Other preservatives include nitrites, sulphites, sorbates, benzoates and essential oils. Essential oils include terpenoids, benzyl benzoates, allylphenols, and propenylphenols. It is dominated by linalool, benzoates, salicylates, and nerolidol. For prochiral arenes (naphthalene, toluene, benzoates, benzopyrene), the epoxides are often obtained in high enantioselectivity. The salts and esters of benzoic acid are known as benzoates . However, unlike benzoates, propionates do not require an acidic environment. Copper(II) benzoates exists in at least two structural forms, depending on the degree of hydration.