Delocalized electrons are present in 1,3-butadiene, C6H6, and 1,3,5-hexatriene.

1. 1,3-butadiene:
In 1,3-butadiene, there are four carbon atoms arranged in a linear chain. Each carbon atom is connected to two other carbon atoms as well as two hydrogen atoms. The presence of a double bond between the carbon atoms leads to the delocalization of electrons. The two pi (π) bonds formed by the overlapping of p orbitals allow for the movement of electrons along the carbon chain.

2. C6H6 (benzene):
Benzene is a cyclic compound composed of six carbon atoms and six hydrogen atoms. Each carbon atom is connected to one hydrogen atom and two other carbon atoms. The carbon-carbon bonds in benzene are all the same length, indicating that the electrons are delocalized. The delocalized π electrons form a ring of electron density above and below the plane of the carbon atoms, known as the pi cloud.

3. 1,3,5-hexatriene:
1,3,5-hexatriene is another linear compound similar to 1,3-butadiene, but with an additional carbon atom in the chain. It contains three double bonds, which result in the delocalization of electrons. The overlapping p orbitals of the carbon atoms allow for the movement of electrons along the chain.

Delocalized electrons:
Delocalized electrons are electrons that are not confined to a specific atom or bond but are free to move throughout a molecule. They are usually found in compounds with conjugated systems, which involve alternating single and multiple bonds or cyclic structures. The delocalization of electrons leads to increased stability and unique properties in these compounds.

In conclusion, delocalized electrons are present in 1,3-butadiene, C6H6 (benzene), and 1,3,5-hexatriene due to the presence of alternating single and multiple bonds or cyclic structures.