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

Part IX of this series appeared in the October, 1997.issue of the Translation Journal.

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V. Organic Oxygen Compounds (continued)

Carboxylic Acids

In Part IX of this series we saw that compounds with two hydroxyl groups bonded to a terminal carbon atom split off a molecule of water spontaneously to form aldehydes. A similar process occurs when a terminal carbon atom carries three hydroxyl groups, giving rise to carboxylic acids as follows:

The carboxylic acids are usually written as RCO₂H, RC(O)OH, or RC(=O)OH, where R can stand for any organic group. When R is an aliphatic group, the acids are called fatty acids. Depending on whether or not the group R contains one or more double bonds, the fatty acids can be saturated or unsaturated (referred to popularly as monounsaturated or polyunsaturated fatty acids).

Some of the more common fatty acids are described below in Table 11.

Table 11. Representative Fatty Acids

R	Trivial (Common) Name	Systematic Name
H	Formic acid	Methanoic acid
CH3-	Acetic acid	Ethanoic acid
CH3CH2-	Propionic acid	Propanoic acid
CH3CH2CH2-	Butyric acid	Butanoic acid
n-C4H9-	Valeric acid	Pentanoic acid
n-C5H11-	Caproic acid	Hexanoic acid
n-C6H13-	Enanthic acid	Heptanoic acid
n-C7H15-	Caprylic acid	Octanoic acid
n-C8H17-	Pelargonic acid	Nonanoic acid
n-C9H19-	Capric acid	Decanoic acid
n-C11H23-	Lauric acid	Dodecanoic acid
n-C13H27-	Myristic acid	Tetradecanoic acid
n-C15H31-	Palmitic acid	Hexadecanoic acid
n-C17H35-	Stearic acid	Octadecanoic acid
n-C8H17CH=CH(CH2)7-	Oleic acid	cis-9-Octadecenoic acid
n-C5H11CH=CHCH2CH=CH(CH 2)7-	Linoleic acid	cis,cis-9,12-Octadecadienoic acid

  Some possible sources of confusion exist between caproic acid and capric acid, and between linoleic acid and linolenic acid (9,12,15-octadecatrienoic acid, which has three double bonds).
   Halogenated fatty acids are also common. Some examples are:
  chloroacetic acid ClCH₂CO₂H,
  trichloroacetic acid Cl₃CCO₂H,
  a-chloropropionic acid (2-chloropropanoic acid) CH₃CHClCO₂H,
  b-bromopropionic acid (3-bromopropanoic acid) BrCH₂CH₂CO₂H,
  and
  g-iodobutyric acid (4-iodobutanoic acid) ICH₂CH₂CH₂CO₂H.

Note that locants can be of either type. The a-position, on the carbon adjacent to the carboxyl group, is the same as the 2-position.
  In German, Carbonsäure nearly always means carboxylic acid, not carbonic acid which is properly Kohlensäure. In compounds, -carbonsäure always means carboxylic acid and -säure means acid. Thus Essigsäure is acetic acid and Propionsäure is propionic acid. In the case of acetic acid, there are two German terms that require some explanation. Pure acetic acid freezes (and conversely melts) at just below room temperature (62°F, 16.7°C), and may thus be solid or liquid depending on laboratory conditions. Since it freezes so readily, pure acetic acid is called glacial acetic acid in English and Eisessig in German. Small amounts of water liquefy the substance, in which case it is called simply acetic acid or Essigsäure. Vinegar, of course, is dilute acetic acid.
  Locants for cyclic ethers are also designated as a, b, or g, or 2, 3, or 4 with respect to the oxygen atom. Thus furan can give rise to a-furoic acid (2-furancarboxylic acid) or b-furoic acid (3-furancarboxylic acid). Names such as 2-tetrahydrofurancarboxylic acid (2-carboxytetrahydrofuran) or analogous names for its 3-isomer are also acceptable.

Dicarboxylic Acids

Dicarboxylic acids are common in nature and in the laboratory, and have been given their own trivial names. They are used with diols to produce polyesters and are also used to produce polyamides (Nylon). Some of the common ones are listed below in Table 12.

Table 12. Representative Dicarboxylic Acids

A simple mnemonic for remembering the names of the saturated aliphatic a,w-dicarboxylic acids is “Oh My, Such Good Apple Pie, Sweet As Sugar!” (This does not include the unsaturated maleic and fumaric acids).
 

Hydroxy Acids

Some of the simple hydroxy acids have also been given trivial names:

Table 13. Representative Hydroxy Acids

Keto Acids

Some examples with trivial names are:

CH3C(=O)CO2H	Pyruvic acid
CH3C(=O)CH2CH2CO2H	Levulinic acid
HO2CCH2C(=O)CH2CO2H	Acetonedicarboxylic acid
CH3C(=O)CH2CO2H	Acetoacetic acid
Unsaturated Acids In addition to maleic and fumaric acids (Table 12), some important unsaturated acids are:
CH2=CHCO2H	Acrylic acid
CH2=C(CH3)CO2H	Methacrylic acid
CH3CH=CHCO2H	Crotonic acid
HO2CCH2C(=CH2)CO2H	Itaconic acid
HO2CC(CH3)=CHCO2H	Citraconic acid
HO2CCH=C(CO2H)CH2CO2 H	Aconitic acid
HCºCCO2H	Propiolic acid

Acrylic and methacrylic acids are widely used in polymerization to prepare polyacrylic resins.
 

IN THE NEWS - Review your comprehension of Parts I to X:

The November 24, 1997, issue of Chemical & Engineering News reports:

“BP Chemicals to build butanediol plant...

BP Chemicals ... will build a $100 million, 140-million-lb-per-year 1,4-butanediol plant ... Geminox uses a direct dual-reactor route to produce 1,4-butanediol and its derivatives using butane instead of acetylene, butadiene, or propylene oxide, as do other technologies ... 1,4-Butanediol is used to make tetrahydrofuran, which is used to make fibers and solvents...”

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.