Question

Would cyclohexanone be a methyl ketone?

Answer 1

No. A methyl ketone has one methyl group and one `"R"` group of some kind, and the carbonyl group itself must not be connected directly onto any ring structures. However, cyclohexanone IS a ketone compound in general.

Do keep in mind though that cyclohexylacetone and cyclohexanone are not the same compounds. They might be easy to mix up visually, but by name, they are fairly different.

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A methyl ketone and a cyclohexanone structure look like this:

One could argue that cyclohexanone doesn't count as a methyl ketone since a methyl ketone requires a methyl group on one side and an `"R"` group on the other, but a methylene (`\mathbf(-"CH"_2-)`) is not the same as a methyl (`\mathbf(-"CH"_3)`) since a methyl has no further connection to another atom.

We could go on and say that a methyl ketone has a carbonyl group that is necessarily not directly connected onto any ring structure, if the `"R"` group is a ring.

For instance, cyclohexylacetone (or cyclohexylethanone, or cyclohexyl methyl ketone) is a methyl ketone:

And you can see that the carbonyl is not directly connected onto the ring; it's separated by one carbon-carbon bond.