Report
TABLE I. API MASS SPECTRA Ion formula C4H6
C4H5 C4H4 C4H3 C4H2
C4H C3H3 C3H2
C3H C2H4 C2H3
C2H
Always insist on genuine
TYBQH ÏUBIH6 For your protection, every foot of genuine Tygon Tubing is branded with the Tygon name and formulation number. crystal-clear · chemically inert non-oxidizing · 73 standard sizes At laboratory supply houses everywhere, or write Norton Plastics and Synthetics Division, Akron, Ohio 44309.
NORTON PLASTICS & SYNTHETICS DIV. FORMERLY U.S. STONCU/ARl INC. 32-144 AKRON. OHIO 44303 Circle No. 43 on Readers' Service Card
30 A
·
ANALYTICAL CHEMISTRY
M/e
Relative intensity 1-3 butadiene
Relative intensity 1-2 butadiene
Relative intensity ethyl acetylene
54 53 52 51 50 49
100 65 11 23 24 8
100 45 12 23 26 1
100 43 8 19 22 8
39 38 37
90 8 6
44 8 1
76 15 9
28 27 26
32 46 15
34 53 18
35 41 15
In a similar way each of the compounds is studied, and the results are tabulated in Table II. A comparison of product ions quickly shows that each compound has at least one distinctive product or feature which characterizes it in an absolute sense. Of the three compounds only ethyl acetylene gives a CSH5+ product at m/e 65. Furthermore, only butadiene 1-3 does not give a C 7 H 7 + product at m/e 91. Using this information and knowledge that the empirical formula must be C 4 H 0 in each case (from the mass of the parent ion), the structure of a pure unknown may be determined by a simple inspection of the spectrum. Furthermore, many peaks in these spectra differ by factors of 4 or 5 from compound to compound so that additional confirmation may be obtained if necessary. It must be pointed out that in a mixture of the three compounds, cross reactions would also occur. It
would be necessary to know in advance the distinctive features of such reactions or to separate the components of the mixture using standard GC techniques. In the example discussed above, the parent ions reacted with their own neutral molecules. It is also possible to obtain information about the reactions of one specific ion with a number of neutral molecules or one molecule with a number of ions. For instance, O - reacts with olefins and diolefins as shown in Reaction 5, O " + RH -> OH + R -
(5)
but no comparable reaction is observed with alkanes or benzene derivatives. An analysis scheme could be constructed which would permit the structure of an unknown to be deduced from a series of known reactions which are dependent upon the functionality of the neutral molecule. Such procedures are often used in organic chemistry
TABLE II. PRODUCT DISTRIBUTIONS—REACTION OF PARENT IONS Ion formula
M/e
Relative intensity 1-3 butadiene
Relative intensity 1-2 butadiene
Relative intensity ethyl acetylene
93 91
100 0
100 78
100 60
80 79 78 77
80 100 6 0
6 25 0 5
8 83 2 30
C5H5
67 66 65
27 26 0
1 5 0
7 8 31
C4H7
55
6
1
21
C7H9 C7H7
CeHs ϋβΗν Ο^Ηβ
CeHs C 6 H, CeHe
