Saturday, October 02, 2021

[yokhrunz] simplest chiral molecule

chlorofluoroamine, perhaps written NHClF, atomic mass 69.466 amu, has a central nitrogen bonded to 1 hydrogen, 1 fluorine, 1 chlorine, and 1 lone pair.  it is therefore a candidate to be the simplest chiral molecule.  however, at room temperature, it seems that lone pair electrons are "liquid" and can sneak to the other side, mirror-imaging the molecule, perhaps going through a planar intermediary.

therefore the simplest chiral molecule, by number of atoms, is bromochlorofluoromethane CHBrClF (147.374 amu).

how big is bromine?  this being chemistry, we probably care about the size of the outer electron shells.  perhaps it is bigger than a methyl group, so 1-chloro-1-fluoroethane, CH3CHClF (82.5044 amu), is smaller, arguably simpler.  what about a fluoromethyl group, i.e., 1,2-difluoropropane CH2F-CHF-CH3 (80 amu)?

smaller electronically than a methyl group (15 amu) might be an hydroxy group (17 amu), so chlorofluoromethanol CHClFOH (84.47 amu), and an amino group (16 amu), so aminofluoromethanol NH2-CHF-OH (65 amu).  1-aminoethanol NH2-CH(OH)-CH3 (61 amu) minimizes mass.  some of these might be self-reactive, not stable.  note that a fluorine atom is 19 amu.

one could attach two different hydrogen isotopes protium (H) and deuterium (D) to the central carbon: deuterated chlorofluoromethane CHDClF (69.46 amu), deuterated ethanol CH3-CHDOH (47 amu).  deuterium sometimes behaves chemically significantly differently from protium; does it happen for either of these compounds?  tritium probably does not behave chemically differently from deuterium, and it's radioactive, not stable.

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