The general formula for the alkanals is RCHO. Alkanals, also known as aldehydes, are a group of organic compounds containing a carbonyl group (-CHO) as the functional group. The carbonyl group is located at the end of a carbon chain, which gives the alkanals their distinctive properties. The R in the formula represents any alkyl group, which is a group of carbon and hydrogen atoms bonded together. Therefore, the general formula for an alkanal can be represented as R-CHO, where R is any alkyl group.