- Email: [email protected]
Reactions of NH with C2H6 and C3H8 in the liquid phase
REACTIONS OF NH WITH C2H6 AND C,H, S. TSUNASHIMA,
15 July 1979
CHEMICAL PHYSICS LETTERS
Volume 64, number 3
IN THE LIQUID PHASE
M. HOTTA and S_ SAT0
Department of Applied Physics. Tokyo Institute of Technology, Ookayama. .Wegzuo-ku. Tokyo, Japan 152
Received 12 March 1979 HNs was photolyzed in CzHh or CsHs solution at the temperature of dry ice-methanol. The main products were N2 and CzHsNHz or nC3H-,NHz and iCsH-,NH2_ NH3 and Hz were also formed as minor products. Possible reaction mechanisms are discussed. It is suggested that alkykunine is mainly formed by the insertion of NH(a ‘A) into the C-H b_ondsof CzH6 or C3H8-
1_ Introduction The diatomic biradical NH is known to exist in comets [I] _ The physical properties of NH have been investigated by spectroscopic methods in the photolysis ofNH3,HN3,0rHNC0 [Z-11]_ForX32-,A311, a ‘A, b ‘Z+, c ‘II, and d ‘Z+ states of NH, the molecular constants and lifetimes are now well known [l-6] _ The quenching rates of the excited states have also been measured [7-lo]_ The metastabie a ‘A state is located at 36.1 kcal/mol above the ground triplet state [l I] _ The reactions of these species, however, have not been established yet. 0 and CH, are isoelectronic with NH. The reactions of both species are well known for the ground triplet and first excited singlet states [12-183 _Tripiet 0(3P) and CH2(3B1) add to the double bond of olefm or abstract an H atom from paraffin:
3x -f-c=c +
c,-!z,
X 3X+RH+XH+R Singlet O(‘D) of paraffm:
(X = 0 or CH,). and CH?(lAl)
insert into the C-H bond
[19,20] ; however, they could not detect NH containing products. Cornell et al. [21] found the formation of NH(X 3 EC-) in the flash photolysis of a mixture of l-IN3 and CzH4_ They could not detect ethyleneimine, which is a possible product in the addition reaction of triplet NH, but the formation of HCN and CH3CN_ Konar et_ al. [22] investigated the photolysis of HN, in the absence and m the presence of C,H, and GC,Hlu. They failed to detect the formation of alkylamine, the insertion product of hW(a IA). Instead, they found the form; tion of white solid as a less volatile product. A part of the solid was identified to be NH4N3 _ These results suggest that alkylamine, if formed, would react with I-IN, to form a quatemary ammonium salt which is not feasible to be analyzed. In a rigid argon matrix at 4 K, Jaco: and Milligan were able to detect ethyleneimine formatio in ‘the photolysis of a mixture of l-W3 and C2H4 by infrared spectroscopy [23] _ Recently, McDonald et al. [24] detected the formation of cyclohexylamine in the photolysis of IIN3 in cyclohexane solution at room temperature_ They attributed the product to be formed by the insertion of NH(a IA)_ But the possibility of radical recombination of NH, and cyclohexyl radical has not been excluded: NH + c-C6Hlz
+ NH2 + c-CGH1l,
lX+RH+RXH_ Similar reactions are expected to occur with hW_ In the gas phase, Back and co-workers investigated
hW, •t c-C6Hll
+- c-C,HllNH,.
the photolysis of HNCO in the presence of hydrocarbons 435
Volume 64. number 3
CHEMICAL PHYSICS LElTERS
HN, was prepared in vacua by heating a mixture containing sodium azide and an excess of stearic acid to approximately lO@C_ HN, was passed over P205 and degassed at --120°C_ Pure grade CzH6 and C,H8 (Takachiho Shoji Co_) were used after distillation at -130°C and at -12O”C, respectively. A quartz tube of 8 mm od_ (20 cm in ieng&&) was used as the reaction cell. C,H6 or C3H8 soIutions of HN3 were irradiated at the temperature of dry ice-methanol with a medium pressure mercury lamp (Wako Denki Co.) through a filter which cuts off the light shorter than 250 nm (Toshiba W 27)_ After irradiation, the non-condensable products at -196°C @I2 and Hz) were collected and measured in a gas burette- Hz was eliminated by means of heated CuO at 300°C After N2 and Hz were removed, solvent was pumped out at -130°C (C2H6) or --120°C (C3H8)_ The residue, a white solid. was anaIyzed with the GL_C_ after having been passed through a trap packed with NaOH coated glass wool. The cohmm used for G-L-C. was packed with KOH treated Celite 545 with Amine 220 as stationary phase (Nishio Kogyo Co.). For the identification of products, a mass spectrometer was also used_
3. Results When C2H6 solution (typically 18 mmol, about 1 ml) of HN, was irradiated with the lamp at the temperature of dry ice-methanol, a white precipitant was obsertied to be formed_ Non-condensable products at -196°C were Nz and a small amount of Hz (about 5% of N2)_ No methane formation was observed. The condensabIe products at -130°C were analyzed with the GLC. after having been passed through a trap packed with NaOH coated glass wool. The products thus observed were C,H,hw, and NH3 _ Probably, the condensable products are quaternary ammonium salts formed between HN, and C2H5hw1 or NH3_ The efficiencies of the formation and the &composition by NaOH of the salts were checked by the following method_ A known amount of C2H5NH2 or NH3 was added to HN, (35 pmol) and C2H6 (15 mmol)_ After keeping it at the temperature of dry ice-methanol for about 30 min, C,H6 was pumped out at --130°C and the residue was passed through the NaOH trap and then anaIyzed with the 436
15 July 1979
I 0
1
2
3
4
5
INITIAL A!WNTS/ 1O-6 IQL
F&_ I_ The amounts of C2HsNH2 and NHs recovered from the decomposition of the salts on NaOH against the amounts introduced_ o C2HsNH2. A NH3_
is shown in fig_ 1, exactly the same amounts of C2H5NH2 and NH3 were recovered by this method. The amounts of C,H,NH,, Hz, and NH3 formed are plotted in fig_ 2 as functions of the amount of N2 formed in the photolysis of the C2H6 solution of HN3 at vario_us irradiation times. The initial HN3/C2H6 ratio was kept constant (19 X 10e3, the amount of C2H6 in the gas phase was corrected). Fig. 3 shows the relative amounts of the products as functions of the initial E-IN3/C2H6 ratio. G_L_C_ As
3r
0
1
2
3N2110kL
5
6
7
Fig- 2- The amounts of products as functions of that of N2
formed in the photolysis of a C2H6 solution of HN3 (35 pmol). o C2H5NH2. 4 NH3, 0 Hz_
Volame 64. number 3
15 July 1979
CHEMICAL PHYSICS LETTERS most important-species system.
initiahy produced in the present
4_2_ The formation of alkylamine (RhW? j TWO mechanisms may be considered for the formation of RNHz, as was suggested in section I- One is the insertion of NH(a ‘A) into the C-H bond as in the case of O(lD)
or CH,(‘A,):
NH(a ‘A) + RH + RNH2-
0
1
~j I Cam
4
3
2 X IO3
Fig_ 3_ Product mtios ZISfunctions of the initizdHN3/C2H, obtained in the phOtOIySiSOf a C2H6 solution 0fHN3. oC2HsNH2/N2. * NH3/N2, o H2/N2.
ratio
(2)
The other is the recombination of NH, and R, which are produced by the abstraction of an H atom from RH by NH(a 'A): NH(a’A)+RH-+NH,
+R,
(3)
NHZ+R+RNW,. H atom abstraction by hW(X formed in the reaction
(4) 32-),
which might be
in the case ofC,H, solution, N?, n-C3H7NH7, iC3H7NH,, HZ, and NH, were detected as products. Neither methane nor hexane formation was observed. The product ratio of n-C3H7NH2/iC3H7NH2 was found to be 1 A independent of the initia1 HN3/C3H8 ratio_ H2 was about 5% of N2_
H+RH+H,+R
4. Discussion
is not important as a source of R, since H2 was a minor product compared -with amine.
4.1. Photodecompasition of I-Ii$ The effective wavelengths for the present system were between 250 and 320 nm. The following reactions are energetically possible and spin allowed: HN3 +hv-+NH(a’A)+N,,
(la)
+NH@‘Z+)+Na,
(lb)
+H+N3_
(lc)
Baronavski et al. [25] showed that the 266 run photolysis of HN3 gives rise to NH fragments exclusively in the a ‘A state. Konar et al. [22 ] showed that the extent of (Ic) is about 5% of the total decomposition in the photolysis at 2139 run_ Paur and Bair [26] showed that the major reactive species is NH(a ‘A) at wavelengths larger than 200 nm. Thus NH in the a ‘A state may be
NH(a *A) + RH (or HN3) + NH(X 32-)
+ RH (or HN3) (5)
is not important, since the reaction is about 4 to 9 kcal/mol endothermic. Similarly, the reaction (6)
in the case of C,H,. both n-C3H7 and LC,H, radicals might be formed by (3). Since the bond energy of the secondary C-H in C3H8 is about 3 kcal/mol smaller than that of the primary C-H, i-C3H7 radical is expected to be formed more than n-C3H7_ This requires the relation i-C3H7NH2 > n&H7NH2. Moreover, if those radicals were formed, the combination of the radicals should compete with (4) and fcrm 2,3-dimethyL butane, Z-methylpentane, and n-hexane_ As was shown in section 3, this was not the case. That is, the radical recombination mechanism is not important for amine formation in the present system. 4.R NH;7 formation As was shown in fig_ 3, the formation of NH3 increased with an increase in the NH,/C,H, ratio along with the decrease in the CzH5NH2 formation. This fact strongly suggests the participation of 437
CHEMICAL PHYSICS LETTERS
Volume 64. number 3
NH(a1Q+I-IN3+NH,+N3,
(7) -
which can compete with (2)_ in the gas phase, Faur and Bair f26] showed that (7) is very fast and occurs with a small activation energy if any. Baronavski et aI_ [2S] showed that the NH, formed by (7) is in the excited state and can fluoresce_ In the liquid phase, the deactivation of the excited NH, should be very fast_ NH, wiil be formed by the abstraction of an H atom from HN, or paraffin by NH, or the disproportionation of h3I, : NH,+HN3-+NH:,+N3,
(8)
hq+RH+-NHs+R,
(9)
NH, •t NH, + NH, t NH_
(10)
The abstraction
from paraffi requires an activation ene_rgy of about 6-7 kcal/mol 1271~ which is expected to be larger than that of(S), since the bond dissociation energy of C-H is much huger than that of H-NS _ The absence of hexane formation suggests that (9) may be negIected, even in the present system. Gehring et aI. [28 ] showed that (10) is not important compared with the recombination of NH, when an excess amount of third body (M) is present: NH, +Nl-L, +M+N2H4
+M_
(11)
4_4_ Hz formation
Hz may be formed by abstraction atom produced by (1~): H+HN3-+H,+N3_
from HN, by H (12)
H atom abstraction from paraffin may be neglected on the same reasoning used in the abstraction by NH,. Another possib!e source of Hz is rI:e disproportionation reaction of NH hW+NH-+H*
+NZ_
(13)
4.X ltirrrertzl bahtce When (1 a), (I c). (2), (7), (8) and (12) are assumed to occur, the following relation is expected to hold between the products
[NJ = 1C2H5NHJ +31I+l 438
-WNH&
(14)
15 July 1979
To derive (14) N3 was assumed to disappear by the bimolecular process 2N3 + 3N,,
(15)
which had previously been suggested [29] _Using the data shown in fig_ 3, the ratio ( [C2Hsh’H2] + 3 [HZ ] + 4jNH3])/[Nz] was cakulated to be 0.71 +- 0.06, independent of the initial HN3/C1H6 ratio. About 30% of NH containing products is missing. This difference, however, can be explained by assuming that the N2H4 formation is about 6% of Nz formation, although we are not yet successful to detect NzH4 as a product.
References [ l] G. Herzberg. Spectrs of diatomic mohcuies
Princeton, 1950)-
[2] RX
(Van Nostmnd
Berry, ix Nitrenes, cd_ W_ Lwowski (Inter-science, New York, 1970) p_ 13. [3] J-M_ Lent% J_ Quant Spectry- RedhtiveTransfer 13 (1973) 297. end references therein [4] W-H. Smith, J. Baozowski and P_ Erman. J. Chem_ Phys_ 64 (1978) 4628. IS] J. Masanet, C- Ldo, G. Durand and C. Vermeil, C&em_ Phys. 33 (1978) 123. I61 D-K Bsu and W-H. Smith, J. Chem- Phys. 66 (1977) 183% I71 H- Qkabe. J. Chem- Phys. 49 (1968) 3726_ [S] hi. Kawasaki. Y. Himta and I_ Tanaka. J_ Chem. Phys. 59 (1973) 648. [9] B. Gelemt. S-V_ Filseth and T. Canington. J. Chem. Phys. 65 (1976) 4940_ [IO] C_ Zetzsch and F_ Stuhl. I- Chem. Phys- 66 (1977) 3107. [l I] C. Zetzsch and F- Stuhl. Ber- Bunsenges. Physik. Chem. 80 (1975) 1349s 1121 RJ. Cvetanovi& Advan- Photochem- I (1963) 11.5. [ 131 H. Yamazaki and R-J. Cvetanovi& J_ Chem. Phys. 4 1 (1964) 3703. [ 141 G. Paraskevopoulos and R.J. Cvetanovi&. J. them_ Phys_ 52 (1970) 5821. [IS] W-B. Dehiorc and S-W- Benson. Advan. Photochem. 2 (1964) 219. [ 161 H-hi_ Frey. Progr_ Reaction Kinetics 2 (1964) 131. [I71 J-A- Bell. J- Phys_ Chem. 75 (1971) 1537_ 1181 F_ Lahmani, J.phys. Chem. 80 (1976) 2623_ 1191 J-L. Brash and R-A- Back, Can. J- Chem- 43 (1965) 1778_ 1201 W-D. WooIIey and R-A. Back, Can. J. Chem. 46 (1968) 295 [21] D-W_ Cornell, R-S- Berry and W. Lwowski. J. Am. Chem. Sot_ 88 (1966) 544_ [22] R-S. Konar. S. Matsumoto and B_ deB. Dar-went. Trans. Faraday Sot. 67 (1971) 1698. [23] ME_ Jacox and D-E- Mill&n. J. Am. Chem- Sot. 85 (1963) 278.
Volume 64. number 3
CHEMICAL PHYSICS LETTERS
[24] J-R. McDonald. R-G. MiUer and A-P. Baronavski. Chem. Phys- 30 (1978) 133_ [2S] A-P- Baronavski. R-G. Mdier and J-R. McDonald. Chem. Phys. 30 (1978) 119. [26] R_J- Paur and E-J_ Bair, Intern. J. Chem- Kinetics 8 (1976) 134_
15 July 1979
[27] R_ Leschlaux and M. Demisey. J. Photochem. 9 (1978) llO_ [28] hl. Gehring, K. Hoyerman. H- Gg- Wagner and J. Wolf&m, Ber. Bunsenges. Physik. Chem. 75 (1971) 1287. [29] B-A_ Thrush, Proc- Roy_ Sot- A235 (1956) 143.
439
15 July 1979
CHEMICAL PHYSICS LETTERS
Volume 64, number 3
IN THE LIQUID PHASE
M. HOTTA and S_ SAT0
Department of Applied Physics. Tokyo Institute of Technology, Ookayama. .Wegzuo-ku. Tokyo, Japan 152
Received 12 March 1979 HNs was photolyzed in CzHh or CsHs solution at the temperature of dry ice-methanol. The main products were N2 and CzHsNHz or nC3H-,NHz and iCsH-,NH2_ NH3 and Hz were also formed as minor products. Possible reaction mechanisms are discussed. It is suggested that alkykunine is mainly formed by the insertion of NH(a ‘A) into the C-H b_ondsof CzH6 or C3H8-
1_ Introduction The diatomic biradical NH is known to exist in comets [I] _ The physical properties of NH have been investigated by spectroscopic methods in the photolysis ofNH3,HN3,0rHNC0 [Z-11]_ForX32-,A311, a ‘A, b ‘Z+, c ‘II, and d ‘Z+ states of NH, the molecular constants and lifetimes are now well known [l-6] _ The quenching rates of the excited states have also been measured [7-lo]_ The metastabie a ‘A state is located at 36.1 kcal/mol above the ground triplet state [l I] _ The reactions of these species, however, have not been established yet. 0 and CH, are isoelectronic with NH. The reactions of both species are well known for the ground triplet and first excited singlet states [12-183 _Tripiet 0(3P) and CH2(3B1) add to the double bond of olefm or abstract an H atom from paraffin:
3x -f-c=c +
c,-!z,
X 3X+RH+XH+R Singlet O(‘D) of paraffm:
(X = 0 or CH,). and CH?(lAl)
insert into the C-H bond
[19,20] ; however, they could not detect NH containing products. Cornell et al. [21] found the formation of NH(X 3 EC-) in the flash photolysis of a mixture of l-IN3 and CzH4_ They could not detect ethyleneimine, which is a possible product in the addition reaction of triplet NH, but the formation of HCN and CH3CN_ Konar et_ al. [22] investigated the photolysis of HN, in the absence and m the presence of C,H, and GC,Hlu. They failed to detect the formation of alkylamine, the insertion product of hW(a IA). Instead, they found the form; tion of white solid as a less volatile product. A part of the solid was identified to be NH4N3 _ These results suggest that alkylamine, if formed, would react with I-IN, to form a quatemary ammonium salt which is not feasible to be analyzed. In a rigid argon matrix at 4 K, Jaco: and Milligan were able to detect ethyleneimine formatio in ‘the photolysis of a mixture of l-W3 and C2H4 by infrared spectroscopy [23] _ Recently, McDonald et al. [24] detected the formation of cyclohexylamine in the photolysis of IIN3 in cyclohexane solution at room temperature_ They attributed the product to be formed by the insertion of NH(a IA)_ But the possibility of radical recombination of NH, and cyclohexyl radical has not been excluded: NH + c-C6Hlz
+ NH2 + c-CGH1l,
lX+RH+RXH_ Similar reactions are expected to occur with hW_ In the gas phase, Back and co-workers investigated
hW, •t c-C6Hll
+- c-C,HllNH,.
the photolysis of HNCO in the presence of hydrocarbons 435
Volume 64. number 3
CHEMICAL PHYSICS LElTERS
HN, was prepared in vacua by heating a mixture containing sodium azide and an excess of stearic acid to approximately lO@C_ HN, was passed over P205 and degassed at --120°C_ Pure grade CzH6 and C,H8 (Takachiho Shoji Co_) were used after distillation at -130°C and at -12O”C, respectively. A quartz tube of 8 mm od_ (20 cm in ieng&&) was used as the reaction cell. C,H6 or C3H8 soIutions of HN3 were irradiated at the temperature of dry ice-methanol with a medium pressure mercury lamp (Wako Denki Co.) through a filter which cuts off the light shorter than 250 nm (Toshiba W 27)_ After irradiation, the non-condensable products at -196°C @I2 and Hz) were collected and measured in a gas burette- Hz was eliminated by means of heated CuO at 300°C After N2 and Hz were removed, solvent was pumped out at -130°C (C2H6) or --120°C (C3H8)_ The residue, a white solid. was anaIyzed with the GL_C_ after having been passed through a trap packed with NaOH coated glass wool. The cohmm used for G-L-C. was packed with KOH treated Celite 545 with Amine 220 as stationary phase (Nishio Kogyo Co.). For the identification of products, a mass spectrometer was also used_
3. Results When C2H6 solution (typically 18 mmol, about 1 ml) of HN, was irradiated with the lamp at the temperature of dry ice-methanol, a white precipitant was obsertied to be formed_ Non-condensable products at -196°C were Nz and a small amount of Hz (about 5% of N2)_ No methane formation was observed. The condensabIe products at -130°C were analyzed with the GLC. after having been passed through a trap packed with NaOH coated glass wool. The products thus observed were C,H,hw, and NH3 _ Probably, the condensable products are quaternary ammonium salts formed between HN, and C2H5hw1 or NH3_ The efficiencies of the formation and the &composition by NaOH of the salts were checked by the following method_ A known amount of C2H5NH2 or NH3 was added to HN, (35 pmol) and C2H6 (15 mmol)_ After keeping it at the temperature of dry ice-methanol for about 30 min, C,H6 was pumped out at --130°C and the residue was passed through the NaOH trap and then anaIyzed with the 436
15 July 1979
I 0
1
2
3
4
5
INITIAL A!WNTS/ 1O-6 IQL
F&_ I_ The amounts of C2HsNH2 and NHs recovered from the decomposition of the salts on NaOH against the amounts introduced_ o C2HsNH2. A NH3_
is shown in fig_ 1, exactly the same amounts of C2H5NH2 and NH3 were recovered by this method. The amounts of C,H,NH,, Hz, and NH3 formed are plotted in fig_ 2 as functions of the amount of N2 formed in the photolysis of the C2H6 solution of HN3 at vario_us irradiation times. The initial HN3/C2H6 ratio was kept constant (19 X 10e3, the amount of C2H6 in the gas phase was corrected). Fig. 3 shows the relative amounts of the products as functions of the initial E-IN3/C2H6 ratio. G_L_C_ As
3r
0
1
2
3N2110kL
5
6
7
Fig- 2- The amounts of products as functions of that of N2
formed in the photolysis of a C2H6 solution of HN3 (35 pmol). o C2H5NH2. 4 NH3, 0 Hz_
Volame 64. number 3
15 July 1979
CHEMICAL PHYSICS LETTERS most important-species system.
initiahy produced in the present
4_2_ The formation of alkylamine (RhW? j TWO mechanisms may be considered for the formation of RNHz, as was suggested in section I- One is the insertion of NH(a ‘A) into the C-H bond as in the case of O(lD)
or CH,(‘A,):
NH(a ‘A) + RH + RNH2-
0
1
~j I Cam
4
3
2 X IO3
Fig_ 3_ Product mtios ZISfunctions of the initizdHN3/C2H, obtained in the phOtOIySiSOf a C2H6 solution 0fHN3. oC2HsNH2/N2. * NH3/N2, o H2/N2.
ratio
(2)
The other is the recombination of NH, and R, which are produced by the abstraction of an H atom from RH by NH(a 'A): NH(a’A)+RH-+NH,
+R,
(3)
NHZ+R+RNW,. H atom abstraction by hW(X formed in the reaction
(4) 32-),
which might be
in the case ofC,H, solution, N?, n-C3H7NH7, iC3H7NH,, HZ, and NH, were detected as products. Neither methane nor hexane formation was observed. The product ratio of n-C3H7NH2/iC3H7NH2 was found to be 1 A independent of the initia1 HN3/C3H8 ratio_ H2 was about 5% of N2_
H+RH+H,+R
4. Discussion
is not important as a source of R, since H2 was a minor product compared -with amine.
4.1. Photodecompasition of I-Ii$ The effective wavelengths for the present system were between 250 and 320 nm. The following reactions are energetically possible and spin allowed: HN3 +hv-+NH(a’A)+N,,
(la)
+NH@‘Z+)+Na,
(lb)
+H+N3_
(lc)
Baronavski et al. [25] showed that the 266 run photolysis of HN3 gives rise to NH fragments exclusively in the a ‘A state. Konar et al. [22 ] showed that the extent of (Ic) is about 5% of the total decomposition in the photolysis at 2139 run_ Paur and Bair [26] showed that the major reactive species is NH(a ‘A) at wavelengths larger than 200 nm. Thus NH in the a ‘A state may be
NH(a *A) + RH (or HN3) + NH(X 32-)
+ RH (or HN3) (5)
is not important, since the reaction is about 4 to 9 kcal/mol endothermic. Similarly, the reaction (6)
in the case of C,H,. both n-C3H7 and LC,H, radicals might be formed by (3). Since the bond energy of the secondary C-H in C3H8 is about 3 kcal/mol smaller than that of the primary C-H, i-C3H7 radical is expected to be formed more than n-C3H7_ This requires the relation i-C3H7NH2 > n&H7NH2. Moreover, if those radicals were formed, the combination of the radicals should compete with (4) and fcrm 2,3-dimethyL butane, Z-methylpentane, and n-hexane_ As was shown in section 3, this was not the case. That is, the radical recombination mechanism is not important for amine formation in the present system. 4.R NH;7 formation As was shown in fig_ 3, the formation of NH3 increased with an increase in the NH,/C,H, ratio along with the decrease in the CzH5NH2 formation. This fact strongly suggests the participation of 437
CHEMICAL PHYSICS LETTERS
Volume 64. number 3
NH(a1Q+I-IN3+NH,+N3,
(7) -
which can compete with (2)_ in the gas phase, Faur and Bair f26] showed that (7) is very fast and occurs with a small activation energy if any. Baronavski et aI_ [2S] showed that the NH, formed by (7) is in the excited state and can fluoresce_ In the liquid phase, the deactivation of the excited NH, should be very fast_ NH, wiil be formed by the abstraction of an H atom from HN, or paraffin by NH, or the disproportionation of h3I, : NH,+HN3-+NH:,+N3,
(8)
hq+RH+-NHs+R,
(9)
NH, •t NH, + NH, t NH_
(10)
The abstraction
from paraffi requires an activation ene_rgy of about 6-7 kcal/mol 1271~ which is expected to be larger than that of(S), since the bond dissociation energy of C-H is much huger than that of H-NS _ The absence of hexane formation suggests that (9) may be negIected, even in the present system. Gehring et aI. [28 ] showed that (10) is not important compared with the recombination of NH, when an excess amount of third body (M) is present: NH, +Nl-L, +M+N2H4
+M_
(11)
4_4_ Hz formation
Hz may be formed by abstraction atom produced by (1~): H+HN3-+H,+N3_
from HN, by H (12)
H atom abstraction from paraffin may be neglected on the same reasoning used in the abstraction by NH,. Another possib!e source of Hz is rI:e disproportionation reaction of NH hW+NH-+H*
+NZ_
(13)
4.X ltirrrertzl bahtce When (1 a), (I c). (2), (7), (8) and (12) are assumed to occur, the following relation is expected to hold between the products
[NJ = 1C2H5NHJ +31I+l 438
-WNH&
(14)
15 July 1979
To derive (14) N3 was assumed to disappear by the bimolecular process 2N3 + 3N,,
(15)
which had previously been suggested [29] _Using the data shown in fig_ 3, the ratio ( [C2Hsh’H2] + 3 [HZ ] + 4jNH3])/[Nz] was cakulated to be 0.71 +- 0.06, independent of the initial HN3/C1H6 ratio. About 30% of NH containing products is missing. This difference, however, can be explained by assuming that the N2H4 formation is about 6% of Nz formation, although we are not yet successful to detect NzH4 as a product.
References [ l] G. Herzberg. Spectrs of diatomic mohcuies
Princeton, 1950)-
[2] RX
(Van Nostmnd
Berry, ix Nitrenes, cd_ W_ Lwowski (Inter-science, New York, 1970) p_ 13. [3] J-M_ Lent% J_ Quant Spectry- RedhtiveTransfer 13 (1973) 297. end references therein [4] W-H. Smith, J. Baozowski and P_ Erman. J. Chem_ Phys_ 64 (1978) 4628. IS] J. Masanet, C- Ldo, G. Durand and C. Vermeil, C&em_ Phys. 33 (1978) 123. I61 D-K Bsu and W-H. Smith, J. Chem- Phys. 66 (1977) 183% I71 H- Qkabe. J. Chem- Phys. 49 (1968) 3726_ [S] hi. Kawasaki. Y. Himta and I_ Tanaka. J_ Chem. Phys. 59 (1973) 648. [9] B. Gelemt. S-V_ Filseth and T. Canington. J. Chem. Phys. 65 (1976) 4940_ [IO] C_ Zetzsch and F_ Stuhl. I- Chem. Phys- 66 (1977) 3107. [l I] C. Zetzsch and F- Stuhl. Ber- Bunsenges. Physik. Chem. 80 (1975) 1349s 1121 RJ. Cvetanovi& Advan- Photochem- I (1963) 11.5. [ 131 H. Yamazaki and R-J. Cvetanovi& J_ Chem. Phys. 4 1 (1964) 3703. [ 141 G. Paraskevopoulos and R.J. Cvetanovi&. J. them_ Phys_ 52 (1970) 5821. [IS] W-B. Dehiorc and S-W- Benson. Advan. Photochem. 2 (1964) 219. [ 161 H-hi_ Frey. Progr_ Reaction Kinetics 2 (1964) 131. [I71 J-A- Bell. J- Phys_ Chem. 75 (1971) 1537_ 1181 F_ Lahmani, J.phys. Chem. 80 (1976) 2623_ 1191 J-L. Brash and R-A- Back, Can. J- Chem- 43 (1965) 1778_ 1201 W-D. WooIIey and R-A. Back, Can. J. Chem. 46 (1968) 295 [21] D-W_ Cornell, R-S- Berry and W. Lwowski. J. Am. Chem. Sot_ 88 (1966) 544_ [22] R-S. Konar. S. Matsumoto and B_ deB. Dar-went. Trans. Faraday Sot. 67 (1971) 1698. [23] ME_ Jacox and D-E- Mill&n. J. Am. Chem- Sot. 85 (1963) 278.
Volume 64. number 3
CHEMICAL PHYSICS LETTERS
[24] J-R. McDonald. R-G. MiUer and A-P. Baronavski. Chem. Phys- 30 (1978) 133_ [2S] A-P- Baronavski. R-G. Mdier and J-R. McDonald. Chem. Phys. 30 (1978) 119. [26] R_J- Paur and E-J_ Bair, Intern. J. Chem- Kinetics 8 (1976) 134_
15 July 1979
[27] R_ Leschlaux and M. Demisey. J. Photochem. 9 (1978) llO_ [28] hl. Gehring, K. Hoyerman. H- Gg- Wagner and J. Wolf&m, Ber. Bunsenges. Physik. Chem. 75 (1971) 1287. [29] B-A_ Thrush, Proc- Roy_ Sot- A235 (1956) 143.
439