Naming Aldehydes and Ketones

Aldehydes are named by replacing the terminal -e of the corresponding alkane name with -al. The parent chain must contain the -CHO group, an the -CHO carbon is numbered as carbon 1. For example  

Note that the longest chain in 2-ethyM-methylpentanal is a hexane, this chain does not include the -CHO group and thus is not considered I parent. 

For more complex aldehydes in which the -CHO group is attached a ring, the suffix -carbaldehyde is used  

Certain simple and well-known aldehydes have common names that are recognized by lUPAC. Some of the more important common names are given in Table 19.1. 

TABLE 19.1 Common Names of Some Simple Aldehydes 

Aldehydes and ketones are most often produced commercially by the oxidation of alcohols. Oxidation of a primary alcohol gives the corresponding aldehyde, for example. 

We obtain the systematic name for an aldehyde from the parent alkane by removing the final -e and adding -al. For ketones, the final -e is replaced by -one, and a number indicates the position of the carbonyl group where necessary. The carbon chain in ketones is numbered such that the 

Ethanal (acetaldehyde) Propanone (acetone) 2-Pentanone 3-Chlorobutanal 

The names in parentheses are common names that are used much more often than the systematic names. 

Another common aldehyde is henzaldehyde (an aromatic aldehyde), which has the structure 

The aldehydes and ketones are closely related classes of compounds. Their 

In a linear expression, the aldehyde group is often written as CHO or CH=0. For example. 

In the linear expression of a ketone, the carbonyl group is written as CO thus 

Formaldehyde is the most widely used aldehyde. It is a poisonous, irritating gas that is very soluble in water. Marketed as a 40% aqueous solution called formalin, the largest use of this chemical is in the manufacture of polymers. About 2.1 billion pounds (9.6 X 10 kg) of formaldehyde are manufactured aimually in the United States. Formaldehyde vapors are intensely irritating to the mucous membranes, and ingestion may cause severe abdominal pains, leading to coma and death. 

Acetone and methyl ethyl ketone are widely used organic solvents. Acetone, in particular, is used in very large quantities for this purpose. The U.S. production of acetone is about 1.9 billion pounds (8.7 x 10 kg) annually. It is used as a solvent in the manufacture of drugs, chemicals, and explosives for removal of paints, varnishes, and fingernail polish and as a solvent in the plastics industry. Methyl ethyl ketone (MEK) is also widely used as a solvent, especially for lacquers. 

Ketones are named by replacing the terminal -e of the corresponding alkane name with -one. The parent chain is the longest one that contains the ketone group, and the numbering begins at the end nearer the carbonyl carbon. As with alkenes (Section 6.3) and alcohols (Section 17.1), the locant is placed before the parent name in older rules but before the suffix in newer IUPAC recommendations. For example  

OBJECTIVE To learn the systems for naming aldehydes and ketones. 

An alternative system for naming ketones specifies the substituents attached to the C=0 group. For example, the compound 

A hydrocarbon derivative containing the carboxyl group (-COOH) 

Why This Chapter Much of organic chemistry is the chemistry of carbonyl compounds. Aldehydes and ketones, in particular, are intermediates in the synthesis of many pharmaceutical agents, in almost all biological pathways, and in numerous industrial processes, so an understanding of their properties and reactions is essential. We ll look in this chapter at some of their most important reactions. 

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ThomsonNOW Click Organic Interactive to use a web-based palette to draw structures of aldehydes and ketones based on their lUPAC names. 

A Fingernail-polish remover is primarily acetone, a ketone. 

Acetone, (CH3)2C=0, is widely used as an industrial solvent approximately 1.2 million tons per year are produced in the United States. 

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In naming aldehydes and ketones, locants should be assigned so as to give the carbonyl group the lowest number possible. 

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