(R)-β-Butyrolactone (C₄H₆O₂) - R or S Configuration

Chiral Center Analysis

(R)-β-Butyrolactone (C₄H₆O₂) contains 1 chiral center. Ring ester with a chiral center in a 4-membered lactone ring. Tests that CIP rules are unchanged by ring context - the ring-O is still O at first level, and the CH₂ path reaches two oxygens via the carbonyl.. 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: -O- (ring) - Oxygen (Z=8) directly bonded - ring context doesn't change atomic number
• Priority 2: -CH₂C(=O)O- (ring) - C at 1st → {C, H, H} at 2nd → C leads to {O, O, O} (=O phantom + ring O) - beats methyl
• Priority 3: -CH₃ - C at 1st → {H, H, H} at 2nd - simple methyl, lowest among carbons
• 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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