Ch. 1 - A Review of General ChemistryWorksheetSee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins

All bonds are not created equal. Some bonds perfectly share their electrons, and others barely share them at all. A dipole moment is the mathematical expression that describes this disbalance. 

Types of Bonds

General rules:

  • Bonds to carbon and hydrogen are always covalent.
  • Bonds between two identical atoms are always covalent
    • Adjacent atoms on the periodic table are polar.
    • Lone pairs are polar.

The sum of all dipole moments is equal to the net dipole. If all dipoles perfectly cancel out, the molecule with have no net dipole.   

Concept #1: How to tell the difference between ionic, polar and covalent bonds. 

Practice: Which molecule/s contain/s net dipoles?

Practice: Which molecule/s contain/s net dipoles?

Practice: Which molecule/s contain/s net dipoles?

Practice: Which of the solvents are apolar and polar?

Additional Problems
Analyze the statement: For a molecule to be polar, the presence of polar bonds is necessary, but it is not a sufficient requirement.
The compounds FCl and ICl have dipole moments μ that are similar in magnitude (0.9 and 0.7 D, respectively) but opposite in direction. In one compound, chlorine is the positive end of the dipole; in the other it is the negative end. Specify the direction of the dipole moment in each compound, and explain your reasoning. 
Which compound in each of the following pairs would you expect to have the greater dipole moment ? Why?  HF or HCl
Which compound in each of the following pairs would you expect to have the greater dipole moment ? Why?  HF or BF3
Which compound in each of the following pairs would you expect to have the greater dipole moment ? Why?  (CH3)3CH or (CH3)3CCl
Which compound in each of the following pairs would have the higher boiling point? Explain your answers.  
Which compound in each of the following pairs would you expect to have the greater dipole moment ? Why?  CHCl3 or CCl3F
Which compound in each of the following pairs would you expect to have the greater dipole moment ? Why? CH3NH2 or CH3OH
Which compound in each of the following pairs would you expect to have the greater dipole moment ? Why? CH3NH2 or CH3NO2
Five pairs of atoms are listed below with dipole moments. Pick the correct ones (maximum of two).                  
For the following molecules, use the dipole moment symbol to show the direction of the molecular dipole moment in all molecules that have an overall molecular dipole. Note for this one you do NOT need to draw the individual bond dipole moments, just the overall molecular dipole moment,
For each compound below, identify any polar covalent bonds, and indicate the direction of the dipole moment using the symbols δ+ and δ-:  (a) HBr 
For each pair of compounds below, identify the one that would be expected to have more ionic character. Explain your choice.  (a) NaBr or HBr 
For each pair of compounds below, identify the one that would be expected to have more ionic character. Explain your choice.  (b) BrCl or FCl 
trans-1,3-Dibromocyclobutane has a measurable dipole moment. Explain how this proves that the cyclobutane ring is not planar.  
Draw a Lewis structure for a compound with molecular formula C4H11N in which three of the carbon atoms are bonded to the nitrogen atom. What is the geometry of the nitrogen atom in this compound? Does this compound exhibit a molecular dipole moment? If so, indicate the direction of the dipole moment. 
Determine whether each compound below exhibits a molecular dipole moment:  (a) CH4 
trans-1,3-Dichlorocyclobutane has a measurable dipole moment. Explain why the individual dipole moments of the C—Cl bonds do not cancel each other to produce a zero net dipole moment.
Which compound is less polar? a) CO2                   or                       b) SO2
Which of the below molecules has no net dipole moment?
For each type of bond below, determine the direction of the expected dipole moment.  (a) C–O 
Which of the following molecules is polar (hint: It has a molecular dipole) a. CO2 b. BF3 c. SO2 d. CH4
Which pair of elements listed below would be expected to form an ionic bond rather than a covalent bond? A. C–Mg           B. C–Li            C. Al–Cl            D. H–F               E. O–Na F. More than one pair, but not all of them, would form ionic bonds rather than covalent bonds. G. All of these pairs would form ionic bonds. H. None of these pairs would form ionic bonds.
Identify the most electronegative element in each of the following compounds:  (a) CH3OCH2CH2NH2 
Identify the most electronegative element in each of the following compounds:  (b) CH2ClCH2F 
Identify the most electronegative element in each of the following compounds:  (c) CH3Li 
Identify which compounds below possess a molecular dipole moment and indicate the direction of that dipole moment: 
Methylene chloride (CH2Cl2) has fewer chlorine atoms than chloroform (CHCl3). Nevertheless, methylene chloride has a larger molecular dipole moment than chloroform. Explain. 
Circle the molecule with the smallest dipole moment. NH3 H2O CH3CN CO2 SO2
Based on the electronegativities of C, H, and Cl, would you expect the   Cl3CCCH molecule to be  polar or  nonpolar? A molecule is polar if the vector sum of its bond dipole moments is not equal to zero. A molecule is nonpolar if the vector sum of its bond dipole moments is equal to zero. Pauling electronegativity values are listed in the periodic table on the last page of this handout. A. Polar molecule B. Nonpolar molecule
In the compound below, identify all carbon atoms that are electron deficient (d+) and all carbon atoms that are electron rich (d-). Justify your answer with resonance structures. 
Ramelteon is a hypnotic agent used in the treatment of insomnia:  (f)  Identify each lone pair as localized or delocalized. 
Why does one expect the cis isomer of an alkene to have a higher boiling point than the trans isomer?
Write a three-dimensional formula for each of the following molecules using the wedge–dashed wedge–line for-malism. If the molecule has a net dipole moment, indicate its direction with an arrow, → . If the molecule has no net dipole moment, you should so state. (You may ignore the small polarity of C - H bonds in working this and similar problems.) (a) CH3F  
Write a three-dimensional formula for each of the following molecules using the wedge–dashed wedge–line for-malism. If the molecule has a net dipole moment, indicate its direction with an arrow, → . If the molecule has no net dipole moment, you should so state. (You may ignore the small polarity of C - H bonds in working this and similar problems.) (b) CH2F2
Write a three-dimensional formula for each of the following molecules using the wedge–dashed wedge–line for-malism. If the molecule has a net dipole moment, indicate its direction with an arrow, → . If the molecule has no net dipole moment, you should so state. (You may ignore the small polarity of C - H bonds in working this and similar problems.) (c) CHF3
Write a three-dimensional formula for each of the following molecules using the wedge–dashed wedge–line for-malism. If the molecule has a net dipole moment, indicate its direction with an arrow, → . If the molecule has no net dipole moment, you should so state. (You may ignore the small polarity of C - H bonds in working this and similar problems.) (d) CF4
Write a three-dimensional formula for each of the following molecules using the wedge–dashed wedge–line for-malism. If the molecule has a net dipole moment, indicate its direction with an arrow, → . If the molecule has no net dipole moment, you should so state. (You may ignore the small polarity of C - H bonds in working this and similar problems.) (e) CH2FCl
Write a three-dimensional formula for each of the following molecules using the wedge–dashed wedge–line for-malism. If the molecule has a net dipole moment, indicate its direction with an arrow, → . If the molecule has no net dipole moment, you should so state. (You may ignore the small polarity of C - H bonds in working this and similar problems.) (f) BCl3
Write a three-dimensional formula for each of the following molecules using the wedge–dashed wedge–line for-malism. If the molecule has a net dipole moment, indicate its direction with an arrow, → . If the molecule has no net dipole moment, you should so state. (You may ignore the small polarity of C - H bonds in working this and similar problems.) (g) BeF2
Write a three-dimensional formula for each of the following molecules using the wedge–dashed wedge–line for-malism. If the molecule has a net dipole moment, indicate its direction with an arrow, → . If the molecule has no net dipole moment, you should so state. (You may ignore the small polarity of C - H bonds in working this and similar problems.) (h) CH3OCH3
Write a three-dimensional formula for each of the following molecules using the wedge–dashed wedge–line for-malism. If the molecule has a net dipole moment, indicate its direction with an arrow, → . If the molecule has no net dipole moment, you should so state. (You may ignore the small polarity of C - H bonds in working this and similar problems.) (i) CH3OH
Write a three-dimensional formula for each of the following molecules using the wedge–dashed wedge–line for-malism. If the molecule has a net dipole moment, indicate its direction with an arrow, → . If the molecule has no net dipole moment, you should so state. (You may ignore the small polarity of C - H bonds in working this and similar problems.) (j) CH2O
For each of the following molecules that contain polar covalent bonds, indicate the positive and negative ends of the dipole, using the symbol ⇸ . Refer to Table 1.3 as needed. (a) HCl
Consider each of the following molecules in turn: (a) dimethyl ether, (CH3)2O Describe the hybridization state of the central atom (i.e., O, N, B, or Be) of each molecule, tell what bond angles you would expect at the central atom, and state whether the molecule would have a dipole moment.
Consider each of the following molecules in turn: (b) trimethylamine, (CH3)3N Describe the hybridization state of the central atom (i.e., O, N, B, or Be) of each molecule, tell what bond angles you would expect at the central atom, and state whether the molecule would have a dipole moment.
Consider each of the following molecules in turn: (d) dimethylberyllium, (CH3)2Be. Describe the hybridization state of the central atom (i.e., O, N, B, or Be) of each molecule, tell what bond angles you would expect at the central atom, and state whether the molecule would have a dipole moment.
Which of the following compounds possesses a net dipole moment?
Which of the following molecules possesses a net dipole moment?
Which one of the following possesses a net dipole moment?
Do the molecules below have a permanent electric dipole moment?
Part A Which of the following molecules has the greatest molecular dipole moment?