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

4. Alkanes and Cycloalkanes

Cis vs Trans

Organic Chemistry

4. Alkanes and Cycloalkanes

Cis vs Trans

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4:55 minutes

Problem 11a

Textbook Question

Name the following alkenes, being sure to specify whether they are cis or trans.
(a)

Verified step by step guidance

Step 1: Identify the longest continuous carbon chain that contains the double bond. This will serve as the parent chain, and its name will be based on the number of carbons in the chain (e.g., 'pentene' for a 5-carbon chain with a double bond).

Step 2: Number the parent chain starting from the end closest to the double bond. This ensures the double bond gets the lowest possible number. Indicate the position of the double bond in the name (e.g., '2-pentene' if the double bond starts at carbon 2).

Step 3: Determine whether the double bond is cis or trans. For cis, the substituents on the double-bonded carbons are on the same side; for trans, they are on opposite sides. Use this information to add the appropriate prefix ('cis-' or 'trans-') to the name.

Step 4: Identify and name any substituents attached to the parent chain. Assign numbers to these substituents based on their position on the parent chain, and include them in the name in alphabetical order.

Step 5: Combine all elements of the name: the cis/trans designation, substituents, position of the double bond, and the parent chain name. Ensure the name follows IUPAC nomenclature rules.

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Key Concepts

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

Alkene Nomenclature

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond. Their naming follows the IUPAC system, which involves identifying the longest carbon chain containing the double bond, numbering the chain to give the double bond the lowest possible number, and using suffixes like '-ene' to indicate the presence of the double bond.

Cis-Trans Isomerism

Cis-trans isomerism, also known as geometric isomerism, occurs in alkenes due to the restricted rotation around the double bond. In cis isomers, substituents are on the same side of the double bond, while in trans isomers, they are on opposite sides. This distinction affects the physical properties and reactivity of the compounds.

Priority Rules for Substituents

To determine whether an alkene is cis or trans, it is essential to apply the Cahn-Ingold-Prelog priority rules. These rules assign priority to substituents based on atomic number; higher atomic numbers receive higher priority. The configuration is then classified as cis if the higher priority groups are on the same side and trans if they are on opposite sides of the double bond.

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