marmomete Electrically heated sand bath . A. Benzopinacolone Charye a snull pear

Question

marmomete Electrically heated sand bath . A. Benzopinacolone Charye a snull pear-shaped flask with 200 mg (0.546 mmol) of benzopinacol." 1 ml of glaciul acetie ucid, und a tiny crystal (about 5 mg) of iodine. Attach a condenser and heat to re lux using a sand-bath (Figure E 36. 1) for abo!: 5 min. Allow the solu- tion to cool. Benzopinacolone separates from solution. Add a little ethanol, mix thor- oughly. and isolate the product by suction filtration on a small Hirsch funnel. Ise additional ethanol to rinse the flask and to remove any iodine color from the product. Suck the benzopinacolone dry for a few minutes, weight it, and determine the yield and mp. The reported mp is 182-184°C. The yield should exceed 70%. EXER C.ISES 4. Because benzopinacol und benzopinacolonc have nearly identical melting points. describe (without using spectroscopic methods) how you might prove that samples of the two compounds are different. 5. (Optional; Spectroscopic) Destribe any impurtant differences between benzopinacol and benzopinacolone in the IR Experiment 36 Carbocation Rearrangements-B

Explanation / Answer

4) Pinacaol has OH functional group while pinacalone has C=O functional group.

We can test for alcohol using metals like Na , when reacted OH in pinacol H2 gas is released. No such reactions in pincalaone. Again alcohol reacts with carboxylic acid to give esters which is possible in pinacol but ot possible in pinacalone.Thus we can differentiate them.

2ROH + 2Na --> 2RONa + H2

5) IR shows peak near 3200-3500 cm-1 range for pinacol since it belongs to OH strech

IR shows peak near 1700 cm-1 for pinacolone since it belongs to C=O strech

H-NMR peak for pincaol will have a small broad peak singlet at near 4 to 5 ppm indicating alcoholic OH peak

no such peaks for benzopinacalone

C-NMR shows peak at 60-90 ppm indicating C attached to alcoholic O for pinacol

C-NMR shows peak at 180 - 200 ppm range indicating C of C=O in pinacalone

These are key differences

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