Which of the following alkenes are E and which are Z?
(a)

Verified step by step guidance

Step 1: Recall the Cahn-Ingold-Prelog priority rules. These rules are used to assign priorities to the groups attached to the double-bonded carbons in the alkene. The group with the higher atomic number gets the higher priority. If there is a tie, move outward to the next set of atoms until a difference is found.

Step 2: Identify the two groups attached to each carbon of the double bond in the given alkene. Assign priorities to these groups based on the Cahn-Ingold-Prelog rules.

Step 3: Determine the relative positions of the higher-priority groups on each carbon. If the higher-priority groups are on the same side of the double bond, the alkene is classified as Z (from the German word 'zusammen,' meaning together). If the higher-priority groups are on opposite sides, the alkene is classified as E (from the German word 'entgegen,' meaning opposite).

Step 4: Repeat the process for each alkene in the problem. Carefully analyze the structure of each alkene to ensure correct assignment of E or Z configuration.

Step 5: Summarize the results by labeling each alkene as either E or Z based on your analysis. Ensure that your assignments are consistent with the priority rules and the spatial arrangement of the groups.

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Key Concepts

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

Alkene Geometry

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C). The geometry around the double bond is planar, leading to two possible configurations: E (entgegen) and Z (zusammen). These configurations depend on the relative positions of the substituents attached to the double-bonded carbons.

Cahn-Ingold-Prelog Priority Rules

To determine whether an alkene is E or Z, the Cahn-Ingold-Prelog priority rules are applied. These rules assign priority to substituents based on atomic number; the higher the atomic number, the higher the priority. The configuration is Z if the highest priority substituents are on the same side of the double bond and E if they are on opposite sides.

Stereoisomerism

Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity but differ in the spatial arrangement of atoms. In alkenes, stereoisomers can exist as E/Z isomers due to the restricted rotation around the double bond, leading to distinct physical and chemical properties.

Which of the following alkenes are E and which are Z? (a)