Insights on the mechanism for synthesis of methylenedianiline from aniline and formaldehyde through HPLC–MS and isotope tracer studies

Wang, Chen Ye; Li, Hui Quan; Wang, Li Guo; Cao, Yan; Liu, Hai Tao; Zhang, Yi

doi:10.1016/j.cclet.2012.10.001

Cited by 11 publications

(9 citation statements)

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“…[12]. On the other hand, the one step formation of aminal (AM) suggested by Wang [13] is unlikely, since the corresponding hypothetical transition state would be crowded around the methylene carbon, therefore reaction of N-methylenebenzeneaminium and aniline is considered as a formation of protonated aminal (AMH + ) instead (for its detailed discussion see Important side reactions section). Before the solvent effect is discussed the gas phase thermochemistry of the species playing role is evaluated.…”

Section: Resultsmentioning

confidence: 99%

“…Overall reaction mechanism for methylene diphenyl diamine (methylenedianiline, MDA) synthesis according Kirk–Othmer Encyclopedia of Chemical Technology [12] as well as Wang [13] compared with our proposed mechanism based on G3MP2B3 computation.…”

Section: Figurementioning

confidence: 99%

“…More recently Wang et al [13] suggested an alternative mechanism in which the reaction of N-hydroxymethylamine and aniline (A) gives N,N’-diphenylmethylenediamine first (so-called aminal noted as AM in Figure 1) before the formation of PABA. Due to the protonation of one of the secondary amine group in AM (AMH + ), the C-N bond is activated for the rearrangement making PABA.…”

Section: Introductionmentioning

confidence: 99%

“…According to Wang, same activation is supposed to happen to the other secondary amine group to form MDA: PABA is protonated (PABAH + ) which then initiates aniline rearrangement. Wang et al found some evidences to support the latter mechanism by isolation and identification of aminal using the combination of isotope labeling and HPLC-MS [13]. Albeit other intermediates has not been characterized at all.…”

Section: Introductionmentioning

confidence: 99%

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An Ab Initio Investigation of the 4,4′-Methlylene Diphenyl Diamine (4,4′-MDA) Formation from the Reaction of Aniline with Formaldehyde

et al. 2019

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The most commonly applied industrial synthesis of 4,4′-methylene diphenyl diamine (4,4′-MDA), an important polyurethane intermediate, is the reaction of aniline and formaldehyde. Molecular understanding of the 4,4′-MDA formation can provide strategy to prevent from side reactions. In this work, a molecular mechanism consisted of eight consecutive, elementary reaction steps from anilines and formaldehyde to the formation of 4,4′-MDA in acidic media is proposed using accurate G3MP2B3 composite quantum chemical method. Then G3MP2B3-SMD results in aqueous and aniline solutions were compared to the gas phase mechanism. Based on the gas phase calculations standard enthalpy of formation, entropy and heat capacity values were evaluated using G3MP2B3 results for intermediates The proposed mechanism was critically evaluated and important side reactions are considered: the competition of formation of protonated p-aminobenzylaniline (PABAH+), protonated aminal (AMH+) and o-aminobenzylaniline (OABAH+). Competing reactions of the 4,4′-MDA formation is also thermodynamically analyzed such as the formation of 2,4-MDAH+, 3,4-MDAH+. AMH+ can be formed through loose transition state, but it becomes kinetic dead-end, while formation of significant amount of 2,4-MDA is plausible through low-lying transition state. The acid strength of the key intermediates such as N-methylenebenzeneanilium, PABAH+, 4-methylidenecyclohexa-2,5-diene-1-iminium, and AMH+ was estimated by relative pKa calculation.

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Section: Resultsmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Ab Initio Investigation of the 4,4′-Methlylene Diphenyl Diamine (4,4′-MDA) Formation from the Reaction of Aniline with Formaldehyde

et al. 2019

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“…Industrial grade MDA is composed of 2-ring MDA and larger multimeric species which are formed by the reaction of aniline and formaldehyde and named according to the number of aniline rings present. 1,2 Structural isomers reflecting attachment of additional anilines at different sites can exist in industrial grade MDA which contributes to heterogeneity in many polyurethane systems. 3 Determining preferred protonation sites and location of aniline attachments for larger MDA multimers is of great interest in polymer chemistry, because isomeric characterization can contribute to an enhanced understanding of structure–property relationships of many commercially relevant MDI-based PUR systems.…”

mentioning

confidence: 99%

Structural Characterization of Methylenedianiline Regioisomers by Ion Mobility-Mass Spectrometry, Tandem Mass Spectrometry, and Computational Strategies. 2. Electrospray Spectra of 3-Ring and 4-Ring Isomers

et al. 2015

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Building on results from our previous study of 2-ring methylenedianiline (MDA), a combined mass spectrometry approach utilizing ion mobility-mass spectrometry (IM-MS) and tandem mass spectrometry (MS/MS) coupled with computational methods enables the structural characterization of purified 3-ring and 4-ring MDA regioisomers in this current study. The preferred site of protonation for the 3-ring and 4-ring MDA was determined to be on the amino groups. Additionally, the location of the protonated amine along the MDA multimer was found to influence the gas phase stability of these molecules. Fragmentation mechanisms similar to the 2-ring MDA species were observed for both the 3-ring and 4-ring MDA. The structural characterization of 3-ring and 4-ring MDA isomers using modern MS techniques may aid polyurethane synthesis by the characterization of industrial grade MDA, multimeric MDA species, and methylene diphenyl diisocyanate (MDI) mixtures.

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Polyurethane Building Blocks

Sonnenschein

2014

Polyurethanes

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Insights on the mechanism for synthesis of methylenedianiline from aniline and formaldehyde through HPLC–MS and isotope tracer studies

Cited by 11 publications

References 0 publications

An Ab Initio Investigation of the 4,4′-Methlylene Diphenyl Diamine (4,4′-MDA) Formation from the Reaction of Aniline with Formaldehyde

An Ab Initio Investigation of the 4,4′-Methlylene Diphenyl Diamine (4,4′-MDA) Formation from the Reaction of Aniline with Formaldehyde

Structural Characterization of Methylenedianiline Regioisomers by Ion Mobility-Mass Spectrometry, Tandem Mass Spectrometry, and Computational Strategies. 2. Electrospray Spectra of 3-Ring and 4-Ring Isomers

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