Label the polar bonds in each molecule. Indicate the direction of the net dipole (if there is on

Label the polar bonds in each molecule. Indicate the...

Key Concepts

Polar Covalent Bonds

Polar covalent bonds form when two atoms with differing electronegativities share electrons unequally, resulting in partial positive and negative charges on the atoms. This concept is fundamental in understanding how bond polarity arises and influences molecular properties such as intermolecular interactions and chemical reactivity.

Electronegativity Differences

Electronegativity is a measure of an atom’s ability to attract shared electrons in a bond. Differences in electronegativity between bonded atoms lead to bond polarity, with the more electronegative atom acquiring a partial negative charge. This concept is critical when predicting the distribution of electron density in a molecule.

Molecular Geometry

Molecular geometry refers to the three?dimensional arrangement of atoms within a molecule. The shape of a molecule affects how individual bond dipoles add up, determining the overall polarity of the molecule. This concept is essential when considering whether a molecule has a net dipole moment or if the individual dipoles cancel out due to symmetry.

Net Dipole Moment

The net dipole moment is the vector sum of all individual bond dipoles in a molecule. It determines the overall polarity of the molecule and affects many physical properties such as boiling point, solubility, and reactivity. Understanding how to calculate and predict the net dipole moment involves considering both the magnitudes and directions of individual bond dipoles.

Transcript

00:01 This is the answer to chapter 1, problem number 77, from the smith organic chemistry textbook.

00:10 And this problem gives us six molecules and asks us to identify the dipoles in each molecule.

00:19 Or sorry, well, yeah, so it asks us to label the polar bonds in each molecule.

00:25 So that's essentially the same thing as i said at first.

00:28 And then also we're asked to indicate the direction of the net dipole if there is a net dipole in the molecule.

00:35 And so i remember the way that we draw the arrow to show polarity in a bond is the arrowhead going towards the electronegative atom and then a little plus sign at the tail of the arrow to show that that's the possible.

00:58 Part of the polar bond.

01:02 And so for a, bromine is much more electronegative than carbon.

01:08 And so bromine is going to be the negative portion of these polar bonds.

01:14 And so the plus sign toward the tail will be at the carbon end.

01:20 And then so we're also asked to identify the net dipole.

01:24 And so in this instance, it's down because each of these these bromines is pulling a little bit down.

01:31 Obviously, the bottom one is pulling totally down.

01:34 And so that's the net dipole there to the right.

01:39 Okay, and so we'll follow this same pattern for the remaining five parts of this problem.

01:45 So in b, this is diethyl ether.

01:49 Oxygen, of course, is much more electronegative than carbon.

01:54 So each carbon bound to the oxygen is going to have a dipole that looks.

01:59 Looks like that, polar bond that looks like that.

02:03 And the net dipole moment here is also going to be down because the oxygen is pulling each of these a little towards the center and down.

02:16 And so the net, the overall, is a downward effect.

02:20 So then looking at c, so in c for the first time, we have a symmetrical molecule.

02:28 So in c, um, so in c, um, each of these carbon bromine bonds is, of course, polarized, as we would expect, with the bromine being negative and the carbon being positive...

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