Bertrand’s Rule

S-Benzylthiuronium salts, I, 168, 171 Bertrands s rule, IV, 226 Betabacterium vermiforme, polysaccharide formation by, II, 219 Betitol, III, 69... 

As Bertrand s rule was finally elaborated, it was shown that a pair of adjacent, cis, secondary hydroxyl groups, next to a primary hydroxyl group, suffice to establish conditions favorable for the oxidation.The reaction eventually became important for the conversion of sorbitol to Z-sorbose, an intermediate in the manufacture of vitamin C. Dihydroxyacetone, which has been used extensively in recent times to tan human skin in vivo (for cosmetic reasons), can also be made on a commercial scale in the same way. A favored organism for these reactions is Acetobacter suboxydans. 

The oxidation of inositols to inososes (cycloses) by Acetobacter suboxydans is of importance in the determination of configuration (e.g., Posternak s work on mi/o-inositol, p. 275) and in the interconversion of inositols by reduction of the inosose. Bertrand s rule (p. 133) accurately predicts the point of attack in the acyclic series, but the situation is more complex in the inositol series. The specificity of A, suboxydans appears to be related to the conformation of the cyclohexane ring of the inositols. Inositols, like other substituted cyclohexanes, may exist in boat or chair forms (86), (See Chapter I.) The chair form in which the distances between the hydroxyl groups is at a maximum appears to be the preferred conformation. Substituents that are oriented nearly parallel to the average plane of the puckered ring are called equatorial. They lie alternately above and below the plane. Substituents that are perpendicular are called axial (formerly, polar) (87), Conversion to the second chair form causes interchange of... 

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