Part 8: STRUCTURE DETERMINATION

A schematic of the solution is shown below. The information from the question is given in black. The types of reactions for each compound are shown in green.

The keys here are (1) being able to draw 1-phenylethanol correctly (2) knowing your reactions and (3) being able to interpret H NMR spectra.

Once the structure of 1-phenylethanol is drawn, the reactions define the functional groups of each compound and the locations of the functional groups. In many cases, students IGNORED the regioselectivity of the reactions and hence failed to confirm structures. Even a quick glance at any of the H NMR spectra should have indicated the presence of a monsubstituted aromatic group in all the compounds.
 

With the structures, identified the key features can be matched to the H NMR spectra :
 

structure
characteristic spectral details
spectra
A
5:1:1:1, vinyl H with complex coupling 5-7ppm
III
B
5:2:3, classic ethyl group coupling pattern
II
C
5:1:3, deshielded 1H quartet and 3H doublet
VI
D
5:1 singlet for 1H for acetylenic H
V
E
5:3 singlet for 3H near 2.2 ppm
I
F
5:1 very deshielded H >10ppm for CO2H
IV