If the chromic acid oxidation is performed with stoichiometric oxidant in the presence of diethyl ether as co-solvent (a method introduced by H.C. Brown), the epimerization of l-menthone to d-isomenthone is largely avoided.
Apple cider vinegar isn't likely to be effective for weight loss. Proponents of the apple cider vinegar diet claim that drinking a small amount of apple cider vinegar before meals or taking an apple cider vinegar supplement helps curb appetite and burn fat. However, there's little scientific support for these claims.
Apple cider vinegar has much of the sugars of the apple naturally fermented into an acidic base that rinses the system and the naturally occurring pectin still helps slow other sugars from being released into the blood. Apples by themselves cannot control blood sugar if you do not watch all aspects of your diet. Simply eating apples does not give you free rein to eat all the sugar-filled foods you desire. Diet-controlled diabetes requires you to pay close attention to how all of the foods you eat react in your body and to each other.