Abstract
From elemental particles to human beings, matter is dissymmetric with respect to mirror symmetry. In 1860, Pasteur conjectured that biomolecular handedness— homochirality—may originate from certain inherent dissymmetric forces existing in the universe. Kipping, a pioneer of organosilicon chemistry, was interested in the handedness of sodium chlorate during his early research life. Since Kipping first synthesized several Si-Si bonded oligomers bearing phenyl groups, Si-Si bonded high polymers carrying various organic groups—polysilanes—can be prepared by sodium-mediated condensation of the corresponding organodichlorosilanes. Among these polysilanes, optically active helical polysilanes with enantiomeric pairs of organic side groups may be used for testing the mirror symmetry-breaking hypothesis by weak neutral current (WNC) origin in the realm of chemistry and material science. Several theoretical studies have predicted that WNC-existing chiral molecules with stereogenic centers and/or stereogenic bonds allow for distinguishing between image and mirror image molecules. Based on several amplification mechanisms, theorists claimed that minute differences, though still very subtle, may be detectable by precise spectroscopic and physicochemical measurements if proper chiral molecular pairs were employed. The present paper reports comprehensively an inequality between six pairs of helical polysilane high polymers, presumably, detectable by (chir)optical and achiral 29Si-/13C- NMR spectra, and viscometric measurements.
Highlights
Why does matter dominantly exist in the universe? Why is the universe inherently chiral and asymmetric? What is the origin of biomolecular handedness in life—homochirality—on the blue planet?Several explanations have already been proposed for these questions and can be seen in many monographs and reviews [1−48]
The present paper reported comprehensively the experimental tests of an equality and an inequality observed in chiroptical, 29Si-/13Si-NMR, and viscometric measurements for six pairs of helical polysilanes carrying ambidextrous chiral side groups
To evaluate the molecular parity violation (MPV) effect induced by weak neutral current (WNC), excluding the effects caused by the PC electromagnetic force, we can compare the apparent dimensionless Kuhn's dissymmetry factors between a pair of helical polysilanes in isotropic solution, which are defined as gCD = Δε/ε, where Δε and ε are the apparent circular dichroism (CD) and UV intensities
Summary
Why does matter dominantly exist in the universe? Why is the universe inherently chiral and asymmetric? What is the origin of biomolecular handedness in life—homochirality—on the blue planet?. A pioneer of organosilicon and polysilane chemistry, and Pope assumed that biomolecular homochirality is applicable to purely inorganic substances They examined thousands of crystals produced from achiral NaClO3 (molecular symmetry, C3v, but, crystal exists as D- and L-forms) to test the preference between left and right by mirror symmetry-breaking crystallization [1]. Schwerdtfeger et al predicted theoretically the large MPV effects for the chiral NWHClI molecule from relativistic density functional theory, revealing mirror symmetry breaking in N–W stretching frequency of 0.7 Hz in IR region Because this value could be detectable by an ultrahigh-resolution CO2 laser spectrometer [66], the work was highlighted as a cover picture of a chemistry journal. The present paper reported comprehensively the experimental tests of an equality and an inequality observed in chiroptical, 29Si-/13Si-NMR, and viscometric measurements for six pairs of helical polysilanes carrying ambidextrous chiral side groups
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