preface to fifteenth edition

SPECTROSCOPY 7.127
Masses 19 and 31 Alcohol
Mass 66 Monobasic carboxylic acid
Masses 77 and 91 Benzene ring
7.8.2.4 Characteristic Low-Mass Neutral Fragments from the Molecular Ion
Mass 18 (H 2 O) From alcohols, aldehydes, ketones
Mass 19 (F) and 20 (HF) Fluorides
Mass 27 (HCN) Aromatic nitriles or nitrogen heterocycles
Mass 29 Indicates either CHO or C 2 H 5
Mass 30 Indicates either CH 2 OorNO
Mass 33 (HS) and 34(H 2 S) Thiols
Mass 42 CH 2 CO via rearrangement from a methyl ketone or an aromatic
acetate or an aryl-NHCOCH 3 group
Mass 43 C 3 H 7 or CH 3 CO
Mass 45 COOH or OC 2 H 5
Table 7.76 is condensed, with permission, from the Catalog of Mass Spectral Data of the American
Petroleum Institute Research Project 44. These, and other tables, should be consulted for further
and more detailed information.
Included in the table are all compounds for which information was available through the C 7
compounds. The mass number for the five most important peaks for each compound are listed,
followed in each case by the relative intensity in parentheses. The intensities in all cases are normalized
to the n-butane 43 peak taken as 100. Another method for expressing relative intensities is
to assign the base peak a value of 100 and express the relative intensities of the other peaks as a
ratio to the base peak. Taking ethyl nitrate as an example, the tabulated values would be
Ethyl nitrate 91(0.01)(P) 46(100) 29(44.2) 30(30.5) 76(24.2)
The compounds are arranged in the table according to their molecular formulas. Each formula is
arranged alphabetically, except that C is first if carbon occurs in the molecules, followed by H if it
occurs. The formulas are then arranged alphabetically and according to increasing number of atoms
of each kind, all C 4 compounds being listed before any C 5 compounds, and so on.
Nearly all these spectra have been recorded using 70-V electrons to bombard the sample molecules.