A method of making a carbonyl compound comprises contacting a compound comprising a secondary hydroxyl group with a basic metal oxide catalyst at a temperature sufficient to maintain the compound comprising a secondary hydroxyl group in a vapor phase. The method for keying human voice audio frequency is very easy and fast. The rail is sized and configured to maintain a portion of at least two of the photovoltaic assemblies, with the leg assemblies extending from the rail in a spaced-apart fashion and terminating in a foot for placement against a rooftop structure for minimally penetration installation.