Nomenclature of Organic Compounds

---

21 Amides and Imides

Downloaded by CORNELL UNIV on June 21, 2012 | http://pubs.acs.org Publication Date: June 1, 1974 | doi: 10.1021/ba-1974-0126.ch021

D

erivatives o f carboxylie acids i n which the O H portion o f the C O O H group has been replaced b y N H (as such or substituted) are called amides or, more accurately, carboxamides. Such compounds have the generic structures RCONH , R C O N H R ' , and R C O N R ' R " , as well as R C O N H C O R , " and R C O N ( C O R ' ) C O R " . The latter two classes may be referred to as secondary amides and tertiary amides, respectively. Compounds containing the group —CONHCO— or —CON(R)CO— as part of a ring are called imides or, more accurately, carboximides. Broadly speaking, the class terms amide and imide also denote the corresponding nitrogen derivatives o f noncarboxylic acids such as those discussed in Chapters 18, 36, and 40—e.g., sulfonamides and amides o f phosphorus acids, as well as ionic derivatives o f ammonia such as sodium amide ( N a N H ). Sulfur analogs o f carboxamides and dicarboximides, called thioamides and thioimides, are included in this chapter. Naming o f peptides, a special subclass made up o f amides derived from α-amino carboxylic acids, is discussed in Chapter 30. 2

2

2

Recommended Nomenclature Practice Compounds o f the type R C O N H are preferably named by changing the ending oic acid i n the corresponding systematic alkanoic or alkanedioic acid name to amide, or the ending carboxylie acid, where that is used in the acid name, to carboxamide. 2

CH

3

CH CH CH CHCONH 3

2

2

2-Methylpentanamide 2

Cyclohexanecarboxamide

H NCOCH CH CH CH CONH 2

2

2

2

2

2

Hexanediamide 166

In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

21.

Amides and Imides

H 2 N

N

167 C O N H 2

^ ^CHCH CH CH^ CONH 2

2

Downloaded by CORNELL UNIV on June 21, 2012 | http://pubs.acs.org Publication Date: June 1, 1974 | doi: 10.1021/ba-1974-0126.ch021

Compounds of the types R C O N H R ' and R C O N R ' R " are named as JV-substituted amides, excepting when the nitrogen atom is part of a ring; in that case they are named as substituted heterocyclic compounds.

CH3 CH3

J J CH CH CH CHCONCH=CH 3

2

2

COCHnCH

I

===

iV-Ethenyl-iV,2-dimethylpentanamide 2

CH^

O -N.

l-( 3-Butenoyl)azacyclopenta-2,4-diene

Likewise, compounds of the types ( R C O ) N H a n d ( R C O ) N , whether all R groups are alike or different, are best treated as N-substituted amides. For unsymmetrical structures the largest or most complex acyl group is preferably expressed in the parent name.. 2

CH CH CONHCOCH CH 3

/ \

2

2

3

N-Propanoylpropanamide

3

\—CON(COC= CCH ) / 3

2

N,N-Di-2-butynoylcyclohexanecarboxamide

Amides in which the —CONH— group is part of a ring, often called lactams, are best named as heterocyclic compounds—i.e., as ketones.

H Azacyclohexan-2-one

In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

168

NOMENCLATURE OF ORGANIC COMPOUNDS

Similar treatment is generally to be preferred for imides, although systematic names expressing the imide function as a suffix may be formed by replacing the edioic acid ending o f the corresponding dibasic acid name with imide or b y changing the ending dicarboxylic acid to dicarboximide. H

Downloaded by CORNELL UNIV on June 21, 2012 | http://pubs.acs.org Publication Date: June 1, 1974 | doi: 10.1021/ba-1974-0126.ch021

Azacyclohexane-2,6-dione Pentanimide

2-Azabenz [f] indan-1,3-dione 2,3-Naphthalenedicarboximide

Thioamides are named analogously to amides b y using the suffixes thioamide and carbothioamide (see Examples 15-18 in Table 21.1). Thioimides should be named as heterocyclic compounds (see Example 19). When the amide or imide function must be named as a substituting group, one o f two types o f prefix names is usually applicable. If attachment is through the carbon atom(s), the prefixes carbamoyl for H N C O — and iminodicarbonyl for —CONHCO— are used; if attachment is through the nitrogen atom, the prefix name is formed b y changing the final e o f the amide or imide name to o although for imide groups heterocyclic names are to be preferred. 2

Methyl 4-carbamoylcyclohexanecarboxylate

H NCO 2

CH =CHCH CONHCH CH COOH 2

2

2

2

3-(3-Butenamido)propanoic acid

2-( 1,3-Dioxo-2-azaindan-2-yl)ethanesulfonic acid 2-( 1,2-Benzenedicarboximido)ethanesulfonic acid

Alternatively, substituting groups of the types ( R C O ) N — and RCON