(2R)-2-methoxypropanoic acid

CAS 23943-96-6

Four carbon atoms are enough to hide several kinds of chemical identity. (2R)-2-Methoxypropanoic acid has the same formula as methyl lactate, but different bonds: its methoxy group sits beside a free carboxylic acid, rather than forming a methyl ester. Carbon 2 also has two mirror-image arrangements, and R specifies one absolute configuration. It does not predict optical rotation for all compounds. A positive rotation reported for this particular material is a separate measured property under stated conditions. Chemical purity and enantiomeric composition likewise answer different questions, since a routine assay need not distinguish mirror images. This compact molecule shows why atom counts, connectivity, handedness, and analytical method all belong in a meaningful description of a chemical sample. The same mass cannot resolve these different structural assignments.