Question

How can we know that which one undergoes addition reaction ? Can anyone help me to understand ?

Answer 1

ADDITION REACTION :-

The reaction in which unsaturated hydrocarbons add hydrogen in the presence of catalysts( The catalysts can include-Palladium or Nickel) to give saturated hydrocarbons is known as addition reaction.

Catalysts are those substances which cause a reaction to occur or proceed at a fast or slow rate as compared to the initial rate without affecting the reaction itself.

now,

we got to know that addition reaction can only take place when the hydrocarbon is an unsaturated hydrocarbon this means that saturated hydrocarbons don't undergo addition reactions.
That is saturated hydrocarbons do not add hydrogen in the presence of any catalyst to give saturated hydrocarbons as they are saturated hydrocarbons themselves.

The general expression of a saturated hydrocarbon that is ALKANE group is :-

$c_nh_{(2n + 2)}$



now,

In the question the following compounds are given :-

1) ETHANE
$c_2h_6$

Ethane is a saturated hydrocarbon as it satisfies the general expression of ALKANES.
So,
It will not undergo Addition reaction.

2)PROPANE

$c_3h_8$
Propane is also a saturated hydrocarbon. hence, it will not undergo addition reaction.

3)PROPENE

$c_3h_6$

Propene is an unsaturated hydrocarbon belonging to the alkene group of Hydrocarbons. Hence, it will undergo addition reaction as it is an unsaturated hydrocarbon.


4)ETHYNE

$c_2h_2$

Ethyne is also an unsaturated hydrocarbon belonging to the alkane group of Hydrocarbons. Hence it will undergo addition reaction as it is an unsaturated hydrocarbon.


5)METHANE

$ch_4$

Methane is saturated hydrocarbon belonging to the alkane group.
So, it will not undergo addition reaction as it is saturated hydrocarbon itself and we know that only unsaturated hydrocarbons undergo addition reaction.


6)BUTENE

$c_4h_8$

Butene is an unsaturated hydrocarbon belonging to the alkene group of Hydrocarbons.
It will undergo addition reaction because it is unsaturated compound.
Butene will add hydrogen in the presence of catalyst such as Palladium or Nickel to turn into a saturated hydrocarbon.


7) BUTYNE

$c_4h_6$

Butyne is an unsaturated hydrocarbon belonging to the alkyne group.
So, it will undergo addition reaction because it is an unsaturated hydrocarbon.



NOTE - I have named the given compound as per the rules of nomenclature assuming that the compounds are straight carbon chains. It is also possible that the compound can be a isomer of the straight chain.
So, it will have a different name if it is an isomer.