Question

Discussion of properties of stereoisomers of C2H₂F₂Cl₂.( RR and SS have the same energy and diple moment. Rs has 0 diple moment) pleas write it cleare

Questions to address in your discussion.

Which isomer(s) were the lowest in energy, and are any isomers the same energy?

Are there any conclusion you can make about the relationship between energy and the type of isomerism (e.g. optical isomers, conformational isomers)?

Discuss the magnitude and origin of the dipole moments. Explain how different stereoisomers might have the same dipole moment, and how a zero dipole moment may be obtained.

Answer 1

Stereoisomers of C₂H₂F₂Cl₂ :-

RS isomer were the lowest in energy because same group are on the opposite side so having minimum repulsion between groups and maximum stability of isomer . Both RR ,SS are having same energy and having energy greater than SR isomer because same group are on the same side so maximum repulsion between groups and minimum stability of isomer.

These are optical (2 chiral center) isomers as well as conformational isomers(C-C rotation). In conformational isomers there is carbon-carbon single bond rotation so leads to the formation of different conformers of the same molecules and different conformers have different energy or some may have same,depends upon the formation arrangement of different atoms.

SR isomer have zero dipole moment because same group are in opposite direction so dipole moment of each atom cancel each others dipole moment. Both RR and SS have same dipole moment because same atoms are on the same side so there is no cancellation of dipole moment and having some net dipole moment value which is same in both isomers.

Dipole moment () origin lie within the molecule,when there is difference in electronegativity of bonded atoms then there is development of dipole moment. Electronegative atom withdraw bonded electron toward itself that create a partial -ve charge on electronegative atom or partial +ve charge on bonded atom.Due to this there is creation of dipole within the molecules.e.g H-Cl.