Subtraction prefix

In chemical nomenclature , subtraction prefixes (subtraction = deduction, deletion; prefix = prefix) are used to indicate that something has been split off from a parent compound or that something is "missing". The designation (the name) of the master connection must then be added accordingly.

Examples of subtraction prefixes

Examples of such subtraction prefixes are Des- , Nor- and Anhydro- :

Of-

• "Des-methyl-" means that the compound in question lacks a methyl group (= has been replaced by a hydrogen atom)
• Deoxy sugars are carbohydrates in which a hydroxyl group has been replaced by a hydrogen atom
• In the des-carotenoids all methyl groups are missing

In rare cases the prefix also stands for the ring opening of a base with the empirical formula remaining the same.

Anhydrous

Anhydro tetracycline with the blue marked C = C double bond, which results from the elimination of water from tetracycline.

Comparison: structural formula of the parent compound tetracycline

North

The prefix can have different meanings, which sometimes leads to confusion:

• Norephedrine contains one less methyl group than ephedrine
• Norbornane contains three fewer methyl groups than bornane
• "Nor-" can also stand for a narrowing of the ring , i.e. the absence of a methylene group (–CH ₂ -) in the ring. For example, norsteroids are those whose ring A is a five-membered ring instead of the usual six-membered ring in the steroid .

Anhydrous

The prefix stands for

• intramolecular dehydration between two hydroxyl groups to form an ether ( IUPAC- compliant designation)
• intramolecular splitting off of water from a mostly complex alcohol with the formation of a C = C double bond

See also

• Descriptor (chemistry)

Individual evidence

1. ^ Duden Online: Subtraction
2. ^ Duden Online: Prefix
3. ^ Philipp Fresenius and Klaus Görlitzer: Organic-chemical nomenclature , Wissenschaftliche Verlagsgesellschaft Stuttgart, 1991, 3rd edition, pp. 136-139, ISBN 3-8047-1167-7 .
4. ^ ^{A b} Wolfgang Holland: The nomenclature in organic chemistry , VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1969, pp. 35-40.
5. ^ Philipp Fresenius and Klaus Görlitzer: Organic-chemical nomenclature , Wissenschaftliche Verlagsgesellschaft Stuttgart, 1991, 3rd edition, p. 139, ISBN 3-8047-1167-7 .