doubts

A conjugated system is like:

CH2=CH-CH=CH2

Now if you see this carefully then itz a double-single-double bond system and so resonance is possible...

CH2=CH-CH=CH2 <----> CH2+-CH=CH-CH2~

where + is positive charge and ~ is negative charge...

Now due to resonace it gains stability because of resonance energy.. So it is more reactive.

So one can see differences in conjugated double bonds like in the case of addition of HBr

At low temprature around -80 degree C 1,2 addition is the major product while at higher temprature of 40 degree C 1,4 addn is the major product...