Synthesis of 3,3 ′ - diamino-4,4 ′ - dihydroxybiphenyl hydrochloride
Wu Chunxin, Chang Yuxi, Chen Dichao, Zhang Jianting,
Jinning people, Zhao Deming
(School of chemical engineering, Zhejiang University of technology, Hangzhou 310014, Zhejiang)
Cited in this paper: Wu Chunxin, Chang Yuxi, Chen Dichao, et al. Synthesis of 3,3 ′ - diamino-4,4 ′ - dihydroxybiphenyl hydrochloride modified by hydroxyl group [J]. Chemical progress, 2020, 39 (2): 696-701
Abstract
In order to improve the poor adhesion of poly (p-phenylenebenzodiazole) (PBO) fiber, the polar group hydroxy was introduced into the benzene ring to modify the chemical molecular structure. 3,3 '- diamino-4,4' - dihydroxybiphenyl hydrochloride (dadhbp · 2HCl) is the key monomer of hydroxy modified PbO. The monomer dadhbp · 2HCl of intermediate 3,3 '- dinitro-4,4' - dihydroxybiphenyls (dndhbp) and hydroxyl modified PbO was synthesized by nitration and reduction of 4,4 '- dihydroxybiphenyls (dhbp), and the reaction conditions were optimized. The results showed that for nitrification, the mixture of toluene and glacial acetic acid was used as the reaction solvent, n (dhbp): n (HNO3) = 1:2, reaction temperature 5 ℃, reaction time 2.5h, yield 81.39%, purity (mass fraction) of high performance liquid chromatography (HPLC) 92.43%; reduction reaction, n (dndhbp): n (FeSO4.7H2O) = 1:9, ethanol as the solvent, ferrous sulfate heptahydrate as the assistant, n (dndhbp): n (n2h4.h The yield of dadhbp · 2HCl was 67.16% and the purity of HPLC was 98.20%. The structures of intermediates and products were confirmed by IR, 1H NMR and ESI.
PbO is an aromatic heterocyclic polymer with benzoxazole ring in its main chain. It has excellent physical and chemical properties, high specific strength, specific modulus, heat resistance and flame retardancy. Based on these performance advantages, it has been widely used in synthetic materials, defense and military industry, transportation and other fields. However, PBO also has some disadvantages, such as poor compression resistance, poor composite adhesion and poor UV radiation resistance. At present, some modification treatment will damage the high-performance fiber, lead to the degradation of the original mechanical properties of PbO, at the same time, increase the treatment cost and greatly reduce the cost performance of the fiber. In order to avoid the performance degradation caused by the surface modification of the fiber, it is urgent to study the modification of the molecular structure. Due to the lack of polar groups on the surface of PBO and the absence of any chemical bond between the molecular chains, the composite bonding and axial compressive properties of PBO are seriously inadequate, which restricts its direct application in the field of advanced composite materials. On the basis of ensuring the original mechanical properties of PbO, the composite bonding performance is improved. Many researchers have synthesized many kinds of polymerized monomers from the molecular structure design of monomers. It is an option for molecular design of composite modified PbO to introduce polar group hydroxyl into the benzene ring of molecular structure, and to use the hydrogen bond produced by hydroxyl on the molecular chain to ensure the improvement of composite bonding performance of PBO on the basis of original mechanical properties. The focus of domestic and foreign research is to modify the polymerized monomers, that is, to introduce dihydroxy into the monomers, and then to increase the polarity by mixing polymerization, such as 2,5-dihydroxyterephthalic acid (2,5-dhta) and 2,4-diaminoresorcinol hydrochloride (DAR · 2HCl) mixed polycondensation to prepare dihydroxy modified PbO. In this paper, we try to prepare 3,3 '- diamino-4,4' - dihydroxybiphenyl hydrochloride (dadhbp · 2HCl), which is modified by hydroxyl group and biphenyl structure.
About the synthesis of dadhbp · 2HCl, the existing literature takes 4,4 ′ - dihydroxybiphenyls as raw material after nitration, hydrazine hydrate as reducing agent, palladium carbon as catalyst to carry out catalytic reduction to obtain the target product, but this route has the disadvantages of long reaction time and high cost. Therefore, in order to shorten the synthesis time and reduce the production cost, dadhbp · 2HCl was synthesized from 4,4 ′ - dihydroxybiphenyls by nitration and reduction with ferrous sulfate heptahydrate as assistant. Hydrazine hydrate and ferrous sulfate heptahydrate are used in the reduction process. Compared with hydrazine hydrate and palladium hydrate, the reduction process has the advantages of cheaper price, better selectivity for nitro reduction, lower cost compared with palladium carbon reduction, and significant reduction effect. The process is shown in Figure 1. After optimization, high purity intermediates 3,3 '- two nitro -4,4' - two hydroxy biphenyl (DNDHBP) and monomer 3,3 '- two amino -4,4' - two hydroxy biphenyl hydrochloride (DADHBP 2HCl) were obtained, and the intermediates and product structures were identified by IR, 1H-NMR and ESI.
Fig. 1 the properties of 3,3 '- diamino-4,4' - dihydroxybiphenyl hydrochloride
synthetic route
1 experimental part
1.1 main reagents and instruments
1.2 experiment process and method
1.2.1 synthesis of dndhbp
1.2.2 synthesis of dadhbp · 2HCl
2 results and discussion
2.1 synthesis of dndhbp
2.1.1 effect of reaction solvent types on dndhbp synthesis
Table 1 Effect of reaction solvent types on dndhbp synthesis
2.1.2 effect of mixed solvent ratio on dndhbp synthesis
Table 2 Effect of mixed solvent ratio on dndhbp synthesis
2.1.3 effect of raw material ratio of nitric acid and dhbp on dndhbp synthesis
Table 3 Effect of raw material ratio of nitric acid and dhbp on dndhbp synthesis
2.1.4 effect of reaction temperature on dndhbp synthesis
Table 4 Effect of reaction temperature on dndhbp synthesis
2.1.5 effect of reaction time on dndhbp synthesis
Table 5 Effect of reaction time on dndhbp synthesis
2.2 synthesis of dadhbp · 2HCl
2.2.1 comparison of dadhbp reduction methods
Table 6 Effect of different reduction methods on products
2.2.2 effect of the amount of ferrous sulfate heptahydrate on the synthesis of dadhbp · 2HCl
Table 7 Effect of the amount of ferrous sulfate heptahydrate on the synthesis of dadhbp · 2HCl
2.2.3 effect of hydrazine hydrate dosage on the synthesis of dadhbp · 2HCl
Table 8 Effect of hydrazine hydrate dosage on the synthesis of dadhbp · 2HCl
2.2.4 effect of reaction time on the synthesis of dadhbp · 2HCl
Table 9 Effect of reaction time on the synthesis of dadhbp · 2HCl
3 conclusion
In this paper, the intermediate dndhbp and dadhbp · 2HCl were successfully prepared from 4,4 '- dihydroxybiphenyls, and their synthesis conditions were optimized. The products were characterized qualitatively by FTIR, 1H NMR and MS, all of which were in accordance with their molecular structures. The results are as follows.
(1) Dndhbp was synthesized with 4,4 ′ - dihydroxybiphenyls as raw materials, toluene glacial acetic acid as reaction solvent, reaction temperature 5 ℃, reaction time 2.5h, n (dhbp): n (HNO3) = 1:2, adding nitric acid slowly in the reaction to prevent temperature rise, so as to control the reaction. 3,3 ′ - dinitro-4,4 ′ - dihydroxybiphenyls were obtained. The mass fraction was 92.43% by HPLC, and the yield was 81.39%.
(2) Dndhbp · 2HCl was synthesized with dndhbp as raw material, ethanol as reaction solvent, ferrous sulfate heptahydrate as assistant, n (dndhbp): n (N2H4 · H2O) = 1:5.5, reaction temperature 78 ℃, reaction for 9h, through thermal filtration and salting out, dadhbp · 2HCl was obtained, yield 67.16%, and HPLC analysis mass fraction 98.20%.
Click "read original" below to view the full text