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

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$\ce{RCHO}$ 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.

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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.

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