The structures for three molecules having the formula C2 H2 Cl2 are Describe the intermolecular

The structures for three molecules having the formula C2 H2...

The structures for three molecules having the formula $\mathrm{C}_{2} \mathrm{H}_{2} \mathrm{Cl}_{2}$ are
Describe the intermolecular forces present in each of these compounds and predict which has the lowest boiling point.

Key Concepts

Boiling Point Trends

Boiling points are influenced by the strength of intermolecular forces; molecules with stronger attractions, such as those with permanent dipoles or significant dispersion forces, require more energy to separate and thus have higher boiling points.

Molecular Geometry and Symmetry

The shape and spatial arrangement of atoms in a molecule determine its symmetry, which in turn affects the net dipole moment. Symmetrical molecules may cancel out individual bond dipoles, leading to nonpolarity, while asymmetrical molecules will have a net dipole moment.

Molecular Polarity

Molecular polarity arises from differences in electronegativity between bonded atoms and the overall geometry of the molecule. This determines whether directional, stronger dipole-dipole interactions will be present, influencing properties like boiling points.

Intermolecular Forces

This concept encompasses the various types of attractions between molecules, which include dipole-dipole interactions, dispersion forces, and, in some cases, hydrogen bonding. The strength and type of these forces directly influence physical properties such as boiling points.

Dipole-Dipole Interactions

These are attractions between polar molecules where positive regions of one molecule are attracted to negative regions of another. Their presence and strength depend on the molecular polarity resulting from differences in electronegativity and molecular geometry.

London Dispersion Forces

Also known as van der Waals forces, these are weak intermolecular attractions that result from temporary fluctuations in electron distribution. They are present in all molecules, becoming the dominant intermolecular force in nonpolar compounds.

Transcript

00:01 In this problem, we want to draw the isomers of the given molecular formula.

00:10 So we can see that from this formula, there's going to be a double bond between the two carbons.

00:19 And then we can either place the two chlorines on the same carbon or on different carbons.

00:27 Then you can either have the chlorine atoms pointing in the same direction, which means that this is cis, and they're on the same.

00:36 Side of the double bond or we can have them pointing in opposite directions making them trans meaning they're on the opposite side of the double bond now we have to discuss the intermolecular forces present in each of these let's take a look at the first one for the first one we can see that clearly we have two very highly electronegative atoms right to the right of the molecule on this carbon, and we don't have any on the left side.

01:21 What that means is the electronegative chlorine atoms are going to pull the electrons towards them, and this is going to be a strong pull due to the fact that the chlorine atoms are highly electronegative.

01:36 So we are going to see a strong dipole pointing towards the chlorine atom.

01:44 So this is the negative end and the positive end will be on the other side.

01:50 So this is very strong.

01:52 And then for the cis isomer, the c .cl bonds also have polarity.

02:00 So we have the less electronegative carbon attached to the more electronegative chlorine.

02:07 So the more electron negative chlorine is going to pull the electrons towards it because it is highly electronegative.

02:16 So therefore there will be a negative dipole around the chlorine and a positive around the carbon.

02:23 So for the other ccl bond, it will be the same thing.

02:27 So we will have the same kind of dipole pointing towards the chlorine atom...

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