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

Molecular Geometry

Organic Chemistry

1. A Review of General Chemistry

Molecular Geometry

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6:16 minutes

Problem 57

Textbook Question

In pent-2-yne (CH₃CCCH₂CH₃), there are four atoms in a straight line. Use dashed lines and wedges to draw a three-dimensional representation of this molecule, and circle the four atoms that are in a straight line.

Verified step by step guidance

Identify the structure of pent-2-yne: The molecule is an alkyne, which means it contains a carbon-carbon triple bond. The structure is CH3-C≡C-CH2-CH3.

Determine the geometry around the triple bond: The carbon atoms involved in the triple bond (C≡C) are linear, meaning they form a straight line with a bond angle of 180 degrees.

Draw the three-dimensional structure: Start by drawing the linear portion of the molecule, which includes the carbon atoms involved in the triple bond and the adjacent carbon atoms. Use dashed lines and wedges to represent the spatial orientation of the remaining bonds. Dashed lines indicate bonds going away from the viewer, while wedges indicate bonds coming towards the viewer.

Circle the atoms in a straight line: In the structure of pent-2-yne, the four atoms in a straight line are the two carbon atoms involved in the triple bond and the two adjacent carbon atoms. Circle these atoms to highlight their linear arrangement.

Review the representation: Ensure that the three-dimensional drawing accurately reflects the linear geometry of the alkyne portion and that the spatial orientation of the other bonds is correctly depicted using dashed lines and wedges.

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Key Concepts

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

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. In organic chemistry, understanding the spatial orientation of atoms is crucial for visualizing molecular structures. For alkynes like pent-2-yne, the linear geometry around the triple bond is a key feature, as it dictates the alignment of atoms in a straight line.

Alkyne Structure

Alkynes are hydrocarbons characterized by a carbon-carbon triple bond, which imparts a linear geometry to the bonded carbon atoms. In pent-2-yne, the triple bond between the second and third carbon atoms results in a linear arrangement of these carbons and the adjacent hydrogen atoms, forming a straight line in the molecule.

Dash and Wedge Notation

Dash and wedge notation is a method used to depict three-dimensional molecular structures on a two-dimensional plane. Solid wedges represent bonds coming out of the plane towards the viewer, while dashed lines indicate bonds going behind the plane. This notation helps visualize the spatial arrangement of atoms, essential for identifying linear alignments in molecules like pent-2-yne.

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Textbook Question

Predict the hybridization of the oxygen atom in water, H₂O. Draw a picture of its three-dimensional structure, and explain why its bond angle is 104.5°.