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.
Likely the most popular use for apple cider vinegar is digestive. I use it as a morning tincture, dissolving a tablespoon into a glass of water to detoxify the digestive system and eliminate toxins from the organs. You can also add a touch of honey if the vinegar is too pungent on its own.