Analysis of Thermal Degradation Products of Allyl Isothiocyanate and Phenethyl Isothiocyanate

Abstract

Allyl isothiocyanate (AITC) or phenethyl isothiocyanate (PEITC) in an aqueous solution were heated and refluxed at 100 C for 1 hr. The reaction mixtures were simultaneously distilled and extracted into methylene chloride using a Likens-Nickerson (L-N) apparatus and then analyzed using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The mixtures in the aqueous phase were analyzed by high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) equipped with an atmospheric pressure chemical ionization (APCI) interface. Nine thermal degradation volatile products including diallyl sulfide, diallyl disulfide, diallyl trisulfide, diallyl tetrasulfide, allyl thiocyanate, 3H-1,2-dithiolene, 2-vinyl-4H-1,3-dithiin, 4H-1,2,3-trithiin, and 5-methyl-1,2,3,4-tetrathiane were identified from AITC; while no volatile degradation products from PEITC were found. N,N'-diallylthiourea and N,N'-diphenethylthiourea, which were the major degradation products in the aqueous phase from the thermal reaction of AITC and PEITC, respectively, were identified by LC-MS (APCI+), direct probe EI-MS and H1-NMR. A possible mechanism for the formation of these products is proposed.