Below is the H NMR spectrum for ethyl acetoacetate from the SDBS database websit

Question

Below is the H NMR spectrum for ethyl acetoacetate from the SDBS database website. I assume this is the ethyl acetoacetate in this keto form, and the peaks are 1.288, 2.273, 3.451, and 4.202. The peak levels are just as identical to the peaks on my spectrum. I was told that there is an enol peak on my spectrum but I cannot seem to tell which one is the enol peak. When we plotted the spectrum and integrated the bands, we may have mislabeled the peak at 3.452 ppm as the enol form.

346 366 388 409 517 719 861 882 902 100 103 15 PPM INTENSITY REL INT LABEL HZ 8.120 1 40521 259.02 118358 23.718 2 4.202 252.14 121233 24.294 3 4.073 244.44 49561 932 4 956 237.42 61.582 5 307307 200.57 342 96.954 6 2.190 483817 131.42 28.097 7 1.379 140208 82.75 282351 56.581 8 263 75.77 27.735 9 138404 1.145 68.72 251258 50.351 10 019 1.14 69.290 11 34 5769 -0.00 000 0,43 12 10 OFI: 360,7 SW 1400 0181 43 PPM ER --DATE: 03/23L17 u 3:44) PTSld: 4096

Explanation / Answer

H NMR spectrum for ethyl acetoacetate

CH3COCH2COOCH2CH3 keto form

CH3C(OH)=CHCOOCH2CH3 enol form (-OH as substituent)

4 types of proton - in keto form -4 peaks

1)CH3COCH2COOCH2CH3 keto form (singlet ,no coupling) 2-2.7ppm

2)CH3COCH2COOCH2CH3 keto form(singlet ,no coupling) 2-3 ppm

3)CH3COCH2COOCH2CH3 keto form(quaret, 3.5-4.0 pm)

4)CH3COCH2COOCH2CH3 keto form(triplet,1-1.2 ppm)

5 types of protons in enol form-5 peaks should be there

1)CH3C(OH)=CHCOOCH2CH3 (singlet ,no coupling) 3-4 ppm

2)CH3C(OH)=CHCOOCH2CH3 (singlet 2-4pm)

3

3)CH3C(OH)=CHCOOCH2CH3 (vinylic H, 4.6-5.9ppm,singlet)

4)CH3C(OH)=CHCOOCH2CH3 ((quaret, 3.5-4.0 pm)

5)CH3C(OH)=CHCOOCH2CH3((triplet,1-1.2 ppm))

so it must be keto form NMR only.

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