Pyrolysis of monosilane

Ring, M. A.; Puentes, M. J.; O’Neal, H. E.

doi:10.1021/ja00719a015

Cited by 58 publications

(24 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[23] proposed the same primary step while Purnell and his group [24] favoured a silylene mechanism SiH 4 4siH 2 + H 2 (12) which has been finally agreed on [25].…”

Section: Discussionmentioning

confidence: 92%

The Reaction of Hydrogen Atoms with Silyl Radicals; the Decomposition Pathways of Chemically Activated Silanes

Reimann

Potzinger

1983

Zeitschrift Für Naturforschung A

View full text Add to dashboard Cite

The reactions of hydrogen atoms with silane and the methylated silanes -with the exception of tetramethylsilane -have been investigated in a fast flow reactor. Under our experimental conditions hydrogen abstraction from the Si-H bond is followed by combination of hydrogen atoms with the corresponding silyl radicals. The molecules formed in this way are activated by about 375 kJ/mol of vibrational energy. Two decomposition channels have been unequivocally identified, namely the elimination of molecular hydrogen and of methane, both with concomittant formation of the respective silylenes. In a subsequent step, silylene inserts into the substrate under formation of disilanes. With increasing degree of methylation. stabilization of the activated molecule competes with decomposition and dominates the kinetics in the case of trimethylsilane. With methyl-and dimethyl-silane, methyl radicals are observed as an additional reaction product. On the basis of RRKM calculations it is unlikely that they originate from a direct decomposition of the activated molecules.Absolute values for the room temperature rate constants of the abstraction reactions are given; for H + CH 3 SiH 3 , Arrhenius parameters have been determined.

show abstract

“…[23] proposed the same primary step while Purnell and his group [24] favoured a silylene mechanism SiH 4 4siH 2 + H 2 (12) which has been finally agreed on [25].…”

Section: Discussionmentioning

confidence: 92%

The Reaction of Hydrogen Atoms with Silyl Radicals; the Decomposition Pathways of Chemically Activated Silanes

Reimann

Potzinger

1983

Zeitschrift Für Naturforschung A

View full text Add to dashboard Cite

show abstract

“…The data and mechanism also provide information about the rates of the effective silylene sink reaction (3). Thus from the silylene and disilane steady state conditions,…”

Section: Qualitative Features Of the Dual Channel Initiation Mechanismmentioning

confidence: 97%

Mechanism of the silane decomposition. I. Silane loss kinetics and rate inhibition by hydrogen. II. Modeling of the silane decomposition (all stages of reaction)

White

Espino-Rios

Rogers

et al. 1985

Int J of Chemical Kinetics

View full text Add to dashboard Cite

Part I : Kinetic d a t a for t h e s t a t i c system s i l a n e pyrolysis ( f r o m 640-703 K , 60-400 torr) are presented. For conversion from 3-304. first-order kinetics a r e obtained, with silane loss rates equal to half the hydrogen formation rates. At conversions greater than 4 0 4 , rate inhibition attributable to the back reaction of hydrogen with silylene occurs. Overall reaction rates are not surface sensitive. but disilane and trisilane yield maxima under some conditions are. A nonchain mechanism capable of describing quantitatively all stages of the silane pyrolysis is proposed. Post 1.05; initiation is both homogeneous (gas phase) and heterogeneous (on the walls), and reaction intermediates are silylenes and disilenes. Free radicals are not involved a t any stage of the reaction. Rate data a t high conversions and with added hydrogen provide kinetics for the addition of silylene to hydrogen [reaction (-1iI relative to its addition to silane [reaction (2)l: k , / k , = 1 0~0 6 5 x e 3 2 0 " c~i ' H T . With E2 = 1300 cal, this gives a highpressure activation energy for silylene insertion into hydrogen of E -, = 8200 cal.Part 11: An analysis is made of each rate constant of the silane mechanism and the modeling results are compared with experimental results. Agreement is excellent. It is concluded that the dominant sink reaction for silylene intermediates is 1,2-H, elitnination from disilane (followed by SiYHl polymerization and wall deposition). The model is in accord with slow isomerization between disilene and silylsilylene and near exclusive 1,2-H2 elimination from S i L H G .It is also concluded t h a t disilene is about 10 kcal/mol more stable than silylsilylene and that the activation energy for isomerization of silylsilylene to disilene is greater than 26 kcal/;nol.

show abstract

“…First, in the toluene inhibited studies, careful examination of the mass spectrum of products has revealed no detectable amounts of methane. However, it has been established that methyl displacement by H atoms from toluene [reaction (5)] is competitive with Hatom abstraction [reaction (6)], and methyl radicals produced in (5) 5 (5)…”

mentioning

confidence: 99%

Kinetics and mechanism of the silane decomposition

Newman

O’Neal

Ring

et al. 1979

Int J of Chemical Kinetics

184

View full text Add to dashboard Cite

The homogeneous gas-phase decomposition kinetics of silane has been investigated using the single-pulse shock tube comparative rate technique (T = 1035-1184°K, P~d = 4000 Torr).The initial reaction of the decomposition SiH4 ! + SiHz + H2 is a unimolecular process in its pressure fall-off regime with experimental Arrhenius parameters of logkl (sec-I) = 13.33 f 0.28-52,700 f 1400/2.303RT. The decomposition has also been studied at lower temperatures by conventional methods. The results confirm the total pressure effect, indicate a small but not negligible extent of induced reaction, and show that the decomposition is first order in silane at constant total pressures. RRKM-pressure fall-off calculations for four different transition-state models are reported, and good agreement with all the data is obtained with a model whose high-pressure parameters are logAl (sec-') = 15.5, El(,) = 56.9 kcal, and AE;;, = 55.9 kcal. The mechanism of the decomposition is discussed, and it is concluded that hydrogen atoms are not involved. It is further suggested that silylene in the pure silane pyrolysis ultimately reacts with itself to give hydrogen: 2SiH2 -(SiZHd)* -(SiH3SiH)* -SizHz + Hz. The mechanism of H -D exchange absorbed in the pyrolysis of SiD4-hydrocarbon systems is also discussed.In a prior paper [l], we reported preliminary single-pulse shock tube kinetic results on the silane decomposition. We showed that the initial reaction of the decomposition is molecular Hz elimination [reaction (l)]+ (1)Production of hydrogen atoms in the overall reaction was suggested by large yields of HD found in the pyrolysis of SiD4 in the presence of excess toluene (see Table I). Silylene decomposition [reaction (2)] was postulated to be the source of the D atoms [l]. However, we now believe that this conclusion n + The simple bond rupture process, SiH4 -SiH3 + H, was eliminated as a possible initiation reaction because its high activation energy (93 kcal) would require a chain process with chain lengths in excess of lo6 in order to match observed reaction rates. Such long chains under shock conditions are clearly impossible. Thus one calculates that on average fewer than 50 collisions between silane (0.01%) and product molecules occur in a typical 200 Fsec shock period.

show abstract

Pyrolysis of monosilane

Cited by 58 publications

References 3 publications

The Reaction of Hydrogen Atoms with Silyl Radicals; the Decomposition Pathways of Chemically Activated Silanes

The Reaction of Hydrogen Atoms with Silyl Radicals; the Decomposition Pathways of Chemically Activated Silanes

Mechanism of the silane decomposition. I. Silane loss kinetics and rate inhibition by hydrogen. II. Modeling of the silane decomposition (all stages of reaction)

Kinetics and mechanism of the silane decomposition

Contact Info

Product

Resources

About