Which of the following statements are true regarding the general preparation of aldehydes and ketones from alcohols? (i) Both can be prepared by the oxidation (dehydrogenation) of the corresponding alcohol using heated copper at about 250^ C - 300^ C . (ii) Both can be prepared by the Oppenauer oxidation of the corresponding alcohol. (iii) Both can be prepared by the oxidation of the corresponding alcohol with aqueou

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Statement (i): When vapours of primary and secondary alcohols are passed over heated copper at 573 K ( 300^ C ), dehydrogenation takes place. Primary alcohols form aldehydes and secondary alcohols form ketones. Thus, this is a general method for preparing both. Statement (ii): Oppenauer oxidation is a specific method used primarily for the oxidation of secondary alcohols to ketones. It is not a general method for preparing aldehydes from primary alcohols, as aldehydes tend to undergo aldol condensation under the ba