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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5:17 minutes

Problem 45b

Textbook Question

Draw and name all stereoisomers of 3-chlorohepta-2,4-diene
b. using the E-Z nomenclature.

Verified step by step guidance

Identify the structure of 3-chlorohepta-2,4-diene. The compound is a heptadiene, meaning it has a seven-carbon chain with two double bonds located at the 2nd and 4th positions. The chlorine atom is attached to the 3rd carbon.

Determine the possible stereoisomers. Since there are two double bonds, each can have E/Z isomerism. The stereochemistry at each double bond needs to be considered separately.

For the double bond at the 2nd position, assign priorities to the substituents on each carbon of the double bond using the Cahn-Ingold-Prelog priority rules. Compare the groups attached to the carbons involved in the double bond to determine if the configuration is E (opposite sides) or Z (same side).

Repeat the priority assignment for the double bond at the 4th position. Again, use the Cahn-Ingold-Prelog priority rules to determine the E or Z configuration for this double bond.

Combine the configurations of both double bonds to name each stereoisomer. For example, if the first double bond is E and the second is Z, the compound would be named (2E,4Z)-3-chlorohepta-2,4-diene. Repeat this process to identify and name all possible stereoisomers.

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Key Concepts

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

Stereoisomers

Stereoisomers are molecules with the same molecular formula and sequence of bonded atoms, but they differ in the three-dimensional orientations of their atoms in space. In the context of alkenes, stereoisomers can be classified as cis-trans or E-Z isomers, depending on the substituents around the double bond. Understanding stereoisomers is crucial for identifying and naming different forms of a compound.

E-Z Nomenclature

The E-Z nomenclature is a system used to describe the stereochemistry of double bonds in alkenes. 'E' (from the German 'entgegen') indicates that the highest priority substituents on each carbon of the double bond are on opposite sides, while 'Z' (from 'zusammen') indicates they are on the same side. Priority is determined using the Cahn-Ingold-Prelog priority rules, which consider atomic number and connectivity.

Cahn-Ingold-Prelog Priority Rules

The Cahn-Ingold-Prelog (CIP) priority rules are used to assign priority to substituents attached to a stereocenter or double bond. The rules state that the atom with the higher atomic number receives higher priority. If two atoms are the same, the next set of atoms along the chain is considered. These rules are essential for correctly applying the E-Z nomenclature to alkenes.

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Related Practice

Textbook Question

Draw the condensed structure for each of the following:

a. (Z)-1,3,5-tribromo-2-pentene

b. (Z)-3-methyl-2-heptene

c. (E)-1,2-dibromo-3-isopropyl-2-hexene

Textbook Question

Identify the following substituted cycloalkanes as cis or trans.

(a)

Textbook Question

Identify the following substituted cycloalkanes as cis or trans.

(c)

Textbook Question

For the compound 1-ethyl-3-isopropylcyclopentane,

(a) draw two different cis and two different trans isomers.

Textbook Question

Some of the following examples can show geometric isomerism, and some cannot. For the ones that can, draw all the geometric isomers, and assign complete names using the E-Z system.

c. 3-bromo-2-methylhex-3-ene

d. penta-1,3-diene

Textbook Question

Some of the following examples can show geometric isomerism, and some cannot. For the ones that can, draw all the geometric isomers, and assign complete names using the E-Z system.

a. 3-bromo-2-chloropent-2-ene

b. 3-ethylhexa-2,4-diene

Textbook Question

Label each structure as Z, E, or neither.

(a)

(b)

(c)

(d)

Textbook Question

1. Determine which of the following compounds show cis-trans isomerism.

2. Draw and name the cis and trans (or Z and E) isomers of those that do.

e. 2,3-dimethylpent-2-ene