Partial Charge Practice Worksheet Answer Key

Partial Charge Practice Worksheet Answer Key:

 

Assign all significant partial charges and dipoles in the following molecules:

1.

Oxygen is a FON element, so it will always create a polar bond unless it is bonded to itself. The dipole created by oxygen is going to oxygen, away from carbon due to oxygen being significantly more electronegative than carbon.

Oxygen delocalizes electron density away from the carbon it is bonded to, making carbon partially positive and oxygen partially negative.

The carbon-carbon bonds and implicit hydrogen-carbon bonds do not have any dipoles shown due to the bonds being non-polar.

 

2.

Nitrogen is a FON element, so it will always create a polar bond unless it is bonded to itself. The dipole created by nitrogen is going to nitrogen, away from carbon due to nitrogen being significantly more electronegative than carbon.

Nitrogen delocalizes electron density away from the carbon it is bonded to, making carbon partially positive and nitrogen partially negative.

The carbon-carbon bonds and implicit hydrogen-carbon bonds do not have any dipoles shown due to the bonds being non-polar.

 

3.

Oxygen is a FON element, so it will always create a polar bond unless it’s bonded to itself. The dipoles created by oxygen are going towards oxygen and away from the carbon and hydrogen it is bonded to due to oxygen being significantly more electronegative than carbon and hydrogen.

Oxygen delocalizes electron density away from the carbon and hydrogen it is bonded to, making carbon and hydrogen partially positive and oxygen partially negative.

Nitrogen delocalizes electron density away from the carbon and hydrogens it is bonded to, making carbon partially positive and nitrogen partially negative.

The carbon-carbon bonds and implicit hydrogen-carbon bonds do not have any dipoles shown due to the bonds being non-polar.

 

4.

Both oxygen and nitrogen are FON elements, so they will always create polar bonds unless they are bonded to themselves. The dipoles created by oxygen and nitrogen are going towards oxygen and nitrogen and away from the atoms they are bonded to due to being significantly more electronegative.

Oxygen delocalizes electron density away from the carbon and hydrogen it is bonded to, making carbon and hydrogen partially positive and oxygen partially negative.

Nitrogen delocalizes electron density away from the carbon and hydrogens it is bonded to, making carbon and hydrogen partially positive and nitrogen partially negative.

 

5.

Hydrogen is more electronegative than boron. Even though hydrogen is not a FON element, we consider these dipoles significant because a B-H bond is one of two bonds where hydrogen becomes partially negative. Because of this, BH3 is commonly used in organic reactions when a partially negative hydrogen is necessary. This is an exception, and is the only non-polar bond we label a dipole on.

The hydrogens delocalize electron density away from the boron they are bonded to, making the boron partially positive and the hydrogens partially negative.

 

6.

Oxygen is a FON element, so it will always create a polar bond unless it is bonded to itself. The dipoles created by oxygen are going to the oxygens, away from carbon due to oxygen being significantly more electronegative than carbon.

The oxygens delocalizes electron density away from the carbon they are bonded to, making carbon partially positive and the oxygens partially negative.

 

7.

Fluorine is a FON element, so it will always create a polar bond unless it is bonded to itself. The dipole created by fluorine is going to fluorine, away from carbon due to fluorine being significantly more electronegative than carbon.

Fluorine delocalizes electron density away from the carbon it is bonded to, making carbon partially positive and fluorine partially negative.

The carbon-carbon bonds and implicit hydrogen-carbon bonds do not have any dipoles shown due to the bonds being non-polar.

 

8.

Nitrogen is a FON element, so it will always create a polar bond unless it is bonded to itself. The dipoles created by nitrogen are going to nitrogen, away from carbon and hydrogen due to nitrogen being significantly more electronegative than carbon and hydrogen.

Nitrogen delocalizes electron density away from the carbon and hydrogens it is bonded to, making the carbon and hydrogens partially positive and nitrogen partially negative.

The carbon-carbon bonds and implicit hydrogen-carbon bonds do not have any dipoles shown due to the bonds being non-polar.

 

9.

Oxygen is a FON element, so it will always create a polar bond unless it is bonded to itself. The dipoles created by oxygen are going to oxygen, away from carbon and hydrogen due to oxygen being significantly more electronegative than carbon and hydrogen.

Oxygen delocalizes electron density away from the carbon and hydrogen it is bonded to, making carbon and hydrogen partially positive and oxygen partially negative.

The carbon-carbon bonds and implicit carbon-hydrogen bonds do not have any dipoles shown due to the bonds being non-polar.

 

10.

Oxygen is a FON element, so it will always create a polar bond unless it is bonded to itself. Even though the oxygen is formally positive, it still ends partially negative. A formal positive charge represents electron deficiency, so the oxygen is starting with less electrons/electron density than it wants. However, because it is so electronegative it will still end up with the excess electron density it wants. The dipoles created by oxygen are going to oxygen, away from the carbon and hydrogens due to oxygen being significantly more electronegative than carbon and hydrogen.

Oxygen delocalizes electron density away from the carbon and hydrogens it is bonded to, making the carbon and hydrogens partially positive and oxygen partially negative.

The carbon-carbon bonds and implicit carbon-hydrogen bonds do not have any dipoles shown due to the bonds being non-polar.

 

11.

Nitrogen is a FON element, so it will always create a polar bond unless it is bonded to itself. Even though the nitrogen is formally positive, it still ends partially negative. A formal positive charge represents electron deficiency, so the nitrogen is starting with less electrons/electron density than it wants. However, because nitrogen is so electronegative it will still end up with the excess electron density it wants. The dipoles created by nitrogen are going to nitrogen, away from carbon and hydrogen due to nitrogen being significantly more electronegative than carbon and hydrogen.

Nitrogen delocalizes electron density away from the carbon and hydrogen it is bonded to, making the carbon and hydrogen partially positive and nitrogen partially negative.

The carbon-carbon bonds and implicit carbon-hydrogen bonds do not have any dipoles shown due to the bonds being non-polar.

 

12.

Hydrogen is more electronegative than aluminum. Even though hydrogen is not a FON element, we consider these dipoles significant because an Al-H bond is polar due to the electronegativity difference between aluminum and hydrogen being greater than 0.4.

The hydrogens delocalize electron density away from the aluminum they are bonded to, making the aluminum partially positive and the hydrogens partially negative.

 

13.

Fluorine is a FON element, so it will always create a polar bond unless it is bonded to itself. The dipole created by fluorine is going to fluorine, away from bromine due to fluorine being significantly more electronegative than bromine. It is important to be able to compare the relative electronegativities of halogens (F, Cl, Br, I) to understand how organic reactions occur, making this a notable example.

Fluorine delocalizes electron density away from bromine, making bromine partially positive and fluorine partially negative.

 

14.

Oxygen is a FON element, so it will always create a polar bond unless it is bonded to itself. The dipoles created by oxygen are going to oxygen, away from carbon and hydrogen due to oxygen being significantly more electronegative than carbon and hydrogen.

Oxygen delocalizes electron density away from the carbon and hydrogen it is bonded to, making carbon and hydrogen partially positive and oxygen partially negative.

There is no dipole between carbon and bromine because bromine is not a FON element, so the dipole is not significant even though bromine is more electronegative than carbon.

The carbon-carbon bonds and implicit carbon-hydrogen bonds do not have any dipoles shown due to the bonds being non-polar.

 

15.

Oxygen is a FON element, so it will always create a polar bond unless it is bonded to itself. The dipoles created by oxygen are going to oxygen, away from carbon and hydrogen due to oxygen being significantly more electronegative than carbon and hydrogen.

Oxygen delocalizes electron density away from the carbon and hydrogen it is bonded to, making carbon and hydrogen partially positive and oxygen partially negative.

There is a dipole between carbon and fluorine because fluorine is a FON element, so the bond is polar. This means the dipole is significant enough to show. Fluorine delocalizes electron density away form the carbon it is bonded to, making carbon partially positive and fluorine partially negative.

The carbon-carbon bonds and implicit carbon-hydrogen bonds do not have any dipoles shown due to the bonds being non-polar.

 

16.

The central carbon is not FON element, however it is formally positive. A formal positive charge represents electron deficiency. The electron deficient carbon will delocalize electron density away from the carbons around it to try and solve the problem of its electron deficiency. Therefore, there are dipoles towards the central carbon and away from the carbons around it.

The central carbon ends up with a partial charge. This is because it is still positive after delocalizing electron density from the surrounding methyl groups. It can delocalize enough electron density to not be fully formally positive, however it cannot delocalize enough to make up for the entire deficiency of being formally positive. Therefore, it is left with a partial positive charge.

The implicit carbon-hydrogen bonds do not have any dipoles shown due to the bonds being non-polar.

 

17.

Oxygen is a FON element, so it will always create a polar bond unless it is bonded to itself. Even though the oxygen is already formally negative, it will still take more electron density away from hydrogen due to the significant electronegativity difference.

Oxygen delocalizes electron density away from the hydrogen it is bonded to, making hydrogen partially positive and oxygen partially negative.

 

18.

Hydrogen is more electronegative than aluminum. Even though hydrogen is not a FON element, we consider these dipoles significant because an Al-H bond is polar. Aluminum starts formally negative, which means it has an excess of electrons/electron density. This does not stop the surrounding hydrogens from taking electron density from aluminum. The only effect it has is that there is more electron density for the hydrogens to take away from aluminum because it is starting with an excess.

The hydrogens delocalize electron density away from the aluminum they are bonded to, making the aluminum partially positive and the hydrogens partially negative.

 

19.

Nitrogen is a FON element, so it will always create a polar bond unless it is bonded to itself. The dipoles created by nitrogen are going to nitrogen, away from the carbons and hydrogen due to nitrogen being significantly more electronegative than carbon and hydrogen.

Nitrogen delocalizes electron density away from the carbons and hydrogen it is bonded to, making the carbons and hydrogen partially positive and nitrogen partially negative.

The carbon-carbon bonds and implicit carbon-hydrogen bonds do not have any dipoles shown due to the bonds being non-polar.

 

20.

Carbon is not a FON element, however lithium is a metal. All metal to non-metal bonds are polar because metals have such low electronegativity values, whatever non-metal atom they are bonded to will be significantly more electronegative and delocalize their electron density away. Therefore in this example, there is a dipole away from lithium and towards carbon.

Carbon delocalizes electron density away from lithium, making lithium partially positive and carbon partially negative.

The carbon-carbon bonds and implicit carbon-hydrogen bonds do not have any dipoles shown due to the bonds being non-polar.