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Organic Chemistry
Found in: Page 212

Short Answer

A sulfonium ion (R3S+) is a stereogenic center if three different alkyl groups are bonded to sulfur because sulfur is surrounded by four different groups, including its lone pair. In assigning an R or S designation to sulfur, the lone pair is always assigned the lowest priority (4). SAM, S-adenosylmethionine, is a biologically active sulfonium ion that we will learn about in Section 7.16. Locate all the stereogenic centers in SAM, and assign an R,S designation to each center.

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Step by Step Solution

Stereogenic centres

These are atoms that have different substituents in a compound such that interchanging the positions of two groups gives two stereoisomers.

R and S nomenclatures.

The priorities are assigned according to the rules of R and S, and the stereogenic centers are named R if the groups ordered from highest priority 1 to the lowest priority are aligned clockwise and vice-versa.

Drawing the structures of the given compounds

The given compound SAM has 6 stereogenic centers. All the stereogenic centers are marked with a (*) and designated as R and S hereunder.

Stereogenic centers marked as R and S

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