and hydrogen chloride gas isomerise to branched chain alkanes. Major products are given below. Some minor products are also possible which you can think over. Minor products are generally not reported in organic reactions.
CH (CH) ) CH Anhy, AICI / HCI n -Hexane CH CH–(CH ) –CH +CH CH –CH–CH –CH -Methylpentane -Methylpenatone ( . ) . Aromatization n -Alkanes having six or more carbon atoms on heating to 773K at - atmospheric pressure in the presence of oxides of vanadium, molybdenum or chromium supported over alumina get dehydrogenated and cyclised to benzene and its homologues. This reaction is known as aromatization or reforming .
( . ) Toluene (C H ) is methyl derivative of benzene. Which alkane do you suggest for preparation of toluene ? .
Reaction with steam Methane reacts with steam at K in the presence of nickel catalyst to form carbon monoxide and dihydrogen. This method is used for industrial preparation of dihydrogen gas CH + H 2IO Ni ∆ CO + 3H ( . ) . Pyrolysis Higher alkanes on heating to higher temperature decompose into lower alkanes, alkenes etc.
Such a decomposition reaction into smaller fragments by the application of heat is called pyrolysis or cracking . ( . ) Pyrolysis of alkanes is believed to be a free radical reaction. Preparation of oil gas or petrol gas from kerosene oil or petrol involves the principle of pyrolysis.
For example, dodecane, a constituent of kerosene oil on heating to 973K in the presence of platinum, palladium or nickel gives a mixture of heptane and pentene. C H Pt/Pd/Ni 973K C H + C H + Other Products Dodecane Heptane Pentene ( . ) . .
Conformations Alkanes contain carbon-carbon sigma ( σ ) bonds. Electron distribution of the sigma molecular orbital is symmetrical around the internuclear axis of the C–C bond which is not disturbed due to rotation about its axis. This permits free rotation about C–C single bond. This rotation results into different spatial arrangements of