or hydrocarbon classified as open chain, cyclic or closed chain, saturated and unsaturated substances.
Saturated and Unsaturated Compounds
- The organic compounds which contain two or more carbon atoms linking by the only a single chemical bond are called unsaturated compounds. Hence methane, ethane, methyl alcohol, ethyl alcohol, etc are examples of unsaturated compounds. Alkanes like methane, ethane, propane, and cycloalkanes are examples of unsaturated hydrocarbon because these compounds are forms by only carbon and hydrogen bonding.
- Therefore the compound contains at least one pair of multiple bonds in adjacent carbon atoms called unsaturated compounds. If the double or triple bond contains on the adjacent carbon atoms known as alkene or olefin and alkynes respectively. In acetaldehyde, the multiple bonds between adjacent carbon and an oxygen atom considered for unsaturation.
Alkane Alkene and Alkyne
- Alkane or paraffin is the saturated hydrocarbons contain the single bond on adjacent carbon atom obtained from natural sources crude petroleum oil.
- Alkene or olefin is also the hydrocarbon contains one double bond or olefinic bond on two adjacent carbon atom.
- Alkyne is an organic hydrocarbon contains one triple bond or acetylenic bond on two adjacent carbon atoms.
Alicyclic and Cyclic Hydrocarbon
- The compounds contain closed rings with carbon atoms collectively known as carbocyclic or homocyclic compounds. When alicyclic compounds resemble aliphatic hydrocarbon, called alicyclic compounds.
- The saturated cyclic hydrocarbons take the names of the corresponding open-chain compounds, proceeds by the prefix cyclo. Therefore, these compounds collectively called cycloparaffins or cycloalkanes. When the alicyclic hydrocarbon is unsaturated, then this hydrocarbon called cycloalkenes.
Aliphatic and Aromatic Hydrocarbons
With the development of learning chemistry, the organic hydrocarbon is divided mainly into two types, aliphatic and aromatic.
- The aliphatic name was given from fatty acids but today these compounds known as open-chain compounds. Therefore, several hydrocarbons coming from natural sources with saturated or unsaturated called aliphatic hydrocarbon.
- The aromatic name obtained from the Greek word aroma means fragrant smell. Hence details examination shows that the aromatic compounds show the property of aromaticity. Therefore, most of the aromatic hydrocarbons related to benzene or its derivative. Hence the cyclic benzenoid compound also an aromatic compound. But the properties of these compounds totally different from alicyclic compounds.
Cracking of Liquid Hydrocarbon
The thermal bond dissociation of organic compounds known as pyrolysis. Therefore, thermal dissociation also applied to hydrocarbon or alkanes to produce a lower number of alkanes by the creaking process. Hence alkanes decomposed to lower alkane by heat 500°C to 600°C. The product obtained from a given alkane depends on, structure, applied pressure, and used catalyst. Therefore, the thermal decomposition of decane given lower alkane octane and ethene.
C10H22 ⇒ C8H18 + CH2=CH2
If we using suitable catalysts, alkanes containing six or more carbon atoms are cyclized. Therefore, in the presence of chemical element platinum as a catalyst decane, cyclized to form benzene.
C6H14 ⇒ C6H12 + H2 ⇒ C6H6 + 3H2
When petroleum oil creaked, most of the liquid hydrocarbon produced. Therefore, most important hydrocarbon are those containing up to four carbon atom which are methane, ethane, ethane, propane, butane, and isobutene.