Question

1 Introduction Now try another simple spectrum, Unknown 1.2. Your structure will be cor- rect if the molecule and its pieces have masses corresponding to those of the spectrum. (Make a serious attempt to solve each unknown before looking at the solution. This is a vital part of the book's instruction) Unknown 1.2 Relative intensity Unknown 1.3 contains carbon, hydrogen, and oxygen atoms. Obviously the possibilities for arranging these in a molecule of molecular weight 32 are limited. Compare any molecular-structure possibilities with the major peaks of the spectrum. Unknown 1.3 Relative Intensity The tubular data for Unknowns 1.1, 1.2. and 1.3 include additional low- abundance peaks that can be important ("Int." is the peak intensity relative to the most intense peak as 100). The mass spectrometer has a dynamic range much greater than the three orders of magnitude shown: that is, ion abundances Page 4 of 16

Answer 1

Unknown 1.2

with m/z = 16 corresponds to methane CH4 (12 +1 x4 = 16)

Unknown 1.3

with m/z =32 M+ peak corresponds to methanol CH3OH (12+3*1+16+1 = 32) is molecular ion peak

however base peak is at m/z = 31 most intense for CH3O+. species.