Ch. 7 - Structure and Synthesis of Alkenes; Elimination

Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook

Wade 9th Edition

Ch. 7 - Structure and Synthesis of Alkenes; Elimination

Problem 1

Chapter 7, Problem 1

1. Draw the structure of cis-CH3CH=CHCH2CH3 showing the pi bond with its proper geometry.2. Draw the trans isomer, and circle the coplanar atoms. Are there still six?

Verified step by step guidance

Identify the structure of cis-CH3CH=CHCH2CH3. The 'cis' configuration means that the two substituents (CH3 and CH2CH3) on the double bond are on the same side.

Draw the structure of cis-CH3CH=CHCH2CH3. Ensure that the double bond is represented with the correct geometry, showing the CH3 and CH2CH3 groups on the same side of the double bond.

Identify the structure of trans-CH3CH=CHCH2CH3. The 'trans' configuration means that the two substituents (CH3 and CH2CH3) on the double bond are on opposite sides.

Draw the structure of trans-CH3CH=CHCH2CH3. Ensure that the double bond is represented with the correct geometry, showing the CH3 and CH2CH3 groups on opposite sides of the double bond.

Circle the coplanar atoms in the trans isomer. Verify if there are still six coplanar atoms, which should include the two carbons of the double bond and the atoms directly bonded to them.

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Key Concepts

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

Cis-Trans Isomerism

Cis-trans isomerism is a type of stereoisomerism where the spatial arrangement of groups around a double bond differs. In cis isomers, similar groups are on the same side of the double bond, while in trans isomers, they are on opposite sides. This geometric distinction affects the physical and chemical properties of the compounds, such as boiling points and reactivity.

Pi Bonds and Geometry

Pi bonds are formed by the sideways overlap of p orbitals, resulting in a bond that restricts rotation around the double bond. The geometry of pi bonds is planar, meaning that the atoms involved in the double bond and the adjacent atoms lie in the same plane. This planarity is crucial for understanding the spatial arrangement of substituents in cis and trans isomers.

Coplanarity in Alkenes

In alkenes, coplanarity refers to the alignment of atoms in the same plane, particularly around the double bond. For trans isomers, the substituents on the double bond are coplanar, allowing for a more stable configuration. Identifying coplanar atoms is essential for visualizing the molecular structure and understanding the overall geometry of the compound.

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The Anti-Coplanar Requirement

Related Practice

Textbook Question

Give five examples of structures with this formula (C₆H₁₂). At least one should contain a ring, and at least one should contain a double bond.

Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)

C = number of carbons

H = number of hydrogens

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Textbook Question

If a hydrocarbon has nine carbon atoms, three double bonds, and one ring, how many hydrogen atoms must it have?

Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)

C = number of carbons

H = number of hydrogens

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Textbook Question

Calculate the number of elements of unsaturation implied by the molecular formula C₆H₁₂.

Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)

C = number of carbons

H = number of hydrogens

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