Received: June 2023

DOI 10.17677/fn20714807.2023.04.02

Fluorine Notes, 2023, 149, 3-4

DECAY SEQUENCES - IONIC SERIES OF MASS SPECTRA FOR 2,4,6‑TRIS(PERFLUOROALKYL)-1,3,5-TRIAZINES

N. D. Kagramanov

A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991, GSP-1, Moscow, B-334, Vavilov St. 28

e-mail: ndkagram@gmail.com

Abstract: This report presents the ion series of mass spectra for eight homologues of 2,4,6‑tris(perfluoroalkyl)-1,3,5-triazines from NIST libraries, including the ion series of two isomers: triazine (C₃F₇)₃C₃N₃ with symmetrical substituents C₃F₇ and triazine (CF₃)₂C₃N₃(C₇F₁₅) with unsymmetrical substituent C₇F₁₅. The influence of molecular weight of substituents and their symmetry on fragmentation of 1,3,5-triazines is discussed. Using [(CF₃)₃CO]₃C₃N₃ homologue with oxaperfluoroalkyl substituents as an example, the effect of (CF₃)₃C groups and oxygen atoms on fragmentation is discussed.

Keywords: 2,4,6-tris(perfluoroalkyl)-1,3,5-triazines, ion series of mass spectra, effect of molecular weight of substituents and their symmetry on peak intensities of fragment ions.

Ionic series of mass spectra for 2,4,6-trifluoro-1,3,5-triazine and 1,3,5-triazine

The first triazine homologues - 1,3,5-triazine and 2,4,6-trifluoro-1,3,5-triazine - are trimers of HCN [1] and, respectively, FCN [2]. Its ionic series are presented separately from other homologues, since it reflects the decays of triazine rings, not complicated by fragmentation of perfluoroalkyl substituents, which have large masses. Figs. 1 and 2 show the ion series of mass spectra for 1,3,5‑triazine and 2,4,6-trifluoro-1,3,5-triazine.

In Fig. 1 the main ionic series of trifluorotriazine is marked with red lines, and two side series - with dotted lines.

Figure 1. Mass spectrum of ion series for2,4,6-trifluoro-1,3,5-triazine, C₃F₃N₃ MW: 135

NIST#: 133291 ID#: 119921 DB: mainlib.

Figure 2. Mass spectrum of ion series for 1,3,5-triazine, C₃H₃N₃ MW: 81 NIST#: 118737

ID#: 49976 DB: mainlib.

In Fig. 2 the main ionic series of 1,3,5-triazine is marked with blue line, and the side fragmentation series - with dotted lines.

Unlike two consecutive emissions of ·F and ·CN occurring during decomposition of fluorine-substituted triazine cycle (see Fig. 1), the fragmentation of molecular ⁺·M radical cation of hydrogen-substituted cycle (see Fig. 2) occurs in three parallel ways, namely with detachments of HCN, NCN and NCHN.

The intensities of peaks for trimeric, dimeric and monomeric ions in the spectra of 1,3,5‑triazine and 2,4,6-trifluoro-1,3,5-triazine have similar values (see Table 1).

Table 1

[C3H3N3]+·	MW: 81	100%	[C3F3N3]+·	MW: 135	100%
[C2H2N2]+·	MW: 54	75%	[C2F2N2]+·	MW: 90	55%
[HCN]+·	MW: 27	42%	[FCN]+·	MW: 45	35%

In NIST library#: 284289 ID#: 17428 DB: mainlib also presents the mass spectrum of (E)‑2,3‑difluoroprop-2-enenitrile, which is a formal dimer of FCN.

Figure 3. Mass spectrum of ion series for (E)-2,3-difluoroprop-2-ennitrile, MW:90 C₂F₂N₂

NIST#: 284289 ID#: 17428 DB: mainlib.

The peak intensity of molecular ion for such a dimer (m/z 90) is (92%), and the peak intensity of monomeric ion [FCN]⁺· (m/z 45) is (100%).

Ionic series of mass spectra of homologues of 2,4,6-tris(perfluoroalkyl)-1,3,5-triazines

Fig. 4 shows the ion series of the mass spectrum of 2,4,6-tris(trifluoromethyl)-1,3,5-triazine.

Figure 4. Ion series of the mass spectrum for 2,4,6-tris(trifluoromethyl)-1,3,5-triazine,

C₆F₉N₃ MW: 285 NIST#: 13755 ID#: 36197 DB: mainlib.

As a result of successive detachments of fluorine atom and ·CF₂CN, [CF₃(CN)₂CF₃]⁺· dimeric ion with m/z 190 (38%) appears. Surprisingly, the intensities of ^+.M, ^+.M-^.F and ‑^.CF₂CN peaks do not change and are equal to 37-38%. At the next detachment, the ion-monomer [CF₃CN]^+. with m/z 95 is not formed. The ejection of ·CF₃ leads to the ion with m/z 121, which loses a fluorine atom, turning into ^+.C₃F₂N₂ with m/z 102. As a result, instead of monomeric ion, the ⁺CF₂CN ion with m/z 76 (50%) appears. Peaks of ions with m/z 69 ⁺CF₃ (100%), 50 ⁺CF₂ (35%) and 31 ⁺CF (23%) result from decay of ions with m/z 121 and m/z 76 (marked with red dotted lines).

Fig. 5 shows the ion series of mass spectrum for 2,4,6-tris(pentafluoroethyl)-1,3,5-triazine.

Figure 5. Mass spectrum of ion series for 2,4,6-tris(pentafluoroethyl)-1,3,5-triazine,

C₉F₁₅N₃ MW: 435 NIST#: 195228 ID#: 46301 DB: mainlib.

As a result of detachments of ^.F and CF₂, the first intense peak of spectrum appears with m/z 366 (C₂F₅)₂[C₃N₃]⁺CF₂ (77%). Subsequent ejections of CF₂ and ^.CN are completed by dimeric ion ^+.[C₂F₅(CN₂C)C₂F₅] with m/z 290 (1%).

The ion with m/z 290 ejects ^.F and CF₂ with formation of C₂F₅(C₂N₂)⁺CF₂ ion weak peak with m/z 221 (1%). The ion with m/z 221 fragments both by successive detachments of CF₂ and ^.F, and .F and CF2, forming a radical cation with m/z 152 (3%). However, the detachment from the ion with m/z 221 with only CF₂ (without ^.F radical) leads to a peak (with medium intensity) of C₂F₅-CN₂⁺C ion with m/z 171 (22%).

The ion with m/z 171 fragments in two ways. As a result of detachment of ^.F,^.CN and CF₂ atoms from it, the base peak of mass spectrum with m/z 76 appears. As a result of ejection of ethanedinitrile NC-CN molecule, the ⁺C₂F₅ ion, its fragment ion ⁺CF₃ and so the ^+.C₂F₄ and ⁺CF₂ ions (marked with red dotted line) are formed (marked with a red dotted line).

Figure 6 shows the ion series of mass spectrum of symmetrical (relative threefold symmetry axis) 2,4,6-tris(heptafluoropropyl)-1,3,5-triazine.

Figure 6. Mass ion series of 2,4,6-tris(heptafluoropropyl)-1,3,5-triazine, C₁₂F₂₁N₃ MW:

585 NIST#: 18443 ID#: 35348 DB: mainlib.

The ionic series C₁₂F₂₁N₃ (see Fig. 6) are similar to C₉F₁₅N₃ series (see Fig. 5).

As a result of detachment of ^.F and C₂F₄, the first intense peak appears with m/z 466 (C₃F₇)₂[C₃N₃]⁺CF₂ (70%). It fragments in two ways. Detachment from the ion with m/z 466 (-2 CF₂) leads to ion with m/z 366 (3%), forming a series of ions: with m/z 176 (3%), 126 (7%) and 76 (83%) (marked with blue lines).

As a result of detachment of rearrangement molecule (-^*CF₂=C=NF) from the ion with m/z 466, the ion with m/z 371 (2%) appears. It fragments with ejection of - C₃F_{6 ,} forming the C₃F₇-CN₂⁺C ion with m/z 221 (5%). The ion with m/z 221 fragments to form both a perfluoroallyl ion with m/z 131 (2%) and a series of perfluoroalkyl ions ending in ⁺CF₃ base ion (marked with red lines).

Fig. 7 shows the ion series of mass spectrum for asymmetric (relative first-order symmetry axis) 2-perfluoroheptyl-4,6-bis(trifluoromethyl)-1,3,5-triazine.

Figure 7. Mass spectrum ion series of 2-perfluoroheptyl-4,6-bis(trifluoromethyl)-1,3,5-triazine,

C₁₂F₂₁N₃ MW: 585 NIST#: 253628 ID#: 36819 DB: mainlib.

The ionic series of unsymmetrical homologue C₁₂F₂₁N₃ (see Fig. 7) differ from those of symmetrical triazine C₁₂F₂₁N₃ (see Fig. 6). The molecular radical cation (see Fig. 7) fragments in two ways. Upon detachment of rearrangement radical (CF₂)₂N^.. the rearrangement ion appears with m/z 471 (5%), which retains the C₇F₁₅ substituent. The subsequent ejection of C₄F₈ leads to formation of the ion ⁺С₆F₉N₂ with m/z 271 (1%), which fragments both with formation of a series of perfluoroalkyl ions ⁺C₃F₇, ⁺C₂F₅ with the base peak ⁺CF₃, and the series of perfluoroalkenyl ions with perfluoroallyl ion ⁺C₃F₅ (m/z 131) (22%) (marked with red lines). Another way of M⁺ fragmentation includes the detachment of fluorine atom and subsequent ejections of ^+.C₅F₁₀ and CF₂ with formation of intense ion peak with m/z 266 (97%). Detachment of -CF₂CN from the ion with m/z 266 (as it happens in spectrum of (CF₃)₃C₃N₃, where the intensity of peak with m/z 266 is only 38%, see Fig. 4), does not occur in spectrum of unsymmetrical isomer (see Fig. 7). As a result, the dimeric ion [CF₃(CN)₂CF₃]^+. with m/z 190 is not formed.

The ion with m/z 266 (100%) (see Fig. 7) rejects -CF₂= СN₂ and -CF₂ (-140), turning into C₃F₄N⁺ ion with m/z 126 (7%) and fragment ion ⁺CF₂СN with m/z 76 (41%).

Fig. 8 shows the ion series of mass spectrum for 2,4,6-tris(perfluoro-tert-butoxy)-1,3,5-triazine C₁₅F₂₇O₃, the compound with three substituents -OC(CF₃)₃ (m/z 235).

Figure 8. Mass spectrum of ion series for 2,4,6-tris(perfluoro-tert-butoxy)-1,3,5-triazine

C₁₅F₂₇N₃O₃ MW: 783 NIST#: 394350 ID#: 222007 DB: mainlib.

After primary detachment of fluorine atom, the ⁺C₁₅F₂₆O₃ ion with m/z 764 (98%) ejects ОС₄F₈, losing one of the three OC(CF₃)₃ substituents and turning into [(CF₃)₃CO]₂C₂N₃⁺C ion with m/z 548 (55 %).

The loss of ·OC(CF₃)₃ substituent also occurs in three successive detachments: -·CF₃, -CF₃CO and ·CF₃ (marked with dotted blue lines).

The ion with m/z 548 fragments in three ways:

• with detachment of second substituent together with CN group of triazine ring of (CF₃)₃COCN molecule, turning into the ion with m/z 287(100%);
• with detachment of ^.C₄F₉ from second substituent, and ^.F atom from third substituent, turning into the ion with m/z 310 (8%);
• with detachment of ^.CF₃ and O-C₃N₂ group of triazine ring or F₃COC₃N₂ rearrangement molecule (marked with dotted red lines), forming the ion with m/z 399 (12%).

The ion with m/z 287 (100%) fragments as if with ejection of C₄F₆N₂ (-190) rearrangement molecule, turning into CF₃⁺C=O ion with m/z 97(12%), which is characteristic of spectra for polyoxaperfluoroalkanes [3] (marked with dotted red lines), and with detachment of CN₂C=O molecule and two fluorine atoms, turning into rearrangement ion CF₃-CF=⁺CF with m/z 181 (4%).

Fragmentation of ion with m/z 181 yields an analogue of CF₃-CF=⁺CF perfluoroallyl ion with m/z 131 (45%) and its fragment ion ⁺CF₃ (90%).

The ion with m/z 310 fragments with detachment of OC₄F₈, forming the ion with m/z 94 (32%) with C₃N₃O triazine ring containing an additional oxygen atom. The ion with m/z 94 fragments with detachment of CN and formation of C₂N₂O ion with m/z 68 (10%).

The ion with m/z 399 fragments with ejection of (CF₃)₂C=N-OCF₃ molecule and formation of perfluoroolefin ions, i. e. ⁺ С₃F₆ and ⁺C₂F₄ (marked with red dotted lines).

Fig. 9 shows the ion series of mass spectrum for 2,4,6 tris(pentadecafluoroheptyl)-1,3,5-triazine.

Figure 9. Mass spectrum of ion series for 2,4,6-tris(pentadecafluoroheptyl)-1,3,5-triazine

C₂₄F₄₅N₃ MW: 1185 NIST#: 62960 ID#: 36982 DB: mainlib.

As a result of primary detachment of fluorine atom and subsequent ejections of six CF₂ groups, the first intense peak of triazine ion with m/z 866 (62%) with two C₇F₁₅ substituents and one ⁺CF₂group is formed. The ion with m/z 866 fragments in three ways (marked in Fig. 9 with dotted lines), with formation of three ionic series.

The first way of fragmentation of the ion with m/z 866 begins with ejection of C₄F₈ molecule from second substituent C₇F₁₅, which has not yet fragmented, to form the ion (C₇F₁₅)(C₃F₇)[C₃N₃]⁺CF₂ with m/z 666 (1%).

The second way of fragmentation of the ion with m/z 866 is detachment of ·CF₂CN (with ring break and detachment of CN) from the first already fragmented substituent and additional ejection of the ·F atom from second substituent, or ejection of CF₂C=NF or CF₃CN molecule with formation of rearrangement ion with m/z 771 (12%). The additional detachment of ·F atom probably comes from CF₂ group of C₇F₁₅ substituent, which is directly linked to fragmenting triazine ring. The subsequent ejection of -CF₂ ends with C₇F₁₅[C₃N₃](C₃F₆^.CF₂)⁺CF₂ ion with m/z 721(1%).

The third way of fragmentation of ion with m/z 866 is detachment of fluorine atom from second, not yet fragmented substituent, with formation of radical C₇F₁₅[C₃N₃](C₆F₁₂^.CF₂)(⁺CF₂) with m/z 847 (0.5%) . The next detachment of C₃F₆ molecule probably also occurs from the second one, which began to fragment the C₆F₁₂^.CF₂ substituent. Detachment of C₃F₆ also leads to radical cation C₇F₁₅[C₃N₃](C₃F₆^.CF₂)⁺CF₂ with m/z 697 (0.1%).

The ion with m/z 666 (C₇F₁₅)(C₃F₇)[C₃N₃]⁺CF₂ (first way) after detachment of two CF₂ groups, is formed by (C₇F₁₅)(CF₃)[C₃N₃]⁺CF₂ ion with m/z 566 (4%). The ion with m/z 566 fragments with ejection of CF₂CN₂ (-90) molecule and detachment of C₂F₄, turning into C₅F₁₁C⁺NCCF₃ ion, which rearranges into ⁺CF₂C₆ F₁₂CN ion with m/z 376 (8%). The series of six further CF₂ detachments: (326, 276, 226, 176) is completed by ⁺CF₂CN ion with m/z 76 (11%).

The ion with m/z 721(1%) (second way) ejects the C₅F₁₀ (-250) molecule turning into ⁺CF₂(CN₂C)(CF₂)₆CF₃ ion with m/z 471 (12%). The next detachment of CF₂ gives rise to the ion with m/z 421 (1%), which fragments in two ways: both with ejection of cyanogen NC-CN and formation of ⁺C₃F₇ ion with m/z 369 (1%), a series of perfluoroalkyl ions, with detachment of ^.CF₂CN₂, leading to ⁺C₇F₁₃ ion with m/z 331(1 %) and series of perfluoroalkenyl ions, the most intense peak of which is the peak of perfluoroallyl ion CF₂=CF-⁺CF₂ with m/z 131 (21%).

The cation-radical with m/z 697 (0.1%) (third way) C₇F₁₅[C₃N₃](C₃F₆^.CF₂)⁺CF₂ ejects four CF₂ groups, transforming it into cation-radical C₇F₁₅[CN^.CNCN]⁺CF₂ 497 (1%). The detachment of .CF₂CN (-76) with breakdown of triazine ring terminates C₇F₁₅[CN₂⁺С] ion with m/z 421 (1%), which fragments in two ways, which we have considered above.

Fig. 10 shows the ion series of mass spectrum for 2,4,6-tri-(perfluorononyl)-1,3,5-triazine C₃₀F₅₇N₃. Like C₂₄F₄₅N₃ homologue (see Fig. 9).

The spectrum of C₃₀F₅₇N₃ consists of three ionic series: perfluoroalkyl ion series ⁺CF₃ with m/z 369-69, CF₂=CF-⁺CF₂ perfluoroalkenyl ion series with m/z 381-131 and ⁺CF₂ (CF₂)_nCN ion series with m/z 476-76. Its difference is that the peak intensities of perfluoroalkyl ions and ⁺CF₂CN ion series in C₃₀F₅₇N₃ spectrum (see Fig. 10) are one and a half times weaker than in C₂₄F₄₅N₃ spectrum (see Fig. 9), while the peak intensities of its perfluoroalkenyl series are the same.

Figure 10. Mass spectrum of ion series for 2,4,6-tris(perfluoronyl)-1,3,5-triazine

C₃₀F₅₇N₃ MW: 1485 ID#: 391974 DB: wiley_nist98.

Detachment of fluorine atom from first intense ion with m/z 866, which occurs in spectrum of C₂₄F₄₅N₃ (see Fig. 9), does not occur (or does not appear) in spectrum of C₃₀F₅₇N₃ (see Fig. 10) with m/z 1066 -F.

Conclusions

A review of ion series of mass spectra for 2,4,6-tris(perfluoroalkyl)-1,3,5-triazines allows us to compare the primary processes of its fragmentation, as well as the intensities of resulting peaks, depending on substituents of triazine ring and its molecular weights.

Fig. 11 shows: the intensities graph of molecular peaks ^+.M of triazine homologues (marked with red dotted lines), the graph of ^+.M-^.F peaks (marked with blue dotted lines), as well as the graph of first intense fragment peaks after the ejection of fluorine atom (marked with green dotted lines).

Figure 11. Intensity graph of triazine homologue molecular ion peaks,

^+.M-^.F peaks and first intense fragment peaks.

The graphs of primary detachments in spectra of two C₁₂F₂₁N₃ isomers with m/z 585 differ in color: the graph of symmetric isomer (C₃F₇)₃C₃N₃, like all graphs of symmetric isomers, is marked with blue lines). The plot of unsymmetrical (CF₃)₂C₃N₃(C₇F₁₅) isomer is marked with purple lines.

With rising in molecular weight of homologue (i. e. in total mass of substituents in triazine ring), the intensity of molecular ion peak decreases from 100% for C₃F₃N₃ to 2% for C₇F₁₅)₃C₃N₃. However, for (C₉ F₁₉)₃C₃N₃ homologue, the intensity of molecular ion peak increases to 6% (marked with red dotted lines in Fig. 11).

During ionization, the peak of ^+.C₃F₃N₃ molecular ion (which has a minimum mass of 135 a.m.u.) acquires the maximum energy and maximum intensity. However, detachment of one fluorine atom from ^+.C₃F₃N₃ leads to a sharp decrease in peak intensity of ^+.M-^.F with m/z 116 (13%). The reason for destabilization of triazine cycle is the loss of one of three symmetrical fluorine atoms. The next ejection of.CN radical leads to formation of a stable symmetrical dimer ^+.[FCNNCF] with m/z 90 (55%).

The peak intensity of molecular ion ^+.(CF₃)₃[C₃N₃] with a mass of 285 a.m.u., 2.1 times greater than that of ^+.C₃F₃N₃, decreases in 2.7 times to 37%. However, when a fluorine atom is detached from ^+.(CF₃)₃[C₃N₃], the intensity of resulting ^+.M-^.F peak remains at level of 37% and only slightly increases to 38% upon detachment of CF₂CN and in appearance of dimeric ion CF₃^+.(C₂N₂)CF₃. For homologs of (C₂F₅)₃C₃N₃ and (C₃F₇)₃C₃N₃ (C2F5) the intensity of ^+.M-^.F peak decreases from 30% to 17%. It remains constant at 17%-18% for homologue (C₇F₁₅)₃C₃N₃.

After detachment of fluorine atom from ^+.(C₉F₁₉)₃C₃N₃ with molecular weight of 1485 a.m.u. (see Fig. 11) there is unprecedented increase in peak intensity ^+.M-^.F with m/z 1466 (51%) - three times greater than that of (C₇F₁₅)₃C₃N₃ homologue. It is possible that this is the result of threefold increase in intensity of ^+.(C₉F₁₉)₃C₃N₃ molecular ion peak (6%) compared to (2%) for (C₇F₁₅)₃C₃N₃ molecular peak with m/z 1166. After appearance of M–F peaks the possibility of subsequent stabilizing detachments of CF₂ is realized, up to formation of most intense peaks of fragment ions with two initial substituents and one ⁺CF₂ group. With successive detachments of CF₂, the insignificant successive increase in peaks of emerging ions occurs. However, only the final ejection of CF₂ with formation of ion with two initial triazine ring substituents and one ⁺CF₂ group leads to the first intense fragmentary peaks.

Comparison of ^+.M peaks intensities of two isomers (symmetric (C₃F₇)₃[C₃N₃] (9%) and unsymmetrical (CF₃)₂[C₃N₃](C₇F₁₅) (0%)) allows us to conclude that, in contrast to ^+.M symmetrical isomer, the ^+.M of unsymmetrical isomer with substituent C₇F₁₅ is unstable (0%).

The minimum difference between the masses of its C₃F₇ and CF₃ substituents is 100 a.m.u., and the maximum difference between the masses of C₃F₇ and C₇F₁₅ is 200 a.m.u. for C₄F₈.

In mass spectra of (C₂F₅)₃[С₃N₃] with m/z 435, (C₃F₇)₃[С₃N₃] with m/z 585, as well as in mass spectra of unsymmetrical isomer (CF₃)₂[C₃N₃](C₇F₁₅) with m/z 585 after detachment of fluorine atom and ejection CF₂, C₂F₄, and, accordingly, C₅F₁₀ +CF₂ molecules, the first intense peaks of stable fragment ions appear: with m/z 366 (77%), m/z 466 (70%) and m/z 266 (97% ) with two symmetrical substituents and one ⁺CF₂ group. The maximum intensity of 97% (stability) is acquired by peak of the (CF₃)₂[C₃N₃]⁺CF₂ ion with a minimum mass of m/z 266, which occurs during fragmentation of asymmetric isomer (CF₃)₂[C₃N₃](C₇F₁₅) with m/z 585. That is, with the same molecular weight of two isomers with different substituents of triazine ring, it is precisely the minimum mass of fragment ion with m/z 266 a.m.u. corresponds to maximum intensity of emerging peak (97%). The lower a molecular weight of fragment ion with two initial substituents and one ⁺CF₂group, the greater a peak intensity of its fragment ion. Decreasing the intensities of first fragment peaks with m/z 366 (77%), 466 (70%) and 866 (62%) correspond to detachments of increasing masses: CF₂ (50), C₂F₄ (100) and C₅F₁₀ ⁺CF₂ (300) (see Fig. 11). However, the dependence graph is disturbed by the peak of fragment ion with m/z 1066 (100%), since expected decrease in its intensity (by analogy with fragment ions of other homologues) does not occur. The peak intensity of fragment ion ^+.M-^.F with m/z 1466 (51%), which is three times higher than peak intensity of ^+.M-^.F with m/z 1166 (18%), seems strange at first glance.

However, this increase in intensity is probably the result of threefold increase in intensity of peak for molecular ion (C₉F₁₉)₃^+.[C₃N₃] (6%) compared to peak intensity of molecular ion (C₇F₁₅)₃^+.[C₃N₃] (2%). The reason for intensity increasing of molecular peak with m/z 1485 a.m.u. there may be an increase in its effective ionization cross section compared to homologue with m/z 1185.

In spectra of homologues C₂₄F₄₅N₃ and C₃₀F₅₇N₃ after detachment of fluorine atom, only the ejection of six CF₂ groups and, accordingly, the ejection of C₂F₄ and six CF₂ groups leads to intense peaks of fragment ions with two symmetrical substituents and one CF₂ group: ((C₇F₁₅)₂[C₃N₃]⁺CF₂ with m /z 866 (62%) and (C₉F₁₉)₂[C₃N₃]⁺CF₂ with m/z 1066 (100%). The increase in peak intensity with m/z 1066 (100%) compared to intensity of peak at m/z 866 (62%) is the result of difference in intensities of its molecular and fragment peaks ^+.M-^.F. Ions with intense peaks are fragmented in several ways, which leads to branching of ionic series.

The branching of ionic series of fragment ions is apparently the result of variants of its isomerization that are close in energy.

In most of presented spectra, the branching of ionic series begins only after detachment of one of triazine ring substituents. The exceptions are: the mass spectrum of triazine with unsymmetrical substituent (CF₃)₂C₃N₃(C₇F₁₅), as well as the mass spectrum of triazine (C₄ F₉O)₃C₃N₃ with three ^.OC(CF₃)₃ groups. In its spectra, the branching of ion series begins immediately upon fragmentation of molecular ions. This may also be the result of isomerization of its ^+.M. Reliable examples of isomerization of molecular ion are: five ion series of benzene spectrum, resulting from rearrangement of its carbon backbone, in accordance with five variants of π-conjugations, eight ion series of 1,3,5,7‑cyclooctatetraene and 15 ion series of 18-annulene [4].

It should be noted that peak intensities graph of mass spectrum (C₄F₉O)₃C₃N₃ (see Fig. 11), as it were, falls out of the graphs of triazines that do not contain oxaperfluoroalkyl groups.

The intensity of peak of (C₄ F₉O)₃C₃N₃ molecular ion with m/z 783 (42%) is higher than the intensity of peak of (CF₃)₃C₃N₃ molecular ion with m/z 285 (37%), but less than that for С₃F₃N₃ with m/z 135 (100 %). In contrast to linear perfluoroalkyl substituents, three OC(CF₃)₃ groups probably promote more efficient ionization processes and redistribution of excitation energy. The efficiency of ionization and transfer of excitation energy depends on effective ionization cross section of molecule, but its determination requires special equipment [5].

In (C₄ F₉O)₃C₃N₃ spectrum, the detachment of fluorine atom leads to a sharp increase in intensity of ^+.M-^.F peak (98%). There is no such intense ^+.M-^.F peak in spectra of any considered homologues.

It is possible that such stabilization, which occurs when a fluorine atom is detached, is associated either with increase in effective ionization cross section of molecule, or with appearance of interaction between the ⁺CF₂ terminal group and oxygen atom of substituent. This is indicated by ejection of OC₄F₈ molecule, although successive but less intense detachments also occur along with CF₂, CF₃C=O and CF₃. As a result, the ion (C₄F₉O)₂⁺C₃N₃ with m/z 548 (55%) appears with preserved triazine cycle (see Fig. 8). Its analogs are the low-intensity peak (C₂F₅)₂⁺C₃N₃ with m/z 316 (0.2%), mass-spectrum of (C₂F₅)₃⁺C₃N₃ and (C₃F₇)₂⁺С₃N₃ peak with m/z 416 (1%) of symmetrical (C₃F₇)₃⁺С₃N₃ mass spectrum. The ⁺CF₂CN ion with m/z 76, characteristic for spectra of triazines with perfluoroalkyl substituents that do not contain oxygen atoms, is not formed in spectrum of C₁₅F₂₇N₃O_3.

Acknowledgements

This work was supported by the Ministry of Science and Higher Education of the Russian Federation and was performed employing the equipment of Center for Molecular Composition Studies of INEOS RAS.

References

1. Nekrasov B.V., Fundamentals of General Chemistry, Moscow, Chemistry, 1967, v. 2, 33. (in Russian)
2. Nekrasov B.V. Fundamentals of General Chemistry, Moscow, Chemistry, 1973, v.1, 523. (in Russian)
3. Kagramanov N.D., Sterlin S.R., Tyutyunov A.A., Decomposition sequences - Ion series of mass spectra of polyoxaperfluoroalkanes and polyoxaperfluoroalkyls with terminal halide atoms, Fluorine notes, 2023, 2(147), 1-2.
4. Kagramanov N.D., Decay sequences - Ion series of mass spectra of benzene, 1,3,5,7‑cyclooctatetraene, [18]-annulene, hexafluorobenzene and its isomers, Fluorine notes, 2022, 3(142), 5-6.
5. Shafranyosh I.I., Svida Yu.Yu., Sukhoviya M.I., Shafranosh M.I., Minaev B.F., Baryshnikov G.V., Minaev V.A. Journ. of Techn. Phys. 2015, 85(10), 16-22. (in Russian)

ARTICLE INFO
Received 29 June 2023
Accepted 03 August 2023
Available online August 2023

Recommended for publication by PhD M.A. Manaenkova

eLIBRARY Document Number (EDN) QKPHPF

Fluorine Notes, 2023, 149, 3-4