chemistry technology

Hydrocarbons   are   compounds   containing   only   carbon   and   hydrogen   atoms.   The   simplest hydrocarbon is methane, CH4. Its molecules are tetrahedral, the four hydrogen atoms lying at the corners
of a regular tetrahedron around the carbon atom, and connected with the carbon atom with single bonds.
Methane is a gas, which occurs in natural gas, and is used as a fuel. It is also used in large quantities for
the manufacture of carbon black, by combustion with a limited supply of air. The hydrogen burn to water, and the carbon is deposited as very finely divided carbon, which finds extensive use as filler for rubber
for automobile tires.

Methane is the first member of a series of hydrocarbons having the general formula CnH2n+2, called
the methane series or paraffin series. The compounds of this series are not very reactive chemically. They occur  in  complex  mixtures  called  petroleum.  The  molecules  heavier  than  ethane  are  characterized  by containing carbon atoms attached to one another by single bonds. The lighter members of the paraffin series are gases, the intermediate members are liquids, and the heavier members are solid or semi-solid substances. Gasoline is the heptane-nonane mixture, and kerosene the decane-hexadecane mixture. Heavy fuel oil is a mixture of paraffins containing twenty or more atoms per molecule. The lubricating oils and solid paraffin are mixtures of still larger paraffin molecules.
The substance ethylene, C2H4, consists of molecules in which there is a double bond between the two carbon atoms. This double bond confers upon the molecule the property of much greater chemical reactivity  than  is  possessed  by  the  paraffins.  Because  of  this  property  of  readily  combining  with  other substances, ethylene and related hydrocarbons are said to be unsaturated.
Acetylene  is  the  first  member  of  a  series  of  hydrocarbons  containing  triple  bonds.  Aside  from acetylene, these substances have not found wide use, except for the manufacture of other chemicals.
The  hydrocarbons,  the  molecules  of  which  contain  a  ring  of  carbon  atoms,  are  called  cyclic hydrocarbons.  Cyclohexane,  C6H12,  is  representative  of  this  class  of  substances.  It  is  a  volatile  liquid, closely similar to normal hexane in its properties.
Another  important  hydrocarbon  is  benzene,  having  the  formula  C6H6.  It  is  a  volatile  liquid/  b.p.
800C/,  which  has  an  aromatic  odor.  For  many  years  there  was  discussion  about  the  structure  of  the benzene molecule. August Kekule suggested that the six carbon atoms are in the form of a ring, and this
has  been  verified:  diffraction  studies  have  shown  that  the  six  atoms  form  a  regular  planar  hexagon  in space, the six hydrogen atoms being bonded to the carbon atoms, and forming a larger hexagon. Kekule suggested that, in order for a carbon atom to show its normal quadrivalence, the ring contains three single bonds and three double bonds in alternate positions. Other hydrocarbons, derivatives of benzene, can be obtained  by  replacing  the  hydrogen  atoms  by  methyl  groups  or  similar  groups.  Benzene  and  its derivatives are used in the manufacture of drugs, explosives, photographic developers, plastics, synthetic
dyes, and many other substances.