The following spectra are taken from a compound that is an important starting material for organic synthesis. Determine the structure, first by considering each spectrum individually, and then by considering all the spectra together. Assign peaks to show that your proposed structure accounts for all the major features of each spectrum. DEPT information is given in blue on the carbon NMR.

From the given IR spectrum, it is deduced that, the dominant functional group peak is at 1685 Cm^-1 , a carbonyl that is conjugated with C=C (lower wave number than normal, very intense peak). The presence of an oxygen and a molecular ion of 96 leads to a formula of C₆H₈O with three elements of unsaturation, a carbonyl bond and one or two C=C .

The six peaks shown by chemical shift are one carbonyl carbon at 196, two alkene carbons at 129 and 151 and three aliphatic carbons at 23,26 and 36. From the DEPT information at the top of the spectrum, the groups are: three methylene groups, two alkenes CH groups and a carbonyl.

Since the structure has one carbonyl and only two alkene carbons, the third element of unsaturation must be a ring. Since the structure has no methyl group, and no H₂C= and all the carbons must be included in the ring. The only way these pieces fit together is in cyclohex-2-enone.

Structural fragments obtained from given spectrum datas

Structure obtained from analysis of given spectrum datas