Textbook Question
Name the following alkenes, being sure to specify whether they are cis or trans.
(a)
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4. Alkanes and Cycloalkanes
Cis vs Trans
3:11 minutesProblem 13a
Textbook Question
Given the name, draw the structure of the following alkenes.
(a) (E)-4-ethyl-5-methyloct-3-ene
Verified step by step guidance1
Step 1: Understand the nomenclature. The name '(E)-4-ethyl-5-methyloct-3-ene' provides information about the structure of the molecule. The 'oct' indicates an 8-carbon chain, '3-ene' specifies a double bond at the 3rd carbon, and the '(E)' configuration means the substituents on the double bond are on opposite sides.
Step 2: Begin by drawing the parent chain. Draw a straight chain of 8 carbons (octane backbone). Number the carbons from 1 to 8, ensuring the double bond starts at the 3rd carbon.
Step 3: Add the substituents. At carbon 4, attach an ethyl group (CH₂CH₃). At carbon 5, attach a methyl group (CH₃). Ensure the substituents are correctly positioned based on the numbering.
Step 4: Apply the (E) configuration to the double bond. For the double bond at carbon 3, arrange the substituents such that the higher-priority groups (based on Cahn-Ingold-Prelog rules) are on opposite sides of the double bond.
Step 5: Verify the structure. Check that the molecule has the correct number of carbons, substituents, and the double bond is in the correct position with the specified stereochemistry.
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Video duration:
3mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkene Structure
Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C). The presence of this double bond affects the geometry and reactivity of the molecule. Understanding the basic structure of alkenes is crucial for drawing their representations, as it dictates the arrangement of atoms and the overall shape of the molecule.
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E/Z Stereochemistry
E/Z stereochemistry is a system used to describe the spatial arrangement of substituents around a double bond. The 'E' (entgegen) configuration indicates that the highest priority substituents on each carbon of the double bond are on opposite sides, while 'Z' (zusammen) indicates they are on the same side. This distinction is essential for accurately representing the geometry of alkenes in structural drawings.
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Nomenclature of Organic Compounds
The IUPAC nomenclature system provides a standardized way to name organic compounds based on their structure. In the case of (E)-4-ethyl-5-methyloct-3-ene, the name indicates the longest carbon chain (oct-3-ene), the position of the double bond, and the substituents (ethyl and methyl) along with their respective positions. Familiarity with nomenclature rules is vital for interpreting names and translating them into structural formulas.
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