Assign an \(R\) or \(S\) configuration to the chiral center in each amino acid. (a) L-Phenylalanine (b) L-Glutamic acid (c) L-Methionine

In each amino acid, the chiral center is the α-carbon, which is the carbon atom attached to the amino group (NH2), carboxyl group (COOH), and the side chain (R group).

Using the Cahn-Ingold-Prelog priority rules, assign priorities to the groups attached to the chiral center. Number the atoms in decreasing order of priority (1 for the highest priority, 4 for the lowest priority). The priority is usually determined by atomic number, with higher atomic numbers having higher priority.

Position the molecule in space so that the lowest-priority group (4) is pointing away from the observer.

Observe the orientation of the remaining three groups around the chiral center. If the order of priority from 1 to 3 is clockwise, the configuration is R (rectus). If the order of priority from 1 to 3 is counterclockwise, the configuration is S (sinister).

(a) L-Phenylalanine: 1. Chiral center: α-carbon 2. Priorities: COOH (1) > NH2 (2) > Phenyl group (3) > H (4) 3. Arrange H away from the observer 4. Orientation: counterclockwise (sinister) Configuration: S (b) L-Glutamic acid: 1. Chiral center: α-carbon 2. Priorities: COOH (1) > NH2 (2) > CH2-COOH (3) > H (4) 3. Arrange H away from the observer 4. Orientation: counterclockwise (sinister) Configuration: S (c) L-Methionine: 1. Chiral center: α-carbon 2. Priorities: COOH (1) > NH2 (2) > CH2-CH2-S-CH3 (3) > H (4) 3. Arrange H away from the observer 4. Orientation: counterclockwise (sinister) Configuration: S In conclusion, the chiral center configurations for each amino acid are L-Phenylalanine (S), L-Glutamic acid (S), and L-Methionine (S).