Question

Which of the following hydrocarbons can decolourise bromine water and which cannot? Why?

$C_6{H}_{12},C_6{H}_{14},C_6{H}_{10}$

Answer 1

$C_6{H}_{12}$ (Hexene) and $C_6{H}_{10}$ (Hexyne or Cyclohexene ) are the hydrocarbons which can decolourize bromine water, as they are unsaturated. Bromine undergo addition reactions with unsaturated compounds like alkenes and alkynes containing a double or a triple bond. When bromine water is added to an unsaturated compound, the former gets added to the latter, thereby turning colourless from its reddish brown colour.

$C_6{H}_{14}$ (Hexane) is a hydrocarbon which cannot decolourize bromine water because it is a saturated compound (alkane). Saturated compounds don't undergo addition reactions; therefore, they don't decolourize bromine water.