The vibrations of dimethoate and omethoates molecular structure, and their corresponding features of varying structures under acidic and basic conditions, were further explored by means of attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). According to the results, ATR-FTIR can significantly distinguish the different vibrational peaks of dimethoate and omethoate. These peaks at 3302 cm^－1 ν_as (NH), 3089 cm^－1 ν_as (CH₂), 1739 cm^－1 ν (C—O), 1554 cm^－1 ν (O＝C—N) II of omethoate were obviously different from corresponding structure vibrational peaks of dimethoate molecule. Under base condition, the vibrational peaks feature of dimethoate in ATR-FTIR at hydrolysis process was that the broad peak 2108 cm^－1 became strong, while the vibrational peaks feature of omethoate showed ν (P＝O) red shift and ν (P—O—C) blue shift. Under different acidic condition, vibrational peaks of NH and CH₃ in dimethoates ATR-FTIR at mid and high band spectra were strong, while all vibrations of omethoates structure in ATR-FTIR were weak, owing to the whole of its molecule chain being destructed. These results were complementary to demonstrate the internal molecular structure differences between dimethoate and omethoate, and to demonstrate the influence changes of vibrational structures caused by hydrolysis process at acidic and basic conditions. The results could provide more information for distinguishing the similar molecular structures, especially having nice structure differences in different molecules, with convenient and efficient tools, and also the results could provide useful reference for studying molecular structures and morphological changes.

Key words: attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), dimethoate, omethoate, hydrolysis