Question

1.) What side reactions occur during the following steps.

2.) How can the IR spectrum be used to show that there is not starting material left and the products are ketones?

3.) Describe the major differences and similarities between the IR spectra of benzoin and benzil. Compare your IR spectrum with those of benzoin and benzil.

Copper-Catalyzed Oxidation of Benzoin 1. Add a stir bar and 1.5 mL of glacial acetic acid, 0.250 g of NH4NO3 and 0.500 g of benzoin to a round bottom flask for refluxing. 2. Add 0.50 mL of the copper acetate solution to the flask. The mixture will not all dissolve in the solution at first and must be heated. 3. Assemble the reflux apparatus. 4. Heat the reaction mixture to a boil, and reflux for 60 minutes. 5. Cool the flask down to about room temperature. 6. Place 10 mL of ice-cold water in a 50 mL beaker in an ice bath. 7. Pour the contents of the flask into the ice-cold water and stir to break up any clumps that may form. Scratching the bottom of the flask with a stirring rod may be necessary to produce crystals. 8. Assemble a vacuum filtration system using the Hirsch funnel. 9. Vacuum filter the solid and wash with 5 mL of distilled water. 10. Allow the crystals to dry in the Hirsch funnel on the vacuum filtration apparatus for 10 minutes with the vacuum on. 11. Weigh the mass of your product and record on your data sheet. 12. Measure the melting point of your dry product and record on the data sheet. 13. Take a small sample of your solid product to run an FTIR and print your spectrum. 14. Place the remaining product in the container labeled "Benzil". All solutions should go in the non-halogenated waste. Wash all glassware and clean up.

Answer 1

17 Reaction: PRODUCTS OH O + cu COAC)2, A CH3COOH, NH4NO3 Benzil) Benzoin NOZ (Nitrogen- dioxide) CH3COOH + NH4NO3 HNO3 + CH3con NH3 Glacial Acetic Ammonium Nitric Acid Acid Side Poroduct Ammonicim Acetate Nitorate Mechanism 0 :0H OH OH H H20;- yo w + LOH N ON JN Ho o 11 ll N = HO H N से GOH2 20 ott ötle Nitrogen dioxide Ho OH

2) The starting material benzoin contain one hydroxyl group (-OH) and one keto (C=O) group. In IR Spectra hydroxyl group (-OH) shows medium wide peak in the region of 3200 cm^-1 to 3500 cm^-1 but in the products Benzil, it does not contain any hydroxyl group (-OH) but it contain two ketone group (C=O) which shows strong sharp peak in the region of 1646 cm^-1. Keto group generally shows sharp peak in the region of 1715 cm^-1 to 1725 cm^-1 but here it shows lower peaks 1646 cm^-1 because double bond of keto (C=O) group participates with benzene ring. So, in the basis of hydroyl group we can say that no starting material left and on the basis of keto group we can say that the products are ketones.

نمی 45 мүмма myning 40 % Transmittance 35 OH a 9F0 30- 4000 3500 3000 2500 1000 2000 1500 Wavenumbers

IR spectra of Benzoin

x Microns (um) 4.0 5.0 2.5 3.0 3.5 6.0 8 10 15 20 3050 cm 1431 cm Transmittance (%) 1582 cm- 0 0 C-C 1646 cm 1192 cm 4000 3500 3000 1500 1000 500 2500 2000 Wavenumber (cm)

IR spectra of Benzil

3) Major differences-

The starting material benzoin contain one hydroxyl group (-OH) and one keto (C=O) group. In IR Spectra hydroxyl group (-OH) shows medium wide peak in the region of 3200 cm^-1 to 3500 cm^-1 and keto group shows sharp peak in the region of 1646 cm^-1

Where as in the products Benzil, it contain two ketone group (C=O) which shows strong sharp peak in the region of 1646 cm^-1 and it does not contain hydroxyl group.

Major similarities-

Both the starting material benzoin and the products Benzil, both contain ketone group (C=O) which shows strong sharp peak in the region of 1646 cm^-1.