Acid-catalyzed decomposition
of dicumyl peroxide in dodecane from
60 to 130 °C produces α-methylstyrene and phenol as the
major products. Pseudo-first-order rate constants were determined
as a function of the temperature for the reaction of DCP with dodecylbenzenesulfonic
acid in dodecane and resulted in an Arrhenius plot exhibiting
two distinct kinetic regimes with differing activation energies:
76.9 kJ/mol at low temperatures (measured from 60 to 90 °C) and
8.50 kJ/mol at higher temperatures (measured from 90 to 130 °C).
With employment of a combination of kinetics, product analysis, and
trapping experiments, evidence is presented to show the intermediacy
of cumene hydroperoxidea reactive intermediate absent
from previous mechanistic descriptions of this process. The
yield of cumene hydroperoxide production is discussed, and the mechanistic
pathways for formation of the observed products are presented.
Supplemental Information S1. Materials Glycine (≥98.5%), 13 C 2-Glycine (99 atom % 13 C), paraformaldehyde (powder, 95%), 13 C-formaldehyde (20 wt. % in H2O, 99 atom % 13 C), L-serine, sarcosine, sodium hydroxide (NaOH), and LC-MS grade water were all purchased from Sigma-Aldrich and used as is. Reactions of Glycine and Formaldehyde Glycine (unlabeled and 13 C 2-labeled) was dissolved in pH 6, 8 or 10 aqueous sodium phosphate buffered solution. Varying molar equivalents of formaldehyde (unlabeled and 13 C-labeled) were then added to the glycine solution. The resulting mixtures was allowed to react at RT, 50°C and 70°C for periods up to two weeks. By varying the stoichiometry, temperature and pH, the optimal reaction conditions for glyoxylate yield could be determined. 13 C NMR Analysis 13 C NMR data were obtained using a Bruker Avance II-500 spectrometer and a Bruker Avance III-400
The reactions of glycine, a simple amino acid, with glyoxylate, a simple α-oxocarboxylate, were investigated in water as a function of time, pH, and temperature and followed using a combination of quantitative 13 C nuclear magnetic resonance and high-resolution mass spectrometry. Three sets of experiments are reported: (1) reaction of 13 C-labeled glycine with unlabeled glyoxylate, (2) reaction of unlabeled glycine with 13 C-labeled glyoxylate, and (3) the reaction of 13 C-labeled glycine with 13 C-labeled glyoxylate. Competing transaminations, aldol reactions, and decarboxylations were observed; the mechanistic description for each of these processes is presented. 3-Hydroxy-2-aminosuccinate, a product of reaction between glycine and glyoxylate, was shown to promote both the decarboxylation of glyoxylate and transamination of glyoxylate to glycine. These observations may have implications for the mechanism of attenuation of ethylene glycol toxicity.
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