Organic Chemistry 201

Chapter 12   Structure Determination: Mass and Infrared Spectroscopy

The following are items that you need to know for Exam V:

Mass Spectra (MS) M.+ = MW

base peak = most prevalent and stable radical-cation or carbocation fragment

Hydrocarbons usually fragment to give the largest R.

Rule of 13: M.+ / 13 = n + r    MF = Cn Hn + r

Rule of 13 substitutions (C = 12H, O = CH4, N = CH2, etc.)

Nitrogen Rule: M.+ is odd for an odd number of N's

IR = fuctional group analysis

1. H - stretch: 3700 - 2500 cm-1   O-H, N-H, C-H, S- H

2. Triple bond stretch: 2400 - 2100 cm-1   CC, CN

3. Double bond stretch: 1850 - 1470 cm-1   C=O, C=N, C=C

4. Finger print 1470 - 650 cm-1

C-C, C-N, C-O stretch

C-H, O-H bend