Question

Question 12 of 20 Map dub w H. Freeman and Company presented Organic Chemistry Peter Vollhardt and Neil The 1H NMR spectrum below corresponds to an unknown compound with the molecular formula C4HBO. Deduce and draw the structure of the molecule that corresponds to the data below. H NMR 3 H 1 H IIH 4,3 1 H 1 H 1 H (CH3)4Si 6,0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 00 300 MHz IH NMR spectrum ppm (s)

Answer 1

a)

We have C4H8O

degree of unsaturation = ( nC x 2 + 2- nH) /2

           = ( 4 x 2 + 2 - 8) /2 = 1 hence we have 1 double bond

IR peaks confirm C=C peak at 1665 cm-1 and we had H-NMR peaks at 5-6 to confirm this.

Since we had three peaks at C=C H-NMR region we had CH=CH2 as last part.

We had CH3 peaks at 1.4 ppm and OH peak at 1.5 ppm

Joining remaining we get

b)

The compound is 1,2-dibromo-1,1-difluoroethane. The spectrum shows a triplet because of the coupling of the protons with the two fluorine atoms on the adjacent carbon. The coupling constant 16.0 Hz corresponds to the coupling between H and F nuclei.