Menthol behavior

Mesitylene, production from acetone, 1 164 Mesityl oxide, 14 589-590 characteristics of, 16 337 hydrogenation, 16 337-338 hydrogen peroxide treatment of, 16 338 Z-menthol from, 24 520 production of, 16 336-337 production from acetone, 1 164, 174 Mesogenic diols, 25 460 Mesogenic molecules, solids of, 15 82 Mesogens, 24 53, 54 Mesomixing, 16 683 Mesomorphic behavior, 24 53-54 Mesomorphic phase transitions, 15 102 Mesomorphism, 15 81. See also Liquid crystalline materials Mesophase pitch-based carbon fiber, 26 734-735... 

Steric effects also play a significant role, as is apparent in the monosubstituted cyclohexanols series (entries 7-9 in Table 13.3) and from comparison between linear and branched substrates (entry 1 vs. entry 3). This effect is so strong that in disubstituted cyclohexanols the reaction takes place at reasonable rates only when the —OH group is in axial conformation, as shown by the comparison of (-)-menthol (entry 16) and neomenthol (entry 17). This particular behavior could once more be exploited for synthetic purposes, in order to set up a kinetic resolution process. This has indeed been achieved in the one-pot hydrogenation of pennyroyal oil into menthol [67]. 

The extent to which a given dose of a menthol is conjugated with u-curonic acid also depends on the isomer fed. Williams (440) has own that menthols of the dextro configuration are excreted as glucuronosides to a greater extent than the Z-menthols. This behavior has been used by Williams (441, 442) for the optical resolution of cZZ-menthol and dZ-isomen-thol. 

The TLC behavior of the stereoisomeric menthols is strongly influenced by the position of the hydroxyl group, which is equatorial (e) in menthol and isomenthol... 

FIGURE 8.10 Chromatographic behavior of some diastereoisomers of menthols on silica gel. Mobile phases (v/v) 1, benzene 2, benzene-methanol (95 + 5) 3, benzene-methanol (75 + 25) 4, methanol. (Data from Petrowitz, H.-J., Angew. Chem., 23, 921,1960.)... 

General Correlations on the Chromatographic Behavior of Menthol and Thujol Diastereoisomers with Hydroxyl Group in Axial or Equatorial Position... 

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