Theory:Old Nomenclature

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Newer Version of IUPAC Nomenclature

The newer version will have the following rules:

(The following system is the brainchild of Yunzhong Hou.)

Basic and Branched Hydrocarbons

The principal tenet of the newer system is mass abbreviation. As a result, we adopt the following syllables for alkanes. In fact, all of the nomenclature under the new system will be composed of discrete syllables, generally shortened forms of the currently more known terms.


  1. Ca, contraction of carbon
  2. Di, contraction of di-carbon
  3. Tri, contraction of tri-carbon
  4. Tet, contraction of tetra-carbon
  5. Pent
  6. Hex
  7. Sept
  8. Oct
  9. Non
  10. Dec

Unless otherwise mentioned, each carbon atom under the new nomenclature is assumed to be surrounded by as many hydrogen atoms as possible.

Unlike under the current nomenclature, the stem would come first, and everything builds off of the stem. Therefore, the first letter of the stem is capitalized, and nothing else is.

For branches, we attach a dash (-) and follow with the syllable for whatever comes next.

Therefore, methane would be Ca, and ethane would be Di. Isopropane would be Tri-ca.

For alkenes, we attach a -de, so that ethene becomes Di-de. In the case that the location of the double bond is questioned, we add the numeric component between the stem and the de. In 2-butene, the double bond is in the middle, so we get Tet-2-de. The two forms of 2-butene are cis-2-butene and trans-2-butene. In the new nomenclature, the former becomes Tet-2-de and the latter becomes Tet-2-trans.

For alkynes, we attach a -y, so that ethyne becomes Di-y. The y is pronounced with a "yee" sound and not an "e" sound to separate it from the Di.

Cyclic Hydrocarbons

Under the new nomenclature, we add a -cy directly after the stem to denote its cyclical nature. For example, cyclobenzene would become Tet-cy. The Tet refers to the four carbons and the cy refers to its cyclical nature.

Benzenes are directly referred to as Z. Therefore, phenol becomes Z-ol (more on alcohol groups later). In addition, each carbon in benzene is also given a number in any order desired (for stems) and a 1 when joined with a chain. If joined with another benzene on a side, it then becomes the same as the numerical value shared on the other side. For example, the side-joined napthalene becomes Z-z or more specifically Z-1,2-z (because there are only two benzenes involved, the middle part is optional because it does not affect meaning). In the case of anthracine, which is composed of a benzene ring joined with other benzene rings on each side, the new nomenclature would be Z-1,2-z-z. Note that if the first benzene's carbons are labeled clockwise, every even benzene's carbons would be labeled counterclockwise and every odd benzene's carbons would be labeled clockwise.

Functional Groups


For the haloalkanes, the new nomenclature simplies:

  • chlor instead of chloro
  • bro instead of bromo
  • io instead of iodo

These are treated just like the methyl/ca groups as described under the alkane section.

Aldehydes and Ketones

The aldehydes and ketones are similar, only instead of a halogen we have an oxygen atom double-bonded to a carbon atom. This is represented by ox instead of the others. Note that under this system, aldehydes and ketones are represented in the same way.


Alcohols' syllable is ol. Therefore, ethanol becomes Di-ol, and 1-butanol becomes Tet-1-ol. Glycerol becomes Di-1,2-ol.

Carboxylic Acids

Carboxylic acids, COOH, become car. Therefore, acetic acid becomes Ca-car.


The syllable for nitrogen by itself is ni.

The syllable for NH2 is am.

The syllable for NO2 is nitro.

Esters and Ethers

These compounds have oxygen in the middle, separating two other compounds.

Oxygen between two carbon subchains is referred to as -ox-. Generally, they would need to be grouped (see below).

Logic in the New Nomenclature


Generally, charges result from additional or reduced Hydrogen atoms. Wherever it is missing, attach -min-, so the syllable for NO is -nitro-min-. Wherever it is in excess, attach -max-, so the syllable for NO3 is -nitro-max-. In the case of multiple hydrogens lost or in excess, the min and max must be stated repeatedly.


In the case of branches with sub-branches, the branches should be placed in structures. For example, consider EDTA (Ethylene-diamine-tetraacetic-acid), a chelate used in lead poison antidotes and measurement of water hardness. The four arms of EDTA are all acetates, and this can therefore be represented with -set-ca-car-end-, in which ca-car refers to acetic acid (or alternatively acetate, depending on what it is attached to) and the set and end signal the beginning and end points of the structure, respectively.

Structures are useful for describing a compound in which sub-branches and/or multiple identical branches exist. For example, we return to EDTA. The following are steps to follow in nomenclature of EDTA:

  1. The center of EDTA is the two carbon atoms. Therefore we have Di-.
  2. Adjacent to each central carbon is a nitrogen atom. Therefore, we now have Di-1,2-set-ni-. The set is used because we are considering each nitrogen and everything attached to it as a structure.
  3. Each nitrogen atom is in turn attached to two acetates. Therefore, we now have Di-1,2-set-ni-1,1-set-ca-car-. The second set signals a sub-structure. Since each nitrogen atom is attached to two acetates, we have to refer to them separately, and the acetates are obviously attached to the first atom in a single nitrogen atom.
  4. We have now considered all of the atoms. We finish by closing the structures. Therefore, we how have Di-1,2-set-ni-1,1-set-ca-car-end-end. This is the final nomenclature for EDTA.

Advantages of the Newer Version

There are now rules for a hydrocarbon with one or more of both a double bond and a triple bond. Can you guess what Tet-1-de-3-y is?

Not as easily confused by the new nomenclature, especially when many distinct components are involved. Granted, the learning of the new nomenclature is what is hard.

Can name compounds with any number of ions.

Benzene compounds can all be described with the above rules, without the need for anything else.

Compounds with multiple distinct formula groups can now easily fit into the syllable structure.

Can now handle sub-branches of branches with ease, to any degree and extent, no matter where the sub-group is. For example, if C20 had a branch with 5 carbons and that branch in turn had a methyl group attached, this would be represented with icosa-8-pent-2-ca.

As with the old system, names from the new nomenclature can be spoken as written.

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