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What is the IUPAC nomenclature of alkane with higher $\ce{C}$ atoms (more than 200)? Example, what is the IUPAC nomenclature of $\ce{C_{205}H_{412}}$?

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2 Answers 2

up vote 15 down vote accepted

The definitive answer is, of course, in the rules established by the IUPAC’s “Commission on nomenclature in organic chemistry”. The reference you are looking for is:

“Extension of Rules A-1.1 and A-2.5 Concerning Numerical Terms Used in Organic Chemical Nomenclature”, Pure Appl. Chem., 1986, 58, 1693-1696

which can be found here as a PDF and here as an HTML version. In particular:

NT-1.1 - The fundamental numerical terms for use in hydrocarbon names or as multiplying prefixes for simple features are given in the following list:

1 mono- or hen-* 10  deca-      100 hecta-      1000  kilia-
2   di- or do-*  20 icosa-**    200 dicta-      2000    dilia-
3   tri-         30 triaconta-  300 tricta-     3000    trilia-
4   tetra-       40 tetraconta- 400 tetracta-   4000    tetralia-
5   penta-       50 pentaconta- 500 pentacta-   5000    pentalia-
6   hexa-        60 hexaconta-  600 hexacta-    6000    hexalia-
7   hepta-       70 heptaconta- 700 heptacta-   7000    heptalia-
8   octa-        80 octaconta-  800 octacta-    8000    octalia-
9   nona-        90 nonaconta-  900 nonacta-    9000    nonalia-

So, C205H412 is the molecular formula of pentadictane. C7547H15096 is heptatetracontapentactaheptaliane.

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Presuming it is linear, then it should follow the trend of the higher alkanes.

For $\ce{C10}: \ce{CH3(CH2)8CH3}$ - the name is decane (deca means ten).

For $\ce{C20}: \ce{CH3(CH2)18CH3}$ - the name is icosane (icos means twenty)

For $\ce{C25}: \ce{CH3(CH2)23CH3}$ - the name is pentacosane

After icosane, the higher alkanes follow the following:

For $\ce{C30}: \ce{CH3(CH2)28CH3}$ - the name is triacontane

For $\ce{C40}: \ce{CH3(CH2)38CH3}$ - the name is tetracontane

For $\ce{C50}: \ce{CH3(CH2)48CH3}$ - the name is pentacontane


For $\ce{C100}: \ce{CH3(CH2)98CH3}$ - the name would be decacontane

For $\ce{C200}: \ce{CH3(CH2)198CH3}$ - the name would probably be icosacontane

And for $\ce{C205}: \ce{CH3(CH2)203CH3}$ - the name might be pentacosacontane

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From wikipedia, the name for $C_{100}$ is hectane. –  lambda23 Nov 18 '12 at 13:12
And I have learned something. –  Ben Norris Nov 19 '12 at 2:23

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