Mechanism and kinetic study of Paal-Knorr reaction based on in-situ MIR monitoring

Ye, Shuliang; Yang, Shumei; Ni, Liwei; Qiu, Wenze; Xu, Qiyue

doi:10.1016/j.saa.2021.120280

Cited by 6 publications

(2 citation statements)

References 33 publications

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“…Results showed that high temperature hindered the accumulation of the intermediate as its maximum concentration decreased with temperatures. This is consistent with our previous work 29 and might be caused by the fact that reaction rates of the second step were more sensitive to temperature variation due to higher activation energy.…”

Section: Paal-knorr Reactionsupporting

confidence: 93%

Reaction Analysis and Process Optimization with Online Infrared Data Based on Kinetic Modeling and Partial Least Squares Quantitation

Qiu

Jin

et al. 2022

Appl Spectrosc

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In-situ Fourier-transform infrared (FTIR) spectroscopy has been recognized as an important technology for online monitoring of chemical reactions. However, analysis of the real-time IR data for identification and quantification of uncertain reactants or intermediates is often ambiguous and difficult. Here we propose an analysis algorithm based on reaction kinetic modeling and the chemometric method of partial least squares (PLS) to comprehensively and quantitatively study reaction processes. Concentration profiles and apparent kinetic parameters can be simultaneously calculated from the spectral data, without the demand of complicated analysis on characteristic absorbance peaks or tedious sampling efforts for multivariate modeling. Paal-Knorr reactions and glyoxylic acid synthesis reactions were selected as typical reactions to validate the algorithm. The quantitative results were verified by measurements and demonstrated great credibility of this method. Moreover, the reaction kinetic models extracted from FTIR data were used to simulate reaction processes and optimize the conditions in order to maximize product yields. This analysis method based on kinetic modeling and the PLS method has been proven as a useful tool to quantitatively study the chemical reaction and has the ability for reaction monitoring and process optimization.

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Section: Paal-knorr Reactionsupporting

confidence: 93%

Reaction Analysis and Process Optimization with Online Infrared Data Based on Kinetic Modeling and Partial Least Squares Quantitation

Qiu

Jin

et al. 2022

Appl Spectrosc

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“…20 It uses 1,4-dicarbonyl compounds and amines as raw materials to obtain pyrrole rings by acid-catalysed condensation reactions. In recent years, many pyrrole series derivatives have been synthesized by this method, in which some antibacterial active substances [21][22][23] have been found, with promising applications. Herein, we synthesized 2,5-dimethyl-N-pyrroleacetic acid by the Paal-Knorr reaction using 2,5-hexanedione and glycine as raw materials.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and pyrolysis of various novel pyrrole ester fragrance precursors

Tian

Han

et al. 2023

Flavour & Fragrance J

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Due to the disadvantages of low fragrance threshold and high volatility of pyrrole monomer under high‐temperature process in tobacco or food, it cannot meet the market requirements. In order to develop pyrrole flavour precursors, 2,5‐dimethyl‐N‐pyrroleacetic acid was synthesized by the Paal–Knorr reaction using 2,5‐hexanedione and glycine as raw materials. Various pyrrole fragrance precursors such as 2‐ethyl‐4‐oxo‐4H‐pyran‐3‐yl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5a), 4‐formyl‐2‐methoxyphenyl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5b), pyridine‐2‐ylmethyl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5c) and thiophen‐2‐ylmethyl 2‐(2,5‐dimethyl‐1H‐pyrrol‐1‐yl)acetate (5d) were synthesized by esterification from 2,5‐dimethyl‐N‐pyrroleacetic acid with ethyl maltol, vanillin, 2‐pyridinemethanol and 2‐thiophenemethanol, respectively. As part of the study, IR, NMR and HRMS were used to characterize the target compounds. Using gas chromatography–mass spectrometry‐olfactometer (GC–MS‐O), the pyrrole esters obtained were evaluated for the characteristics of their aromas. The thermal stability was analysed using thermogravimetric analysis and pyrolysis gas chromatography/mass spectrometry. In addition, the pyrolysis mechanism was speculated. With TG‐DTG results, the main mass loss phase of 5a occurred between 108°C and 450°C, with a dramatic mass loss reduction of 83.07%. At 118.60°C and 450°C, 5b showed a mass loss reduction of 60.80%. Furthermore, according to the Py‐GC/MS analysis results, compounds 5a and 5b formed 8 and 7 pyrolysis products. The main pyrolysis products of 5a and 5b were 1‐ethyl‐2,5‐dimethyl‐1H‐pyrrole, ethyl maltol, and vanillin, which are all aroma components used to blend cigarette smoke, can slow down the rate at which aromas are lost and mask unpleasant smoke. Study results provide a reference for the tobacco industry to further develop new high‐temperature release aroma ingredients.

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Mechanism study of the N-butoxycarbonyl-2,5-dimethylpyrrole synthesis reaction based on in-situ FTIR monitoring

Yang

Qiu

et al. 2023

Vibrational Spectroscopy

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Mechanism and kinetic study of Paal-Knorr reaction based on in-situ MIR monitoring

Cited by 6 publications

References 33 publications

Reaction Analysis and Process Optimization with Online Infrared Data Based on Kinetic Modeling and Partial Least Squares Quantitation

Reaction Analysis and Process Optimization with Online Infrared Data Based on Kinetic Modeling and Partial Least Squares Quantitation

Synthesis and pyrolysis of various novel pyrrole ester fragrance precursors

Mechanism study of the N-butoxycarbonyl-2,5-dimethylpyrrole synthesis reaction based on in-situ FTIR monitoring

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