ˈwȯldən- noun
Usage: usually capitalized W
Etymology: after Paul Walden died 1957 Latvian organic chemist
: an inversion of configuration of one optically active compound into another that may or may not lead to a change in the direction of optical rotation and that may be of either of two general types:
a. : inversion involving two reactions in which an optically active compound is changed to another by substitution at its asymmetric center and then regenerated (as dextro -alanine is changed to levo -bromo-propionic acid by nitrosyl bromide and then to levo -alanine by ammonia) but as the optical isomer of the original compound
b. : inversion involving one reaction of an optically active compound at its asymmetric center with resulting configurational change from d to l or vice versa regardless of change in optical rotation (as from levorotatory l -bromo-propionic acid to levorotatory d -alanine by ammonia but not from dextrorotatory l -alanine to levorotatory l -bromo-propionic acid because no inversion of configuration occurs although optical inversion does)