MCAT Organic Question — IUPAC Molecule
- Nov 11, 2014
- MCAT Blog, MCAT Organic, MCAT Question of the Day
What is the correct IUPAC name for this molecule?
A) 2, 2, 4, 4-tetrachloro-1-isopropylcyclopentane
B) 1, 1, 3, 3-tetrachloro-4-isopropylcyclopentane
C) 2-isopropylcyclopentyl-1, 1, 2, 2-chloride
D) 1, 1, 4, 4-tetrachloro-2-isopropylcyclopentane
IUPAC rules state that when naming constituents on a ring, the numbering should be arranged to give the substituents the lowest numbers. Beginning the numbering with the two chlorine groups at the top (as carbon 1), we would proceed to the left (to give the isopropyl group #2) until we arrive at the chlorine groups at the bottom (carbon number 4).
A: Numbering should begin with one of the carbon atoms bearing a chlorine, a higher priority group than the isopropyl group.
B: Placing the isopropyl group at carbon 4 produces substituents on carbons 1, 3, 4. When numbering you should aim to minimize those numbers. So the correct numbering produces substituents on carbons 1, 2, 4 as explained above.
C: The chlorides are not on carbons 1 and 2 as this choice would indicate.
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