L-Lysine (H₂N(CH₂)₄CH(NH₂)COOH) - R or S Configuration
Is L-Lysine R or S?
L-Lysine (H₂N(CH₂)₄CH(NH₂)COOH) has 1 chiral center. A basic amino acid with a terminal amine on a four-carbon chain. Despite having NH₂ at the end, the side chain nitrogen is 5 atoms from the α-carbon - far too distant to affect the CIP ranking.. The configuration is S based on CIP priority rules.
| Formula | H₂N(CH₂)₄CH(NH₂)COOH |
| Name | L-Lysine |
| Number of Chiral Centers | 1 |
| Configuration(s) | S |
| Difficulty | Intermediate |
Chiral Center Analysis
L-Lysine (H₂N(CH₂)₄CH(NH₂)COOH) contains 1 chiral center. A basic amino acid with a terminal amine on a four-carbon chain. Despite having NH₂ at the end, the side chain nitrogen is 5 atoms from the α-carbon - far too distant to affect the CIP ranking.. 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: -NH₂ - Nitrogen directly bonded (atomic number 7) - highest first-atom priority
- Priority 2: -COOH - Carboxyl: C bonded to O, O, O at second level - highest among carbon substituents
- Priority 3: -(CH₂)₄NH₂ - Aminobutyl: C bonded to C, H, H at second level - terminal NH₂ is 5 atoms away. COOH's O, O, O wins
- Priority 4: H - Hydrogen always lowest (atomic number 1)
R/S Configuration
With the lowest priority group (priority 4) oriented away from the viewer, the remaining three substituents trace a counterclockwise path from priority 1 to 2 to 3. This gives the S configuration.
Interactive stereochemistry explorer with guided walkthroughs and practice quizzes.
Assign R/S Configuration for L-Lysine Step by StepRelated Topics
L-Alanine - R or S?
Determine the R/S configuration of L-Alanine
(S)-Lactic Acid - R or S?
Determine the R/S configuration of (S)-Lactic Acid
(R)-Glyceraldehyde - R or S?
Determine the R/S configuration of (R)-Glyceraldehyde
Isomer Explorer
Compare enantiomers, diastereomers, and constitutional isomers in 3D
Drug Chirality
See how chirality affects drug activity with real pharmaceutical examples
Bromochlorofluoromethane - R or S?
Determine the R/S configuration of Bromochlorofluoromethane