Preparation of Flame-Resistant Liquids Based on Mixed Tri(phenyl, p-tert -butylphenyl) Phosphates by Transesterification
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NIC SYNTHESIS AND INDUSTRIAL ORGANIC CHEMISTRY
Preparation of Flame-Resistant Liquids Based on Mixed Tri(phenyl, p-tert-butylphenyl) Phosphates by Transesterification of Triphenyl Phosphate with p-tert-Butylphenol Yu. G. Noskova, T. E. Krona, O. G. Karchevskayaa, and G. A. Korneevaa,* a Joint
Research and Development Center, Moscow, 119333 Russia *e-mail: [email protected]
Received November 13, 2019; revised April 5, 2020; accepted April 17, 2020
Abstract—The possibility of controlling the composition of a mixture of triphenyl phosphate, p-tert-butylphenyl diphenyl phosphate, di(p-tert-butylphenyl)phenyl phosphate, and tri(p-tert-butylphenyl) phosphate, formed by transesterification of triphenyl phosphate with p-tert-butylphenol, was demonstrated. The amount of p-tertbutylphenol necessary for transesterification of triphenyl phosphate to yield a mixture of phosphates of required composition was determined. If necessary, the composition of the phosphates can be adjusted by selective distillation of triphenyl phosphate in a vacuum. Keywords: transesterification, triphenyl phosphate, p-tert-butylphenol, flame-resistant liquids DOI: 10.1134/S1070427220080170
Low-toxic biodegradable flame-resistant oil based on mixed p-tert-butylphenyl phenyl phosphates is widely used as an additive to polymers and lubricants; it is the base of the majority of liquids for hydraulic systems and working lubricating liquids, ensuring accident-free operation of turbines with high parameters of the working medium, including power facilities of nuclear power plants [1–3]. Wide range of functionalized phosphates, phosphonates, and phosphinates can be prepared by catalytic esterification of compounds containing P(O)–OH groups with diaryliodonium triflates [4], with phenols in the presence of silicon chlorides as catalysts [5], and when using as phosphorylating agents white phosphorus [6], phosphorus pentoxide [7], and phosphorylpyridine derivatives [8]. Singh and Nolan [9] reported preparation of phosphates by transesterification in the presence of N-heterocyclic carbenes. However, the process that is widely used for commercial synthesis of triaryl phosphates is based on the reaction of phenols with phosphorus oxychloride: O=PCl3 + 3ArOH → (ArO)3P=O + 3HCl.
(1)
Synthetic flame-resistant butylated oil is prepared using a mixture of phenol and p-tert-butylphenol (BP). The reaction yields an equilibrium mixture of esters 1–4 (Scheme 1) with statistical distribution of components, usually containing 15–30% 1 (in some cases, up to 50%) [1–3, 10]. The quantitative composition of a mixture of esters 1–4 strongly influences the physicochemical and operation properties of the mixture (viscosity–temperature characteristics, pour point, lubricating properties, resistance to hydrolysis and oxidation, deaeration, etc.) and its toxicological characteristics. The composition is usually optimized to impart to the oil the properties meeting the specific requirements. The major components of the oil used for turbine systems are unsymmetrical esters 2 and 3 at minima
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