Benzoic Acid → Thiourea, (5-phenyl-1,2,4-thiadiazol-3-yl)-

Participants

Reaction Conditions

Reaction Steps

3-[N′-(benzoyl)thioureido]-5-phenyl-1,2,4-thiadiazole (BzPTT; 1 kg, 2.94 moles) was placed in a 12-L reaction vessel. A solution of KOH (8.8 L; 3.0 M in water) was added with stirring. The reaction milieu (initially yellow) was heated to 60° C. for about 1 hour or until completion with vigorous stirring. Completion of the reaction was determined either by a color change, e.g., from yellow (BzPTT) to white (PTT), or by monitoring by NMR. Concentrated HCl (2.2 L) was added with stirring at 0-10° C. to lower the pH to about 2-3 by Litmus paper. Concentrated ammonium hydroxide (241 mL) was added to the reaction milieu to raise the pH to about 8, which is more than 4 pH units greater than the pKa of the benzoic acid. After cooling in an ice bath for 30 minutes, the PTT was isolated by filtration in a Büchner funnel over filter paper and dried at room temperature overnight until dryness. The yield of PTT was about 97.4% and the product was about 99.7% pure as determined by HPLC. The H1NMR and 13C NMR spectrum of the product was consistent with that of a reference sample. Mp (253-255° C.) and mass spectroscopy were also used to identify the product.

Provenance & Evidence