Naming the Aldehydes and Ketones

For the purposes of naming, the carbonyl function is the highest-ranking group we have encountered so far. The aldehyde function takes precedence over that of ketones. For historical reasons, the simpler aldehydes often retain their common names. These names are derived from the common name of the corresponding carboxylic acid, with the ending -ic or -ok acid replaced by -aldehyde, as shown in the examples below. 

Many ketones also have common names, which consist of the names of the substituent groups followed by the word ketone. Dimethyl ketone, the simplest example, is a common solvent best known as acetone. Phenyl ketones have common names ending in -phenone. 

We will adhere to lUPAC names, which treat aldehydes as derivatives of the alkanes, with the ending -e replaced by -al. An alkane thus becomes an alkanal. Methanal, the systematic name of the simplest aldehyde, is accordingly derived from methane, ethanal from ethane, propanal from propane, and so forth. However, Chemical Abstracts retains the common names for the first two, and so shall we. We number the substiment chain beginning with the carbonyl carbon. 

Notice that the names parallel those of the 1-alkanols (Section 8-1), except that the position of the aldehyde carbonyl group does not have to be specified its carbon is defined ai Cl. A dialdehyde is denoted as a -dial. 

When the -CHO group is attached to a ring, the compound is called a carbaldehyde and the carbon atom bearing the -CHO group is Cl. The parent aromatic aldehyde, for instance, is benzenecarbaldehyde, although its common name, benzaldehyde, is so widely used that it is accepted by Chemical Abstracts. 

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Naming the Aldehydes and Ketones 17-2 Structural and Physical Properties 17-3 Spectroscopy... 

Section 17 1 The substitutive lUPAC names of aldehydes and ketones are developed by identifying the longest continuous chain that contains the carbonyl group and replacing the final e of the corresponding alkane by al for aldehydes and one for ketones The chain is numbered m the direction that gives the lowest locant to the carbon of the carbonyl group... 

Like the other organic compounds you have encountered, the names of aldehydes and ketones are based on the names of the parent alkanes. 

To name a ketone, follow the steps on the next page. The Sample Problem that follows gives examples for naming both aldehydes and ketones. 

Aldehydes use the parent name of their corresponding alkanes and the ending al. Therefore, the simplest aldehyde is meth-anal, but it goes by its common name formaldehyde. Aldehydes and ketones are often produced by the oxidation of alcohols. For example, formaldehyde is produced by the oxidation of methanol according to the following reaction ... 

Name all the aldehydes and ketones that have the formula C5H]0O. 

The organic acids represent a still higher stage of oxidation of hydrocarbons than the aldehydes and ketones namely, the stage... 

From the structures, write the common and I.U.P.A.C. names of aldehydes and ketones. 

In this chapter, we will study the naming of aldehydes and ketones, as well as some of their important reactions. These concepts will be very useful when we study the chemistry of carbohydrates in Chapter 7. 

Carbohydrate (Section 22.1 A) A group of naturally occurring compounds that are usually defined as polyhydroxyaldehydes or polyhydroxyketones, or as substances that undergo hydrolysis to yield such compounds. In actuality, the aldehyde and ketone groups of carbohydrates are often present as hemiacetals and acetals. The name comes from the fact that many carbohydrates possess the empirical formula Cx(H20)y. 

Write the lUPAC and common names for aldehydes and ketones draw the condensed structural formulas when given their names. 

Draw the condensed structural formulas and give the lUPAC names for aU the aldehydes and ketones that have the formula C5H10O. (12.3)... 

Nitriles contain the —C=N functional group We have already discussed the two mam procedures by which they are prepared namely the nucleophilic substitution of alkyl halides by cyanide and the conversion of aldehydes and ketones to cyanohydrins Table 20 6 reviews aspects of these reactions Neither of the reactions m Table 20 6 is suitable for aryl nitriles (ArC=N) these compounds are readily prepared by a reaction to be dis cussed m Chapter 22... 

A cyanohydrin is an organic compound that contains both a cyanide and a hydroxy group on an aUphatic section of the molecule. Cyanohydrias are usually a-hydroxy nitriles which are the products of base-cataly2ed addition of hydrogen cyanide to the carbonyl group of aldehydes and ketones. The lUPAC name for cyanohydrias is based on the a-hydroxy nitrile name. Common names of cyanohydrias are derived from the aldehyde or ketoae from which they are formed (Table 1). 

Like other alkaloids of this group, quinine forms molecular compounds with a variety of organic substances. With benzene and toluene it produces compounds of the formulae B. CgHg and B. C,Hg respectively, with phenol it gives the crystalline product B. CgHjOH, and similar combinations with polyhydric phenols, ethers, aldehydes and ketones are known. One of the most characteristic of these substances is cupreine-quinine, a combination of the two alkaloids, obtainable from cuprea bark, and at first regarded as a new alkaloid, and named homoquinine. ... 

Problem 19.1 Name the following aldehydes and ketones according to 1UPAC rules ... 

Draw and name the seven aldehydes and ketones with the formula CsH O. Which are chiral ... 

Aldehydes and ketones with an a hydrogen atom undergo a base-catalyzed carbonyl condensation reaction called the aldol reaction. For example, treatment of acetaldehyde with a base such as sodium ethoxide or sodium hydroxide in a protic solvent leads to rapid and reversible formation of 3-hydroxybutanal, known commonly as aldol (aidehyde + alcohol), hence the general name of the reaction. 

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