(R)-2-Chloro-1-phenylethanol (C₈H₉ClO) - R or S Configuration

Chiral Center Analysis

(R)-2-Chloro-1-phenylethanol (C₈H₉ClO) contains 1 chiral center. Tests -CH₂Cl vs phenyl at the second level. Students assume the phenyl ring "outranks" everything, but Cl (Z=17) at the 2nd level beats the ring's C,C,C.. Each chiral center is analyzed below using CIP (Cahn-Ingold-Prelog) priority rules to determine R or S configuration.

CIP Priority Assignment

The four substituents on the chiral center are ranked by atomic number of the directly attached atom, with ties broken by exploring outward along each branch.

• Priority 1: -OH - Oxygen (Z=8) directly bonded - highest at first atom
• Priority 2: -CH₂Cl - C at 1st → {Cl(17), H, H} at 2nd - Cl at 2nd level beats phenyl's {C, C, C}
• Priority 3: -C₆H₅ - C at 1st → {C, C, C} at 2nd - aromatic carbons (Z=6) lose to Cl (Z=17)
• Priority 4: H - Hydrogen (Z=1) - always lowest

R/S Configuration

With the lowest priority group (priority 4) oriented away from the viewer, the remaining three substituents trace a clockwise path from priority 1 to 2 to 3. This gives the R configuration.

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