Advices For Studying Organic Chemistry

Table 4.1 Typical Fractions Obtained by distillation of Petroleum

Boiling Range of

Fraction (°C)

Number of Carbon
Atoms per Molecules Use
Below 20 C 1 –C 4 Natural gas, bottled gas, petrochemicals
20–60 C 5 –C 6 Petroleum ether, solvents
60–100 C 6 –C 7 Ligroin, solvents
40–200 C 5 –C 10 Gasoline (straight-run gasoline)
175–325 C 12 –C 18 Kerosene and jet fuel
250–400 C 12 and higher Gas oil, fuel oil, and diesel oil
Nonvolatile liquids C 20 and higher Refined mineral oil, lubricating oil, grease
Nonvolatile solids C 20 and higher Paraffin wax, asphalt, and tar

4.1C CRACKING

1. Catalytic cracking: When a mixture of alkanes from the gas oil fraction (C 12
   and higher) is heated at very high temperature (~500 °C) in the presence of a
   variety of catalysts, the molecules break apart and rearrange to smaller, more
   highly branched alkanes containing 5-10 carbon atoms.


2. Thermal cracking: tend to produce unbranched chains which have very low
   “octane rating”.


3. Octane rating:
   
   
   1. Isooctane: 2,2,4-trimethylpentane burns very smoothly in internal combustion
      engines and has an octane rating of 100.
   
   
   
   

H 3 CCCH 2

CH 3

CH 3

CH

CH 3

CH 3

2,2,4-trimethylpentane (“isooctane”)

2) Heptane [CH 3 (CH 2 ) 5 CH 3 ]: produces much knocking when it is burned in

internal combustion engines and has an octane rating of 0.