AbstractThe sulfines1–9in which theo‐positions of the aryl ring A are substituted by methyl groups, have a high rotational barrier about the aryl A to sulfine bond (bond α). Due to this α‐barrier, sulfines1and2exist as a pair of rotational enantiomers (atropisomerism). The symmetrically substituted sulfines3,4,7,8and9possess a prochiral centre,viz. the mesityl‐CSO part, provided rotation about bond α is restricted. With rapid rotation about bond α this prochirality disappears (thermally labile prochirality). Chiral lanthanide shift reagents are employed to uncover these chiral properties. The atropisomerism in the sulfines1and2and the thermally labile prochirality in the sulfines3,4, 7, 8and9are demonstrated by use of chiral shift reagent. Moreover, chiral shift reagents are successfully used to determine the α‐barrier in the su