Kinetic study of the proton transfer reaction between 1-nitro-1-(4-nitrophenyl)alkanes and P1-t-Bu phosphazene base in THF solvent

Equilibrium and kinetic study of the proton transfer reactions between nitroalkanes and strong organic bases — phosphazenes in tetrahydrofuran solvent

“…It is interesting that a similar anomaly has been observed by Wisłocka et al [11] for the reaction of these carbon acids with P 1 -t-Bu, having energetic barriers of 18 and 11 kJ mol -1 for the NPNE and MNPNP reaction, respectively. These variations in energetic barriers, which are sometimes not much larger from the value for viscous flow, are difficult to explain.…”

“…The increase of the alkyl substituent mass by replacement of the methyl with an ethyl or iso-propyl group causes a further decrease of the rate constant a few times over. The second order rate constants obtained for P 1 -t-Bu and nitroalkanes were: 9357, 2.31, 0.66, 0.09 dm 3 mol -1 s -1 for H, Me, Et, and i-Pr substituents, respectively [11]. These results show that the steric factor and ordering effects in forming the transition state play an important role, confirmed by negative and relatively large entropies of activation: ∆S ‡ = -149.7, -176.5, -178.7, -227.8 J mol -1 K -1 .…”

“…The rate constant for the reaction of 1-nitro-1-(4-nitrophenyl)alkane with P 1 -t-Bu phosphazene base is 9357 dm 3 mol -1 s -1 . The exchange of the hydrogen atom attached to the α-carbon atom for the methyl group decreases the rate constant by three orders of magnitude [11]. The increase of the alkyl substituent mass by replacement of the methyl with an ethyl or iso-propyl group causes a further decrease of the rate constant a few times over.…”

“…Our previous study reported the results obtained for the proton transfer reaction between P 1 -t-Bu phosphazene base and a series of nitroalkanes with increasing substituent masses at the reaction center [11]. The rate constant for the reaction of 1-nitro-1-(4-nitrophenyl)alkane with P 1 -t-Bu phosphazene base is 9357 dm 3 mol -1 s -1 .…”

Primary kinetic hydrogen isotope effects in deprotonations of carbon acids

“…The table also contains data for deprotonations by amine or amidine bases in aprotic solvents of widely ranging polarity (toluene, THF and acetonitrile) 29, 31, 32, 42, 45. Products here are ion pairs, which may dissociate appreciably in acetonitrile, but less so in toluene or THF.…”