Quantum Low-Temperature Limit of a Chemical Reaction Rate

Abstract

The radiation-induced polymerization of formaldehyde has been studied in the solid state. The time of addition of one new link to a polymer chain increases exponentially in accordance with the Arrhenius law at 140 to 80 K, but approaches a constant value (approximately 10(-2) second) at temperatures below 10 K. Thus, a low-temperature limit to a chemical reaction rate has been observed. It is interpreted as a quantum effect caused by tunneling from the zero vibration level of the initial state, and a semiquantitative theory is given. The phenomenon should be taken into account for understanding tunneling of electrons in biological systems when such tunneling is accompanied by conformational changes. It could also be significant in slow, exothermic chemical reactions at low and ultralow temperatures, which may have had a role in chemical and biological evolution (cold prehistory of life?).

The Hund paradox and stabilization of molecular chiral states

“…where # "[exp(E/k ¹ )!1]\ is the occupation number for phonons with energy E. Taking into account that in (20) summation over k can be replaced by integration and making evident transformations, we arrive at the following expression for the incoherent tunnelling rate (21) is identical to the expression for ¼ obtained in earlier publications [12,36].…”

“…It relies on the phenomenon of the low-temperature quantum limit of a chemical reaction rate [20] and on the discovery of some fairly complex organic compound (ranging up to amino acids) in the interstellar medium [21][22][23][24]. According to this concept, the main stage of the formation of prebiotic polymers is hypothetically represented by the grains of dust of dense interstellar clouds and more explicitly, by the dirty ice mantles surrounding the cores of these grains.…”

Comets as a possible source of prebiotic molecules

“…To the first group belong the experiments of Goldanskii et al (1973), Brown et al (1978, 1980, 1982, 1983a, 1983b, 1985), Strazulta et al (1984, Pirronello (1985), Khare et aL (1989), and Sandford and Allamandola (1990). To the second group belong the experiments of Greenberg (1982), Allamandola et al (1988 and Schutte et al (1992).…”

Organic reactions in the solid state: accident and design

“…But it has recently been established by Goldanskii and coworkers (46,47) that the polymerization of formaldehyde, as well as certain reactions of olefinic double bonds, is kinetically independent of temperature in the range 140 to 4 K.…”