Which of the following compounds is most likely to be formed from an elimination reaction that produces a Z alkene?

Question

Quizplus · Accepted Answer

11ecba2d_12b5_9fac_a3bf_b99ab42d4dc3_MD0008_00 Alkenes belong to a class of diastereomers known as geometric isomers, and the substituents on these molecules differ in their arrangement about a double bond. Double bonds can be di-, tri-, or tetra-substituted and are classified as either E/Z or cis/trans. Classification is assigned based on the Cahn-Ingold-Prelog priority rules. If the higher-priority groups are on the same side of the double bond, the alkene is Z, whereas it is E when the higher-priority groups are on opposite sides of the double bond. On the left side of the double bond in Choice B, the isopropyl group has higher priority than the methyl group (−CH₃) because the isopropyl carbon has three bonds to carbon and one bond to hydrogen whereas −CH₃ has three bonds to hydrogen. Because carbon has a greater atomic number than hydrogen, it is higher priority. The carbon on the right side of the double bond is bonded to two −CH₂ groups, so the next atom in each chain must be examined. The −CH₂ bonded to −OCH₃ is higher priority than the one bonded to −CH₃ because oxygen has a higher atomic number than carbon. Because the higher-priority groups are on the same side (top) of the double bond, the alkene is classified as Z. Therefore, the structure for Choice B is most likely to form from an elimination reaction that produces a Z alkene. (Choices A, C, and D) Each of these structures has the higher-priority groups on opposite sides of the double bond (one above, one below). Therefore, these alkenes are E and would not be products in a reaction that forms a Z alkene. Educational objective: Alkenes are geometric isomers that differ in the substituent arrangement about a double bond and can be classified as either E or Z. When the higher-priority substituents are on the same side of the double bond (top or bottom), the alkene is Z, and it is E when the higher-priority substituents are on opposite sides of the double bond.

Which of the Following Compounds Is Most Likely to Be