Question

Question 4 Consider the data provided in appendix B containing the mass spectrum, the IR spectrum and the 'H NMR of an unknown compound. Determine the structure of this compound base on the data provided. (Make sure to show your work).

Answer 1

Answer:

From the MS:

The molecular ion peak is at m/z = 117, which is an odd number. It means that the compound is a N containing compound and it contains odd number of N atom.

IR spectra:

The strong peak at around 2250cm-1 confirms the presence of a Cyanide (-CN) group. Also this Cyanide group is not in conjugation with any other conjugating fragment because cyanides in conjugation with others show this peak at below 2240 cm-1

The two peaks between 3000-3100 cm-1 indicates presence of olefinic or aromatic proton.

The two peaks between 2900-3000 cm-1 are for C-H stretching of saturated C-H bonds or methylene C-H bond.

The two strong peaks in between 600-800 cm-1 indicates that this is a monosubstituted benzene ring. These peaks arise due to out of plane bending of C-H bonds.

NMR:

The multiplets above 7ppm is because of aromatic hydrogens and the singlet peak at 3.7 ppm is because of the methylene H connected to the benzane ring and also to the cyanide ring.

From these available data, we can conclude that this compound is benzyl cyanide or phenyl acetonitrile.

The structure is shown below-

H ㅂ CEN - H J hs M I IH