A Translator’s Guide to Organic Chemical Nomenclature

From context faxed to me, it was clear that the "FG" (Fluchtgruppe) was the focal point of a reaction with an arylamine, as follows:

+  ArNH2   →

+  HFG.

FG was also defined as being -Cl, -Br, or p-CH₃C₆H_4SO₂- (a p-toluenesulfonyl group). We concluded that FG had nothing to do with alignment, perspective, or vanishing point (which our dictionaries suggested), but rather with "escape." Our ultimate decision was:

Fluchtgruppe = "leaving group."

A more conventional term in German would be "Austrittsgruppe" (in French "groupe partant").

As for Fluchtpunkt, this turned out (we believe) to be entirely unrelated to either "Fluchtgruppe," alignment, or vanishing point. The only available context was:

Fluchtpunkt = 173-175 °C.

We believe Fluchtpunkt may have been an incorrect expansion of Fp (Fliesspunkt, melting point), or is intended to imply a "melting range" or "flow point" instead of a distinct melting point. Feedback on our interpretation would be welcome.

Let's return now to our patent from Part XX, in which we discussed thiazoles and oxazoles with the formula

It would be a good exercise to look at the structures permitted by the patent for R₅:

R₅ eine Hydroxy-, Alkoxy-, Carboxy-, Alkoxycarbonyl-, Aminocarbonyl-, Alkylaminocarbonyl-, oder Dialkylaminocarbonylgruppe, eine Alkoxygruppe mit 1 bis 6 Kohlenstoffatomen, die endständig durch eine Carboxy-, Alkoxycarbonyl-, Aminocarbonyl-, Alkylaminocarbonyl- oder Dialkylaminocarbonylgruppe substituiert ist, eine Alkoxygruppe mit 2 bis 7 Kohlenstoffatomen, die endständig durch eine Hydroxy-, Alkoxy-, Phenylalkoxy-, Amino-, Alkylamino-, Dialkylamino-, Pyrrolidino-, Piperidino- oder Hexamethyleniminogruppe substituiert ist, oder eine gegebenenfalls durch eine Alkylgruppe substituierte Ethenylengruppe, die endständig durch eine Carboxy-, Alkoxycarbonyl-, Aminocarbonyl-, Alkylaminocarbonyl- oder Dialkylaminocarbonylgruppe substituiert ist,

wobei alle vorstehend erwähnten Alkyl-, Alkoxy- oder Alkanoylgruppen, sofern nichts anderes erwähnt wurde, jeweils 1 bis 3 Kohlenstoffatome und die vorstehend erwähnten Alkenylgruppen 3 bis 5 Kohlenstoffatomen enthalten können, bedeutet, deren optische Isomere und deren Diasteromere sowie deren Säureadditionsalze.

The translation of this provision is completely straightforward. Let's review each of these permitted substituents one at a time:

hydroxy	-OH
alkoxy	-OR
carboxy	-COOH
alkoxycarbonyl	-COOR
aminocarbonyl	-CONH2
alkylaminocarbonyl	-CONHR
dialkylaminocarbonyl	-CONR2
phenylalkoxy	-OCH2CH2C6H5 (an example)
amino	-NH2
alkylamino	-NHR
dialkylamino	-NR2
pyrrolidino		(preferably called 1-pyrrolidinyl)
piperidino		(preferably called 1-piperidinyl)
hexamethylenimino
ethenylene (group)	-CH=CH-

To choose one of the very numerous options available for the compound, let's decide that R₅ is an alkoxy group with 5 carbon atoms, substituted by a terminal dialkylaminocarbonyl group in which the alkyl group has one carbon atom.

Our compound is now

.

The product has two optical isomers with (R) and (S) configurations around the chiral center marked with an asterisk. It can form salts with acids at the ring nitrogen and at the nitrogen attached to R₄.

Hexamethylenimine, depicted as its radical above, is a common name for azacycloheptane. The term "imine" generally implies a ring nitrogen atom single-bonded to two carbon atoms, or a double-bonded nitrogen as in R₂C=NH. The term can also be used loosely as in "iminodiethanol" for diethanolamine HOCH₂CH₂NHCH₂CH₂OH. Iminourea is another name for guanidine (NH₂)₂C=NH.

It's worth pointing out that the patent is published in German, French, and English. The German "Ethenylengruppe," however, has been mistranslated as "ethylene group" in the English version, which is obviously inconsistent. Such errors can lead to patent validity lawsuits and very unpleasant legal situations. Even patent attorneys can be wrong!

As a last exercise from this patent, we will now attempt to explain how a chemical structure can be derived from the formidable chemical name in Claim 5:

N-[2-(4-carboxymethoxyphenyl)-1-methylethyl]-2-(2-trifluoromethylthiazol-4-yl)morpholine.

First, it's easiest to start with everything that is not within parentheses, namely N-, 2-, and morpholine. The compound is morpholine with substituents on the nitrogen and in the 2-position:

Next consider the substituent on N. To do this, first look at what is inside the square brackets but not in parentheses: 2-, and 1-methylethyl. This will be a 1-methylethyl group with a substituent in the 2-position:

The substituent in the 2-position of 1-methylethyl is 4-carboxymethoxyphenyl:

We now have the N-substituent in its entirety:

The 2-substituent is 2-trifluoromethylthiazol-4-yl:

It remains only to reassemble the morpholine molecule with its two substituents:

The ability to reconstruct a compound's structure from its name may seem to a translator to be an exotic or unnecessary talent, but it leads to a more thorough understanding of the subject matter and inevitably to a better translation. It may surprise those who have followed this Series diligently that they have acquired this ability. All of the steps in this discussion have been discussed in earlier installments. All that is now needed is practice.

Try it!