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How do you name ketones?

Answer 1

As alkanones, with a number specifying the position of the carbonyl group on the chain.

It's obvious that I need a three-carbon backbone in order to build a ketone, but why?

For #H_3C-C(=O)CH_3#, #"2-propanone"# is clearly a misnomer because I don't have to specify the position of the carbonyl; it must be at #C2# to be a ketone. Of course we could (and would) call it acetone. Butanone is likewise unambiguous without a number to specify the position of the carbonyl. Why not?

But when we get to pentanone, we could have 3-pentanone, the symmetric ketone, #H_3C-CH_2C(=O)CH_2CH_3#, or 2-pentanone, #H_3C-C(=O)CH_2CH_2CH_3#. Why can I not have 1-butanone?

Do these ideas make sense?

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Answer 2

Nolan Allen

Ketones are named by identifying the longest carbon chain containing the ketone group and naming it as the parent alkane. The ketone group is then named as a prefix, using "oxo" or "keto," followed by the number of the carbon atom where the ketone group is attached.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.