Question

A student decided that the configuration of the asymmetric centers in a sugar such as D-glucose could be determined rapidly by simply assigning the R configuration to an symmetric center with an OH group on the right and the S configuration to an symmetric center with an OH group on the left. Is he correct?

Accepted Answer

Step 1: Understand the problem. The student is proposing a simplified method to assign R and S configurations to asymmetric centers in D-glucose based on the position of the OH group (right = R, left = S). We need to evaluate whether this approach is correct. Step 2: Recall the rules for assigning R and S configurations. The Cahn-Ingold-Prelog priority rules are used to determine the configuration of a chiral center. These rules involve assigning priorities to substituents based on atomic number and arranging the molecule so the lowest priority group is pointing away from the observer. Step 3: Analyze the structure of D-glucose. D-glucose has four asymmetric centers (chiral carbons). The OH groups are positioned on either the right or left side in the Fischer projection. However, the Fischer projection does not directly indicate the spatial arrangement required for R/S determination. Step 4: Explain why the student's method is incorrect. The configuration (R or S) of a chiral center depends on the 3D spatial arrangement of the substituents, not simply their position in a 2D Fischer projection. The position of the OH group (right or left) in the Fischer projection does not guarantee the correct R/S assignment without applying the priority rules and visualizing the molecule in 3D. Step 5: Conclude that the student’s method oversimplifies the process and does not account for the necessary application of the Cahn-Ingold-Prelog rules. To correctly assign R and S configurations, the molecule must be analyzed in 3D, and the priorities of all substituents must be considered.

비슷한 문제에 대한 검증된 영상 답변:

주요 개념

Asymmetric Centers

Cahn-Ingold-Prelog Priority Rules

D- and L- Configuration in Sugars