 Delta-tocopherol

Delta-tocopherol is 8-methyltocol: the tocopherol with one additional aromatic methyl group on the tocol parent.^[ref] The methyl already attached at position 2 belongs to tocol and is not counted again in “8-methyl”. Its structure-derived molecular formula is ${\mathrm{C}}_{27}{\mathrm{H}}_{46}{\mathrm{O}}_2$.

The substitution count provides an original atom-balance example. Replacing an aromatic hydrogen by a methyl group adds net $\mathrm{C}{\mathrm{H}}_2$. Adding one such group at position 5 gives the beta-tocopherol ring pattern; adding one at position 7 gives the gamma-tocopherol pattern. Adding both gives alpha-tocopherol. These are structural comparisons, not assertions that a chosen methylation reaction selectively produces those compounds.

Consequently a mixture cannot be characterized by total carbon count alone. Suppose a stipulated sample contains 30 micromoles delta-tocopherol and 20 micromoles alpha-tocopherol. Across its 50 micromoles of molecules, the mean number of additional aromatic methyl groups isNo molecule in that mixture has 1.8 such groups. An ensemble average need not describe an individual molecular structure.

Chromatography can test the composition if the separation and calibration discriminate the forms. A family-total tocopherol measurement instead combines different molecules. Ring methylation, stereochemistry and chemical activity are separate descriptors; the delta name alone does not specify an assay response.