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

5. Chirality

Test 3:Disubstituted Cycloalkanes

Organic Chemistry

5. Chirality

Test 3:Disubstituted Cycloalkanes

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4:39 minutes

Problem 5a,b,c

Textbook Question

For each compound, determine whether the molecule has an internal mirror plane of symmetry. If it does, draw the mirror plane on a three-dimensional drawing of the molecule. If the molecule does not have an internal mirror plane, determine whether the structure is chiral.
(a) methane
(b) cis-1,2-dibromocyclobutane
(c) trans-1,2-dibromocyclobutane

Verified step by step guidance

Step 1: Understand the concept of a mirror plane of symmetry. A molecule has a mirror plane of symmetry if it can be divided into two halves that are mirror images of each other. If a molecule lacks a mirror plane, it may be chiral, meaning it is non-superimposable on its mirror image.

Step 2: Analyze methane (CH₄). Methane is a tetrahedral molecule with four identical hydrogen atoms bonded to a central carbon atom. Due to its symmetrical geometry, methane has multiple mirror planes of symmetry. Draw a three-dimensional representation of methane and indicate one of the mirror planes passing through the carbon atom and two hydrogen atoms.

Step 3: Examine cis-1,2-dibromocyclobutane. In the cis configuration, the two bromine atoms are on the same side of the cyclobutane ring. This arrangement creates a plane of symmetry that divides the molecule into two mirror-image halves. Draw a three-dimensional representation of cis-1,2-dibromocyclobutane and indicate the mirror plane passing through the ring and bisecting the bromine atoms.

Step 4: Investigate trans-1,2-dibromocyclobutane. In the trans configuration, the two bromine atoms are on opposite sides of the cyclobutane ring. This arrangement eliminates any internal mirror plane of symmetry. Since the molecule lacks a mirror plane and is non-superimposable on its mirror image, it is chiral. Draw a three-dimensional representation of trans-1,2-dibromocyclobutane and confirm its chirality by showing that it has no mirror plane.

Step 5: Summarize the findings. Methane has multiple mirror planes and is achiral. Cis-1,2-dibromocyclobutane has a mirror plane and is achiral. Trans-1,2-dibromocyclobutane lacks a mirror plane and is chiral. Ensure the three-dimensional drawings clearly illustrate the symmetry or lack thereof for each molecule.

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Key Concepts

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

Symmetry in Molecules

Symmetry in molecules refers to the arrangement of atoms in a way that allows for certain operations, such as reflection, rotation, or inversion, to yield an indistinguishable configuration. An internal mirror plane of symmetry divides a molecule into two mirror-image halves. Identifying symmetry is crucial for understanding molecular properties, including chirality.

Chirality

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. A chiral molecule typically has at least one carbon atom bonded to four different substituents, leading to two distinct enantiomers. Recognizing chirality is essential for predicting the behavior of molecules in biological systems and their interactions.

Drawing Molecular Structures

Drawing molecular structures involves representing the three-dimensional arrangement of atoms in a molecule on a two-dimensional plane. This includes using wedge and dash notation to indicate bonds that are oriented above or below the plane of the paper. Accurately depicting molecular geometry is vital for visualizing symmetry elements and understanding the spatial relationships between atoms.

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