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A plus or minus in brackets before a compound's name.
Also known as: Dextrorotatory sign, Laevorotatory sign, Plus and minus rotation, Bracketed plus or minus
(+) and (−) say which way a solution of the compound rotates plane-polarised light, and they can only be found by measuring — no amount of structure drawing predicts them. That is precisely why they are not interchangeable with R/S or D/L, which are assigned from structure alone.
Denote the direction in which a substance rotates the plane of polarised light: clockwise for (+), anticlockwise for (−).
Contexts: Laboratory
Are determined experimentally and cannot be deduced from a structure, unlike the R/S and D/L descriptors.
Contexts: Laboratory
Replace the older d- and l- lowercase prefixes, which were dropped because they were confused with the small-capital D and L configuration labels.
Contexts: Laboratory
A plus or minus sign enclosed in round brackets, set before a compound's name and followed by a hyphen.