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.     

Infrared spectroscopy studies of the cyclic anhydride as the intermediate for the ester crosslinking of cotton cellulose by polycarboxylic acids. I. Identification of the cyclic anhydride intermediate

The mechanism of esterification of cotton cellulose by a polycarboxylic acid was investigated using Fourier transform infrared spectroscopy (FT-IR). The infrared spectroscopic data indicate that a polycarboxylic acid esterifies with cotton cellulose through the formation of an acid anhydride intermediate. A five-member cyclic anhydride intermediate was identified in the cotton fabric treated with poly(maleic acid). The five-member cyclic anhydride is a reactive intermediate and readily esterifies when reaction sites are available. We also found that those polycarboxylic acids, which form five-member cyclic anhydride intermediates, crosslink cotton cellulose more effectively than those polycarboxylic acids which form six-member cyclic anhydride intermediates. © 1993 John Wiley & Sons, Inc.     

Infrared spectroscopy studies of the cyclic anhydride as the intermediate for the ester crosslinking of cotton cellulose by polycarboxylic acids. II. Comparison of different polycarboxylic acids

Polycarboxylic acids have been used as crosslinking agents for cotton cellulose. In our previous research, we used Fourier transform infrared (FT-IR) spectroscopy to investigate the formation of five-membered cyclic anhydride intermediates on cotton fabric by different polycarboxylic acids. In this research, we found that those polycarboxylic acids capable of forming both five- and six-membered cyclic anhydrides form only five-membered cyclic anhydrides. We compared the effectiveness of the polycarboxylic acids with different molecular structures for esterifying cellulose. Those polycarboxylic acids, which have their carboxyl groups bonded to the adjacent carbons of their molecular backbones and are capable of forming five-membered cyclic anhydrides, are more effective for esterifying cellulose than those polycarboxylic acids having their carboxyl groups bonded to the alternative carbons. The only six-membered cyclic anhydride identified is the anhydride formed on the cotton fabric treated with poly(acrylic acid). © 1996 John Wiley & Sons, Inc.     

Infrared spectroscopy studies of the cyclic anhydride as the intermediate for the ester crosslinking of cotton cellulose by polycarboxylic acids. III. Molecular weight of a crosslinking agent

Polycarboxylic acids have been used as nonformaldehyde crosslinking agents for cotton fabrics to replace the traditional N-methylol reagents. In this research, we compared 1,2,3,4-butanetetracarboxylic acid (BTCA) with poly(maleic acid) (PMA) as crosslinking agents for cotton cellulose. BTCA and PMA have similar molecular structures with carboxyl groups bonded to their molecular backbones, and both form five-membered cyclic anhydride intermediates during a curing process. However, BTCA is a more effective crosslinking agent for cotton cellulose than PMA. This is mainly attributed to the differences in the mobility of the anhydride intermediates to access the cellulosic hydroxyl groups during a curing process. The mobility of the anhydride intermediate of PMA is reduced due to its molecular size and multiple bonding between a PMA molecule and cellulose. Consequently, more anhydride and less ester are detected on the cotton fabric treated with PMA than on the fabric treated with BTCA. The amount of the unreacted anhydride intermediate on the fabric treated with PMA is reduced whereas the amount of ester is increased when another hydroxyl-containing compound of low molecular weight is present. Thus, the infrared spectroscopy data show a clear link between the molecular weight of a polycarboxylic acid and its effectiveness for crosslinking cotton cellulose. © 1997 John Wiley & Sons, Inc.     

Flame retardant finishing of cotton fleece: part VII. Polycarboxylic acids with different numbers of functional group

In our previous research, multifunctional carboxylic acids have been used as flame retardants to reduce the flammability of cotton fleece so that the garment made of cotton fleece can pass the US mandatory requirement specified by the government regulation “Standard for the Flammability of Clothing Textiles” (16 CFR 1610). In this research, we studied and compared the effectiveness of the polycarboxylic acids having different numbers of carboxylic groups as the durable flame retardants for cotton fleece. The cotton fabrics were treated with 1,2,3,4-butanetetracarboxylic acid (BTCA), citric acid (CA), succinic acid (SUA) and malic acid (MLA). We compared the reactivity of those polycarboxylic acids to esterify cotton cellulose and their effectiveness to reduce the flammability of the cotton fleece. The data indicated that the polycarboxylic acids with higher functionalities (BTCA and CA) form more esterlinkages on cotton and are more durable to home launderings than that treated with their bifunctional counter parts (SUA and MLA, respectively). In addition, the cotton fabrics treated with BTCA and CA have higher dimensional stability and higher strength loss. All those differences can be attributed to the fact that only those acids with three or more carboxylic groups, i.e., BTCA and CA, are able to crosslink cotton cellulose whereas the bifunctional acids (SUA and MLA) only form single esterlinkage with cotton.     

Catalytic actions of alkaline salts in reactions between 1,2,3,4-butanetetracarboxylic acid and cellulose: I. Anhydride formation

1,2,3,4-Butanetetracarboxylic acid (BTCA) reacts with cellulose in two steps: anhydride formation of adjacent carboxyl groups in BTCA and esterification of anhydride with cellulose, which are generally catalyzed by alkaline salts including sodium hypophosphite. The role of the salts in the reactions has been unclear. As an effort in fully understanding the catalytic effects of the salts, reaction mechanisms of alkaline metal ions and acid anions of the salts were investigated in details in the reactions. In this research, functions of alkaline metal ions on the formation of anhydride were studied. Results indicated that the existence of lithium, sodium or potassium promoted the formation of anhydride, and potassium ion was the most efficient one among these three ions. Besides, the reactions of a BTCA molecule with cellulose undergo a step-by-step process, i.e. formation of one anhydride and esterification of the anhydride with cellulose, and then formation of another anhydride and esterification of it to establish cross-linking by the BTCA.     

Products from dehydration of dicarboxylic acids derived from anthranilic acid

Treatment of N-(carboxymethyl)-anthranilic acids 1 with several dehydrating agents, gave the cyclic ortho amides 6, or the 7-membered anhydrides 7. After reaction of N-(carboxymethyl)-anthranilic acid (1a) with acetic anhydride, a diacetylated fused diketopiperazine indole dimer (18) could be isolated. Dehydrations of 2,2'-iminobis-benzoic acid led to the corresponding cyclic ortho amides 23. The dynamic behaviour of some of these compounds, and their precursors, was studied.     

FT-IR Determination of degree of esterification in polycarboxylic acid cross-link finishing of cotton

Cross-linking of cotton with polycarboxylic acids, applied with catalysts based on phosphorus-containing inorganic acids, produces fabrics with excellent smooth-drying properties and which release no formaldehyde at any stage of preparation or on storage. The reaction produces cellulose ester linkages and unreacted carboxylic acid groups. Fourier transform infrared spectroscopy was used to determine the degree of esterification of polycarboxylic acids that occurred on cross-linking of cotton. The height of the carbonyl peak at 1730 cm ^–1 was determined on the same treated fabrics after soaking in dilute acid to convert ionized groups to free acid and then in dilute base to convert free acid to carboxylate ion. The carbonyl peak for the base rinsed fabric (ester only) was ratioed against the same peak for the acid-rinsed fabric (total carbonyl, ester plus acid) to obtain a measure of the degree of esterification. This ratio minimizes the problems of different molar extinction coefficients that are encountered when peaks from different functional groups are used.     

Selective esterifications of alcohols and phenols through carbodiimide couplings

Esterification of carboxylic acids capable of forming ketene intermediates upon treatment with carbodiimides permits the selective acylation of alcohols in the presence of phenols lacking strong electron-withdrawing groups. The selectivity of acylations involving highly acidic phenols could be reversed through the addition of catalytic amount of acid. Esterification of other carboxylic acids was found to proceed through the formation of symmetric anhydrides and provide the opposite chemoselectivity. In both cases the relative acylation rates of substituted phenols are consistent with a reaction mechanism involving an attack of phenolate anions on electrophilic intermediates such as ketenes and symmetric anhydrides, with the carbodiimides serving both as an activating reagent and as a basic catalyst.     

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.     

2-chloro-4,6-disubstituted-1,3,5-triazines a novel group of condensing reagents

The title, compounds form in reaction with carboxylic acids highly reactive intermediates, which are useful as acylating reagents in the preparation of esters, amides, acid anhydrides, and peptides in 64–98% yield.     

Solid‐state 13C NMR study on thermal dehydration process of poly(methacrylic acid)(PMAA)

Thermal dehydration process of PMAA was investigated by solid‐state ¹³C NMR. For heat‐treated PMAA at 150°C, at which the dehydration goes very slowly, we observed three ¹³C peaks at 172, 178, and 187 ppm in the carboxyl group region. The peak at 172 ppm is due to the intramolecular cyclic anhydrides by comparing the reported value of ¹³C chemical shift. The peaks at 178 and 187 ppm were assigned to regularly aligned free carboxylic acids and intermolecular acid dimers, respectively, from the 2D‐exchange ¹³C NMR spectra, ¹³C chemical shift values and IR spectra. We concluded that by heat‐treatment the rearrangement of intermolecular hydrogen bonding of the carboxylic acids in PMAA occurs firstly to form the regularly aligned acid dimers, and the dimers dissociated to be the regularly aligned free carboxylic acids at high temperatures. The adjacent free carboxyl acids dehydrate with each other, resulting in the formation of intramolecular anhydrides. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2007–2012, 1999     

The first asymmetric esterification of free carboxylic acids with racemic alcohols using benzoic anhydrides and tetramisole derivatives: an application to the kinetic resolution of secondary benzylic alcohols

A variety of optically active carboxylic esters are produced by the kinetic resolution of racemic secondary benzylic alcohols using free carboxylic acids with benzoic anhydride and tetramisole derivatives. 4-Methoxybenzoic anhydride (PMBA) is the best reagent to use in producing the corresponding esters in high ee when the reaction is catalyzed by (+)-benzotetramisole (BTM); by contrast, when non-substituted benzoic anhydride is used as a coupling reagent, the resulting optically active alcohols are obtained with high selectivities. This protocol directly produces chiral carboxylic esters from free carboxylic acids and racemic secondary alcohols by utilizing the trans-acylation process to generate mixed anhydrides from acid components and benzoic anhydride derivatives under the influence of chiral catalysts.     

An effective method for the synthesis of carboxylic esters and lactones using substituted benzoic anhydrides with Lewis acid catalysts

An efficient mixed-anhydride method for the synthesis of carboxylic esters and lactones using benzoic anhydride having electron withdrawing substituent(s) is developed by the promotion of Lewis acid catalysts. In the presence of a catalytic amount of TiCl₂(ClO₄)₂, various carboxylic esters are prepared in high yields through the formation of the corresponding mixed-anhydrides from 3,5-bis(trifluoromethyl)benzoic anhydride and carboxylic acids. The combined catalyst consisting of TiCl₂(ClO₄)₂ together with chlorotrimethylsilane functions as an effective catalyst for the synthesis of carboxylic esters from free carboxylic acids and alcohols with 4-(trifluoromethyl)benzoic anhydride. Various macrolactones are prepared from the free ω-hydroxycarboxylic acids by the combined use of 4-(trifluoromethyl)benzoic anhydride and titanium(IV) catalysts together with chlorotrimethylsilane under mild reaction conditions. The lactonization of trimethylsilyl ω-(trimethylsiloxy)carboxylates using 4-(trifluoromethyl)benzoic anhydride is also promoted at room temperature in the presence of a catalytic amount of TiCl₂(ClO₄)₂. An 8-membered ring lactone, a synthetic intermediate of cephalosporolide D, is successfully synthesized according to this mixed-anhydride method using 4-(trifluoromethyl)benzoic anhydride by the promotion of a catalytic amount of Hf(OTf)₄.     

Paradigms and Paradoxes: Aspects of the Energetics of Carboxylic Acids and Their Anhydrides

Making use of the enthalpies of formation of the well-established acetic acid and acetic anhydride, the energetics of other carboxylic acid anhydrides (with four or fewer carbons) are discussed. Some of these species are also well known, such as succinic and maleic anhydride. Others are less well known, such as ketene and carbon suboxide and even diatomic carbon and malonic anhydride. Still others are more evasive, such as the classical anhydrides of formic and oxalic acid.     

Complications in the Castagnoli-Cushman reaction: An unusual course of reaction between cyclic anhydrides and sterically hindered indolenines

Attempted reaction of indolenines (which represent rather sterically hindered cyclic imines) with a series of dicarboxylic acid anhydrides yielded no expected product, the Castagnoli-Cushman lactam. Instead, products presumably formed via N-acyliminium species trapping by a carboxylate anion. Among them, hydrolytically labile 2:2 adducts of an indolenine and a cyclic anhydride, containing a 16-membered cyclic core, are particularly intriguing. This result contradicts the recently reported successful Castagnoli-Cushman reaction of indolenines with homophthalic anhydride suggesting a mechanistic switch in the course of the reaction.     

Identification and quantification of cotton-bound,cyclic polycarboxylic acids by means of isocratic HPLC

Cotton fabrics are modified by means of polycarboxylic acids (PCA) in combination with an inorganic catalyst in order to impart durable press properties. To evaluate the effectiveness of cyclic PCA, 100% cotton fabrics were treated with 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (CH-HCA), 1,3,5-cyclohexanetricarboxylic acid (CH-TCA), 1,2,3,4-cyclopentanetetracarboxylic acid (CP-TCA), and 1,2,3,4-tetrahydrofurantetracarboxylic acid (THF-TCA) in combination with sodium hypophosphite (SHP) as catalyst. The amount of PCA that reacted with the cellulosic material was determined by means of isocratic HPLC (Aminex HPX-87-H). The results clearly indicate that the cyclic PCA are less effective in respect of durable press performance. CH-TCA does not react with the cellulosic material thus confirming the assumption that the crosslinking reaction between PCA and the cellulose proceeds via a five-membered cyclic anhydride.     

Acylation of novobiocin by carboxylic acid anhydrides: preparation and characterization of semi-synthetic novenamines

The acylation of novobiocin by carboxylic acid anhydrides leading to preparation of three families of semi-synthetic acylated novenamine analogues is reported. ESI-MS was used to monitor the reaction progress and enabled the isolation of intermediate compounds that provided insights into the sequence of acylation steps during the reaction. The chemoselectivity of the reaction depends on the carboxylic acid anhydride. The potential of the acylated novenamine analogues as leads for the development of antibacterial agents is discussed.     

Synthesis of symmetric anhydrides using visible light-mediated photoredox catalysis

A new approach to anhydride formation is reported via activation of C-O bonds by the Vilsmeier-Haack reagent formed by Ru(bpy)(3)Cl(2) and CBr(4) in DMF. Various aryl and alkyl carboxylic acids are converted to the corresponding anhydrides in excellent yields.     

Reaction of anthranilic acid amides with cyclic anhydrides

Anthranilic acid amide reacts with cyclic anhydrides to give the corresponding N-acyl derivatives at the amino group, while analogous reactions of o-aminobenzohydroxamic acid lead lead to formation of 3-hydroxy-quinazolin-4-ones under mild conditions. N-Acyl derivatives of anthranilic acid amide undergo intramolecular cyclization to imides on microwave irradiation or on melting, and their treatment with acetic anhydride in the presence of sodium acetate on heating yields quinazolin-4-ones.