17126-11-3Relevant academic research and scientific papers
Experimental and theoretical study of the kinetic of proton transfer reaction by ion mobility spectrometry
Valadbeigi,Farrokhpour,Rouholahnejad,Tabrizchi
, p. 105 - 111 (2014)
Rate constants of the proton transfer reactions RH+ + DMP → R + DMP·H+, where R was acetone (Ac), trimethyl amine (TMA) or H2O and DMP was 2,4-dimethyl pyridine have been measured by ion mobility spectrometry (IMS). The Reactant R was injected into the ionization region of IMS to produce RH+ while DMP was continuously delivered to the drift region to react with the RH+ pulsed into the drift tube by a shutter grid. Since DMP.H+ was generated along the drift tube, a tail appeared in the IMS spectrum that contained kinetic information. To prevent proton-bound dimer formation, the reactions were carried out at elevated temperatures (170-230 °C). We measured rate constants of 1.17 × 10-9, 0.90 × 10-9 and 0.68 × 10-9 cm3 s-1 for proton transfer from H3O +, Ac·H+ and TMA·H+ to DMP, respectively. The experimental rate constants were almost temperature independent, indicating that no activation energy was involved in those proton transfer reactions. The rate constants were also calculated by using average dipole orientation (ADO) theory at B3LYP and MP2 levels. The calculated values revealed acceptable agreement between the experimental and theoretical trends. 2014 Elsevier B.V.
Carbon-Hydrogen Bond Dissociation Energies in Alkylbenzenes. Proton Affinities of the Radicals and the Absolute Proton Affinity Scale
Meot-Ner (Mautner), Michael
, p. 5 - 10 (2007/10/02)
Rate constants (k) were measured for proton-transfer reactions from alkylbenzene ions RH+ to a series of reference bases B, i.e., RH+ + B -> BH+ + R*.For exothermic reactions (ΔH -1.For example, the reaction C6H5CH3+ + B -> BH+ + C6H5CH2* is fast (reaction efficiency = k/kcol >/= 0.5) when B = MeO-t-Bu or stronger bases, but k/kcol is significantly smaller when B is n-Pr2O or weaker bases.From the falloff curve of reaction efficiency vs.PA(B), we find PA(n-Pr2O) = PA(C6H5CH2*) + 0.8 kcal mol-1 = 200.0 kcal mol-1.Since PA(C6H5CH2*) is obtained from known thermochemical data, this relation defines the absolute PA of n-Pr2O.Through a ladder of known PA, we then obtain PA(i-C4H8) = 186.8 kcal mol-1; we also obtain the absolute PAs of other oxygen bases.Falloff curves of reaction efficiencies of 3-FC6H4CH3+, C6H5C2H5+, C6H5-n-C3H7+, and C6H5-i-C3H7+ with these reference bases give then the following PAs of R* and R-H bond dissociation energies (Do) (all in kcal mol-1) as R*, PA(R*), Do(R-H): 3-FC6H4CH2*, 197.2, 89.4; , 197.9, 86.2; , 199.1, 86.1; , 199.6, 86.1.In similar manner, rate constants for H+ transfer from C6H5NH2+ to reference pyridines and amines yield PA(C6H5NH*) = 221.5 and Do(C6H5NH-H) = 85.1 kcal mol-1 (1 kcal mol-1 = 4.18 kJ mol-1).
Amine boranes. III. Propanolysis of pyridine boranes
Ryschkewitsch,Birnbaum
, p. 575 - 578 (2008/10/08)
The solvolysis kinetics in 1-propanol of a number of alkyl-substituted pyridine boranes was studied. The reactions were first order in amine borane. Linear variation of log k with pKa of the pyridinium ion was observed for groups of compounds with the same ortho substituents; steric enhancement of rate was attributed to 1.1 and 3.5 kcal./mole of strain relief in the transition state for one or two o-methyl groups, respectively. It was concluded that the solvolysis mechanism involves B-N cleavage in the slow step. It was found that the free energy of the transition state referred to the dissociation products was invariant with substitutions on the pyridine ring.
