In order to explore high-performance polymer modified by orderly hydroxy group

the synthesis method of the key intermediates

hydroxyterephthalic acid monomethyl esters(α-MHT and β-MHT)

was studied for preparating new AB-type monomers.The theory and reaction mechanism were discussed in different position esterification and mono-hydrolysis

and a current synthesis and purification technology of terephthalic acid mono-esters with unsymmetrical introduction of hydroxy group was established.The results showed that methyl 2-hydroxy-4-carboxy benzoate(α-MHT)was high-selectivity synthesized by di-esterification of hydroxyterephthalic acid(HTA)with methanol in the presence of SOCl2 as promoter

then mono-hydrolysis reaction of the di-ester in alkaline solution

the total yield was up to 76%

and methyl 3-hydroxy-4-carboxybenzoate(β-MHT)was directly prepared by mono-esterification of HTA with methanol under sulfuric acid catalysis

with yield nearly 70%.At the same time the synthesis technology and reaction mechanism were effectively applied to preparing 2

6-dihydroxyterephthalic acid mono-ester compounds:alpha-mono methyl ester(α-MDHT)and beta-monomethyl ester(β-MDHT).