Question

06 question (2 points) open ebook section 6.3 the two molecules depicted here are structural isomers. they contain exactly the same atoms but arranged differently. as you might expect, the slight differences in their molecular structures lead to differences in their physical properties. cl h cl h h h h h h cl cl h h h h h clch2ch2cl chcl2ch3 molecule a molecule b 1st attempt part 1 (1 point) see periodic table see hint one of the molecules pictured above has a normal boiling point of 57°c, while the other has a normal boiling point of 84°c. rank the two molecules by increasing boiling point.

Explanation:

Step1: Analyze molecular symmetry and dipole - dipole interactions

Molecule \(A(CICH_{2}CH_{2}Cl)\) is more symmetrical. In \(CICH_{2}CH_{2}Cl\), the two \(Cl\) atoms are on opposite ends. The bond dipoles can cancel out to some extent (although not completely due to the tetrahedral geometry of carbon, but it has a lower net dipole moment compared to \(CHCl_{2}CH_{3}\)). Molecule \(B(CHCl_{2}CH_{3})\) has a higher net dipole moment.
Dipole - dipole forces are stronger when the net dipole moment of a molecule is larger. The stronger the intermolecular forces (in this case, dipole - dipole forces as these are polar molecules and not capable of hydrogen bonding), the higher the boiling point.

Step2: Relate intermolecular forces to boiling point

Since \(CHCl_{2}CH_{3}\) (Molecule \(B\)) has stronger dipole - dipole forces than \(CICH_{2}CH_{2}Cl\) (Molecule \(A\)):
The order of increasing boiling point is based on the strength of intermolecular forces. Lower intermolecular forces lead to lower boiling points.

Answer:

Molecule \(A(CICH_{2}CH_{2}Cl)<\) Molecule \(B(CHCl_{2}CH_{3})\)