Chemistry 252 Name _________________ Synthesis Unit: Claisen-Schmidt Organic Chemistry Unit 5: Synthesis of Substituted Chalcones Post-lab Exercises 1.) Write the chemical equation for the reaction you performed: 2.) Complete the following table indicating the mass and mmole amounts actually used in the experiment. Use appropriate significant figures when reporting masses and volumes. Record Rf values to two decimal places. Compound Name MW mass (mg) or mmol Rf volume (µL ) used or collected 4-methoxy acetophenone B= 15 M NaOH
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C= 3a.) What solvent system did you use for TLC? How were the TLC plates visualized? 3b). From your TLC results, is your product pure? Explain (sketching your TLC data would help your explanation). 4a.) What was the theoretical yield of C according to the reaction you performed? Show your work. _________mg 4b.) What was the percent yield of crude C in your reaction? Show your work. __________% 4c.) What was the percent yield of recrystallized C in your reaction? Show your work. 1
__________% 5a.) What was the melting point range of the crude sample of C?______ C to ______ o C 5b.) What solvent was used to recrystallize the crude sample? 5c.) What was the melting point range of the purified sample of C?_____ o C to _____ o C 6.) Complete the following table. Use the spectrum of the sample of C that you prepared for the measured frequencies. Compare your product IR to the starting materials (acetophenone and B) – are any new absorbances present or are any ones missing? IR data for most of the starting materials can be found in the literature at http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/cre_index.cgi?lang=eng Staple your IR spectrum to this sheet. Make sure it is labeled with your name, the name of the compound, a structural drawing of the compound, and a reference to the page in your notebook where you describe the synthesis of the compound. Each of the bands in the table below should be labeled on your spectrum. Band Vibration Expected Measured Wavenumber, Wavenumber, cm-1 cm-1 1 Alkene sp2 C-H stretch 2 Arene sp2 C-H stretch 3 Ketone C=O stretch, conjugated 4 Arene C-H out of plane bending (4H) 5 Arene C=C ring stretch (ν8a ) 6 Arene C=C ring stretch (ν8b ) 7 Arene C=C ring stretch (ν19a ) 8 Arene C=C ring stretch (ν19b ) 9 Arene C-C ring o-o-p bend 10 C-O stretch 11 For substituent on B 12 Other prominent diagnostic bands 7a.) What NMR solvent did you dissolve the chalcone sample in? What is the experimental integration ratio? What is the expected integration ratio? 7b.) Staple the H-NMR and C-NMR spectra of C that you prepared to this report. Make sure it is labeled with your name, the name of the compound, a structural drawing of the compound, and a reference to the page in your notebook where you describe the synthesis of the compound. o
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7c.) Label the resonances in the 1 H-NMR spectrum a,b,c, etc. starting with the most upfield (lowest ppm value) resonance. Label the resonances in the 13 C-NMR spectrum 1,2,3, etc. starting with the most upfield resonance. Draw the structure of compound C on the back of this page and label the protons a,b,c, etc. Draw the structure again and label the carbons 1,2,3, etc. In other words, interpret and correlate the structure and the spectrum.
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8.) a.) What was the GC retention time of your sample of the substituted chalcone? _____minutes b.) What was the m/z value of the parent ion in your MS? _____m/z c.) What was the m/z value of the base peak in your MS? _____m/z d.) Identify an additional m/z value; what fragment was lost to form this peak? e.) From your GC results, is your product pure? Explain. The mass spectrum must correspond to the retention time of the peak of substituted chalcone in your gas chromatograph. If more than one significant band is present in the gas chromatograph, be sure to include its mass spec.
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