Chapter 28: Problem 46

Draw the dashed-wedged line structure for ( \(R\) )-proline and (S)-valine.

Short Answer

Expert verified

The line-angle structures of R-proline and S-valine should properly reflect the indicated stereochemistry, with wedged and dashed lines indicating the spatial orientation of the constituent atoms.

Step by step solution

Recall the structures of the amino acids

Proline and Valine, like all amino acids, consist of a carboxylic acid group, an amino group, and a distinct side chain. The primary difference between these two amino acids lies in the structure of the side chain. Proline has a unique structure, where the side chain forms a five-membered ring to the nitrogen. Valine on the other hand, has a branched chain with one chiral center in the side chain.

Understand the concept of the R and S designations

The R- and S- designations provide information about the spatial arrangement of the atoms in a particular chiral center. For R configurations, the group with the lowest priority (usually Hydrogen) when assigning priorities is directed away from you, the atoms connected to the chiral center are arranged in decreasing priority in a clockwise direction. For S configurations, it is counterclockwise.

Draw line angle structures

When drawing line angle structures for these amino acids, we must indicate stereochemistry with wedged and dashed lines. Where there is a chiral center, atoms pointing towards us should be on full wedged lines, atoms pointing away from us should be on dashed lines.

Draw the structure of proline

The R configuration would mean that when looking at the chiral center, the atoms are arranged in decreasing priority, from highest to lowest, in a clockwise direction. For proline, the chiral center is on the carbon within the ring structure, and in the R configuration, the carboxylic acid group is oriented away (on a dashed line), leaving the nitrogen and its attached groups on the wedged line.

Draw the structure of valine

Valine has a chiral center in its side chain. In the S configuration of valine, the hydrogen atom is oriented away (on a dashed line), while the larger substituents are oriented in a counterclockwise manner starting from the highest priority.

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Draw the dashed-wedged line structure for ( \(R\) )-proline and (S)-valine.

Short Answer

Step by step solution

Recall the structures of the amino acids

Understand the concept of the R and S designations

Draw line angle structures

Draw the structure of proline

Draw the structure of valine

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