I'm trying to figure out whether this is in R/S configuration....I thought it would be R since the groups seem to be decreasing in priority in the clockwise direction (since F has the largest atomic number). However, the answers say that it is actually in the S configuration....could someone explain this to me? Have I incorrectly assigned priority?

  • $\begingroup$ So what if F has the largest atomic number? It is not like we look at the whole group and count the largest atomic numbers. No, we look at the first atom alone, and think of it for a while. If that's indecisive, we look further... $\endgroup$ Jan 14, 2020 at 5:17
  • $\begingroup$ Oh ok....so does that mean that the MeO group has highest priority followed by CF3...? $\endgroup$
    – MatH
    Jan 14, 2020 at 5:28
  • 3
    $\begingroup$ Looks like so.$\,$ $\endgroup$ Jan 14, 2020 at 5:44
  • $\begingroup$ The priority is MeO > CF3 > COOH. I think the configuration is R. $\endgroup$
    – joehua
    Jan 15, 2020 at 15:04


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