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Download the zipped version of installments 1 - 7 of this series, originally published in the Sci-Tech Translation Journal, of the American Translators Association. The file is approximately 87 KB.

Installments 8 - 15 of this series appeared in the July 1997, October 1997, January 1998, April 1998, July 1998, October 1998, January 1999, and April 1999 issues of the Translation Journal.

VIII. Organic Nitrogen Compounds (continued)

Amides and Polyamides

A carboxylic acid, an ester, an acyl halide, or an acyl anhydride can react with ammonia or with a primary or secondary amine under proper conditions to form an amide, in which nitrogen has replaced an oxygen atom in the carboxyl group:

HC(=O)OH + (CH3)2NH ® H2O + HC(=O)N(CH3)2	N,N-Dimethylformamide (DMF)
CH3C(=O)OH + NH3 ® H2O + CH3C(=O)NH2	Acetamide
CH3C(=O)Cl + CH3NH2 ® HCl + CH3C(=O)NHCH3	N-Methylacetamide
CH3CH2C(=O)OCH3 + C2H5NH2 ® CH3OH + CH3CH2C(=O)NHC2H5	N-Ethylpropionamide
	Maleamic acid
	Maleimide

In 1954, Wallace M. Carothers of E. I. du Pont de Nemours and Company extended the synthesis of amides to dicarboxylic acids and diamines, producing a linear polyamide he called Nylon (a contraction of NY and London):

n HO₂C(CH₂)₄CO₂H + n H₂N(CH₂)₆NH₂ ®
n HO-[C(=O)(CH₂)₄C(=O)NH(CH₂)₆NH]_n-H + (2n - 1) H₂O
Nylon-6,6

The name Nylon-6,6 of course denotes the use of a 6-carbon dicarboxylic acid (adipic acid) and a 6-carbon diamine (hexamethylenediamine). Other forms of Nylon can be made similarly with other starting materials; examples would be Nylon-6,4, Nylon-4,6, Nylon-5,5, and so on.

Amino Acids and Lactams

Any organic compound that contains one or more amino groups and one or more carboxyl groups is rightly called an amino acid. However, in this age of molecular biology, one can be forgiven for immediately thinking of the a-amino acids essential to life, which carry an amino group and a carboxyl group attached to the same carbon atom. They are constituents of proteins, enzymes, antibodies, and other vital compounds contained in all living things, and will be discussed in the next section.
    b-Amino acids can form internal amides (b-lactams) in the form of 4-membered rings:

H2NCH2CH2CO2H ®
	b-Propiolactam

Penicillin, first used in the 1940s as one of the first antibiotics, and later synthesized by Professor John C. Sheehan at M.I.T., proved to be a b-lactam:

Penicillin V

e-Caprolactam (the lactam from e-aminocaproic acid) is the raw material for the manufacture of Nylon-6. This version of Nylon has only a single 6-carbon precursor and thus has only a single digit in its name:

n

+ H2O ® H-[NH(CH2)5CO]n-OH   Nylon-6

IX. a-Amino Acids, (Poly)peptides, and Proteins

All of life, whether animal or vegetable, is based on proteins. Nearly all proteins are linear polyamides (some are cyclic or crosslinked). All are based on the same set of 20 a-amino acids H₂NCH(R)CO₂H, condensed end-to-end (head-to-tail) and therefore linked by -CONH- groups, called peptide linkages.
   The a-carbon in all but the first member of the series of a-amino acids is chiral in nature since it carries four different substituents, -NH₂, -H, -R, and -CO₂H. What is most surprising about the amino acids of proteins found in living matter, whether a gardenia or an aardvark, is that all of them have the levo (S) configuration. In fact, you are levorotatory yourself! In theory, life based on (R)-amino acids should be just as viable as the life that actually exists on Earth (assuming the availability of suitable (R)-nutrients). When life originated from a primordial “soup,” there was just as great a chance that it would have had the (R) configuration as the (S). This fact has been advanced as evidence that life (on Earth at least) originated only once, and that all living forms evolved from this original self-replicating system. At the risk of diverging somewhat from the subject of organic nomenclature, the following article from Chemical & Engineering News (9/22/97) is of more than passing interest in this regard:

The essential a-amino acids are invariably designated by their trivial names. For convenience they have been assigned the three-letter abbreviations shown below.

The 20 Essential a-Amino Acids

Undoubtedly most readers will be familiar with L-glutamic acid in its half-neutralized form of monosodium glutamate (MSG). Other amino acids in the list sometimes find use as dietary supplements.
   A careful study of the formula of penicillin given above will reveal that it contains the structural skeletons of cysteine and valine:

(Illustration from William H. Brown, Introduction to Organic Chemistry, © 1975 by Willard Grant Press, Boston, MA; p. 389).
   The complex structural and sterochemical nature of proteins is clearly illustrated by the following depiction of a polypeptide that constitutes a small portion of a protein:

Ala-Ser-Asp-Leu-Glu-Phe-Val

(From Daniel S. Kemp and Frank Vellaccio, Organic Chemistry, © 1980 by Worth Publishers, Inc., New York, NY; p. 1001).

Part XVII will continue the discussion of proteins and polypeptides.

Readers are urged to e-mail questions, comments, or suggestions for further topics in the field of organic nomenclature to the author at: 74654.1335@compuserve.com.