Reactions of borane (BH3). VII. Reactions with ketene

Fehlner, Thomas P.

doi:10.1021/j100668a004

Cited by 4 publications

(2 citation statements)

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“…Dimethylketene trimethylsilylacetal (47) undergoes a 1,3-migration of a trimethylsilyl group from oxygen to carbon on heating, yielding (48). This contrasts with the behaviour of such acetals of ketene or dimethylketene which revert to the ketenelo8.…”

Section: Other Reactionsmentioning

confidence: 99%

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Kinetics and mechanisms (excepting cycloadditions)

Blake¹

Ketenes, Allenes and Related Compounds: Vol. 1 (1980)

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Section: Other Reactionsmentioning

confidence: 99%

“…Similarly, hydroxide ions abstract a proton, leaving a carbanion. Carbanions formed in this way react with molecular oxygen as in equation (48). …”

Section: A Gas Phasementioning

confidence: 99%

Kinetics and mechanisms (excepting cycloadditions)

Blake¹

Ketenes, Allenes and Related Compounds: Vol. 1 (1980)

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ChemInform Abstract: RK. VON BORAN (BH3) 7. MITT. RK. MIT KETEN

Fehlner¹

1973

Chemischer Informationsdienst

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On the fast addition reactions of BH₃

Fehlner

1975

Int J of Chemical Kinetics

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Borane is a rather unique reactive species in that it has a low lying empty boron 2p atomic orbital [ l ] and, thus, serves as a good model for an electrophilic species. One advantage of BHB as a reagent is that the addition reactions are examined in the gas phase, thereby eliminating solvent effects. A second advantage is that the amount of energy deposited in the initial adducts is much less than in the case of oxygen atoms, for example. Thus the initial adduct can usually be directly observed. Finally, as BH3 adds rapidly to reagents with differing electronic structures to form observable adducts, the rate constants of these reactions constitute an unusual probe of the relationship of reaction rates to electronic structures.We have recently measured the rate constants for the rapid addition of BH3 to various substrates. The experimental absolute rate constants for eight of these reactions are gathered in Table I. In all these cases the simple adduct was observed, and all the data are consistent with the formation of a donor-acceptor adduct in the first instance. In two cases the activation energy was measured and was found to be small.It is known that the rates of the fast reactions of many reactive species correlate to some extent with the ionization potential of the substrate [9]. However, as illustrated in Figure l(a), this is not the case for BH3. On the other hand [ Figure 1 (b)] there does seem to be a good correlation of rate with the nuclear charge on the atom to which BH3 adds, i.e., the rate for P = 0 < N < C < B. This observation can be qualitatively explained as follows.The reactions considered are all very rapid in an absolute sense and therefore an early transition state is expected. Thus it will be the initial interactions that will control the barrier height and reaction rate. Although repulsive interactions .are important, it appears that the attractive interactions are the controlling factors [ 10-121. The attractive interaction between borane and the donor species can be approximately represented by the mixing of the B (2p) orbital on BHa and the highest filled orbital on the substrate [lo]. The attractive interaction at constant temperature may be written as Eat,, = -aS2/(E + I ) 633

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Reactions of borane (BH3). VII. Reactions with ketene

Cited by 4 publications

References 6 publications

Kinetics and mechanisms (excepting cycloadditions)

Kinetics and mechanisms (excepting cycloadditions)

ChemInform Abstract: RK. VON BORAN (BH3) 7. MITT. RK. MIT KETEN

On the fast addition reactions of BH₃

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Reactions of borane (BH3). VII. Reactions with ketene

Cited by 4 publications

References 6 publications

Kinetics and mechanisms (excepting cycloadditions)

Kinetics and mechanisms (excepting cycloadditions)

ChemInform Abstract: RK. VON BORAN (BH3) 7. MITT. RK. MIT KETEN

On the fast addition reactions of BH3

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On the fast addition reactions of BH₃