![]() ![]() Other catalytic transformations such as double bond oxidation and olefin metathesis could possibly be used to prepare other modified starches for various applications. Complete hydrogenation was obtained at 40 ☌ under 30 bar of H2 after 12 h using 0.8-wt.% Rh-catalyst. The etherified starch was further transformed by hydrogenation of the double bonds to yield the corresponding linear octyl groups using catalyst soluble in EtOH-H20 mixtures. Reducing the temperature has no effect since free radical processes have a zero activation energy. Exposure to oxygen and ultraviolet light should be avoided. Another is to use anti-oxidants that act as free radical traps. One way is to ensure that no double bonds are present. Oxidative rancidity can be prevented or reduced by several different routes. This is an entirely different process in which oxygen free radicals add across double bonds. The second way in which fats deteriorate is oxidative lipolysis. ![]() 87f.) are largely selected from this area. Our examples for regio- and stereoselective C C double bond oxidations as well as the examples for C C double bond cleavages (see p. Many regio- and stereoselective oxidations have been developed within the enormously productive field of steroid syntheses. The related cleavage of cyclohexene rings to produce 1,6- dioxo compounds has already been discussed in section 1.14. Oxidation of olefins and dienes provides the classic means for syntheses of 1,2- and 1,4-difunctional carbon compounds. ![]()
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