29342-38-9Relevant articles and documents
The kinetics of proton and deuteron transfer from 1-(4-nitrophenyl)-1-nitroethane to 1,8-diazabicycloundec-7-ene in aprotic solvents
Leffek, Kenneth T.,Pruszynski, Przemyslaw
, p. 1692 - 1695 (1982)
1-(4-Nitrophenyl)-1-nitroethane reacts with the base 1,8-diazabicycloundec-7-ene (DBU) in both acetonitrile and toluene solvents in a normal second-order proton-transfer reaction, in contrast to its behaviour with the base 2,7-dimethoxy-1,8-bis(dimethylamino)naphthalene in acetonitrile.The primary isotope effect, kH/kD = 12.0 at 25 deg in toluene is very similar to that observed by other workers for the reaction of 4-nitrophenylnitromethane with DBU under the same conditions.In acetonitrile solvent a kH/kD ratio of 7.8 was found at 25 deg C.The isotope effecs on the activation parameters for the reaction in both solvents indicate that tunnelling of the proton through the potential energy barrier makes a significant contribution to the reaction rate.
Kinetic study of the proton transfer reaction between 1-nitro-1-(4-nitrophenyl)alkanes and P1-t-Bu phosphazene base in THF solvent
Wis?ocka, Zaneta,Nowak, Iwona,Jarczewski, Arnold
, p. 152 - 158 (2007/10/03)
The rates of proton transfer reactions between C-acids of the series of nitroalkanes with increasing bulk of R=H, Me, Et, i-Pr substituents as 4-nitro-phenylnitromethane (1), 1-(4-nitrophenyl)-1-nitroethane (2), 1-(4-nitrophenyl)-1-nitropropane (3), 2-methyl-1-(4-nitrophenyl)-1-nitropropane (4) and the P1-t-Bu phosphazene have been measured in THF at pseudo-first-order conditions. The product of the proton transfer reaction with P1-t-Bu is associated into ion pair. The equilibrium constants decrease along with growing bulk of alkyl substituent in the reacting C-acid: >100 000, 1170, 590, and 11.8 for 1, 2, 3, 4, respectively. The second order rate constants (k2H) for this very strong base and C-acids are rapidly declining: 9357, 2.31, 0.66, 0.09 dm3 mol-1 s-1 for 1, 2, 3, 4, respectively, and could not be accounted for the small values of the enthalpies of activation Δ HH≠ = 6.1, 18.0, 20.7 and 11.1 kJ mol- 1. The appropriate values of the entropies of activation were all negative and relatively large Δ SH≠ = - 149.7, - 176.5, - 178.7, - 227.8 J mol- 1 deg- 1 indicating an importance of steric and ordering effects in forming the transition state. The primary deuterium kinetic isotope effects are large showing tendency of reverse relation towards steric hindrance of the reacting C-acids, kH/kD=15.8, 13.6, 13.2 for 1, 2, and 3, respectively. The explanation of the unusual slow proton transfer abstraction caused by this extremely strong base is undertaken.
Kinetics, Isotope Effects, and Mechanism of the Reaction of 1-Nitro-1-(4-nitrophenyl)alkanes with DBU in Acetonitrile
Galezowski, Wlodzimierz,Jarczewski, Arnold
, p. 1647 - 1656 (2007/10/02)
The kinetics of the reaction of O2NC6H4C(L)(R)NO2 (R = Me, Et, Pri, NNPE, NNPP, or MNNPP, respectively; L = H, D) with 1,8-diazabicycloundec-7-ene (DBU) in acetonitrile (MeCN) are reported.The nature of the product indicates that substantial dissociation into free ions occurs.The usefulness of Benesi-Hildebrand relationship for distinguishing between ion pairs and ions of the product is discussed in detail.The reaction shows low activation enthalpy value ΔH(excit.) = 15.4, 17.8, and 19.9 kJ mol-1 and large negative entropies of activation ΔS(excit.) = -131, -134, and -147 J mol-1 K-1 for NNPE, NNPP, and MNNPP respectively.The kinetic isotope effects kH/kD (12.5, 12.4, and 12.3) are large, showing no variation, the more sterically hindered the substrate.The values of the isotope effects exerted on the activation parameters indicate the contribution of a tunnelling effect QH/QD = 1.35 at 25 deg C.The influence of water on the kinetics is also examined and discussed with respect to reliability of kinetic measurements of such reactions systems.
