organic chem?

Question

hi guys

what is the difference between aldehydes and ketones? are they the same thing?

and aren't they old names for something else, like alkanones or something?

Answer 1

First of all, aldehydes and ketones are different things although both have the organic group C=O. A simple way to differentiate between the two is as follows:

Aldehydes has the group C=O but the carbon atom in the group is bonded to at least one hydrogen atom.

H
|
C=O
|
R

(Where R is another H or an alkyl group such as CH3 or C2H5)

Ketones have the group C=O, however the carbon atom in the organic group has to be bonded with at least another carbon atom.

.....R
.....|
R-C-R
.....|
....C=O
.....|
.....R

(Do not take any notice of the dots please.)

Answer 2

A carbonyl group (C=O) with two organic groups is a Ketone. With one organic group and one Hydrogen, it is an Aldehyde.

Yes, they are both currently under the naming system of alkanones. Aldehydes are always 1-alkanones and ketones have prefixes greater than 1.

Acetylaldehyde or Ethylaldehyde (CH3CHO) is seldom called 1-Ethanone or Ethan-1-one although it is called Ethanal.

Acetone (CH3COCH3) is called both Dimethyl ketone and 2-propanone.

Answer 3

Aldehydes and ketones are the oxygen analogs of alkenes. Figure 1 compares the structures of formaldehyde, the simplest aldehyde, with that of ethene, the simplest alkene, as well as the structure of acetone, the simplest ketone, with 2-methylpropene, its hydrocarbon analog.