US EPA

7443828 

Journal Article 

RATE CONSTANTS FOR CYANATE HYDROLYSIS TO UREA - A RAMAN-STUDY 

Wen, NP; Brooker, MH 

1994 

Yes 

Canadian Journal of Chemistry
ISSN: 0008-4042
EISSN: 1480-3291 

NATL RESEARCH COUNCIL CANADA 

OTTAWA 

72 

4 

1099-1106 

English 

10.1139/v94-139 

WOS:A1994NN83000011 

http://www.nrcresearchpress.com/doi/10.1139/v94-139
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Raman spectra of aqueous solutions of potassium cyanate have been obtained at suitable time intervals. It was found that the peaks attributed to cyanate became less intense, while the peaks attributed to urea, carbamate and carbonate, centred at 1003, 1034, and 1065 cm −1 , respectively, enhanced greatly with the passage of time. Further Raman spectroscopic studies revealed that the cyanate ion hydrolysed slowly and spontaneously at room temperature. Urea, carbamate, and carbonate were formed even without additional ammonium. Raman intensity measurements were used to monitor species concentrations as a function of time. The results suggested a complicated hydrolysis process: the hydrolysis of cyanate ion to form carbonate and ammonium, a rearrangement type reaction of aqueous cyanate ion with aqueous ammonium to formed urea, and an equilibrium reaction of carbonate and ammonium to form carbamate. The initial hydrolysis of cyanate with pure water was found to be first order with rate constant k 1  = (2.67 ± 0.53) × 10 −4  min −1 at 22 °C. The reaction of cyanate with aqueous ammonium was found to be second order with rate constant k 2  = (4.64 ± 0.93) × 10 −4  mol −1 •L•min −1 . The equilibrium reaction of carbonate and ammonium to form carbamate was very fast. Urea and carbamate were formed in parallel reactions. It was not possible to convert urea to carbamate or carbamate to urea at room temperature. 

Ammonium compounds; Carbonates; Hydrolysis; Ions; Nitrogen compounds; Potassium compounds; Raman spectroscopy; Solutions; Urea; Carbamate; Cyanate; Equilibrium reaction; Rate constants; Reaction kinetics