Abstract
The aim of this study was the conclusion of simple kinetic equations to describe <i>ab initio</i> initiated nonbranched-chain processes of the saturated free-radical addition to the double bonds of unsaturated molecules in the binary reaction systems of saturated and unsaturated components. In the processes of this kind the formation rate of the molecular addition products (1:1 adducts) as a function of concentration of the unsaturated component has a maximum. Five reaction schemes are suggested for this addition processes. The proposed schemes include the reaction competing with chain propagation reactions through a reactive free radical. The chain evolution stage in these schemes involves three or four types of free radicals. One of them is relatively low-reactive and inhibits the chain process by shortening of the kinetic chain length. Based on the suggested schemes, nine rate equations (containing one to three parameters to be determined directly) are deduced using quasi-steady-state treatment. These equations provide good fits for the nonmonotonic (peaking) dependences of the formation rates of the molecular products (1:1 adducts) on the concentration of the unsaturated component in binary systems consisting of a saturated component (hydrocarbon, alcohol, etc.) and an unsaturated component (alkene, allyl alcohol, formaldehyde, or dioxygen). The unsaturated compound in these systems is both a reactant and an autoinhibitor generating low-reactive free radicals. A similar kinetic description is applicable to the nonbranched-chain process of the free-radical hydrogen oxidation, in which the oxygen with the increase of its concentration begins to act as an oxidation autoingibitor (or an antioxidant). The energetics of the key radical-molecule reactions is considered.
Highlights
A free radical may be low-reactive if its unpaired p-electron may be delocalized, e.g., over conjugated bonds as in the case of allyl radical CH2=CHĊH2 or along a double bond from carbon to the more electron-affine oxygen as in the case of formyl radical HĊ=O
Curve 1 represents the results of simulation in terms of Eq (3b) for the observed 1:1 adduct formation rate as a function of the mole fraction of the unsaturated component in the phosphorus trichloride–methylpropene1 reaction system at 303 K [19]
The concentration x of the free formaldehyde species in solutions was determined by high-temperature UV spectrophotometry in the range 335–438 K at the total formaldehyde concentration c0 of 1.0–8.4 mol dm–3 in water, ethanediol, methanol, ethanol, 1-propanol, 2-propanol, and 2-methyl-2-propanol [28]
Summary
A free radical may be low-reactive if its unpaired p-electron may be delocalized, e.g., over conjugated bonds as in the case of allyl radical CH2=CHĊH2 or along a double bond from carbon to the more electron-affine oxygen as in the case of formyl radical HĊ=O. American Journal of Polymer Science and Technology 2017; 3(3): 29-49 accumulates an energy of 90–130 kJ mol–1, which is released upon the transformation of the C=C bond to an ordinary bond (according to the data reported for the addition of nonbranched C1–C4 alkyl radicals to propene and of similar C1 and C2 radicals to 1-butene in the gas phase under standard conditions [1,2,3,4]) Such adduct radicals, which do not decompose readily for structural reasons, can abstract the most labile atom from a neighbor molecule of the saturated or unsaturated component of the binary reaction system, turning into a 1:1 adduct molecule.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
