Volume changes in the proton ionization of amines in water. 2. Amino alcohols, amino ethers, and diamines

Abstract

15) (a) a's for processes a. b, and c are defined by the following relation: a = [-K+ (K+ 4 Kct/2]/2c°, where Kand c°are the dissociation constant and the initial concentration of B, BH+, or BH22+, respectively, in processes a, b, or c. (b) The value of a for process d is calculated from: a = 2(K'1//C2)1,2/[1 + 2(K1/K2)V2j, where K, and K2 are the dissociation constants for proton ionization processes b and c. In deriving a, processes b and c for the products of disproportionation have been assumed to be negligible. This is a valid assumption for the solutions of the monohydrochlorides of the diamines here examined, because the difference between cB and Cbh22+ does not exceed 1 ppm. The pK for process d is related to p/ , and pK2 by pK= 2( -pK2).

Apparent Molar Volumes and Adiabatic Compressibilities of Some Amino Acids in Aqueous Sucrose Solutions at 298.15 K

“…Also listed in Table 4 are the various groups contributing to the V 0 φ of L-glycine [25], L-alanine, and L-valine in aqueous sucrose solutions at 298.15 K. The values of V 0 φ for CH 2 -(L-glycine), CH 3 CH-(L-alanine), CH 3 CH 2 CH 2 CH-(L-valine), and zwitterionic end groups (NH 3 + COO − ) were estimated by least squares fitting of V 0 φ of the amino acids containing the group vs. the molecular weight of the hydrocarbon portion of the amino acid. Values for V 0 φ of -CH 2 , -CHCH 3 , and NH 3 + COO − agree well with the literature values [16,[45][46][47] in case of water. The value of V 0 φ for NH 3 + COO − is larger than the value of V 0 φ for -CH 2 and increase with the increase in the concentration of sucrose (except at 15 mass % of sucrose).…”

Apparent molar volumes of aqueous solutions of some organic solutes at the pressure 28 MPa and temperatures to 598 K

“…All measurements were made at p= (28. (11) and (12), and the bottom value from equations (11) and (13). e Calculated from V a 2 for 1,3 propanediamine (59) with a correction DV a 2 =16.0 cm 3 ·mol −1 added for the appropriate number of CH2 groups to produce V a 2 for the solute. f Calculated from V a 2 for 1,5 pentanediol and 1,7 heptanediol, (61) with correction DV a (11) and (12), and the bottom value is from equations (11) and (13).…”

Hydrothermal Experiments with Protonated Benzylamines Provide Predictions of Temperature-Dependent Deamination Rates for Geochemical Modeling

“…As an example, pH controls the speciation of amines between unprotonated and protonated forms and thus influences their reaction pathways. ,, Based on the p K a values of aliphatic aminiums (9–11 at 25 °C), − deamination of unprotonated amino groups may predominate at hyperalkaline conditions, such as in serpentinized fluids. − However, deamination of protonated amino groups is expected to occur more readily than unprotonated amino groups on the basis of leaving group stability, , so even if only a small fraction of an amino group is protonated at high pH, , it may be sufficient to approximate overall deamination rates using only aminium deamination kinetics as long as one accounts for pH-dependent speciation. As examples, in serpentinizing fluids sampled at the Lost City hydrothermal vents (pH range of ∼9–11 measured at 25 °C), , the amino group of aspartic acid (p K a of 10.2 at 25 °C) would be speciated ∼13–93% in its aminium form and the amino group of methylamine (p K a of 10.6 at 25 °C) , would be speciated ∼29–97% in its aminium form. For even higher pH fluids, such as the serpentinizing fluids of the Samail Ophiolite (pH of ∼11.5 at ∼25 °C), , the fraction of aminium that would form is ∼4% for aspartic acid and ∼11% for methylamine.…”