(i) Saturated vs Unsaturated Hydrocarbons:
Saturated hydrocarbons contain only single bonds between carbon atoms. They are called alkanes.
Example — Ethane:
$$\text{H}-\text{C}-\text{C}-\text{H} \quad (CH_3-CH_3)$$
(with all single bonds and H atoms filled)
Unsaturated hydrocarbons contain one or more double or triple bonds between carbon atoms. They are called alkenes (double bond) or alkynes (triple bond).
Example — Ethene:
$$CH_2=CH_2$$
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(ii) Conversion of Unsaturated to Saturated Hydrocarbon:
Unsaturated hydrocarbons are converted to saturated hydrocarbons by hydrogenation — adding hydrogen in the presence of a nickel (Ni) catalyst.
$$CH_2=CH_2 + H_2 \xrightarrow{Ni} CH_3-CH_3$$
This reaction is used in the vegetable oil (vanaspati) / food industry to convert liquid vegetable oils into solid fats (vanaspati ghee).
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(iii) Hydrocarbon with a double bond and four carbon atoms:
Name: But-1-ene (Butene)
Structure:
$$CH_2=CH-CH_2-CH_3$$
Source: Chapter 4, Sections 4.2.2 and 4.3
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