The Foundations of Chemistry

Diethyl ether is a very low boiling liquid (bp 35°C). Dimethyl ether is a gas that is used

as a refrigerant. The aliphatic ethers of higher molecular weights are liquids, and the

aromatic ethers are liquids and solids.

Even ethers of low molecular weight are only slightly soluble in water. Diethyl ether

is an excellent solvent for organic compounds. It is widely used to extract organic

compounds from plants and other natural sources.

ALDEHYDES AND KETONES

Aldehydes and ketones contain the carbonyl group,. In aldehydes,at least one

H atom is bonded to the carbonyl group. Ketoneshave two carbon atoms bonded to a

carbonyl group. Models of formaldehyde (the simplest aldehyde) and acetone (the simplest

ketone) are shown in Figure 27-16.

Aldehydes are usually called by their common names. These are derived from the name

of the acid with the same number of C atoms (Table 27-9). The systematic (IUPAC) name

is derived from the name of the parent hydrocarbon. The suffix -alis added to the char-

acteristic stem. The carbonyl group takes positional precedence over most other

substituents.

Formaldehyde has long been used as a disinfectant and as a preservative (including

embalming fluid) for biological specimens. Its main use is in the production of certain

plastics and in binders for plywood. Many important natural substances are aldehydes and

ketones. Examples include sex hormones, some vitamins, camphor, and the flavorings

extracted from almonds and cinnamon. Aldehydes contain a carbon–oxygen double bond,

so they are very reactive compounds. As a result, they are valuable in organic synthesis,

particularly in the construction of carbon chains.

O

RHC

aliphatic

aldehyde

O

RRC

aliphatic

ketone

O

Ar C H

O

Ar C Ar

aromatic

ketone

O

Ar C R

mixed

ketone

aromatic

aldehyde

C O.

27-11

The simplest aldehyde, formaldehyde,

O
B
HXCXH, has two H atoms and no
alkyl or aryl groups.

1072 CHAPTER 27: Organic Chemistry I: Formulas, Names, and Properties

Figure 27-16 (a) Models of formaldehyde, HCHO, the simplest aldehyde. (b) Models of

acetone, CH 3 XCOXCH 3 , the simplest ketone.

(a) (b)