1,3-pentadiene has two double bonds which are conjugated, which undergo electrophilic addition reaction on reacting with [tex]HCl[/tex].
The structure of 1,3-pentadiene is shown in the image.
When strong acid such as [tex]HCl[/tex] reacts with 1,3-pentadiene, the electrophilic addition reaction can occur either on double bond at 1,2-position or at 3,4-position. The reaction that occurs is shown in the image.