1-CH(CH3)CH2F 2-CHCl2 3-CH2Br 4-C(CH3)3

this is the order i did using the system but i am having a hard time understanding it and was wondering if anyone could tell me if my answer is correct, and if it is not, explain to me please


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The keys are:

  1. going outwards, only look one bond at a time
  2. look for the first point of difference
  3. to break ties follow the chains of highest priority first

So, going out from the point of attachment, the first atom in each chain is a carbon, so we expand from there to the next three atoms in each case (in red). Draw these out in priority order (ie. highest to lowest atomic number), top to bottom. Now compare the highest priority atom on each chain, ie. C vs Cl vs Br vs C. Bromine has the highest atomic number, so this makes that whole substituent number 1 priority, chlorine is next, so that whole group is number 2 priority, the remaining two groups are a tie, so we go down their list of attached atoms, looking for the first point of difference. The second atom on each is a carbon - ie. a tie. The final atom is a hydrogen on the first group, but a carbon on the final group, so the latter has the higher overall priority. In this particular example, there is no need to go further out along the chains to determine priority order for the substituents.

CIP rules example

So, the final priority order is: (1) -CH2Br, (2) -CHCl2, (3) -C(CH3)3, (4) -CH(CH3)CH2F


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