The cycloalkene (X) on bromination consumes one mole of bromine per mole of (X) and gives the product (Y) in which C : Br ratio is 3:1. The percentage of bromine in the product (Y) is %. (Nearest integer) (Given : molar mass in g mol-1 H : 1, C : 12, O : 16, Br : 80)
Answer
66
Solution
Cycloalkene (X) = CnH2n-2 (one ring + one C=C)
Addition of one mole of Br2:
CnH2n-2 + Br2 CnH2n-2Br2 (Y)
C : Br = n : 2 = 3 : 1
n = 6
X = cyclohexene (C6H10), Y = 1,2-dibromocyclohexane (C6H10Br2)
Molar mass of Y = 6(12) + 10(1) + 2(80) = 242 g mol-1
% Br = 160242 100 = 66.1 66
Answer: 66