Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

1. A Review of General Chemistry

Formal Charges

Organic Chemistry

1. A Review of General Chemistry

Formal Charges

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3:54 minutes

Problem 33

Textbook Question

Calculate the formal charge on the non-hydrogen atoms in the molecules shown. Use the arrow-pushing formalism to 'move' an electron pair such that it is shared between two (formerly) charged atoms. Your arrow should account for the formation of the molecule on the right from the molecule on the left.

Verified step by step guidance

Identify the formal charge formula: Formal charge = (Valence electrons of the atom) - (Non-bonding electrons) - (1/2 × Bonding electrons).

For each non-hydrogen atom in the molecule on the left, calculate its formal charge using the formula. Count the valence electrons, non-bonding electrons, and bonding electrons for each atom.

Examine the arrow-pushing formalism provided. Arrows indicate the movement of electron pairs. Follow the arrows to determine how electrons are redistributed between atoms.

Recalculate the formal charges for the non-hydrogen atoms in the molecule on the right after the electron redistribution. Use the same formal charge formula.

Compare the formal charges of the atoms in the molecule on the left and the molecule on the right. Verify that the electron movement accounts for the change in formal charges and ensures overall charge conservation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Formal Charge

Formal charge is a theoretical charge assigned to an atom in a molecule, calculated by considering the number of valence electrons, the number of bonds, and the number of non-bonding electrons. It helps in determining the most stable structure of a molecule by minimizing the charge separation. The formula is: Formal Charge = Valence Electrons - (Non-bonding Electrons + 1/2 Bonding Electrons).

Arrow-Pushing Formalism

Arrow-pushing formalism is a method used in organic chemistry to illustrate the movement of electrons during chemical reactions. Arrows indicate the direction of electron flow, with a double-headed arrow showing the movement of a pair of electrons and a single-headed arrow indicating the movement of a single electron. This technique is essential for visualizing reaction mechanisms and understanding how reactants transform into products.

Molecular Structure and Bonding

Molecular structure refers to the arrangement of atoms within a molecule and the types of bonds that hold them together. Understanding bonding, including covalent and ionic interactions, is crucial for predicting molecular behavior and reactivity. The formation of new bonds during a reaction often involves the sharing or transfer of electron pairs, which is central to the arrow-pushing formalism and the calculation of formal charges.

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Related Practice

Textbook Question

Calculate the formal charge of the indicated atom in the following molecules or ions.

(d)

Textbook Question

Draw the Lewis structure for the following ions. Be sure to calculate the formal charge of each atom to confirm that your structure is correct.

(b) H⁺

Textbook Question

Draw the Lewis structure for the following ions. Be sure to calculate the formal charge of each atom to confirm that your structure is correct.

(d) AlCl₄^-

Textbook Question

Calculate the formal charge of the indicated atoms in the ions shown.

Textbook Question

Looking ahead in Chapter 3, we describe how the formal charge on an atom can be used to predict the number of lone pairs. Given the charge, or lack of charge, on each atom, fill in the electron pairs.

(a)

Textbook Question

Based on the formal charge, determine how many lone pairs are on each indicated atom.

(a)

Textbook Question

Give each atom the appropriate formal charge:

Textbook Question

Draw the missing lone-pair electrons and assign the missing formal charges for the following:

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