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

7. Substitution Reactions

Substitution Comparison

Organic Chemistry

7. Substitution Reactions

Substitution Comparison

Previous problemNext problem

5:12 minutes

Problem 110a,b

Textbook Question

Draw the substitution products for each of the following S_N2 reactions. If the products can exist as stereoisomers, show which stereoisomers are formed:
a. (3S,4S)-3-bromo-4-methylhexane + CH₃O^-
b. (3S,4R)-3-bromo-4-methylhexane + CH₃O^-

Verified step by step guidance

Step 1: Identify the type of substitution reaction taking place. Since CH3O- is a strong nucleophile and base, the reaction is likely to proceed via an SN2 mechanism, which involves a single-step nucleophilic substitution. SN2 reactions are stereospecific and result in inversion of configuration at the carbon undergoing substitution.

Step 2: Analyze the structure of the starting material. For part (a), the compound is (3S, 4S)-3-bromo-4-methylhexane. The bromine atom is attached to the 3rd carbon, which is a stereocenter. The methyl group is attached to the 4th carbon, which is also a stereocenter. For part (b), the compound is (3S, 4R)-3-bromo-4-methylhexane, with similar structural features but differing stereochemistry at the 4th carbon.

Step 3: Determine the stereochemical outcome of the substitution. In an SN2 reaction, the nucleophile (CH3O-) attacks the carbon bonded to the leaving group (Br) from the opposite side, leading to inversion of configuration at the 3rd carbon. For part (a), the 3rd carbon changes from S to R configuration. For part (b), the 3rd carbon also changes from S to R configuration.

Step 4: Consider the stereochemistry of the 4th carbon. Since the substitution occurs only at the 3rd carbon, the stereochemistry of the 4th carbon remains unchanged. For part (a), the 4th carbon retains its S configuration. For part (b), the 4th carbon retains its R configuration.

Step 5: Draw the products. For part (a), the product is (3R, 4S)-3-methoxy-4-methylhexane. For part (b), the product is (3R, 4R)-3-methoxy-4-methylhexane. Ensure that the stereochemistry is clearly indicated in the drawings, showing the inversion at the 3rd carbon and the unchanged configuration at the 4th carbon.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile. In this context, the nucleophile is CH3O-, which attacks the carbon atom bonded to the bromine in the bromoalkane. Understanding the mechanism (either SN1 or SN2) is crucial, as it influences the stereochemistry of the products formed.

Stereochemistry and Stereoisomers

Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their chemical behavior. Stereoisomers are compounds that have the same molecular formula and connectivity but differ in the orientation of their atoms in space. In the given reactions, the stereochemistry of the starting materials will determine the types of stereoisomers produced, which may include enantiomers and diastereomers.

Chirality and Optical Activity

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, often due to the presence of a chiral center (a carbon atom bonded to four different groups). Molecules that are chiral can exist as two enantiomers, which rotate plane-polarized light in opposite directions. Recognizing chirality in the reactants is essential for predicting the stereoisomeric products of the reactions.

Watch next

Master How do we predict if the mechanism is SN1 or SN2? with a bite sized video explanation from Johnny

Start learning