(a) What value is expected for the dipole moment of the anti conformation of 1, 2-dibromoethane, Br—CH₂—CH₂—Br? Explain.

(b) The dipole moment μ of any compound that undergoes internal rotation can be expressed as a weighted average of the dipole moments of each of its conformations by the following equation:

in which μ_i is the dipole moment of conformation i, and N_i is the mole fraction of conformation i. (The mole fraction of any conformation i is the number of moles of i divided by the total moles of all conformations.)

There are about 82 mole percent of anti conformation and about 9 mole percent of each gauche conformation present at equilibrium in 1,2-dibromoethane, and the observed dipole moment μ of 1,2 dibromoethane is 1.0 D. Using the preceding equation and the answer to part (a), calculate the dipole moment of a gauche conformation of 1,2-dibromoethane.

Transcribed Image Text:

μ = μ₁N₁ + μ₂N₂ + μ3N3