What is the IUPAC nomenclature of alkane with large numbers of C atoms (more than 200)?

What is the IUPAC nomenclature for alkanes with large numbers of $\ce{C}$ atoms (more than 200)? For example, what is the IUPAC accepted name for $\ce{C\_{205}H\_{412}}$?




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](http://www.iupac.org/publications/pac/1986/pdf/5812x1693.pdf) and [here as an HTML version](http://www.chem.qmul.ac.uk/iupac/misc/numb.html). 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:
> 
> 
> \begin{array}{|c:c|c:c|c:c|c:c|}\hline
>  1&\rm \text{mono- or hen-} &10 &\rm \text{deca-}&100&\rm \text{hecta-}& 1000&\rm \text{kilia-} \\\hline
>  2&\rm \text{di- or do-}&20&\rm \text{icosa-}&200&\rm \text{dicta-}&2000&\rm \text{dilia-}\\\hline
>  3&\rm \text{tri-}& 30&\rm \text{triaconta-}&300&\rm \text{tricta-}&3000&\rm \text{trilia-} \\\hline
>  4&\rm \text{tetra-}&40&\rm \text{tetraconta-}&400&\rm \text{tetracta-}&4000&\rm \text{tetralia-} \\\hline
>  5&\rm \text{penta-}&50&\rm \text{pentaconta-}&500&\rm \text{pentacta-}&5000&\rm \text{pentalia-}\\\hline
>  6&\rm \text{hexa-}&60&\rm \text{hexaconta-}&600&\rm \text{hexacta-}&6000&\rm \text{hexalia-}\\\hline
>  7&\rm \text{hepta-}&70&\rm \text{heptaconta-}&700&\rm \text{heptacta-}&7000&\rm \text{heptalia-}\\\hline
>  8&\rm \text{octa-}&80&\rm \text{octaconta-}&800&\rm \text{ octacta-}&8000&\rm \text{octalia-}\\\hline
>  9&\rm \text{nona-}&90&\rm \text{nonaconta-}&900&\rm \text{nonacta-}&9000&\rm \text{nonalia-}\\\hline
> \end{array}
> 
> 
> 


So, $\ce{C\_205H\_412}$ is the molecular formula of pentadictane. $\ce{C\_7547H\_15096}$ is heptatetracontapentactaheptaliane.


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Presuming it is linear, then it should follow the trend of the [higher alkanes](http://en.wikipedia.org/wiki/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 


So... 


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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