Answer:
The water is not pure i.e. It contains some hydroxide and bromobutane ions that is why the upper phase contains 1-bromopentane
Step-by-step explanation:
The upper phase after reflux will contain 1-bromopentane even when its density is 1.276g/cm^3 because even though the density of water = 1.00g?cm^3 the water is not pure i.e. It contains some hydroxide and bromobutane ions making it to stay at the bottom while 1- bromobutane stays at the upper phase