The carbonyl group by itself does not produce colour, but when two adjacent groups occur in the molecule, as for example in the a-diketones (such as di-acetyl and benzil), a yellow colour is produced.
HYDRAZONE, in chemistry, a compound formed by the condensation of a hydrazine with a carbonyl group (see Alde Hydes; Ketones).
The carbonyl group is not ketonic in character since it yields neither an oxime nor hydrazone.
On oxidation, the molecule is split at the carbonyl group and a mixture of acids is obtained.
Thus a double bond of oxygen, as in the carbonyl group CO, requires a larger volume than a single bond, as in the hydroxyl group - OH, being about 12.2 in the first case and 7.8 in the second.