Question

The low-resolution mass spectrum of an unknown monosubstituted benzene showed a molecular ion (M+) peak at m/z 150. Combustion analysis of a sample of this compound indicated that the compound contained C, H, and O only and had an empirical formula of C3H1002. The IR spectrum of the unknown compound is shown below. The 'H NMR spectrum of the unknown compound did not show a peak in the 9.10 ppm range. D 4000 9000 2000 1500 1000 RAVENUGERII What is the molecular formula of the unknown? Which peak from the IR spectrum is most revealing about the chemical structure of this unknown? Provide its approximate wavenumber in cm2 What functional group does this IR peak represent? What functional group is not present due to absence of a peak in the 9 - 10 ppm range in the 'H NMR spectrum? In the spaces provided, clearly draw the Lewis structures of three monosubstituted benzenes that are consistent with all of the given information

Answer 1

Molecular ion peak (m ) = 150 Empiricel fomula -cg H 002 Empiriccel formula mass= = 9x12 + 1oxi+ 16x 2 - 108+10+32 = 150 - molecular formula mass = Empirical formula mass . Molecular formula = Cg Hooz ew , n at IR Peak redealing structure 174on is most about the chemicel I.R. Peak 1740 cm is due to -c=o streen als estero. IR peak 1740cmt represents ester functionel group

* the The peak 9-10 pom range in 'H NMR spectrum is due to aldehydic hydrogen. R c -HE 9-10 ppm aldehydic functional group is not present due to absence ols a peak in the galoppm range in 'H NMR Lewis structures of three mono- -substituted benzerses. :0: Ica) ö CH2-CH3 LE (0) th- ö- c- CH2 cc) ettz