Organic Chemistry As a Second Language, 3e: First Semester Topics

Published by John Wiley & Sons
ISBN 10: 111801040X
ISBN 13: 978-1-11801-040-2

Chapter 7 - Configurations - 7.2 Determining The Configurations Of A Stereocenter - Problems - Page 140: 7.21


1 - Br 2 - Cl 3 - (Right) Carbon 4 - (Left) Carbon

Work Step by Step

1. Identify the stereocenter. 2. List all atoms connected to the stereocenter, and rank them by the atomic number. - Br, Cl, C, C Ranked by atomic number: - Br, Cl, C, C 3. As we can see, there are 2 equal atoms, and there are two methods for finding their order. First Method (Faster): - Find the closest variation in the chain (Double bond, Substituent). - The chain with the closer variation gets priority. In this case the right chain has a double bond, so the right carbon gets priority. Second Method: - Compare the atoms connected to each carbon, and if you don't get the answer, then look at the atoms connected to them. In this case: Already ranked by atomic number: Left Carbon: C, H, H Right Carbon: C, H, H They are equal, so we will proceed to compare these new 2 carbons. Second Left Carbon: C, H, H. Second Right Carbon: C, C, H. ** If there is a double bond, we count the atom connected 2 times. - Since (C>H), the Second Right Carbon gets priority, therefore, the Right Carbon gets priority. 4. Put the numbers on the stereocenter atoms: 1 - Br 2 - Cl 3 - (Right) Carbon 4 - (Left) Carbon
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