# What is the priority order of the four groups?

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?

• 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... – Ivan Neretin Jan 14 at 5:17
• Oh ok....so does that mean that the MeO group has highest priority followed by CF3...? – MatH Jan 14 at 5:28
• Looks like so.$\,$ – Ivan Neretin Jan 14 at 5:44
• The priority is MeO > CF3 > COOH. I think the configuration is R. – joehua Jan 15 at 15:04