The nucleophilic aromatic substitution reaction and thia-Michael addition using thiourea as an odorless, cheap, and easy-to-handle sulfur source in water are described, which can be used to teach upper-division undergraduates the role of thiourea in the formation of C-S bonds and the principles of green chemistry. The use of a cheap, nontoxic surfactant Triton X-100 proves to promote both reactions obviously by contrast reactions. The structures of products obtained from the two reactions by students are determined via analyzing nuclear magnetic resonance spectral data. Students also propose the mechanisms of the two reactions and point out the green and nongreen aspects of this experiment. [Note: This paper was published ASAP on August 4, 2016, with incomplete hazards details. The corrected version was reposted on January 18, 2017.]