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Al-Ithawi WKA, Aluru R, Baklykov AV, Khasanov AF, Kovalev IS, Nikonov IL, Kopchuk DS, Novikov AS, Santra S, Zyryanov GV, Ranu BC. Mechanosynthesis of Polyureas and Studies of Their Responses to Anions. Polymers (Basel) 2023; 15:4160. [PMID: 37896404 PMCID: PMC10611254 DOI: 10.3390/polym15204160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 08/31/2023] [Accepted: 09/05/2023] [Indexed: 10/29/2023] Open
Abstract
Polyureas (PUs) have already found wide practical applications, and various methods of their synthesis have been reported. In this manuscript, we wished to report the very first mechanochemical approach towards aromatic PUs via reactions between isomeric 2,2'-, 3,3'-, and 4,4'-diaminobiphenyls and triphosgene under solvent-free conditions following ball-milling. By using this synthetic approach, both PUs and azomethine-capped Pus were obtained. The fluorescence response of the above-mentioned PUs towards various anions in solutions were studied and selective fluorescence responses towards the hydroxyl and fluoride anions were observed.
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Affiliation(s)
- Wahab K. A. Al-Ithawi
- Chemical Engineering Institute, Ural Federal University, 19 Mira St., Yekaterinburg 620002, Russia; (W.K.A.A.-I.); (R.A.); (A.F.K.); (I.S.K.); (I.L.N.); (D.S.K.); (S.S.); (B.C.R.)
- Energy and Renewable Energies Technology Center, University of Technology-Iraq, Baghdad 10066, Iraq
| | - Rammohan Aluru
- Chemical Engineering Institute, Ural Federal University, 19 Mira St., Yekaterinburg 620002, Russia; (W.K.A.A.-I.); (R.A.); (A.F.K.); (I.S.K.); (I.L.N.); (D.S.K.); (S.S.); (B.C.R.)
| | - Artem V. Baklykov
- I. Ya. Postovsky Institute of Organic Synthesis of RAS (Ural Division), 22/20 S. Kovalevskoy/Akademicheskaya St., Yekaterinburg 620219, Russia;
| | - Albert F. Khasanov
- Chemical Engineering Institute, Ural Federal University, 19 Mira St., Yekaterinburg 620002, Russia; (W.K.A.A.-I.); (R.A.); (A.F.K.); (I.S.K.); (I.L.N.); (D.S.K.); (S.S.); (B.C.R.)
| | - Igor S. Kovalev
- Chemical Engineering Institute, Ural Federal University, 19 Mira St., Yekaterinburg 620002, Russia; (W.K.A.A.-I.); (R.A.); (A.F.K.); (I.S.K.); (I.L.N.); (D.S.K.); (S.S.); (B.C.R.)
| | - Igor L. Nikonov
- Chemical Engineering Institute, Ural Federal University, 19 Mira St., Yekaterinburg 620002, Russia; (W.K.A.A.-I.); (R.A.); (A.F.K.); (I.S.K.); (I.L.N.); (D.S.K.); (S.S.); (B.C.R.)
- I. Ya. Postovsky Institute of Organic Synthesis of RAS (Ural Division), 22/20 S. Kovalevskoy/Akademicheskaya St., Yekaterinburg 620219, Russia;
| | - Dmitry S. Kopchuk
- Chemical Engineering Institute, Ural Federal University, 19 Mira St., Yekaterinburg 620002, Russia; (W.K.A.A.-I.); (R.A.); (A.F.K.); (I.S.K.); (I.L.N.); (D.S.K.); (S.S.); (B.C.R.)
- I. Ya. Postovsky Institute of Organic Synthesis of RAS (Ural Division), 22/20 S. Kovalevskoy/Akademicheskaya St., Yekaterinburg 620219, Russia;
| | - Alexander S. Novikov
- Institute of Chemistry, Saint Petersburg State University, Universitetskaya Nab., 7/9, Saint Petersburg 199034, Russia;
- Research Institute of Chemistry, Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya Street, 6, Moscow 117198, Russia
| | - Sougata Santra
- Chemical Engineering Institute, Ural Federal University, 19 Mira St., Yekaterinburg 620002, Russia; (W.K.A.A.-I.); (R.A.); (A.F.K.); (I.S.K.); (I.L.N.); (D.S.K.); (S.S.); (B.C.R.)
| | - Grigory V. Zyryanov
- Chemical Engineering Institute, Ural Federal University, 19 Mira St., Yekaterinburg 620002, Russia; (W.K.A.A.-I.); (R.A.); (A.F.K.); (I.S.K.); (I.L.N.); (D.S.K.); (S.S.); (B.C.R.)
- I. Ya. Postovsky Institute of Organic Synthesis of RAS (Ural Division), 22/20 S. Kovalevskoy/Akademicheskaya St., Yekaterinburg 620219, Russia;
| | - Brindaban C. Ranu
- Chemical Engineering Institute, Ural Federal University, 19 Mira St., Yekaterinburg 620002, Russia; (W.K.A.A.-I.); (R.A.); (A.F.K.); (I.S.K.); (I.L.N.); (D.S.K.); (S.S.); (B.C.R.)
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
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Shlyaykher A, Tambornino F. Synthesis and Stability of Ammonium Selenocyanate [NH 4][SeCN] and Its Reactivity toward Ag[SeCN]. Inorg Chem 2023. [PMID: 37453070 DOI: 10.1021/acs.inorgchem.3c01345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
[NH4][SeCN] and Ag[SeCN] were synthesized by salt metathesis starting from the respective chlorides and K[SeCN]. Both products were fully characterized by single-crystal and powder X-ray diffraction, differential scanning calorimetry-thermogravimetric analysis (DSC-TGA), and solid-state IR and Raman spectroscopy. Quantum-mechanical calculations allowed for detailed assignment and interpretation of vibrational spectra. For dissolved [NH4][SeCN], nuclear magnetic resonance spectra were collected. High-temperature powder X-ray diffraction (HT-PXRD) allowed for the analysis of the thermal behavior of solid [NH4][SeCN]. Furthermore, the reaction of [NH4][SeCN] with Ag[SeCN] leads to the formation of the ternary salts [NH4][Ag(SeCN)2] and [NH4]3[Ag(SeCN)4]. The structures of the latter were determined from single-crystal X-ray diffraction (SC-XRD) data, and bulk analysis was performed by Rietveld refinement, Raman spectroscopy, and elemental analysis.
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Affiliation(s)
- Alena Shlyaykher
- Fachbereich Chemie, Wissenschaftliches Zentrum für Materialwissenschaften (WZMW), Philipps-Universität Marburg, Hans-Meerwein-Straße 4, D-35043 Marburg, Germany
| | - Frank Tambornino
- Fachbereich Chemie, Wissenschaftliches Zentrum für Materialwissenschaften (WZMW), Philipps-Universität Marburg, Hans-Meerwein-Straße 4, D-35043 Marburg, Germany
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Schulz A, Surkau J. Main group cyanides: from hydrogen cyanide to cyanido-complexes. REV INORG CHEM 2022. [DOI: 10.1515/revic-2021-0044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Homoleptic cyanide compounds exist of almost all main group elements. While the alkali metals and alkaline earth metals form cyanide salts, the cyanides of the lighter main group elements occur mainly as covalent compounds. This review gives an overview of the status quo of main group element cyanides and cyanido complexes. Information about syntheses are included as well as applications, special substance properties, bond lengths, spectroscopic characteristics and computations. Cyanide chemistry is presented mainly from the field of inorganic chemistry, but aspects of chemical biology and astrophysics are also discussed in relation to cyano compounds.
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Affiliation(s)
- Axel Schulz
- Chemie , Universität Rostock , Albert-Einstein-Straße 3a, 18059 Rostock , Mecklenburg-Vorpommern , Germany
| | - Jonas Surkau
- Chemie , Universität Rostock , Albert-Einstein-Straße 3a, 18059 Rostock , Mecklenburg-Vorpommern , Germany
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Zhu N, Qian F, Xu X, Wang M, Teng Q. Thermogravimetric Experiment of Urea at Constant Temperatures. MATERIALS 2021; 14:ma14206190. [PMID: 34683779 PMCID: PMC8539392 DOI: 10.3390/ma14206190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 10/11/2021] [Accepted: 10/14/2021] [Indexed: 11/23/2022]
Abstract
There are still many unsolved mysteries in the thermal decomposition process of urea. This paper studied the thermal decomposition process of urea at constant temperatures by the thermal gravimetric–mass spectrometry analysis method. The results show that there are three obvious stages of mass loss during the thermal decomposition process of urea, which is closely related to the temperature. When the temperature was below 160 °C, urea decomposition almost did not occur, and molten urea evaporated slowly. When the temperature was between 180 and 200 °C, the content of biuret, one of the by-products in the thermal decomposition of urea, reached a maximum. When the temperature was higher than 200 °C, the first stage of mass loss was completed quickly, and urea and biuret rapidly broke down. When the temperature was about 240 °C, there were rarely urea and biuret in residual substance; however, the content of cyanuric acid was still rising. When the temperature was higher than 280°C, there was a second stage of mass loss. In the second stage of mass loss, when the temperature was higher than 330 °C, mass decreased rapidly, which was mainly due to the decomposition of cyanuric acid. When the temperature was higher than 380 °C, the third stage of mass loss occurred. However, when the temperature was higher than 400 °C, and after continuous heating was applied for a sufficiently long time, the residual mass was reduced to almost zero eventually.
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Affiliation(s)
- Neng Zhu
- School of Automotive and Transportation Engineering, Wuhan University of Science and Technology, Wuhan 430081, China; (N.Z.); (X.X.)
| | - Feng Qian
- School of Automotive and Transportation Engineering, Wuhan University of Science and Technology, Wuhan 430081, China; (N.Z.); (X.X.)
- Correspondence: ; Tel.: +86-180-6206-0988
| | - Xiaowei Xu
- School of Automotive and Transportation Engineering, Wuhan University of Science and Technology, Wuhan 430081, China; (N.Z.); (X.X.)
| | - Mingda Wang
- Chinese Academy of Environmental Sciences, Beijing 100012, China; (M.W.); (Q.T.)
| | - Qi Teng
- Chinese Academy of Environmental Sciences, Beijing 100012, China; (M.W.); (Q.T.)
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Ugliengo P. The rise of computer modeling in prebiotic chemistry: Comment on "Prebiotic chemistry and origins of life research with atomistic computer simulations" by A. Pérez-Villa et al. Phys Life Rev 2019; 34-35:139-142. [PMID: 30948234 DOI: 10.1016/j.plrev.2019.03.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 03/25/2019] [Indexed: 11/15/2022]
Affiliation(s)
- Piero Ugliengo
- Department of Chemistry and NIS Centre, University of Torino, Via P. Giuria 7, 10125 Torino, Italy.
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Decomposition of 8 mol·L−1 Urea Solution at 298.15 K. J SOLUTION CHEM 2018. [DOI: 10.1007/s10953-018-0762-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Nicolle A, Cagnina S, de Bruin T. First-principle based modeling of urea decomposition kinetics in aqueous solutions. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.10.032] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Abstract
1. Although the major pathways involved in drug metabolism have been elucidated, there remain those routes that may be considered as minor, esoteric, or even artifactual. 2. Conjugation with urea, an abundant, non-toxic, small water soluble molecule, is such a disputed and debatable Phase II pathway. 3. The present article collates data gleaned from the literature concerning xenobiotic-urea conjugation, presents pertinent information resurrecting the controversy and poses questions as to the nature of the phenomenon.
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Affiliation(s)
- Stephen C Mitchell
- Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London , South Kensington, London , UK
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Dana AG, Shter GE, Grader GS. Thermal analysis of aqueous urea ammonium nitrate alternative fuel. RSC Adv 2014. [DOI: 10.1039/c4ra04381b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
TGA/DTA/MS and DSC under high pressure of aqueous urea ammonium nitrate alternative fuel is reported.
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Affiliation(s)
- Alon Grinberg Dana
- The Nancy and Stephen Grand Technion Energy Program
- Technion – Israel Institute of Technology
- Haifa 3200003, Israel
| | - Gennady E. Shter
- The Wolfson Department of Chemical Engineering
- Technion – Israel Institute of Technology
- Haifa 3200003, Israel
| | - Gideon S. Grader
- The Wolfson Department of Chemical Engineering
- Technion – Israel Institute of Technology
- Haifa 3200003, Israel
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Adamczyk K, Dreyer J, Pines D, Pines E, Nibbering ETJ. Ultrafast Protonation of Cyanate Anion in Aqueous Solution. Isr J Chem 2009. [DOI: 10.1560/ijc.49.2.217] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Schädler HD, Schroth W, Weiss C. Theoretische Untersuchungen zum Zerfallsgleichgewicht des Harnstoffs in Gasphase und in wäßriger Lösung. ACTA ACUST UNITED AC 2004. [DOI: 10.1002/prac.19833250511] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Tsipis CA, Karipidis PA. Mechanism of a chemical classic: quantum chemical investigation of the autocatalyzed reaction of the serendipitous wöhler synthesis of urea. J Am Chem Soc 2003; 125:2307-18. [PMID: 12590561 DOI: 10.1021/ja020656n] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The detailed reaction pathways for the ammonium cyanate transformation into urea (Wöhler's reaction) in the gas phase, in solution, and in the solid state have exhaustively been explored by means of first-principles quantum chemical calculations at the B3LYP level of theory using the 6-31G(d,p) basis set. This serendipitous synthesis of urea is predicted to proceed in two steps; the first step involves the decomposition of the ammonium cyanate to ammonia and isocyanic or cyanic acid, and the second one, which is the main reaction step (and probably the rate-determining step), involves the interaction of NH(3) with either isocyanic or cyanic acid. Several alternative pathways were envisaged for the main reaction step of Wöhler's reaction in a vacuum involving the formation of "four-center" transition states. Modeling Wöhler's reaction in aqueous solution and in the solid state, it was found that the addition of NH(3) to both acids is assisted (autocatalyzed) by the active participation of extra H(2)O and/or NH(3) molecules, through a preassociative, cooperative, and hydrogen-transfer relay mechanism involving the formation of "six-center" or even "eight-center" transition states. The most energetically economic path of the rate-determining step of Wöhler's reaction is that of the addition of NH(3) to the C=N double bond of isocyanic acid, directly affording urea. An alternative pathway corresponding to the anti-addition of ammonia to the Ctbd1;N triple bond of cyanic acid, yielding urea's tautomer HN=C(OH)NH(2), seems to be another possibility. In the last case, urea is formed through a prototropic tautomerization of its enolic form. The energies of the reactants, products, and all intermediates along with the barrier heights for each reaction path have been calculated at the B3LYP/6-31G(d,p) level of theory. The geometry optimization and characterization of all of the stationary points found on the potential energy hypersurfaces was performed at the same level of theory.
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Affiliation(s)
- Constantinos A Tsipis
- Laboratory of Applied Quantum Chemistry, Faculty of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
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Steel CJ, Brady F, Luthra SK, Brown G, Khan I, Poole KG, Sergis A, Jones T, Price PM. An automated radiosynthesis of 2-[11C]thymidine using anhydrous [11C]urea derived from [11C]phosgene. Appl Radiat Isot 1999; 51:377-88. [PMID: 10464914 DOI: 10.1016/s0969-8043(99)00051-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
2-[11C]Thymidine has been produced from [11C]methane via [11C]phosgene and [11C]urea. Anhydrous [11C]urea was prepared from [11C]phosgene by reaction with liquid ammonia. This novel approach avoids the problems associated with the synthesis of anhydrous [11C]urea from [11C]cyanide. A fully automated system based on a modular approach and under PLC control has been developed. The system provides 2-[11C]thymidine reliably and reproducibly for clinical PET studies. The radiosynthesis takes 45-50 min from [11C]methane and the average yield was 1.5-3.3 GBq (40-90 mCi). The specific radioactivity was typically in the range 29.6-51.8 GBq mumol-1 (0.8-1.4 Ci mumol-1) at EOS corresponding to 6-12 micrograms of stable thymidine. The radiochemical yield of 2-[11C]thymidine was ca. 14% from [11C]methane.
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Affiliation(s)
- C J Steel
- MRC Cyclotron Unit, Imperial College School of Medicine, Hammersmith Hospital, London, UK
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Dunitz JD, Harris KDM, Johnston RL, Kariuki BM, MacLean EJ, Psallidas K, Schweizer WB, Tykwinski RR. New Light on an Old Story: The Solid-State Transformation of Ammonium Cyanate into Urea. J Am Chem Soc 1998. [DOI: 10.1021/ja983285c] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jack D. Dunitz
- Organic Chemistry Laboratory Swiss Federal Institute of Technology ETH-Zentrum, CH-8092 Zürich, Switzerland School of Chemistry, University of Birmingham Edgbaston, Birmingham B15 2TT, United Kingdom Daresbury Laboratory, Warrington Cheshire WA4 4AD, United Kingdom Department of Chemistry, University of Alberta Edmonton, Alberta T6G 2G2, Canada
| | - Kenneth D. M. Harris
- Organic Chemistry Laboratory Swiss Federal Institute of Technology ETH-Zentrum, CH-8092 Zürich, Switzerland School of Chemistry, University of Birmingham Edgbaston, Birmingham B15 2TT, United Kingdom Daresbury Laboratory, Warrington Cheshire WA4 4AD, United Kingdom Department of Chemistry, University of Alberta Edmonton, Alberta T6G 2G2, Canada
| | - Roy L. Johnston
- Organic Chemistry Laboratory Swiss Federal Institute of Technology ETH-Zentrum, CH-8092 Zürich, Switzerland School of Chemistry, University of Birmingham Edgbaston, Birmingham B15 2TT, United Kingdom Daresbury Laboratory, Warrington Cheshire WA4 4AD, United Kingdom Department of Chemistry, University of Alberta Edmonton, Alberta T6G 2G2, Canada
| | - Benson M. Kariuki
- Organic Chemistry Laboratory Swiss Federal Institute of Technology ETH-Zentrum, CH-8092 Zürich, Switzerland School of Chemistry, University of Birmingham Edgbaston, Birmingham B15 2TT, United Kingdom Daresbury Laboratory, Warrington Cheshire WA4 4AD, United Kingdom Department of Chemistry, University of Alberta Edmonton, Alberta T6G 2G2, Canada
| | - Elizabeth J. MacLean
- Organic Chemistry Laboratory Swiss Federal Institute of Technology ETH-Zentrum, CH-8092 Zürich, Switzerland School of Chemistry, University of Birmingham Edgbaston, Birmingham B15 2TT, United Kingdom Daresbury Laboratory, Warrington Cheshire WA4 4AD, United Kingdom Department of Chemistry, University of Alberta Edmonton, Alberta T6G 2G2, Canada
| | - Katerina Psallidas
- Organic Chemistry Laboratory Swiss Federal Institute of Technology ETH-Zentrum, CH-8092 Zürich, Switzerland School of Chemistry, University of Birmingham Edgbaston, Birmingham B15 2TT, United Kingdom Daresbury Laboratory, Warrington Cheshire WA4 4AD, United Kingdom Department of Chemistry, University of Alberta Edmonton, Alberta T6G 2G2, Canada
| | - W. Bernd Schweizer
- Organic Chemistry Laboratory Swiss Federal Institute of Technology ETH-Zentrum, CH-8092 Zürich, Switzerland School of Chemistry, University of Birmingham Edgbaston, Birmingham B15 2TT, United Kingdom Daresbury Laboratory, Warrington Cheshire WA4 4AD, United Kingdom Department of Chemistry, University of Alberta Edmonton, Alberta T6G 2G2, Canada
| | - Rik R. Tykwinski
- Organic Chemistry Laboratory Swiss Federal Institute of Technology ETH-Zentrum, CH-8092 Zürich, Switzerland School of Chemistry, University of Birmingham Edgbaston, Birmingham B15 2TT, United Kingdom Daresbury Laboratory, Warrington Cheshire WA4 4AD, United Kingdom Department of Chemistry, University of Alberta Edmonton, Alberta T6G 2G2, Canada
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Siddiqui AU, Siddiqui AH, Ramaiah TS. SYNTHESIS OF C-24 THIAZOLIDINONE AND OXAZOLIDINONE DERIVATIVES OF BILE ACIDS. ORG PREP PROCED INT 1993. [DOI: 10.1080/00304949309457938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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18
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Boothe TE, Emran AM, Finn RD, Vora MM, Kothari PJ. Use of 11C as a tracer for studying the synthesis of [11C]urea from [11C]cyanide. THE INTERNATIONAL JOURNAL OF APPLIED RADIATION AND ISOTOPES 1985; 36:141-4. [PMID: 3980120 DOI: 10.1016/0020-708x(85)90229-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The use of reversed-phase liquid chromatography and radiochemical detection with carbon-11 (t1/2 = 20.4 min) as a tracer allowed the study of the preparation of [11C]urea from [11C]cyanide at no-carrier-added concentrations. [11C]cyanate was readily prepared by permanganate oxidation of [11C]cyanide at 75 degrees C. The conversion of NH4O11CN (approximately 0.03 mM) to [11C]urea in the presence of excess ammonium ions (0.28 M) was found to best fit pseudo first order reaction kinetics with a rate constant of 0.065 +/- 0.008 min-1 at 75 degrees C. Heating at higher temperatures (180-200 degrees C) revealed that the conversion of NH4O11CN to [11C]urea occurred in high yield in less than 3 min. The hydrolysis of [11C]cyanate to [11C]carbonate, a possible side reaction, was found to proceed at a rate of 0.010 +/- 0.001 min-1 at 113 degrees C.
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