Can $\ce{CD4}$ or $\ce{CT4}$ be considered an alkane?

I know that an alkane is $\ce{C_nH_p}$ where $p = 2n + 2$. An alkane is considered a "hydro"carbon, i.e., a compound containing purely carbon and "hydrogen" only. However, "hydrogen" has mainly three isotopes: protium ($\ce{^1_1H}$ or $\ce{H}$), deuterium ($\ce{^2_1H}$ or $\ce{D}$) and tritium ($\ce{^3_1H}$ or $\ce{T}$).

Thus, in general, can $\ce{C_nH_xD_yT_z}$ be considered an alkane/ene/yne, where $x, y, z \in \{ 0, 1,\dots,2n + 2 / 2n /2n-2 \}$ and $x + y + z = 2n + 2 / 2n /2n-2$?

  • 1
    $\begingroup$ What is the meaning of $2/2n/2n$ ? $\endgroup$
    – Maurice
    Mar 29, 2023 at 8:34
  • $\begingroup$ @Maurice Correlate it with alkane/ene/yne : 2n+2/2n/2n-2. $\endgroup$
    Mar 29, 2023 at 9:50
  • $\begingroup$ You are asking a question about CD4 before introducing D. This is bad. $\endgroup$ Mar 29, 2023 at 9:59

1 Answer 1


Yes, they are still alkanes and they are named deuterated/tritiated alkanes. It's correct that alkanes are primarily considered hydrocarbons but if the hydrogen is replaced with deuterium/tritium, the names are also changed and this replacement is not a theoretical one. Practically this is possible (ACS Catal. 2018, 8, 3, 2296–2312).

  • $\begingroup$ Can we call them D/T-substituted alkane? $\endgroup$
    Mar 29, 2023 at 5:07
  • 3
    $\begingroup$ @CHEMUMAN Is $\ce{H2^{18}O}$ water? Yes, it is. $\ce{CD4}$ is nothing else but $\ce{C^{2}H4}$. Do not let convention $\ce{^{2}H}$ being written as $\ce{D}$ confuse you. H in CH4 means hydrogen, not protium. $\endgroup$
    – Poutnik
    Mar 29, 2023 at 10:57
  • $\begingroup$ @Poutnik What do you mean is that $\ce{CH_4}$ is actually a mixture of various compounds of isotopes of carbon & isotopes of hydrogen(e.g.: $\ce{^14_6C _1^3H_4}$ is also methane), isn't it? $\endgroup$
    Mar 29, 2023 at 11:17
  • 6
    $\begingroup$ @CHEMUMAN Yes, I do. There is nowhere said methane is a compound of carbon-12 and hydrogen-1. Molecules differing just by isotopic composition are called Isotopologues // Hydrogen is exception just formally, having dedicated symbols for its isotopes, as they have relatively biggest differences due the biggest relative mass differences. So H, D, T as hydrogen-1, hydrogen-2 and hydrogen-3 formally look like 3 different elements, while being just one. $\endgroup$
    – Poutnik
    Mar 29, 2023 at 12:03
  • $\begingroup$ @Poutnik The link provided by you really helped. Thanks. $\endgroup$
    Mar 29, 2023 at 13:27

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