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Is the radioisotope of hydrogen considered as a new atom? Can you detect it with an H NMR?

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  • $\begingroup$ Just to address what the answers don't answer - yes, you should be able to pick this up the 1H or 3H NMR as the couplings are different in these two different species. $\endgroup$
    – Ian Bush
    Mar 21, 2018 at 8:43

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Yes isotopes can induce geometric isomerism. You can induce chirality by using different isotopes of atoms; the molecule $\ce{CHDClF}$ is chiral with the deuterium atom (you do not need radioactivity) while ordinarily $\ce{CH_2ClF}$ is not. Chirality won't work for ethylene (that molecule is still planar and thus mirror-symmetric about its own plane no matter what iostopes are used for any atoms), but cis-trans isomerism with two deuterium atoms still can work.

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  • $\begingroup$ So compounds like $\ce{CHDTCl}$ rotate the plane-polarized light or in other words show optical activity. Could you please tell whether my conclusion from your answer is correct, as I think optical activity (due to difference in the counter-rotating circularly polarizing light) is because of chemical properties (attributed to valence electrons, spatial orientation, etc.,) and not physical properties (like different atomic masses of isotopes) ? $\endgroup$
    – Vishnu
    Sep 22, 2019 at 8:54
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    $\begingroup$ Neutrons are made up of quarks which are charged, so can interact with electromagnetic radiation. Differences in number of neutrons can thus show up as rotation of polarized light. $\endgroup$ Sep 22, 2019 at 9:44
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Actually we define geometric isomerism to just differ between compounds. As the cis and trans forms of that compound are different they will have geometric isomerism.

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