Novel cellulose derivatives. V. Synthesis and thermal properties of esters with trifluoroethoxy acetic acid

Esters of cellulose with trifluoroethoxy acetic acid (TFAA) were prepared in homogeneous phase using a mixed anhydride with p‐toluenesulfonic acid. Esters with low degree of substitution (DS), and with DS rising from 0 to 3, had hydrophobic character that prevented the usual association with moisture, which is otherwise typical of cellulose esters with low DS. Cellulose trifluoroethoxy acetate (CT) had T_g's declining by about 40 °C per DS‐unit (from 160 to 41 °C) as DS rose from 1 to 3. Mixed esters, cellulose derivatives with acetate and trifluoroethoxy acetate substituents (CAT), exhibited glass‐to‐rubber and melting transitions by DSC. A linear relationship between both T_g and T_m with respect to DS was recorded with the T_g and T_m separated by 30° to 40 °C. This is consistent with cellulose esters described elsewhere. Surprisingly, the T_g's of CT and CAT were found to be identical when the DS was equivalent to the DS of the fluoro substituents (DS_F). © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 486–494, 2000     

Phosphonic-Acid Analogues of the N-Acetyl-2-deoxyneiiraniinic Acids: Synthesis and Inhibition of Vibrio cholerae Sialidase

The phosphonic acids 3 and 4 were prepared to compare their inhibitory activity on Vibrio cholerae sialidase with the one of the corresponding N-acetyl-2-deoxyneuraminic acids 5 and 6 . Thus, hydrogenation and benzylation of methyl N-acetyl-2,3-didehydro-2-deoxyneuraminate (1MeNeu2en5Ac; 7) gave a mixture of the fully O-benzylated benzyl and methyl esters 9 and 10 , the partially O-benzylated benzyl and methyl esters 11 and 12 , and the fully O-and N-benzylated benzyl and methyl esters 13 and 14 (Scheme 1). Transesterification of 9 to 10 and hydrolysis of 10 gave the acid 15 . Oxidative decarboxylation of 15 with Pb(OAc)₄ gave a 1:9 mixture of the α-and β-D-glycero-D-galacto-acetates 16 and 17 . Phosphonoylation of 17 with P(OMe)₃ and Me₃SiOTf gave a 1.3:1 mixture of the phosphonates 18 and 19 , which were deprotected to give the (4-acetamido-2,4-dideoxy-D-glycero-α-and β-D-galacto-octopyranosyl)phosphonic acids 3 and 4 , respectively. The acid 6 was obtained by epimerization of the tert-butyl ester 23 with lithium N-cyclohexylisoproylamide and deprotection. The phosphonic acids 3 (K_i 5.5 10_-5 M) and 4 (K_i 2.3.10^?4 M ) are stronger inhibitors of Vibrio cholerae sialidase than the anomeric N-acetyl-2-deoxyneuraminic acids 5 (K_i 2.3 10^?3 M ) and 6 . Both 3 and 4 inhibit the Vibrio cholerae sialidase, while only the carboxylic acid 5 , possessing an equatorial COOH group is an inhibitor.     

Novel cellulose derivatives. IV. Preparation and thermal analysis of waxy esters of cellulose

Cellulose esters with linear aliphatic acyl substituents ranging in size from C₁₂ (lauric acid) to C₂₀ (eicosanoic acid) were prepared in homogeneous solution (DMAc/LiCl) using a novel synthetic method based on the use of a mixed p-toluenesulfonic/carboxylic acid anhydride. The resulting waxy cellulose esters had a high degree of substitution (DS), between 2.8 and 2.9, and showed little degradation. Thermal analysis of these cellulose derivatives by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) revealed a series of transitions that represented motion by both ester substituents and cellulosic main chain. Broad crystallization and melting transitions attributed to side-chain crystallinity were observed in the range between −19 and +55°C; these side-chain T_m and T_c transition temperatures increased by 10°C per carbon atom of the ester substituent. The T_g of these derivatives increased linearly with increasing substituent size from 94°C for C₁₂ (cellulose laurate) to 134°C for C₂₀ (cellulose eicosanoate). Evidence of “main-chain” crystallization was not observed for these samples, except in the case of peracetylated C₁₂ and C₁₄ esters, which had T_m values of 96°C and 107°C, respectively. © 1996 John Wiley & Sons, Inc.     

Dicationic surfactant based catalytic systems for alkaline hydrolysis of phosphonic acid esters

Use of aqueous micellar solutions of dicationic surfactants with the general formula [R(CH₃)₂N(CH₂)₆N(CH₃)₂R]²⁺2Br⁻ (R = n-C₁₀H₂₁ to n-C₁₆H₃₃) as the reaction medium for the alkaline hydrolysis of phosphonic acid esters has revealed a strong catalytic effect of the surfactants, which can increase the reaction rate by two orders of magnitude. This effect depends on the surfactant structure, shows itself at low surfactant concentrations, and is substrate-specific. The effect of the micelles on the phosphonate hydrolysis rate is largely determined by the hydrophobicity factor.     

Cellulose alkyl ester/poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone) blends: characterization of miscibility and crystallization behaviour

Cellulose valerate (CV)/poly(ε-caprolactone) (PCL) blends were investigated to clarify the effect of the degree of substitution (DS) of the cellulose ester component on the miscibility. CVs of DS > 2.15 were miscible with PCL in their amorphous states, as judged from the detection of a single T _g by differential scanning calorimetry (DSC). This result and other complementary data for cellulose acetate (CA), propionate (CP), and butyrate (CB) blends with PCL made up a miscibility map as a function of the number N of carbons in the normal acyl substituent as well as of DS. CB of N = 4 and CV of N = 5, the ester side-chains of which make a higher similarity in chemical structure with a repeating unit of PCL, were found to be miscible with the aliphatic polyester at a comparatively lower DS; the critical butyryl DS of ∼1.85 being still lower than 2.15. For PCL-rich compositions of CB(DS > 2.0)/PCL and CV(DS > 2.2)/PCL blends, isothermal melt-crystallization behaviour was characterized by calorimetry and polarized optical microscopy. The CB and CV components gave rise to a marked diminution of the crystallization rate of PCL, as a result of the diluent action of the cellulose esters in the respective miscible, molten mixtures. Through a quantitative analysis of the kinetics, it is suggested regarding the supramolecular morphology that the bulky cellulose esters would be trapped not only on the fold surfaces but also on the growth faces of PCL lamellar crystals, to form a non-crystalline mixed polymer phase in the crystal boundary regions.     

Simultaneous introduction of phosphonic and carboxylic acid functions to hydroxylated macromolecules

Novel diblock and dihydrophilic ionic–nonionic copolymers, having phosphonic and carboxylic functions at the same carbon atom in the repeating units of the ionic block, were prepared. The addition of 2-diethylphosphono-ethyl acrylate (PC) to hydroxyl groups of the polyglycidol block of the poly(ethylene glycol)-b-polyglycidol block copolymer was followed by the dealkylation of phosphonic acid esters and the hydrolysis of carboxylic acid esters. The polymer was characterized by ¹H, ¹³C, and ³¹P NMR. The kinetics of the PC addition and the hydrolysis of the ethyl carboxylate function were also studied, and a simple bimolecular second-order reaction was established. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 432–443, 2004     

Synthesis of periodic copolymers via ring‐opening copolymerizations of cyclic anhydrides with tetrahydrofuran using nonafluorobutanesulfonimide as an organic catalyst and subsequent transformation to aliphatic polyesters

To synthesize polyesters and periodic copolymers catalyzed by nonafluorobutanesulfonimide (Nf₂NH), we performed ring‐opening copolymerizations of cyclic anhydrides with tetrahydrofuran (THF) at 50–120 °C. At high temperature (100–120 °C), the cyclic anhydrides, such as succinic anhydride (SAn), glutaric anhydride (GAn), phthalic anhydride (PAn), maleic anhydride (MAn), and citraconic anhydride (CAn), copolymerized with THF via ring‐opening to produce polyesters (M_n = 0.8–6.8 × 10³, M_n/M_w = 2.03–3.51). Ether units were temporarily formed during this copolymerization and subsequently, the ether units were transformed into esters by chain transfer reaction, thus giving the corresponding polyester. On the other hand, at low temperature (25–50 °C), ring‐opening copolymerizations of the cyclic anhydrides with THF produced poly(ester‐ether) (M_n = 3.4–12.1 × 10³, M_w/M_n = 1.44–2.10). NMR and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra revealed that when toluene (4 M) was used as a solvent, GAn reacted with THF (unit ratio: 1:2) to produce periodic copolymers (M_n = 5.9 × 10³, M_w/M_n = 2.10). We have also performed model reactions to delineate the mechanism by which periodic copolymers containing both ester and ether units were transformed into polyesters by raising the reaction temperature to 120 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Novel cellulose derivatives. III. Thermal analysis of mixed esters with butyric and hexanoic acid

Cellulose derivatives with low degrees of substitution (i.e., DS < 1.5) often fail to reveal glass transition temperatures (T_g) by virtue of their tenacious adherence to moisture, thus preventing systematic analysis of substituent effects (size and DS) on T_g and T_m transitions. On the other hand, cellulose triesters have T_ms that decline with acyl substituent size except when the substituent size becomes very large (i.e., > C₆), and they have T_gs within 5–20°C of their T_ms. This proximity is unusual for a semicrystalline material, and it interferes with the crystallization process that occurs between T_m and T_g. Triesters of cellulose with mixed acyl substituents (one smaller and one larger) allow not only unambiguous observation of T_gs and T_ms but also an adjustable Δ(T_m ? T_g) window that depends upon the size and the DS of the larger substituent. The materials studied including cellulose acetate butyrate triesters (DS_bu 0.8–2.6), cellulose acetate hexanoate triesters (DS_hex 0–3.0), and cellulose acetate (DS_ac 2.44), revealed that only the mixed esters, in which the bulkier acyl group is in the range of DS 0.3–1.0, had a Δ(T_m ? T_g) value in excess of 40°C. Although the T_m of cellulose acetate hexanoate declined by ca. 150°C per unit of DS_hex as DS_hex rose from 0 to 1, this was only ca. 25°C between DS_hex of 1 and 3. Frequently observed dual-melt endotherms were attributed to two separate crystal morphologies. ©1995 John Wiley & Sons, Inc.     

Gas chromatographic determination of isocitric and malic acid in the presence of a large excess of citric acid

Derivatization yields of different esters (methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl) of citric, malic and isocitric acids with various acylating agents, such as acetic anhydride, propionic anhydride, trifluoroacetic anhydride and heptafluorobutyric anhydride, were investigated. The formation of acylated malic and isocitric acid esters is rapid and quantitative whereas the acylation of citric acid esters was slow and partial in most instances. It was found that selective analytical conditions can be achieved with the O-heptafluorobutyryl n-butyl esters. The analytical applicability of the separation and determination of the malic, isocitric and citric acid contents of model solutions and of pressed lemon juice is discussed. Concentrations of 1.2 × 10^?3 ?9.0 × 10^?3g per 100 g of isocitric acid and 4.2 × 10^?3 ?3.5 × 10^?2 g per 100 g of malic acid in the presence of 9.3 × 10^?1 g per 100 g of citric acid were measured with relative standard deviations of 7.5 and 4.2%, respectively.     

Preparation of poly(p‐oxybenzoyl) crystals using direct polymerization of p‐hydroxybenzoic acid in the presence of boronic anhydrides

Poly(p‐oxybenzoyl) (POB) crystals were prepared by reaction‐induced crystallization during direct polymerization of p‐hydroxybenzoic acid in the presence of boronic anhydrides. Polymerizations were carried out at 300 °C in dibenzyltoluene at a concentration of 1% with three kinds of anhydrides of boronic acid such as 3,4,5‐trifluorophenylboronic acid (TFB), 4‐methoxyphenylboronic acid (MPB) and 4‐biphenylboronic acid (BPB). The POB crystals were formed as precipitates in the solution and the morphology was considerably influenced by both the structure of the boronic anhydride and its concentration (c_B). Needle‐like crystals were firmed in the presence of TFB anhydride (TFBA) at c_Bs of 5 and 10 mol % by the spiral growth of lamellae. Spherical aggregates of slab‐like crystals were formed at c_Bs from 50 to 100 mol %. The polymerization with MPB anhydride and BPB anhydride (BPBA) also yielded the needle‐like crystals at c_Bs of 50 and 5 mol %, respectively. The polymerization with TFBA at lower c_B was favorable to prepare the needle‐like crystal. Molecular weight was also influenced by the structure of the boronic anhydride and c_B. M_n increased generally with c_B and BPBA gave the highest M_n of 14.7 × 10³ at c_B of 100 mol %. The loose packing of the molecules in the crystal caused by the bulkiness of the end‐groups made the polymerization in the crystals more efficiently. Morphology and molecular weight of the POB crystals could be controlled by the chemical structure and the content of boronic anhydride. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

31P NMR Study of Complexation between Thallium(III) and Diethylenetriaminopentakis(methylenephosphonic Acid)

Aqueous solutions containing thallium(III) and diethylenetriaminopentakis(methylenephosphonic acid) (DTPP, H₁₀Dtpph) in a ratio of 1 : 1 were studied by ³¹P NMR spectroscopy in a pH range from 4 to 11. Complexation between DTPP and thallium in aqueous solutions gave complexes [TlH _n Dtpph] ^{n – 7}, which are highly stable on the NMR time scale. Each complex contains three nonequivalent phosphonic groups characterized by ^2,3 J(³¹,Tl) spin–spin coupling constants of 560 to 310 Hz. All the five phosphonic groups of DTPP are involved in coordination. The structure of the complex [TlH _n Dtpph] ^{n – 7} was proposed.     

The true molecular weight distributions of acrylate polymers formed in propagating fronts

We have analyzed fractionated samples of poly(methacrylic acid) produced in a propagating front for the amount of anhydride that formed and determined that a large percentage of acid groups exist as anhydrides (>20%). By analyzing the samples after cleavage, we found that the molecular weight dropped significantly (from M_n = 1.4 × 10⁵ to M_n = 1.0 × 10⁴). We conclude that the high molecular weights observed previously were the result of intermolecular anhydride formation. Poly(butyl acrylate), which cannot form anhydride bonds, produced in fronts had broad (M_w/M_n = 1.7–2.0) but unimodal molecular weight distributions with M_u < 10⁵. The average molecular weight decreased with increasing initiator concentrations. © 1996 John Wiley & Sons, Inc.     

Gel-permeation chromatography of cellulose esters. Effect of average DP,DS, substituent size,and primary hydroxyl content

Hydrolyzed cellulose acetates and cellulose tripropionates prepared over wide ranges of intrinsic viscosity (DP) were fractionated by gel-permeation chromatography (GPC). An increase was observed in the polystyrene equivalent length (PSEL) at 50% cumulative height with increasing DP of the ester. Cellulose acetates and propionates over wide range of acyl content (DS), and a homologous series of triesters (propionate through heptanoate) of the same DP were fractionated by GPC. Increased amount and size of acyl gave relatively small increases in PSEL. The molecular size of cellulose acetates was not affected by the amount of primary hydroxyl present in the esters. The breadth of molecular weight distribution of the cellulose esters, as measured by the weight-average to number-average molecular size ratio, M?_w/M?_n, was not affected by any variation in the composition of the esters. A blend of cellulose tripropionates of widely differing DP gave a broadened GPC curve in agreement with that calculated from the components of the blend.     

P and H NMR studies of the transesterification polymerization of polyphosphonate oligomers

Polymeric phosphonate esters are an interesting class of organophosphorus polymers because both the polymer backbone and phosphorus substituents can be modified. These polymers have been prepared by ring-opening polymerizations of cyclic phosphites, stoichiometric polycondensations of dimethyl phosphonate with diols in conjunction with diazomethane treatment and by transesterification of polyphosphonate oligomers. Our initial attempts to prepare high molecular weight polymeric phosphonate esters by the transesterification methods were unsuccessful. Results indicate that the reactions of dimethyl phosphonate with diols to form polyphosphonate oligomers with only methyl phosphonate end groups are plagued by a serious side reaction that forms phosphonic acid end groups. These end groups do not participate in the transesterification reaction and limit the molecular weights of the polymers that can be obtained. The phosphonic acid end groups can be converted into reactive methyl phosphonate end groups by treatment with diazomethane, however diazomethane is explosive and the polymerization is slow. An alternative route for the production of high molecular weight polymers is the transesterification of the 1,12-bis(methyl phosphonato)dodecane, formed by the reaction of excess dimethyl phosphonate and 1,12-dodecanediol, with a Na₂CO₃ promoter. This allows polymers with molecular weights of up to 4.5×10⁴ to be prepared, and no phosphonic acid end groups are observed in these polymers. Thermal analyses of the poly(1,12-dodecamethylene phosphonate) have shown that this polymer has reasonable thermal stability (onset of thermal decomposition at 273 °C). This polymer also undergoes a cold crystallization process at 15 °C similar to that which has been observed in some polyesters, polyamides and elastomers.     

Synthese von N-Di(alk-, ar-)oxyphosphoryl-tri(alk-, ar-)-oxyphosphazenen, (RO)2P(O)?NP(OR)3, durch P?N-Bindungsknüpfung

Synthesis of N-Di(alk-, ar-)oxyphosphoryl-tri(alk-, ar-)oxyphosphazenes, (RO)₂P(O)? N?P(OR)₃, by P? N-Bond Formation The title compounds can be prepared from di- and triesters of phosphorous acid, sodium azide, and carbon tetrachloride in a single step procedure and in high yields. Due to the combination of the Atherton-Todd and the Staudinger reaction toxic phosphoric acid ester azides are formed only in situ and their concentration is kept very small. As by-products trichloromethane phosphonic acid esters, (RO)₂P(O)CCl₃, esters of phosphoric acid and condensed phosphoric acids as well as N-alkylimidodiphosphoric acid esters, [(RO)₂P(O)]₂NR, are formed. Their formation can be avoided or reduced by choosing suitable reaction conditions. The mechanism of the reaction is discussed.     

Synthesis of E- and Z-o-Methoxy-Substituted 2,3-Diphenyl Propenoic Acids and Its Methyl Esters

A series of stereoisomeric o-methoxy-substituted 2,3-diphenyl propenoic acids and their methyl esters have been synthesized. The E isomers were prepared by a modified Perkin condensation (substituted benzaldehyde, phenylacetic acid, Et₃N/acetic anhydride). The difficult to access Z isomers were obtained conveniently in good yields when the appropriate coumarin derivatives were allowed to react with KOH and CH₃I in DMSO.     

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.     

Mechanochemical synthesis of dodecyl sulfate anion (DS−) intercalated Cu-Al layered double hydroxide

Dodecyl sulfate anion (DS⁻) was successfully intercalated into the gallery space of Cu-Al layered double hydroxides (LDH) by a non-heating mechanochemical route, in which basic cupric carbonate (Cu₂(OH)₂CO₃) and aluminum hydroxide (Al(OH)₃) were first dry ground and then agitated in SDS solution under ambient environment. The organics modified Cu-Al LDH showed good adsorption ability toward 2,4-dichlorophenoxyacetic acid (2, 4-D). The prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), CHS elemental analysis and Scanning electron microscopy (SEM). The LDH precursor prepared by ball-milling could directly react with SDS molecules forming a pure phase of DS⁻ pillared Cu-Al LDH, which was not observed with the LDH product through the ion-exchange of DS⁻ at room temperature. The process introduced here may be applied to manufacture other types of organic modified composites for pollutants removal and other applications.     

Amino acid‐functionalized ethyl cellulose: Synthesis,characterization, and gas permeation properties

Amino acid esters of ethyl cellulose [R′ = H ( 1 ), CH₃ ( 2 ), CH₂CH(CH₃)₂ ( 3 ), CH₂CONH₂ ( 4 ), CH₂OCH₂C₆H₅ ( 5 , 5′ ), CH₂CH₂CH₂CH₂NHOCOC(CH₃)₃ ( 6 )] were synthesized in moderate to quantitative yields (30–99%) by the reaction of t‐butoxycarbonyl (t‐Boc)‐protected amino acids or an activated ester derivative with hydroxy groups of ethyl cellulose [EC; degree of substitution (DS_Et), 2.69]. The amino acid functionalities displaying varied chemical nature, shape, and bulk were used, and bulk of the substituent on the α‐carbon of amino acids was elucidated to be of vital significance for the observed degree of incorporation (DS_Est). ¹H NMR spectra were used to determine the degree of incorporation of amino acid moiety (DS_Est), and almost complete substitution of the hydroxy protons was revealed in 1 , 2 , and 5′ . The onset temperatures of weight loss of 1 – 6 were 198–218 °C, indicating fair thermal stability. The glass transition temperatures of the derivatized polymers were 30–40 °C lower than that of EC (T_g 131 °C; cf. T_g of 1 – 6 , 93.5–103 °C). Free‐standing membranes of EC and its amino acid esters ( 1 , 2 , 5 , 5′ , and 6 ) were fabricated, and enhanced permselectivity for CO₂/N₂ and CO₂/CH₄ gas pairs was discerned, when compared with EC. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3986–3993, 2010     

Stereochemical applications of mass spectrometry. II—Chemical ionization mass spectra of isomeric dicarboxylic acids and derivatives

The H₂ and CH₄, chemical ionization mass spectra of the cis dicarboxylic acids, maleic and citraconic acid, show much more extensive loss of H₂O from [MH]⁺ than the trans isomers, fumaric acid and mesaconic acid. Similarly, esters of maleic acid show a much more facile loss of ROH (R=alkyl or phenyl) from [MH]⁺ than do esters of fumaric acid. Similar differences are observed in the chemical ionization mass spectra of the isomeric phthalic and isophthalic acids and derivatives, where the ortho isomers show more extensive fragmentation of [MH]⁺ than the meta isomers. The facile fragmentation of [MH]⁺ for the cis and ortho isomers is attributed to ROH elimination involving interaction between the two carboxylate functions and forming the stable cyclic anhydride structure for the fragment ion. By contrast ROH elimination from [MH]⁺ for the trans and metu isomers requires a symmetry-forbidden [1,3]-H migration in the carboxyl protonated species and cannot lead to the cyclic anhydride structure. The chemical ionization mass spectra of cis and trans cyclohexane-1,2-dicarboxylic acids are essentially identical and show extensive fragmentation of the [IMH]⁺ ion. Experiments using deuterium labelling show extensive carboxyl group interactions for both isomers. The chemical ionization mass spectra of maleanilic and phthalanilic acids and of the related anhydrides and imides also are reported, as are the electron impact mass spectra of diphenyl maleate, diphenyl fumarate, diphenyl phthalate, maleanilic acid and phthalanilic acid.