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Organic Compounds:Reactions

Addition and Substitution Reactions Of Carbon And Its Compounds

Do you know what happens when petrol is burned?  It is broken down into simpler substances on heating. This is called thermal cracking.

Thermal cracking is defined as the process in which hydrocarbons are heated in the absence of oxygen and broken down into simpler substances. It is a thermal decomposition process. Thermal cracking is of utmost importance in petroleum industry as petroleum, on cracking, yields useful products such as petrol, kerosene, wax, etc.

Do you know?

The thermal cracking method (also known as "Shukhov cracking process") was invented by Russian engineer Vladimir Shukhov and was modified by the American engineer William Merriam Burton.  He developed a thermal cracking process in 1912 which operated at 370°C – 400°C and was known as the Burton process. Then in 1921, C.P. Dubbs, an employee of the Universal Oil Products Company, developed a more advanced thermal cracking process which operated at 400°C – 460 °C and was known as the Dubbs process. This process

was used extensively by many refineries, until the early 1940s when catalytic

cracking came into use.

Hydrocarbons containing large number of carbon atoms cannot serve as efficient fuel as they are viscous and do not burn effectively. This is where thermal cracking comes into picture. It breaks the large hydrocarbon molecules into smaller and more useful molecules. It involves the breaking of C-H and C-C bonds and it is an endothermic process. It can be explained with the help of the example given below:

Thermal cracking of decane C10H22: When decane is decomposed in the presence of heat and absence of oxygen, it forms pentane, propene and ethane.

Different kinds of molecules are obtained on cracking of decane and as already discussed it involves the breaking of C-C and C-H bonds of hydrocarbon.  The products of thermal cracking depend on the nature of hydrocarbon, temperature, catalyst used and pressure.

Given table shows the varieties of products obtained by thermal cracking of petroleum:

Products obtained from cracking of petroleum

Number of carbon atoms

Appearance

Uses

Refinery gas

1 - 4

Colourless

Gaseous fuel, making variety of chemicals

Gasoline (petrol)

4 - 12

Colourless to pale yellow

Fuels for vehicles such as car, motor bikes fuel, making chemicals

Kerosene (paraffin)

11 - 15

Colourless to yellow

Heating fuel, jet fuel

Diesel oil

15 - 19

Brown

Diesel fuel for trucks, buses, trains, etc. and heating fuel

1. Lubricating oil,

2. heavy fuel oil, and

3. bitumen

20–30, 30–40,

50 and above

 

Dark brown

 

Fuels for power stations, ships, etc.

Do you know what happens when petrol is burned?  It is broken down into simpler substances on heating. This is called thermal cracking.

Thermal cracking is defined as the process in which hydrocarbons are heated in the absence of oxygen and broken down into simpler substances. It is a thermal decomposition process. Thermal cracking is of utmost importance in petroleum industry as petroleum, on cracking, yields useful products such as petrol, kerosene, wax, etc.

Do you know?

The thermal cracking method (also known as "Shukhov cracking process") was invented by Russian engineer Vladimir Shukhov and was modified by the American engineer William Merriam Burton.  He developed a thermal cracking process in 1912 which operated at 370°C – 400°C and was known as the Burton process. Then in 1921, C.P. Dubbs, an employee of the Universal Oil Products Company, developed a more advanced thermal cracking process which operated at 400°C – 460 °C and was known as the Dubbs process. This process

was used extensively by many refineries, until the early 1940s when catalytic

cracking came into use.

Hydrocarbons containing large number of carbon atoms cannot serve as efficient fuel as they are viscous and do not burn effectively. This is where thermal cracking comes into picture. It breaks the large hydrocarbon molecules into smaller and more useful molecules. It involves the breaking of C-H and C-C bonds and it is an endothermic process. It can be explained with the help of the example given below:

Thermal cracking of decane C10H22: When decane is decomposed in the presence of heat and absence of oxygen, it forms pentane, propene and ethane.

Different kinds of molecules are obtained on cracking of decane and as already discussed it involves the breaking of C-C and C-H bonds of hydrocarbon.  The products of thermal cracking depend on the nature of hydrocarbon, temperature, catalyst used and pressure.

Given table shows the varieties of products obtained by thermal cracking of petroleum:

Products obtained from cracking of petroleum

Number of carbon atoms

Appearance

Uses

Refinery gas

1 - 4

Colourless

Gaseous fuel, making variety of chemicals

Gasoline (petrol)

4 - 12

Colourless to pale yellow

Fuels for vehicles such as car, motor bikes fuel, making chemicals

Kerosene (paraffin)

11 - 15

Colourless to yellow

Heating fuel, jet fuel

Diesel oil

15 - 19

Brown

Diesel fuel for trucks, buses, trains, etc. and heating fuel

1. Lubricating oil,

2. heavy fuel oil, and

3. bitumen

20–30, 30–40,

50 and above

 

Dark brown

 

Fuels for power stations, ships, etc.

We use soaps and detergents in our homes for almost all cleaning purposes. What are soaps and detergents? Soaps are sodium or potassium salts of higher fatty acids such as oleic acid (C17H33COOH), stearic acid (C17H35COOH), palimitic acid (C15H31COOH), etc. On the other hand, detergents are salts of higher sulphonic acids such as dedecylbenzenesulphonate (C18H30SO3Na).

Preparation of Soaps and Detergents:

Soaps are prepared by gentle heating of oil or fat with sodium hydroxide solution till it boils. After few minutes of boiling sodium chloride is added to the solution to separate out soap. The solution is cooled and soap is obtained at the top of the solution. To obtain glycerol which is a byproduct of the formation of  soap is obtained by hydrolyzing oil in presence of bases such as potassium hydroxide.

Oil + NaOH → Soap + Glycerol

This process is known as saponification.

Similarly, the long chain hydrocarbons obtained after refining of petroleum when treated with concentrated su…

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