Textbook Question
Two compounds with the formula CH3–CH=N–CH3 are known.
b. What two compounds have this formula?
c. Explain why only one compound with the formula (CH3)2CNCH3 is known.
4. Alkanes and Cycloalkanes
Cis vs Trans
4: minutesProblem 12
Textbook Question
Draw the Z isomer of an alkene that has a CH3 and an H on one sp2 carbon and isopropyl and butyl groups on the other sp2 carbon.
Verified step by step guidance1
Identify the structure of the alkene: The problem specifies that the molecule is an alkene, meaning it contains a carbon-carbon double bond (C=C). Each sp² carbon in the double bond is bonded to two substituents.
Assign the substituents to each sp² carbon: One sp² carbon is bonded to a CH₃ (methyl) group and an H (hydrogen) atom. The other sp² carbon is bonded to an isopropyl group (CH(CH₃)₂) and a butyl group (CH₂CH₂CH₂CH₃).
Understand the Z isomer: The Z (zusammen) isomer of an alkene has the higher-priority substituents on the same side of the double bond. Use the Cahn-Ingold-Prelog priority rules to assign priorities to the substituents on each sp² carbon. Higher atomic number atoms or groups with greater mass take priority.
Assign priorities to the substituents: On the first sp² carbon, CH₃ has a higher priority than H. On the second sp² carbon, the butyl group has a higher priority than the isopropyl group because the butyl group has a longer carbon chain.
Draw the Z isomer: Place the higher-priority groups (CH₃ and butyl) on the same side of the double bond, while the lower-priority groups (H and isopropyl) are on the opposite side. Ensure the double bond is clearly shown, and the spatial arrangement reflects the Z configuration.
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Video duration:
4mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Z and E Isomerism
Z and E isomerism refers to the geometric isomerism in alkenes based on the arrangement of substituents around the double bond. In Z isomers, the highest priority substituents on each carbon of the double bond are on the same side, while in E isomers, they are on opposite sides. This distinction is crucial for understanding the spatial orientation of the groups attached to the double bond.
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Priority Rules (Cahn-Ingold-Prelog)
The Cahn-Ingold-Prelog priority rules are used to determine the priority of substituents attached to the double-bonded carbons in alkenes. The priority is assigned based on atomic number; the higher the atomic number, the higher the priority. If two substituents have the same atom, the next atoms in the chain are considered until a difference is found, which is essential for correctly identifying Z and E configurations.
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Alkene Structure and Hybridization
Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C), characterized by sp2 hybridization of the carbon atoms involved in the double bond. This hybridization leads to a trigonal planar geometry around the sp2 carbons, influencing the physical and chemical properties of the alkene, including its isomerism. Understanding the structure helps in visualizing the spatial arrangement of substituents.
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