Question

Evaluate and investigate the following IR Spectrum, ¹³C NMR Spectrum and ¹H NMR Spectrum. Identify the most important peaks and correlate the results as much as you can from the obtained product in the multi-step synthesis of ethyl acetoacetate. This is Product E from this multi-step synthesis where Product C was identified as in the figure below and as such, identify what product can be obtained after the synthesis from the spectra provided. Use the template below in analysing the spectra. With this, draw splitting trees and graph the multiplet(s) present in the spectrum and provide an explanation for each.

Figure 1 (above): IR Spectrum of Product E

(EXAMPLE ONLY)

Frequency (cm-1)	Relative Intensity or Shape	Vibrational Assignment
2950	Medium	C-H Stretch
1715	Sharp and Strong	C double bond O Stretch

Figure 2 (above): ¹H NMR Spectrum of Product E (Full View and Zoomed)

(EXAMPLE ONLY)

Hydrogen Number	Integral	Signal Multiplicity	Exptl. $\delta$(parts per million)	Assignment	Expected Chemical Shift, $\delta$(parts per million)
H1	(Example: 1, 2 or 3)	Triplet	1.32	CH3C-O-	1.2

Figure 3 (above): ¹³C NMR Spectrum of Product E

(EXAMPLE ONLY)

Cabon No.	Observed Shift, $\delta$ (ppm)	Assignment	Expected Chemical Shift, $\delta$ (ppm)
C1	137	C=C	135-140
C2	140	C=C	135-140
C3	151	C=C	135-140

The procedure is also given below:

Procedure

Step 4B [Product C to Product E]
   Place product [C] (0.5 g) in a 50 mL round bottomed flask, add acetone (15 mL), and concentrated HCl (2.5 mL). Boil under reflux on a water bath for 30 minutes. The solution should become pinkish-orange. Add water (30 mL), with swirling, then extract with ether (2 x 10 mL). Wash the combined ether layers with saturated sodium bicarbonate (3 x 10 mL), then water (2 x 10 mL). Dry the ether solution with anhydrous sodium sulfate, filter, and evaporate the ether to yield a yellow oil. This crude product [E] may be purified by rapid column chromatography.

Obtain a column with stopcock. If it does not have a sintered glass disc at the bottom, place a plug of cotton wool in the constriction. Clamp the column vertically, add 15 g of silica gel to the column, tap with rubber tubing to settle the packing, then place a 1 cm layer of sand on the top of the silica gel. Prepare 100 mL of 50/50 diethyl ether/petroleum ether (b.p. 40-60 °C). This mixture is referred to as “eluent” below. Keep the prepared mixture in a covered Erlenmeyer flask until needed. The successive steps must follow each other quickly, so prepare everything in advance.

1. Prewashing of column: Add eluent to the column, without disturbing the top of the packing. Open the stopcock, adding more eluent until the packing is saturated and liquid drips from the bottom. Tapping the column with rubber tubing will displace large bubbles, but if you delay here, more bubbles will form, especially on a warm day. When the column is prepared, allow it to run until liquid is just above the sand, then close the tap. Proceed immediately to the next step.

2. Application of the sample: Dissolve your crude product [E] in about 1 mL of eluent, transfer this solution by Pasteur pipette to the top of the packing. Rinse the flask with a further 2 mL of eluent, and transfer the rinsings to the column. As with all types of chromatography, your aim is to apply the sample in a narrow, concentrated band.

3. Elution of the product: Open the stopcock to allow the sample to flow on to the packing. Add more eluent to avoid the column drying out. The product will travel rapidly as a yellow band. Collect this band in a clean, dry, pre-weighed 100 mL round bottomed flask. When the yellow band has eluted, allow the column to run dry. Dispose of the used silica gel as instructed.

Evaporate the solvent to leave the pure product [E] as a yellow oil. Leave the flask on the rotary evaporator in the hot water for several minutes after all solvent appears to have gone, to make sure the last traces of solvent are removed. Measure the yield, and record the IR and ¹H and ¹³C NMR spectra. The product may discolor on standing, so show an Instructor the fresh material for checking.

OH dil. HCI acetone 8767536 3569549 205154472589078 704 2110821858355 8665-806376862 557407202871411563642 6554432111000825276394975- 26 67851 9 9691 8 Wavenumber cm-1 Heighb ppin 7.439 1250.695 ProductE 7.435 2024.963 7.428 13814.53 7.423 11684.18 5 7.416 7975.205 6 7.411 6542.117 7.404 1437.242 7.4 2521.02 9 7.387 785.704 .376 726.749 7.371 1279.704 .368 747.268 7.368 2667.857 7,357 1554.08 7.354 2015.795 7.35 4489.111 7.346 2171.762 7.342 4927.825 14 15 18 7.339 2465.881 20 7.334 5422.391 7.328 30231.48 22 7.321 10429.49 7.319 T059.539 19 24 7.315 9479,407 25 7.307 65.145 26 7.257 950.32 7.249 6611.82 28 7.244 6911.849 .2 2103.729 .236 4697.619 7.500 7.450 7.400 7.350 7.300 7.250 7.200 ppm (ti) 7.232 3603.535 7.225 5077.923 7.219 975.48 6.635 687.983 31 6.628 16741.33 36 2.202 991,725 1915 2563.141 1.908 59730.1 2.0 0 5.0 3 6.0 4.0 7.0 pm() Product E Solvent CDCI3 ppm 200.22 153.98 140.802 138.995 129.641 129.491 128.813 128.456 128.429 127.731 77.409 77.091 76.773 30.362 129.50 129.00 128.50 128.00 ppm (t1) 200 150 100 ppm (t1)

Answer 1

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