In the Classroom
edited by
tested demonstrations
George Gilbert Denison University Granville, OH 43023
Classroom Demonstration of Solid State Reaction at Room Temperature Submitted by:
Lixu Lei, Xuebin Yao, and Xinquan Xin* State Key Lab of Coordination Chemistry and Institute of Coordination Chemistry, Nanjing University Nanjing 210093, China
Checked by:
Jim Niewahner Northern Kentucky University, Highland Heights, KY 41099-1905
It is well known that solid state reactions can occur at high temperatures, and this Journal has documented many such experiments for students in solid state lab (1–4). However, it is not well known—and it is even doubted—that some solid state reactions can take place at room temperature. We have done a lot to eliminate the doubts, and have found that room temperature offers some synthetic advantages (5, 6). A recent demonstration proved very successful. It shows that reaction between two solids can not only take place at room temperature, but can also go to completion in a very short time. The procedure is as follows. Newly prepared 200-mesh CuCl2 ?2H 2O and 2aminopyrimidine (AP) were weighed in a 1:1 molar ratio and transferred into a small test tube with cover. They were easily well mixed by shaking the test tube. That the reaction took place as soon as the materials were mixed *Corresponding author.
was indicated by a color change from blue to yellow-green. That color change is much more easily distinguished with a reference of CuCl2?2H2O in another tube. The reaction is completed in about 15 min if the mixture of starting materials is first ground for 2 min to mix it better. This can be verified by comparing the XRD pattern (Fig. 1) and the UV-vis reflectance spectrum (Fig. 2) of the mixture with the corresponding observations of the starting materials. The reaction is: CuCl2?2H 2O + AP → Cu(AP)Cl2 (blue)
(yellow-green)
The IR absorptions of the ligand ν s(NH2) is 3170 cm{1 for free ligand and 3248, 3215 cm{1 for ligand in Cu(AP)Cl2. The ν C=N (ring vibration) of ligand shifts from 1559 to 1579 cm{1. The composition of Cu(AP)Cl 2 after washing with absolute alcohol is C: 20.83 H: 2.23 N: 18.09 Cu: 27.22; calculated C: 20.23 H: 2.20 N: 18.30 Cu: 27.68. Literature Cited 1. 2. 3. 4. 5. 6.
Figure 1. XRD patterns (using Cu Kα radiation, λ = 1.5405 Å) of (a) 2-aminopyrimidine (AP); (b) CuCl 2?2H2O; and (c) Cu(AP)Cl2 . There are no peaks of the starting material in (c); therefore, the reaction went to completion.
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Djurovich, P. I.; Watts, R. J. J. Chem. Educ. 1993, 70, 497. Scott, E. S. J. Chem. Educ. 1992, 69, 1028. Wold, A. J. Chem. Educ. 1980, 57, 531. Ribas, J.; Escuer, A.; Serra, M.; Vicente, R. J. Chem. Educ. 1988, 65, 85. Xin, X.-Q.; Zheng, L.-M. J. Sol. State Chem. 1993, 106, 451. Lang, J.-P; Xin, X.-Q. J. Sol. State Chem. 1994, 108, 118.
Figure 2. UV-vis reflectance spectra of (a) 2-aminopyrimidine (AP); (b) CuCl 2?2H2O; and (c) Cu(AP)Cl2 . The spectra are different and the original absorptions of free salt and ligand have shifted.
Journal of Chemical Education • Vol. 73 No. 11 November 1996
