Synthesis of bis-naphthoic acid disulfide: An aged soot aerosol model

CHED 480

Kassandra A. Koopman, kakoopman@viterbo.edu, Ronald T. Amel, rtamel@viterbo.edu, and Kyle M. Backstrand, kmbackstrand@viterbo.edu. Department of Chemistry, Viterbo University, 900 Viterbo Drive, La Crosse, WI 54601
As soot aerosol ages, semi-volatile organic compounds in the atmosphere adsorb onto soot aerosol. This changes the surface chemical composition and variety of surface functional groups. Carboxylic acid functional groups have been identified as the most prevalent functional group on soot aerosol. However, the reactivity of soot aerosol as a function of age is not known. Therefore, a model soot aerosol surface is needed in order to study these particles. This research entailed the synthesis of bis-naphthoic acid disulfide, to be used in later studies as an aged soot aerosol model. This model will form a self-assembled monolayer when placed upon a gold surface. The synthesis was based on a known synthesis of thiosalysilic acid. The starting material was 6-amino-2-naphthoic acid. In the synthesis the amine functional groups were converted to diazonium salts which produced the corresponding disulfide upon reaction with a solution of sodium sulfide and powdered sulfur. Fourier transform infrared spectroscopy was used to analyze the material. An important peak appeared at 476 cm-1, which is the region where disulfide bonds absorb. Carboxylic acid OH was found from 2560 cm-1 to 3500 cm-1 and the carbonyl absorption was found at 1690 cm-1.