Mass Spectral Fragmentation Pattern of N,N'-Diphenylformamidines
N e i l G. K e a t s , J e a n E. R o c k l e y , and L i n d s a y A. S u m m e rs
Department of Chemistry, The University of Newcastle, 2308, New South Wales, Australia
(Z. N aturforsch. 32 b, 1156-1159 [1977]; received Ju n e 27, 1977)
Mass Spectra, N,N'-Diphenylformamidine, N,N'-Di(chlorophenyl)formamidines
The base peaks in the mass spectra o f N,N'-diphenylformamidine, N,N'-di-(4-chlorophenyl)formamidine and N,N'-di-(3-chlorophenyl)formamidine are due to the molecular
ions of aniline, 4-chloroaniline and 3-chloroaniline respectively. The species responsible for
the base peaks are thought to be formed by rupture of the C H -N H bond with concomitant
hydrogen migration.
There has been very little investigation of the
mass spectral fragmentation of formamidines on
electron impact1. The rearrangement processes
involved in the fragmentation of N,N-dimethyl-N'phenylformamidines have been the subject of some
study 2-6 but there has been no report of the frag­
mentation of simple formamidines. This paper is
concerned with the mass spectral fragmentation of
N,N'-diphenylformamidine (1) and two symmetri­
cally substituted N,N'-di(chlorophenyl)formamidines (2) and (3).
The base peak in the spectrum of N,N'-diphenylformamidine (1) (Fig. 1) is not due to the molecular
ion at mass 196. The base peak is at mass 93 due to
a species of formula C6H?N®\ The molecular ion at
mass 196 gives rise to a peak of 41 % of the intensity
of the base peak. Loss of H ‘ from the molecular ion
gives the M-l ion which is responsible for the peak
at mass 195 (11%).
~80-
40
---- p-au----- --------60
80
| ---------- 1------------ 1------------ 1------------ 1--------““-T
100
, 120
140
160
180
20C
m /e
Fig. 1. Mass spectrum of N,N'-diphenylformamidine.
ci
ci
3
Requests for reprints should be sent to Prof. Dr.
L. A. S u m m e r s , Department of Chemistry, The U ni­
versity of Newcastle, 2308, New South Wales, Aus­
tralia.
The fragmentation pattern of N^'-diphenylformamidine (1) (Scheme) is an interesting one. The
initial disintegration of the molecular ion of 1 at
mass 196 involves rupture of the CH-NH bond to
afford the two fragments at mass 104 (10%) and
92 (4%) due to CtHcN® and CeHöN® ions respect­
ively. This bond rupture, however, may be ac­
companied by a hydrogen migration to afford the
two species at mass 103 (2%) and 93 (100%) of
empirical formula CtHsN®- and C e ^ N ®1 depicted
as the phenylisocyanide and aniline molecular ions
respectively. A strong metastable peak in the
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N . G. K eats et dl. ■Mass Spectral F ragm entation P a ttern o f N .N '-D iphenylform am idines
1157
©
c6h6n^
O -®
m/e 92 (4%)
>*
*
n @ ‘
CjH,,© ’
m/e 64 (2%)
C13H12N2
M+ m/e 196 (41%)
CS«,0
c 13h 11n 2 ®
m/e 195 (11*)
m/e 63 (1%)
.©
C5H6'
m/e 66 (7%)
C7H5N
c
m/e 103 (2%)
spectrum at mass 44.2 corresponds to the transition
196^-93. The aniline molecular ion (at mass 93)
which is known to be a very stable one 7 is in fact the
base peak in the spectrum of N,N'-diphenylformamidine.
The subsequent fragmentation of the C7H 6N®,
CeHeN®, CrHsN®- and Ce^N®' species involves the
loss of HCN in each case. Metastable peaks are
observed for these transitions. This results in the
formation of the species giving rise to peaks at mass
77 (26%; C6H5®), 65 (6 %; C5H5®), 76 (2 %; C6H4®-)
and 66 (7%; CsHe®-). The species considered to be
the phenylisocyanide molecular ion at mass 103
(C7HsN®-) may also lose CN- (cf. 8) and this frag­
mentation route provides another source of the
CöHs® ion at mass 77. Successive losses of H- from
the C5H 5®ion at mass 65 account for the small peaks
(1-2%) at mass 64 (CsH4®-) and 63 (C5H 3®). The
peaks below a mass of 60 in the spectrum are typical
of those to be expected from further disintegration
of the species shown in the Scheme and require no
comment.
6h 7 n
m/e 93 (100%)
Table I. Empirical formula o f fragment ions* in the
mass spectrum o f NjN'-diphenylformamidine (1).
m/e
Formula
196
195
194
104
103
93
92
91
77
76
C13 H 12 N 2
Ci3H n N 2
C13 H 10 N 2
c 7 h 6n
C7 H 5 N
c 6h 7n
c 6h 6n
c 6h 5n
c 6h 5
c 6h 4
c 5h 6
C5 H 5
c 5h 4
C5H 3
c 4h 3
c 4h 2
66
65
64
63
51
50
Intensity [%]
41
11
2
10
2
10 0
4
1
26
2
7
6
2
1
11
3
* Only those ions of mass > 49 and of intensity > 1 %
o f the base peak are recorded. Peaks due to 13C
species are om itted from the table.
The spectra of N,N'-di-(4-chlorophenyl)-formamidine (2) (Fig. 2) and N,N'-di-(3-chk>rophenyl)formamidine (3) (Fig. 3) are very similar and their
fragmentation pathways follow much the same
route as that observed with N,N'-diphenylformamidine (1). In both cases the base peak is at mass
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1158
N . G. K ea ts et al. • Mass Spectral F ragm entation P attern o f N ,N '-D iphenylform am idines
100,—
127
_80 —
».60 —
"20
in
75
65
264
138
I
jjU l
40 ’
60
80
100
120
140
160
180
200
220
240
2Ij O
2^0
m/e
Fig. 2. Mass spectrum of N,N'-di-(4-chlorophenyl)-formamidine.
127
lOOr—
'8 0
'S 60
40
75
520
138
50
65
92
- n lr , i 1 , I al. I|
40
60
80
100
264
LA
120
140
, 160
m/e
~l— ~ 1— —I—
180
200
220
240
260
—r
280
Fig. 3. Mass spectrum of N^N'-di-^-chlorophenylJ-formamidine.
127 due to the molecular ion of the corresponding
chloroaniline of formula CeHeNCl. The molecular
ion of the di-(chlorophenyl)-formamidines at mass
264 gives rise to a peak of 18% of the intensity of
the base peak with the 4-chloro derivative (2 ) and
14% of the intensity of the base peak with the
3-chloro analogue (3). The peaks at mass 138 (13%;
C7H 5NCI®) and mass 126 (2 - 6 %; CeHsNCl®) are
likewise considered to arise largely by rupture of
the CH-NH bond while those at mass 137 (1%;
C7HiNC1®) and 127 (100%; CeHeNCl®-) are formed
by hydrogen migration accompanying the rupture
of this bond. The peaks at mass 111 (15-26%;
C6H 4C1®), 99 (3%; C5H 4C1®), 110 (1%; C6H 3C1®),
and 100 (3%; CsHsCl®-) may be formed by sub­
sequent loss of HCN but metastable peaks were
observed only for the transitions 138->-111 and
127 ->100. It is interesting to note that the central
bond rupture occurs before loss of Cl- from the
molecular ions of 2 and 3. The peaks below a mass
of 99 in the spectra of 2 and 3 require little comment
(see Table II). They are typical of those to be
expected from benzene, chlorobenzene and chloro­
aniline derivatives.
Table II. Empirical formula of fragment ions* in the
mass spectra of N,N'-di -(chlorophenyl)-formamidines.
Intensity [ % ]
Formula
m/e
2
8
10
12
Ci3 Hio 37 C12N 2
14
Ci3 Hio 35C12N 2
18
5
5
c 7 h 537c i n
13
13
c 7 h 535c i n
1
1
C7 H 435C1N
26
31
c 6 h 637c i n
10 0
10 0
C6H 635C1N
6
2
c 6 h 535c i n
8
5
C6 H 437 C1
28
15
C6H 435C1
111
1
1
CeHg^Cl
110
3
3
C5 H 535C1
10 0
3
3
C5 H 435C1
99
6
4
C6 H 6N
92
3
2
c 6 h 5n
91
1
1
c 6h 4n
90
1
1
C4 H 235C1
85
2
1
77
c 6h 5
4
2
c 6h 4
76
19
11
c 6h 3
75
3
2
c 6h 2
74
2
1
c 6h
73
6
4
65
c 5h 5
3
1
c 5h 4
64
5
3
c 5h 3
63
1
1
c 5h 2
62
*
l_ii---- - :__ _____ — aa
_ 1 0/
of the base peak are recorded. Peaks due to 13C
species are om itted from the table.
266
264
140
138
137
129
127
126
113
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N . G. K ea ts et al. • M ass Spectral Fragm entation P a tte m o f N ,N '-D ip h en ylform am id in es
1159
Experimental
The mass spectra were determined with an A. E. I.
MS-30 mass spectrometer. The samples were ana­
lysed by a direct insertion probe at an ionizing
current of 70 eV. The ion source temperature was
140 °C. Elemental compositions were obtained by
the peak matching method.
N,N'-Diphenylformamidine, N,N'-di-(4-chlorophenyl)-formamidine and N,N'-di-(3-chlorophenyl)formamidine were analytically pure.
in S. P a t a i (ed.): The Chemistry of
Amidines and Im idates, p. I, W iley, New York 1975.
A. K . B o s e , I. K u g a j e v s k y , P . T. F u n k e , and
K . G . D a s , Tetrahedron L ett. 1965, 3065.
H. F . G r ü t z m a c h e r and H. K u s c h e l , Org. Mass
Spectrom. 3, 605 [1970].
H. K u s c h e l and H. F . G r ü t z m a c h e r , Org. Mass
Spectrom. 9, 395 [1974].
H. K u s c h e l a n d H. F. G r ü t z m a c h e r , Org. M a s s
Spectrom. 9, 403 [1974].
6 H. K u s c h e l a n d H. F. G r ü t z m a c h e r , Org. M a s s
Spectrom. 9, 408 [1974].
7 P. N. R y l a n d e r , S. M e y e r s o n , E. L. E l i e l , a n d
J. D. M c C o l l u m , J. A m . C h e m . Soc. 85, 2723 [1963].
8 B. Z e e h , Org. Mass Spectrom. 1, 315 [1968].
1 G . H ä f e l in g e r
2
3
4
5
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