Determine the point groups for a. Ethane (staggered conformation) b. Ethane (eclipsed conformation) c. Chloroethane (staggered conformation) d. 1,2-Dichloroethane (staggered anti conformation)

Answer and Explanation:

Every molecule has a set of symmetry operations that helps in determining its overall symmetry. This set of operations determines the point group of a molecule.

(a) Ethane (staggered conformation)

Ethane in the staggered conformation has:

two axis (the C-C line)3 perpendicular rotational axis bisecting the C-C line, in the plane of the two C's and H's on the opposite sides of the two C'sno σ planebut has 3σ planes containing two carbons and anti two hydrogens

hence the point group of ethane in staggered conformation is  

(b) Ethane (eclipsed conformation)

Ethane in the eclipsed conformation has:

two axis (the C-C line)three perpendicular axis (in the plane of the two C's and H's on the same side of the two C's)mirror planes include σ and 3σ

Hence the point group of ethane in eclipsed conformation is

(c) chloroethane (staggered conformation)

Chloroethane in the staggered conformation has:

no rotational axis σ plane containing two carbons and chlorine and the anti hydrogen of Cl

Hence the point group of staggered conformation in chloroethane is

(c) 1,2-Dichloroethane (staggered anti conformation)

1,2-Dichloroethane in the staggered anti conformation has:

axis perpendicular to the C-C bond and perpendicular to the plane of Cl-C-C-Clcontain a σ plane through Cl-C-C-Cl, and an inversion centre

Hence the point group in the staggered anti conformation of 1,2-Dichloroethane is

It would be a lease.