Formation Of Cyclic Anhydride Research Articles

Two-dimensional correlation infrared spectroscopy of heat-induced esterification of cellulose with 1,2,3,4-butanetetracarboxylic acid in the presence of sodium hypophosphite

The heat-induced esterification reaction between cellulose and 1,2,3,4-butanetetracarboxylic acid (BTCA), catalyzed with sodium hypophosphite (SHP) was investigated by FTIR spectroscopy in combination with the perturbation correlation moving window (PCMW) technique and two-dimensional correlation Infrared spectroscopy (2Dcos). Two main stages could be identified in the heating process between 30 and 160 °C for the reaction system. Weakening of hydrogen bonding interactions within polar groups, such as C=O and O–H, and water evaporation takes place in the first stage (30–100 °C). The reaction process, which consists of cyclic anhydride formation and esterification, between BTCA and cellulose gradually occurs after heating above 100 °C. It is believed that both the presence of SHP and heating, leading to hydrogen bond breakage, contribute to the formation of cyclic anhydrides and further esterification. Moreover, it is shown in the 2Dcos analysis that ester groups appear immediately after the formation of anhydrides, suggesting that the reaction happens in a progressive way. Furthermore, through PCMW maps, we find that the esterification reaction mainly occurs in the temperature region between 126 and 142 °C and is fastest at 132 °C.

Correlating In-Depth Mechanistic Understanding with Mechanical Properties of High-Temperature Resistant Cyclic Imide Copolymers

We break new ground in the in-depth mechanistic understanding of the molecular behavior of tert-butyl methacrylate (t-BMA) and N-isopropylacrylamide (NIPAM) copolymers upon thermal treatment and correlate this understanding with the mechanical properties of the resulting materials. We explore—via nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic measurements—the formation of cyclic anhydride and imide structures and exploit high-resolution mass spectrometry (HRMS) coupled to size-exclusion chromatography (SEC) as well as tandem MS (MS/MS) to correlate the time and temperature dependent cyclization processes. Critically, we propose a reshuffling mechanism describing dynamic ring-opening events involving the anhydride and imide structures, which enables the in-depth understanding of the dynamic material properties. Drawing on information from low-molecular-weight model systems, we translate our findings to high-molar-mass polymers, showing that our mechanistic model enables the understanding ...

In situ DRIFT studies of alkane adsorption on vanadia supported titania-doped catalysts

In-situ DRIFT studies of alkane adsorption (ethane and propane) are performed over well characterized 90Ti-M (M = Si, Al, and W) and 2V90Ti-M catalysts at different temperatures and partial pressures of alkanes. The titania-doped mixed oxide supports are synthesized by the sol-gel method and supported vanadia catalysts are prepared by the incipient wet impregnation method. The supported vanadia catalysts possess only surface vanadia species coordinated with titania and/or silica, alumina and tungsten in the corresponding catalysts. Analysis of the in situ DRIFT spectra of alkane adsorption confirms the formation of various surface oxygenated species, such as ethoxide/isopropoxide, acetaldehyde/ketone, acetate, formate and cyclic anhydride. The alkoxides (ethoxide and isopropoxide) are formed due to the breaking of the CH bond of the parent alkane and are the precursor for the formation of olefins (ethylene and propylene). The unstable alkoxide species are further oxidized to form aldehyde or ketone, respectively. The carboxylates species (acetate and formate) are formed due to further oxidation of acetaldehyde and acetone at high temperatures. Deposition of vanadia suppresses the formation of cyclic anhydride, a precursor for the formation of CO2. In-situ DRIFT studies of propane ODH reaction reveal that isopropoxide is not a readily detectable surface species in the presence of oxygen even at low temperature. However, the carbonate species and propylene are identified during propane ODH reaction. Furthermore, the intensity of overtone VO vibration decreases and shifts from 2030 cm−1 to 2025 cm−1 during alkane adsorption.

DSC-FTIR microspectroscopy used to investigate the heat-induced intramolecular cyclic anhydride formation between Eudragit E and PVA copolymer

Thermal-dependent six-membered cyclic anhydrides were formed in the Eudragit E and polyvinyl alcohol (PVA) copolymer via intramolecular ester condensation by using differential scanning calorimeter (DSC)-Fourier transform infrared microspectroscopy. The temperature for intramolecular ester condensation was started from 180 °C for Eudragit E, but from 167 °C for PVA copolymer. The amount of intramolecular anhydride formed in the film of Eudragit E was found to be higher than that formed in the film of PVA copolymer during the heating process.

Thermal degradation of copolymers of styrene with dicarboxylic acids – II: Copolymers obtained by radical copolymerisation of styrene with maleic acid or fumaric acid

Thermal degradation processes in copolymers of styrene with two stereoisomers of 1,2-ethylenedicarboxylic acids (i.e. maleic acid (the cis-isomer) and fumaric acid (the trans-isomer)) have been studied by mass spectrometry, FTIR and TG measurements. The influence of the chemical composition on thermal degradation of copolymers with acid by non-isothermal thermogravimetric analysis (TG) was also studied. The stereo-configuration of carboxyl groups in copolymers was analysed by potentiometric titration. It was found that copolymers degrade in two main complex stages. The initial step in the decomposition involves the formation of cyclic five-membered anhydrides. The presence of trans configuration of carboxyl groups hinders the formation of cyclic anhydrides and shifts the decomposition to higher temperatures, making decarboxylation competitive. At higher temperatures anhydride decomposition takes place and finally the degradation of main chains occurs.

Copolymers from Methacrylic Acid and Trimethylsilyl Methacrylate ‐ Synthesis, Reactivity Ratios and Thermal Properties

AbstractCopolymers from methacrylic acid (1) and trimethylsilyl methacrylate (2) have been synthesized by free radical copolymerisation and by controlled desilylation of poly(trimethylsilyl methacrylate) (3). The reactivity ratios were r1 = 2.75, r2 = 0.004. Differential scanning calorimetry showed a linear correlation between the peak temperature of the endotherm for the formation of cyclic anhydrides and the content of methacrylic acid in the copolymer. Obviously, the acid catalyses this reaction. The copolymers as well as poly(trimethylsilyl methacrylate) have a ceiling temperature. Sequence distributions were calculated and used to predict glass transition temperatures for comparison to the experimental results. The microstructure of the copolymers obtained by the different synthetic routes is different as shown from Tg and from their solubility. Those from desilylation are random with “reactivity ratios” of 1, those from copolymerisation seem to have longer sequences of methacrylic acid leading to formation of intermolecular aggregates. Dependence of DSC peak temperature of anhydride formation on methacrylic acid content.magnified imageDependence of DSC peak temperature of anhydride formation on methacrylic acid content.

IR spectroscopy study of cyclic anhydride as intermediate for ester crosslinking of cotton cellulose by polycarboxylic acids. V. Comparison of 1,2,4‐butanetricarboxylic acid and 1,2,3‐propanetricarboxylic acid

AbstractIn recent years extensive efforts have been made to use multifunctional carboxylic acids as formaldehyde‐free crosslinking agents for cotton to replace the traditional formaldehyde‐based N‐methylol reagents. In our previous research we found that a polycarboxylic acid esterifies cellulose through the formation of a five‐membered cyclic anhydride intermediate by dehydration of two adjacent carboxyl groups. In this research we used Fourier transform IR (FTIR) spectroscopy to study the formation of cyclic anhydride intermediates and crosslinking of cotton by 1,2,4‐butanetricarboxylic acid (BTA) and 1,2,3‐propanetricarboxylic acid (PCA). BTA and PCA form five‐membered cyclic anhydrides in the same temperature range. Both acids form the anhydrides at lower temperatures when a catalyst is present. When an acid molecule is bonded to cotton through an ester linkage, only PCA is able to form a second anhydride intermediate. We found that PCA is a more effective crosslinking agent, and it imparts higher levels of wrinkle resistance to the cotton fabric than BTA. Therefore, the formation of a five‐membered cyclic anhydride by a polycarboxylic acid accelerates the esterification of cotton by the acid. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2142–2150, 2001

FT-IR and FT-raman spectroscopy study of the cyclic anhydride intermediates for the esterification of cellulose: III. Cyclic anhydrides formed by the isomers of cyclohexanedicarboxylic acid

Multifunctional carboxylic acids have been used as crosslinking agents for cotton and wood pulp cellulose. In our previous research, we found that a polycarboxylic acid esterifies cellulose through the formation of a 5-membered cyclic anhydride intermediate by the dehydration of two carboxyl groups. In this research, we studied the formation of cyclic anhydride intermediates by different isomers of cyclohexanedicarboxylic acid (CHA) so that we can elucidate the effects of molecular structure on the formation of the anhydride intermediates. We found that both cis-and trans-1,2-CHA form 5-membered anhydride intermediates when temperature reaches their melting points and that cis-1,2-CHA forms the cyclic anhydride at temperatures lower than does trans-1,2-CHA. 1,3-CHA forms 6-membered cyclic anhydride at temperatures much higher than its melting point. The formation of a 5-membered cyclic anhydride intermediates takes place at temperatures lower than that of a 6-membered anhydride. This is probably the main reason why those polycarboxylic acids with their carboxylic acid groups bonded to the adjacent carbons of the molecular backbones are more effective crosslinking agents for cellulose than those with their carboxylic groups bonded to the alternative carbons. No formation of cyclic anhydride was found for 1,4-CHA. The formation of a five-membered cyclic anhydride was accelerated by monosodium phosphate, which is used as a catalyst for the esterification of cotton cellulose by polycarboxylic acids.

Thermal stability of methacrylic acid copolymers of Eudragits L, S, and L30D and the acrylic acid polymer of carbopol

The thermal stability of the powder or film forms of Eudragits L, S, and L30D and carbopol polymers was qualitatively investigated by microscopic reflectance Fourier transform infrared spectroscopy equipped with differential scanning calorimetry (FT-IR/DSC microscopic system). DSC and thermogravimetric analysis (TGA) were also used to study the thermal behavior of the pulverized powders of the raw material and the films of these polymers. The results indicate that a 6-membered ring cyclic anhydride formation was respectively produced by a heating process in the molecular structures of Eudragits L, S, and L30D and carbopol polymers via inter- or intrapolymer condensation. The peak intensity of the carbonyl stretching absorption of cyclic anhydride-related IR peaks appeared sharply near 1801 and 1759 (1751) cm−1, and a peak near 1006 (1018) cm−1 related to the antisymmetric stretching mode of COC also appeared suddenly beyond the marked reaction temperature. The initial reaction temperature of anhydride formation for the Eudragits L, S, and L30D and carbopol polymers was observed respectively from near 186, 180, 170, and 100°C, whereas the rapid and marked reaction temperature from about 206, 188, 170, and 183°C appeared accurately from the reflectance FT-IR spectra. The DSC thermograms and TGA curves also confirmed these results. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2061–2067, 1999

Storage modulus changes with temperature in poly(vinyl alcohol), PVA,/poly(acrylic acid), PAA, blends

Poly(vinyl alcohol), PVA, and poly(acrylic acid), PAA, blends were prepared by solution casting. These polymers were found to be miscible in the whole composition range as determined by DSC even though some crystallinity remains in blends with PVA concentrations above 50wt%. Dynamic mechanical measurements of these blends and PAA as a function of temperature show an increase in storage modulus, E', when they reach a temperature of 140°C that is well beyond their softening point. The E' increase in PAA beyond 140°C is attributed to an intramolecular reaction of cyclic anhydride formation that stiffens the chain. Isothermal storage modulus test as a function of time and FTIR measurements at 160°C of PAA and three blends show that this increase in E' is due to cyclic anhydride formation.

Effect of Stereoregularity on the Thermal Behavior of Poly(methacrylic acid)s. 2. Decomposition at Low Temperatures

The effect of tacticity on the thermal degradation behavior under nitrogen of poly(methacrylic acid)s has been investigated. The structural changes occurring in the polymer chains during the first of the two stages of decomposition, at temperatures lower than 300 °C, were followed by FTIR and NMR. In this stage, the degradation of highly isotactic poly(methacrylic acid)s essentially consists of the formation of sequences of six-membered cyclic anhydrides by intramolecular dehydration. This process is likely to be favored by local conformations in which adjacent acid groups are fairly close. The presence of an increasing amount of syndiotactic units hinders the formation of cyclic anhydrides and shifts the decomposition at higher temperatures, making other reactions competitive, such as decarboxylation, formation of double bonds, and cross-linking. As a result, weight losses, solubility, and glass-transition temperatures of residues after the first degradation stage are proportional to their syndiotacticity.

Separation of Ground State and Transition State Effects in Intramolecular and Enzymatic Reactions. 2. A Theoretical Study of the Formation of Transition States in Cyclic Anhydride Formation

Ab initio gas phase calculations at the RHF/6-31+G(d) level have been used to define the geometries of the transition states for the intramolecular displacement reactions with monophenyl esters of glutaric (I), succinic (II), and 3,6-endoxo-Δ4-tetrahydrophthalic (III) acids to provide the corresponding anhydrides plus phenolate. As determined experimentally, the rate determining step was found to involve transition states in which phenoxide is departing. Intrinsic reaction coordinate (IRC) calculations from transition state toward reactant and product sides provided intramolecular ion−molecule complexes (IIMC) of I and II and the tetrahedral intermediate of III and the product ion−molecule complexes (IMC) of the phenoxide and anhydride of I, II, and III. Vibrational frequency calculations were performed for all stationary states. Single point calculations using an electron correlation method and different solvation methods were performed on optimized reactant side gas phase geometries. The transition states formed from I, II, and III are essentially identical in bond lengths (ester carbon to leaving phenoxide 1.77, 1.79, or 1.80 Å; carbonyl oxygen to ester carbon 1.20 or 1.21 Å; nucleophilic oxygen to ester carbon 1.44 or 1.43 Å; and α-carbon to ester carbon 1.52 or 1.53 Å) and angles (characterized by the attacking oxygen, ester carbon, and leaving oxygen 97.8°, 97.3°, 96.7°; attacking oxygen, ester carbon, and ester carbonyl oxygen 117.0°, 117.4°, 113.7°). Transition state stabilization as a result of restricting low frequency vibrations is determined by comparing the frequencies of the IIMC (and tetrahedral intermediate) to the corresponding TS. The total number of frequencies does not change in going from the IIMC (or TI) to the TS for each ester. For those frequencies lower than 1000 cm-1, the number of frequencies remains constant. On comparing the ratio between the number of frequencies below 1000 cm-1 and the total number of frequencies in the transition states formed from I, II, and III, we find 0.49, 0.51, and 0.55, respectively. By the criteria of superimposable TS structures and lack of evidence for frequency changes in the TS in the direction of increasing rate, we conclude that the rate ratios of ∼230-fold in comparing I/II and II/III reside in ground state phenomena. This conclusion is supported by the geometries of IIMC and TS structures. Gas phase reaction coordinates and derived enthalpy and entropy values are provided and discussed. Conversion of ground state intramolecular anion ester complexes (IIMC) of esters I and II to their respective TSs involves a decrease in computed ΔH⧧ while ΔS⧧ remains invariant. In a previous investigation, the formation of ground state conformations (NACs) of geometry that allows entrance to the IIMC and then TS was found to be related to ΔH° rather than ΔS°. The importance of these findings to a general concept of entropy driven kinetic processes is discussed.

Rearrangements in Spiro-λ4-sulfane Chemistry

The reactions of possible spiro-λ4-sulfane precursor diaryl sulfoxides with dehydrating agents have been studied resulting in the formation of cyclic anhydride, spiro-λ4-sulfane, cyclic sulfonium-ylide, lactam-sulfoxide, cyclic sulfonimide and cyclic sulfilimine type of intermediates or products. The structures of the intermediates or products depend on the functional groups attached to the aryl rings at ortho positions and on the reaction conditions applied.

Ground State Conformations and Entropic and Enthalpic Factors in the Efficiency of Intramolecular and Enzymatic Reactions. 1. Cyclic Anhydride Formation by Substituted Glutarates, Succinate, and 3,6-Endoxo-Δ4-tetrahydrophthalate Monophenyl Esters

Intramolecular and enzymatic reactions require conformations in which the orbitals of reactants are properly aligned and van der Waals surfaces are in a near-attack conformation (NAC). Much of the changes in steric and electrostatic energies that take place in moving from the favored ground state conformation (FGSC) to the transition state are accounted for when the NAC has been assumed. Upon assessing the steric, electrostatic, and zero point energies, one is in position to calculate the probability of NAC formation. Using a series of monoesters of dicarboxylic acids, we have (i) created, via stochastic search, 10 000−40 000 minimized conformations per ester; (ii) chosen only the unique local minima conformations for each ester; (iii) determined the energies of each minimum conformation using MM3(92); (iv) identified the geometry of the NACs where the van der Waals overlap has not begun for the approach of carboxyl anion and ester carbonyl; and (v) calculated the mole fraction (probability, P) of each es...

Investigation on the mechanism of peptide chain prolongation on montmorillonite

Experiments with reduced-charge montmorillonites with gradually collapsed interlayer space prove that peptide formation processes occur mainly at the edges of the clay mineral. Activation of peptides and amino acids and the intermediate formation of cyclic anhydrides are found to be the two dominant processes determining the formation of higher peptides on the mineral surface.

A study of the thermal degradation of poly(mono‐n‐alkyl itaconates)

AbstractThe thermal degradation of the first six members of poly(mono‐n‐alkyl itaconates) by thermogravimetry (TG), differential scanning calorimetry (DSC), Fourier Transform infrared (FTIR) and FTIR evolved gas analysis (FTIR‐EGA) was studied. The degradation mechanism involves cyclic anhydride formation followed by crosslinking due to the linear anhydride formation. In both processes water and/or alcohol evolution was detected. Also, decarboxylation processes take place on all polymers at high temperatures ( > 180°C). A mechanism of the degradation process is proposed.

Photoinduced molecular transformations. Part 106. The formation of cyclic anhydrides via regioselective β-scission of alkoxyl radicals generated from 5-and 6-membered α-hydroxy cyclic ketones

The irradiation of the hypoiodites of 5- or 6-membered cyclic α-ketols in benzene containing mercury(II) oxide and iodine (each 3 equiv.) resulted in the formation of the corresponding cyclic anhydrides arising from the insertion of an oxygen. A novel formation of a methylenedioxy group arising from an intramolecular hydrogen abstraction, on the other hand, was found when a steroidal α,α-dimethoxy alcohol hypoiodite was irradiated in benzene. An 18O labelling study of the formation of the cyclic anhydride on photolyses of 17β-hydroxy-4β-methoxy-5α-androstan-16-one hypoiodite generated in situ by an excess of mercury(II) oxide and iodine in benzene indicated that the heavy oxygen of Hg 18O is incorporated as the ring oxygen of the anhydride. On the basis of this result, a pathway involving a regioselective β-scission of the alkoxyl radical is proposed as leading to formation of the cyclic anhydride.

INFRARED SPECTRA OF HUMIC ACIDS

Heating preformed KBr pellets effectively eliminated interference arising from hygroscopic moisture in infrared studies of humic acids. Structural changes in humic acid during heating were confined to the formation of cyclic anhydrides from carboxy1 groups. The use of thallous bromide as a nonhygroscopic pelleting matrix and perfluorokerosene as a mulling agent can be recommended in infrared investigations of humic substances.

Structural Arrangement of Functional Groups in Soil Humic Acid as Revealed by Infrared Analyses

AbstractHumic acid from a brunizem soil was subjected to a series of treatments (methylation, saponification, acetylation) to determine the number and arrangement of functional groups when analyzed by a combination of chemical and infrared techniques. One‐third of the COOH groups (total COOH, 390 meq/100 g) occurred in positions close enough to form cyclic anhydrides; two‐thirds of the OH groups (total OH, 290 meq/100 g) were phenolic. Some phenolic OH groups in the samples failed to methylate wth diazomethane. Potassium bromide catalyzed the formation of cyclic anhydrides by mild thermal treatment of acid‐treated and methylated‐saponified humic acids, but not of untreated humic acid. Acetylation gave a small amount of brown material (acetyl content, 20%) whose infrared pattern was characteristic of an acetylated carbohydrate. Tests for quinone and H‐bonded phenolic OH groups were negative.

The Route of Cyclic Anhydride Formation from Mono-O-tolylsulfonyl Glycols1

The Route of Cyclic Anhydride Formation from Mono-O-tolylsulfonyl Glycols¹