# RCOH and RCHO Nomenclature [duplicate]

In terms of nomenclature, is there a difference between RCHO and RCOH when referring to an aldehyde?

$\ce{RCHO}$ is preferred. The problem with $\ce{RCOH}$ is that it gives the misleading impression that the hydrogen is attached to the oxygen. In fact, I don't believe I've ever seen a reference in literature to an aldehyde using the latter representation.

The Graphical Representation Standards for Chemical Structure Diagrams (IUPAC Recommendations 2008), include recommendations for contracted labels (labels representing more than one non-hydrogen atom) in structure diagrams. In particular

GR-2.3.8 Ordering of multiple symbols attached to the same atom
If a single atom is bound to both hydrogen atoms and non-hydrogen atoms, any hydrogen atoms should be presented adjacent to the first atom, followed by the others, reading outward from the bond.

Therefore, a contracted label representing an aldehyde group should be written as $\ce{-CHO}$, since the carbon atom is bound to a hydrogen atom and a non-hydrogen (oxygen) atom, and the hydrogen should be presented adjacent to the first (carbon) atom, followed by the other (oxygen) atom.