Quantitative and qualitative 1H, 13C,and 15N NMR spectroscopic investigation of the urea–formaldehyde resin synthesis

Urea–formaldehyde resins are bulk products of the chemical industry. Their synthesis involves a complex reaction network. The present work contributes to its elucidation by presenting results from detailed NMR spectroscopic studies with different methods. Besides¹H NMR and¹³C NMR,¹⁵N NMR spectroscopy is also applied.¹⁵N‐enriched urea was used for the investigations. A detailed NMR signal assignment and a model of the reaction network of the hydroxymethylation step of the synthesis are presented. Because of its higher spectral dispersion and the fact that all key reactions directly involve the nitrogen centers,¹⁵N NMR provides a much larger amount of detail than do¹H and¹³C NMR spectroscopy. Symmetric and asymmetric dimethylol urea can be clearly distinguished and separated from monomethylol urea, trimethylol urea, and methylene‐bridged urea. The existence of hemiformals of methylol urea is confirmed. 1,3,5‐Oxadiazinan‐4‐on (uron) and its derivatives were not found in the reaction mixtures investigated here but were prepared via alternative routes. The molar ratios of formaldehyde to urea were 1, 2, and 4, the pH values 7.5 and 8.5, and the reaction temperature 60 °C. Copyright © 2014 John Wiley & Sons, Ltd.     

Kinetic Study of the Thermal Polymerization Reactions between Diazide and Internal Diyne

The reaction kinetics between diazide(4,4′‐biphenyl dibenzyl azide) and internal diyne(bis[2‐(phenyl)ethynyl]dimethylsilane) was studied in this study by means of differential scanning calorimetry (DSC) and nuclear magnetic resonance spectra (¹H NMR). DSC was carried out to analyze the reaction in bulk polymerization condition, whereas ¹H NMR for solution reaction polymerization. The apparent activation energy (e_α) calculated by Kissinger's method was 90.83 kJ/mol, which was confirmed by Friedman's method, and 87.67 kJ/mol by ¹H NMR, respectively. The polymerization between the diazide and internal diyne was the second‐order reaction based on calculation from both of DSC and ¹H NMR.     

Synthesis of bacillamide 3 and its analogue

The bacillamide 1 is a new algaecide from the marine bacterium Bacillus sp. SY-1. Its analogues bacillamide 3 and alkaloid 4 were firstly synthesized effectively from d-alanine. The key step was a coupling reaction via the mixed anhydride. All structures were confirmed by ¹H NMR and ¹³C NMR. The final compounds were confirmed by ¹H NMR, ¹³C NMR and HRMS and the results are consistent with the reported natural products.     

An NMR study of sequential intermediates and collateral products in the conversion of 1,3,6,8-tetraazatricyclo[4.4.1.1]dodecane (TATD) to 1,3,6,8-tetraazatricyclo[4.3.1.1]undecane (TATU)

In situ ¹H nuclear magnetic resonance spectroscopy was used to investigate the processes that occur during the synthesis of 1,3,6,8-tetraazatricyclo[4.3.1.1^3,8]undecane (TATU). NMR analysis showed a reaction mixture containing more than one compound. The production of these intermediates and collateral products was rationally supported by a careful ¹H NMR monitoring study. We characterized 1,3,5-triazabicyclo[3.2.1]octane (TABO, 4) and 3-(2-aminoethyl)-1,3,5-triazabicyclo[3.2.1]octane (AETABO, 7) by ¹H and ¹³C NMR in D₂O solution inside the NMR sample tube, as an intermediate and collateral product of the reaction, respectively. Further, a reaction of 1,3,6,8-tetraazatricyclo[4.4.1.1^3,8]dodecane (TATD) with ¹⁵N-labeled ammonium chloride was carried out. The ¹⁵N NMR and GC-MS experiments indicated that ¹⁵N was incorporated into TATU, TABO, and urotropine.     

Phosphate Derivatives of Natural Lactones. II. Synthesis of Novel Dialkylphosphonates of Arteannuin B

Novel dialkylphosphonates of arteannuin B were synthesized in 45-47% yields by reaction of this cadinanolide with dialkylphosphites. Their structures were established using IR, PMR, ¹³C and ³¹P NMR spectroscopy, and two-dimensional ¹H-¹H NMR (COSY) spectroscopy. The reaction of arteannuin B and dialkylphosphites is highly stereoselective.     

The joint action of trisdimethylaminophosphine (TDAP) and carbon tetrachloride on some vicinal diols

The joint action of trisdimethylaminophosphine and carbon tetrachloride on vicinal diols affords either trans epoxides or spirophosphoranes. The mutarotation of these spirophosphoranes is described by ¹H NMR and ³¹P NMR spectra. The mechanism of reaction providing either epoxides or spirophosphoranes is discussed.     

α-酮酯和α-酮酰胺的Henry反应

用三乙胺催化环状α-酮酯和α-酮酰胺同硝基甲烷的Henry反应, 首次合成了12个多官能团的β-硝基醇, 它们的结构用元素分析、红外光谱和核磁共振进行了表征. 这一反应速度较快, 室温下进行, 条件温和, 产率较好, 是合成多官能团硝基醇的有效方法.     

Efficient,Convenient and Mild Three Component Template Preparation and Characterization of Some New Schiff Base Complexes

A few kinds of novel Schiff base complexes have been prepared by three component reaction of the substituted hydroxyacetophenone with several aliphatic diamines and transition metals such as; Ni(II), Zn(II) and UO₂(II) under mild reaction conditions. The products have been afforded with excellent yields and appropriate reaction times. The structure of these ligands has been characterized by their IR, ¹H NMR, ¹³C NMR and MS spectral and physical data.     

The Preparation of a New Kind of Carbosilane Dendrimer with 4‐(Naphthalen‐1‐yl)phenyl Core‐An Application of Suzuki Coupling Reaction

Using the divergent method, carbosilane dendrimers with p‐bromophenyl core were synthesized by using alternating Grignard and hydrosilylation reactions. And then, α‐naphthalenyl was connected to the core by using Suzuki coupling reaction. This gave a new carbosilane dendrimer with a 4‐(naphthalen‐1‐yl)phenyl core. All the products were characterized by IR, ¹H NMR, ¹³C NMR, ²⁹Si NMR, and MS. The study shows that Suzuki Coupling reaction is an effective and powerful core‐functionalization method and a satisfactory result can be achieved through prolonging the reaction time.     

Preparation,characterization and use of sulfonylbis(1,4-phenylene)<Emphasis Type="Italic">bis</Emphasis>(sulfamic acid) as an eco-benign,efficient, reusable and heterogeneous catalyst for the synthesis of mono- and <Emphasis Type="Italic">bis</Emphasis>-chromenes

Sulfonylbis(1,4-phenylene)bis(sulfamic acid) (SPSA) is easily prepared and recognized as a new heterogeneous catalyst by the reaction of 4,4′-sulfonyldianiline with chlorosulfonic acid. This reagent was used for the synthesis of the mono- and bis-chromene derivatives. All reactions were performed under mild reaction conditions in high to excellent yields. The advantages of using the SPSA as a heterogeneous catalyst in these reactions are: being environmentally friendly, low cost, commercially availability and easy to separate from the mixture of the reaction and high reusable catalyst. Using this catalyst, results in acceptable reaction time and high yields with high purity of the obtained products without utilizing any organic solvents. The catalyst was characterized by FT-IR, ¹H NMR, ¹³C NMR, mass and TGA studies. All the products were characterized by FT-IR, ¹H, ¹³C NMR, HRMS, melting point and elemental analyses.     

Synthesis and Characterization of New Boron Compounds Using Reaction of Diazonium Tetraphenylborate with Enaminoamides

A family of oxazaborines, diazaborinones, triazaborines, and triazaborinones was prepared by reaction of polarized ethylenes, such as β-enaminoamides, with 4-methylbenzenediazonium tetraphenylborates. The reaction conditions (stirring in CH₂Cl₂ at room temperature (Method A) or stirring with CH₃COONa in CH₂Cl₂ at room temperature (Method B) or refluxing in the CH₂Cl₂/toluene mixture (Method C)) controlled the formation and relative content of these compounds in the reaction mixtures from one to three products. Substituted oxazaborines gradually rearranged into diazaborinones at 250 °C. The prepared compounds were characterized by ¹H NMR, ¹³C NMR, IR, and UV–Vis spectroscopy, HRMS, or microanalysis. The structure of individual compounds was confirmed by ¹¹B NMR, ¹⁵N NMR, 1D NOESY, and X-ray analysis. The mechanism of reaction of enaminoamides with 4-methylbenzenediazonium tetraphenylborate was proposed.     

The Synthesis and Characterization of Resorcinol-Crotonaldehyde Resins

The structure, course of the reaction, and molecular weight distribution for resorcinol-crotonaldehyde resins were determined by HET2DJ ¹³C NMR, ¹H NMR, and GPC. In the first step of the reaction, the free reactive Positions 4 and 6 of resorcinol react with crotonaldehyde. Due to steric hindrance, Position 2 is less reactive in spite of its high electron density. In the next step, addition products react with themselves or monomers to form higher products. Water is eliminated during the reaction. The final molecular weight of the resins is up to 10 000.     

Observation and Kinetic Characterization of Transient Schiff Base Intermediates by CEST NMR Spectroscopy

In aqueous solution, many biochemical reaction pathways involve reaction of an aldehyde with an amine, which progresses through generally unstable, hydrated and dehydrated, Schiff base intermediates that often are unobservable by conventional NMR. There are 4 states in the relevant equilibrium: 1) gem‐diol, 2) aldehyde, 3) hemiaminal, and 4) Schiff base. For the reaction between protein amino groups and DOPAL, a highly toxic metabolite of dopamine, the ¹H resonances of both the hemiaminal and the dehydrated Schiff base can be observed by CEST NMR, even when their populations fall below 0.1 %. CEST NMR reveals the quantitative exchange kinetics between reactants and Schiff base intermediates, explaining why the Schiff base NMR signals are rarely observed. The reactivity of DOPAL with N^α‐amino groups is greater than with lysine N^?‐amines and, in the presence of O₂, both types of Schiff base DOPAL–peptide intermediates rapidly react with free DOPAL to irreversibly form dicatechol pyrrole adducts.     

Synthesis of Heterocyclic Pentavalent Phosphorus Compounds from Phosphite Derivatives and Indane-1,2,3-Trione

Reaction of trialkylphosphite derivatives with indane-1,2,3-trione proceeds smoothly at room temperature to afford the corresponding heterocyclic pentavalent [P(V)] phosphorus compounds via an intermolecular [4+1] cycloaddition reaction in excellent yields under solvent-free conditions. We also used dimethylphosphite and diethylphosphite instead of trialkylphosphites in this reaction, but the corresponding pentavalent phosphorus compounds were not isolated, and in both cases phosphate derivatives were obtained. The structures of the products were deduced from their IR, ¹H NMR, ¹³C NMR, and ³¹P NMR spectra, and mass spectrometry.     

The Reaction Activity of Aromatic Carbonyl Compounds with Diphenylphosphine Oxide Studied by 31P NMR

Abstract

A series of α-hydroxyphosphine oxides were prepared by the reactions of diphenylphosphine oxide and aromatic carbonyl compounds and characterized by ¹H NMR, ¹³C NMR, ³¹P NMR, FT-IR, ESI-MS, and HR-MS spectra. The reaction rates and experimental conditions of aromatic aldehydes and aromatic ketones were obviously different due to the activity of their carbonyls. The different substituents of the aromatic aldehydes affected the reaction rate too, and the quantitative reactivity of their substituent conformed to the Hammett equation. The results were confirmed by ³¹P NMR spectroscopy.     

A simple route for the synthesis of 3,3,3′,3′-tetramethyl-2,3,3′,4′-tetrahydro-1H,1′H-[4,9′-bixanthene]-1,1′(2′H,9′H)-dione and its derivatives catalyzed by Mn and other transition metal cations

A simple and efficient unusual coupling reaction of 9-(2-hydroxy-4,4-dimethyl-6-oxocyclohex-1-en-1-yl)-3,3-dimethyl-2,3,4,9-tetrahydro-1H-xanthen-1-one and its derivatives was accomplished in the presence of Mn²⁺, Cu²⁺, Cd²⁺, Hg²⁺, Fe³, or La³⁺. The structure elucidation was accomplished by IR, ¹H NMR, ¹³C NMR, X-ray crystallography, UV-Visible and elemental analysis. A reaction mechanism is proposed.     

1,5-苯并二氮杂的合成及其生物活性研究

采用两种方法: 以三氧化铝为载体邻苯二胺与查尔酮为原料的无溶剂合成法和以PPA(多聚磷酸)为催化剂邻苯二胺与苯乙酮的一锅合成法, 合成了1,5-苯并二氮杂, 产物收率为53.7%～74.5%. 通过¹H NMR, ¹³C NMR, MS, IR, 元素分析等手段对所合成的化合物进行了结构确定, 并测试了它们对菌和乙酰胆碱酶的抑制活性.     

Efficient,Convenient and Mild Three‐Component Template Preparation and Characterization of Some New Schiff Base Complexes

A few kinds of novel Schiff base complexes have been prepared by three‐component reaction of the substituted hydroxyacetophenone with several aliphatic diamines and transition metals such as; Cu(II), Co(II), Mn(II), Zn(II) and UO₂(II) under mild reaction conditions. The products have been afforded with excellent yields and appropriate reaction times. The structures of these ligands have been characterized by their IR, ¹H NMR, ¹³C NMR and MS spectral and physical data.     

The proton exchange reaction between indene and the indenyl anion

The proton exchange reaction between the indenyl carbanion and its parent compound indene has been studied by NMR as a function of temperature. The rate of this bimolecular reaction is very low and has been found to be strongly dependent on the polarity of the solvent. In solvents like dimethoxyethane (? = 7·2) and diglyme the reaction becomes manifest in the NMR spectrum only at elevated temperatures (T > 150°C). In hexamethylphosphortriamide (? = 30) the rate is much greater and line broadening may be observable at room temperature. The reaction in this solvent is characterised by a frequency factor f = 7 × 10⁷ 1 mol^?1 s^?1, an activation enthalpy ΔH ≠ = 9·5 kcal mol^?1 and an entropy of activation ΔS≠ = ?23 e.u. The low reaction rate and its solvent dependence are briefly discussed.     

Study of Lysozyme Glycation Reaction by Mass Spectrometry and NMR Spectroscopy

The Advanced Glycation End Products (AGEs) are the causative substances of lifestyle‐habit illness. To elucidate the glycation mechanism of the protein, the reaction of lysozyme with D ‐glucose was analyzed by the fluorescence, TOF‐MS, and ¹³C‐NMR spectroscopy under the physiological condition. The fluorescence intensity of lysozyme in the glycation solution increased proportionally with a reaction time of ten weeks. The MALDI‐TOF‐MS spectra of the reaction solution after two weeks showed a peak at m/z 15066, which indicated the presence of a larger molecule than the native lysozyme (m/z 14331), and new peaks at m/z 30105 (dimer) and 45000 (trimer) were also observed. The spectral analysis supported the assumption of a continuous glycation reaction of D ‐glucose with lysozyme and a 30% transformation of lysozyme to the dimeric form during ten weeks. The ¹³C‐NMR spectra of lysozyme showed six [¹³C]‐labeled signals by the glycation reaction with [¹³C]‐glucose after two weeks of reaction. The combined analysis of TOF‐MS and ¹³C‐NMR spectra uncovered that first products of the glycation reaction of lysozyme with D ‐glucose can be observed already three hours after starting the reaction and that nine D ‐glucose units are attached during ten weeks at 37°.