Number of bromo derivatives obtained on treating ethane with excess of Br$$_2$$ in diffused sunlight is ______

Ethane (C₂H₆) when treated with excess Br₂ in diffused sunlight undergoes free radical halogenation. With excess bromine, all possible bromo derivatives can be formed.

The general formula for bromo derivatives is C₂H₆₋ₙBrₙ where n = 1, 2, 3, 4, 5, 6.

n = 1: CH₃CH₂Br (bromoethane) → 1 isomer

n = 2: CH₃CHBr₂ (1,1-dibromoethane), CH₂BrCH₂Br (1,2-dibromoethane) → 2 isomers

n = 3: CH₃CBr₃ (1,1,1-tribromoethane), CHBr₂CH₂Br (1,1,2-tribromoethane) → 2 isomers

n = 4: CBr₃CH₂Br (1,1,1,2-tetrabromoethane), CHBr₂CHBr₂ (1,1,2,2-tetrabromoethane) → 2 isomers

n = 5: CBr₃CHBr₂ (pentabromoethane) → 1 isomer

n = 6: C₂Br₆ (hexabromoethane) → 1 isomer

Total number of bromo derivatives = 1 + 2 + 2 + 2 + 1 + 1 = 9.