The C l spectra obtained for compounds 1 - 1 0 (Table
1 ) were similar to those obtained previously for phos
phonates with hydrocarbons,’ the major high molecu lar weight signal being due to the protonated molecu lar ions [ M + l] ’ . Useful structural data could be ob tained from ammonia C l spectra. For example, the spectrum of tetra-isopropyl methylene bisphosphonate
(1) (Fig. 1) contained peaks at m/z 345 (6.6% ) , 303
(4.0%), 261 (6 .2 % ), 2 19 (3 .2 % ) and 177 (3 .5 % ), indicating the successive loss of C ,H ft (42 u) and con firming the presence of a tetra-isopropyl ester (Table 2) . The corresponding signals were scarely discernible in the E l spectrum of 1. The C l spectra of the tetra-
isopropyl esters of monochloro- (2), monobromo- (3)
and dibromo- (4> -methylene bisphosphonates all
showed similar families of peaks consisting of the protonated molecular ion and ions derived from the
J Figur* 1 . A m m o n i a C l m a s s a p e c t r u m o f t a t r a - i s o p r o p y l m e t h y l e n e b i s p h o s p h o n a t e ( 1 ) . CCC-0030-493X/83/0018-0057*01.50 O R G A N I C M A S S S P E C T R O M E T R Y , V O L . 1 8 , N O , 2 , 1 9 8 3 5 7 © Wiley Heyden Ltd. 1983
P A . C L O A D A N D D. W H U T C H IN S O N
Table 1. Compounds studied
Elemental
Name Formula com position M ol. wt
Phosphonates
1 Tetra-isopropyl methylene (Me2CH0)2P(0)CH2P(0)(0CHMe2)2 C ^ Hj oO . Pj 344
bisphosphonate
2 Tetra-isopropyl monochloromethylene (Me2CHO)2P(OICHCIP(OXOCHMe2)2 C13H 20CIO,P2 378
bisphosphonate 380
3 Tetra-isopropyl monobromomethylene (Me2CH0)2P(0)CHBrP(0X0CHMe2)2 C,3HM BrOBP2 422
bisphosphonate 424
4 Tetra-isopropyl dibromomethylene ( M e 2CH0)2P<0)CBr2P(0)(0CHMe2)2 500
bisphosphonate 502,504
5 Triethyl phosphonoacetate <EtO)2P(0)CH2COOEt c8h17o,p 224 6 Triethyl 2-phosphonopropionate (EtO)2P(0)CHMeCOOEt C„H,„OsP 238 7 Diethyl phosphonoacetonitrile (EtO)2P(0)CH2CN c„h,2n o3p 177 8 Diethyl allylphosphonate (EtO)2P(0)CH2CH CH2 c2h,6o3p 178 9 Benzyl diethyl phosphonoformate (EtO)2P(0)COOCH2Ph C,2H,7O sP 272 10 Diethyl phosphonoacetic acid (EtO)2P(OICH2COOH C.H13O bP 196
Phosphates
11 Trimethyl phosphate (MeO)jPO c3h.o4p 140 12 Triethyl phosphate (EtO)3PO c bh,bo4p 182 13 Tri-isopropyl phosphate (Me2CHO)3PO c„h2,o4p 224 14 Tri-n-butyl phosphate (BuO)3PO c,2h27o„p 266 15 Triphenyl phosphate <PhO)3PO c,.h,b0 4p 326
Phosphites
16 Trimethyl phosphite (MeO)jP c3h„o3p 124 17 Triethyl phosphite (EtO)3P c„H,Bo 3p 166 18 Triphenyl phosphite (PhO)3P c,.h,bo3p 310
Phosphoramidates
19 Di-isopropyl phosphoramidate (Me2CHO)2P(OINH2 c,h10n o3p 181 20 Hexamethyl phosphoramide (Me2N)3PO C.H,bN 3OP 179
successive loss of propene residues. This decomposi tion presumably arises from the protonation of the phosphoryl oxygen followed by elimination of olefin (Scheme 1). As might be expected, owing to the presence of halogen atoms, the protonated molecular
ion and related ions in 2 were doublets (ratio 1 : 2 .8),
doublets (ratio 1 : 1 ) for 3 and triplets (ratio 1 : 2 : 1) for
4 (Table 2).
Structural information could also be obtained from the C l mass spectra of the ethyl esters 5-1 0. In addition to the protonated molecular ion, other major ions corresponding to the successive loss of 28 u (pre sumably ethene) were present, confirming the pres
ence of P—O—C 2H , residues. The C l mass spectra of
5 and 6 also showed ions corresponding to the loss of
ethanol from the protonated molecular ion. This loss
must involve the C O O C j H , group as this fragmenta
tion does not occur in compounds 7-10. The C l mass
spectrum of the carboxylic acid diethyl phosphonoacetic
acid (10) showed a peak due to [M + N H 4]4 m lz 214
(4 .2% ), as well as a large peak due to the protonated molecular ion (2 9 .5 % ). Peaks due to loss of carbon
d?»R o h r
C H ^ - r ---• CH,CH—CHj + O— V
CH, X R X R
Sebum* 1. Ducompouition of th* protonated molecular Ion of Isopropyl eater of oxyacld of phosphorus.
dioxide (m/z 153 , 1 1 .7 % ) and ethene (m/z 169, 1.9 % ) from the protonated molecular ion were also present. Phosphates
Previous C l studies’ did not include phosphate esters
although their E l mass spectra have been studied
extensively.6 For phosphate esters, as might be ex
pected, the major high molecular weight ion in their
C l mass spectra was [ M + 1]*. Again, families of peaks
could be observed in the C l spectra from which infor
mation could be deduced as to the nature and number of groups bonded to phosphorus. Thus, the trialkyl
esters 12-14 gave [M + l]4 and ions due to the succes
sive loss of three molecules of olefin (ethene, propenc
and butene respectively) (Fig. 2). Trimethyl (11) and
triphenyl (15) phosphates showed little fragmentation
in their CT mass spectra. The fragmentation of the
trialkyl phosphates could be observed in their E l mass spectra. However, as the ion current carried by the
molecular ion was less than 1% of the total ion current
in all cases, the fragmentation patterns were much
more difficult to observe than in the C l mass spectra.
Phosphites
Ammonia C l mass spectrometry was also useful for
the detection of esters of oxyacids of trivalent phos-
M A S S SPECI R A O F O X Y A C I D S O F P H O S P H O R U S m ental 'position IO.P, *>.P2 lriO | P ;2 •P p 3P 344 378 380 422 424 500 502,504 224 238 177 178 272 196 P -P 4P 4P 140 182 224 266 326 P 3P 124 166 310 181 179 ethene (m/z 169, 1 .9 % ) jr ion were also present.
include phosphate esters sctra have been studied esters, as might be ex- cular weight ion in their . Again, families of peaks spectra from which infor- o the nature and number orus. Thus, the trialkyl d ions due to the succes- f olefin (ethene, propenc
. 2). Trimethyl (11) and
'wed little fragmentation c fragmentation of the ybserved in their E l mass current carried by the % of the total ion current ion patterns were much
in the C l mass spectra.
J I