?4) There is a cluster of peaks in the 1 H NMR spectrum between ? 7-8 ppm. Which

Question

?4) There is a cluster of peaks in the 1 H NMR spectrum between ? 7-8 ppm. Which hydrogen atoms in your product do those peaks correspond to, and why?

5) identify the peak in the 1H NMR spectrum corresponding to the OH hydrogen in the product.

6)You have now assigned five of the protons in the molecule. Now, consider the peaks from ? 3-5.5 ppm labeled 1 - 4 in the 1H NMR spectrum. How many chemically inequivalent hydrogen atoms are left in this molecule? Explain how you determined your answer

7) a)Describe the coupling pattern (i.e. doublet, triplet, doublet of doublets etc) for the peak at ? 5.31, and calculate the coupling constant .Note - the 1H NMR spectrum was obtained on a 300 MHz spectrometer b) Describe the coupling pattern (i.e. doublet, triplet, doublet of doublets etc) for the peak at ? 4.29, and calculate the coupling constant (J) value(s). c) Describe the coupling pattern (i.e. doublet, triplet, doublet of doublets etc) for the peak at ? 3.60, and calculate the coupling constant (J) value(s). d) Describe the coupling pattern (i.e. doublet, triplet, doublet of doublets etc) for the peak at ? 3.25, and calculate the coupling constant (J) value(s).

(8) Using the coupling constants you calculated in Q7, identify which protons 1 - 4 couple to each other (i.e. does 1 couple with 2, etc).

(9) I have labeled the 4 protons in the product Ha - Hd below. Ignoring the identity of X and Y (we'll get to that later) assign the 1H NMR spectrum (i.e. which of the numbered peaks 1-4 correspond to protons HA-D?). Use your answer to Q8 to help.

Explanation / Answer

4) The peaks between 7-8 are aromatic peaks, it's bcoz aromatic peaks are highly deshielded due to anisotropic effect of the pi electron cloud on the ring which creates magenetic field which is allined in the applied magnetic field and deshields the protons attached to the carbons

5) A broad singlet at 2.5 is the OH peak

6) The 4 Hs, Ha, Hb, Hc and Hd and chemically unequivalent bcoz they have different neighbors or geometrically they are in different environment in the space.

7) a) peak at 5.3 is doublet. It must be Ha, since it has just one proton (Ha) available in it's neighbour available for 3 bond coupling. since it's just 3oo MHz NMR, only protons with 3 bond or 2bond will split. bcoz of available 1 neighbouring proton it splits into a doublet as (2nI +1) = [(2 * 1 * 1/2) + 1] = 2. here n = no. of neighboring protons, and I is constant and for hydrogen = 1/2. Coupling Constant = (5.310 - 5.286) X 300 = 0.024 = 7.2Hz

b)peak at 4.29 is quartet and coupling constant = (4.294 -4.270) X 300 = 7.2 Hz

c) peak at 3.60 is doublet of doublet and has two coupling constants. The first J value = (3.601 -3.564) X 300 = 9.1 Hz and second J value (3.601 -3.554) X 300 = 14.1Hz

d) peak at 3.25 is also doublet of doublet, the first J value = (3.253 - 3.229) X 300 = 0.024 X 300 = 7.2 Hz and second J value is (3.253 - 3.190) X 300 = 0.063 X 300 = 18.9 Hz

8) since coupling constants of 1 and 2 are same and also one of the coupling constant of 4 is same therefore they couple with each other.

9) 1 is Ha, 2 is Hb, 3 and 4 are Hc and Hd, its tough to pin point between Hc and Hd.

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