Formation Of Acid Anhydride Research Articles

Elemental Sulfur-Mediated Transformation of Carboxylic Acids to Acyl Fluorides by Electrophilic Fluorinating Reagent, Selectfluor.

The elemental sulfur-mediated synthesis of acyl fluorides from carboxylic acids is achieved using Selectfluor. A broad range of acyl fluorides are accessible from carboxylic acids while avoiding the formation of acid anhydrides. 19F NMR spectra suggest that S8-fluoro-sulfonium cation A and neutral S8-difluoride A' generated in situ are the reactive species in this deoxyfluorination reaction.

1,2-Dibromotetrachloroethane: an efficient reagent for many transformations bymodified Appel reaction

An efficient and facile method has been developed for the synthesis of alkyl bromides from various alcohols under mild conditions using a triphenylphosphine (PPh$_{3})$/1,2-dibromotetrachloroethane (DBTCE) complex in excellent yields and very short time (5 min). This method can also be applied for the transformation of chiral alcohols to their corresponding bromides in very high enantiomeric excess. The PPh$_{3}$/DBTCE complex is also successfully applied to ring-opening reactions of cyclic ethers in mild conditions. Esterification, amidation, and formation of acid anhydrides under very mild experimental conditions are also successfully accomplished by following a modification of the Appel reaction protocol in this work.

Electrophilic Carboxamidation of Ferrocenes with Isocyanates.

Ferrocenes undergo one-step carboxamidation by reaction with isocyanates in CF3SO3H solution. The chemistry is most efficient in excess superacid, and it has been accomplished with aryl and aliphatic isocyanates. In conversions with ferrocene carboxylic acids, isocyanates provide imides in good yields. A mechanism for this conversion is suggested involving carbamic acid anhydride formation and subsequent intramolecular reaction at the substituted cyclopentadienyl ring.

Markers, Reactions, and Interactions during the Aging of Pinus Resin Assessed by Raman Spectroscopy.

The resin extracted from the species of the Pinus genus (Pinaceae family) is a widely used material. Primarily, resins are made up of two types of diterpenoids: abietanes and pimaranes. Their composition changes with aging, affecting their chemical and physical properties; however, the chemical changes that occur during aging are not yet fully known. Understanding the evolution of pimaranes and abietanes and the chemical composition of the aged resins is essential to make the most of this substance and of its derivatives. A systematic study of the aging of Pinus resin with Raman complemented with infrared (IR) spectroscopy was carried out. This study provided new information about the interactions among the constituting molecules in resins aged over many years. In particular the formation of intermolecular hydrogen bonds in aged samples was detected for the first time, and the formation of acid anhydrides from the reaction between pimaranes was demonstrated. Furthermore, Raman and IR spectra band assignments are proposed, and the specific markers of the main compounds of the resin are tagged. This will facilitate the qualitative analysis of resin compounds.

ChemInform Abstract: Acid Anhydrides and the Unexpected N,N‐Diethylamides Derived from the Reaction of Carboxylic Acids with Ph3P/I2/Et3N.

Abstract The formation of acid anhydrides from the phosphorous-mediated activation of carboxylic acids was investigated. Under various systems, activation of benzoic acid in the presence of base led to the formation of benzoic anhydride at different rates depending on the reactivity of the reagents. Using the Ph 3 P–I 2 /Et 3 N combination, most aryl acids were converted into the corresponding anhydrides in high yields within 5–10 min. However, for nitro-substituted derivatives, unexpectedly, N , N -diethylamides were isolated without anhydride formation. These results indicated the pronounced effect of substituents in governing these potential side reactions which can significantly affect the yields of acylation reactions promoted by phosphonium species.

Acid anhydrides and the unexpected N,N-diethylamides derived from the reaction of carboxylic acids with Ph3P/I2/Et3N

The formation of acid anhydrides from the phosphorous-mediated activation of carboxylic acids was investigated. Under various systems, activation of benzoic acid in the presence of base led to the formation of benzoic anhydride at different rates depending on the reactivity of the reagents. Using the Ph3P–I2/Et3N combination, most aryl acids were converted into the corresponding anhydrides in high yields within 5–10min. However, for nitro-substituted derivatives, unexpectedly, N,N-diethylamides were isolated without anhydride formation. These results indicated the pronounced effect of substituents in governing these potential side reactions which can significantly affect the yields of acylation reactions promoted by phosphonium species.

Domino Catalysis in the Direct Conversion of Carboxylic Acids to Esters

AbstractThe combined use of high concentration conditions, auxiliary bases, and new catalysts allows for the rapid synthesis of sterically hindered carboxylic acid esters at room temperature. Mechanistic analysis indicates the intermediate formation of acid anhydrides and subsequent rate‐limiting transformation to the ester products.

High-Resolution Solid-State NMR Studies of Poly(vinyl phosphonic acid) Proton-Conducting Polymer: Molecular Structure and Proton Dynamics

The structure and the local proton mobility of poly(vinyl phosphonic acid) were studied by solid-state NMR under fast magic-angle spinning. At elevated temperatures, the signature of the hydrogen-bonded P-OH protons is observed in 1H magic-angle spinning (MAS) NMR as a single resonance at 10.5 ppm. Both 1H double-quantum NMR and variable-temperature experiments demonstrate that P-OH protons are mobile and thus able to contribute to proton conductivity. Below room temperature, two different types of hydrogen-bonded P-OH resonances are observed at 10.5 and 15 ppm, and 1H double-quantum NMR demonstrates that these protons are immobile on the NMR time scale. By means of first-principles calculations of a model polymer, we have assigned the additional hydrogen-bonded species at lower temperatures to phosphonic acid anhydride and charged anhydride. Also, in the 31P MAS NMR spectrum, two distinct resonances appear, arising from "normal" phosphonic acid and phosphonic acid anhydride. 31P double-quantum NMR experiments reveal that there is no phase segregation between normal and phosphonic acid anhydride and the condensation reaction occurs randomly throughout the system. The formation of acid anhydride leads to a decrease in proton conductivity through two mechanisms, (1) decrease in the number of charge carriers and (2) blockage of charge transport pathways through immobilization of charge carriers together with a hindered reorientation of the anhydride group. Our results provide strong evidence for these mechanisms by demonstrating that the conductivity is greatly influenced by the presence of phosphonic acid anhydride.

Theoretical Study of Formic Acid Anhydride Formation from Carbonyl Oxide in the Atmosphere

We report the first theoretical study on the formation mechanism of tropospheric formic acid anhydride (FAA). Experimental studies on this subject have raised controversy, and the reaction mechanisms proposed are examined here with the help of theoretical calculations at the density functional theory and various correlated ab initio levels (MP4, CCSD, CASSCF, CASPT2) using extended basis sets. The investigated processes are initiated by the reaction of carbonyl oxide with either formaldehyde or formic acid. In the first case, a secondary ozonide is formed that then isomerizes to hydroxymethylformate (HMF). Stepwise and concerted mechanisms have previously been proposed for the isomerization process on the basis of experimental results. Our calculations confirm the existence of both mechanisms, but the stepwise one appears to be more favorable. HMF decomposition into FAA and H2 is shown to be unlikely (activation barrier about 90 kcal/mol). Conversely, reaction of HMF with molecular oxygen in the singlet state leads to FAA and H2O2 through a small barrier close to 9 kcal/mol at the B3LYP level. In the case of the carbonyl oxide + formic acid pathway, the transitory product is hydroperoxymethylformate (HPMF). Decomposition of HPMF into FAA and H2O proceeds through a large activation barrier (about 50 kcal/mol). The process may be assisted by a formic acid molecule, lowering the activation barrier for FAA formation to 29.8 kcal/mol at the B3LYP level. Reactions energies are −113.7 kcal/mol for H2COO + H2CO → FAA + H2, −174.6 kcal/mol for H2COO + H2CO + O2 → FAA + H2O2, and −101.7 kcal/mol for H2COO + HCOOH → FAA + H2O (values at the B3LYP level with ZPE corrections). Therefore, the mechanism involving singlet O2 appears to be the most favorable one in atmospheric conditions, both kinetically and thermodynamically.

Fourier-transform infrared spectroscopic studies of the adsorption of ketene on silica

FTIR spectroscopy has been applied to study the adsorption of ketene (H2CCO) on the surface of silica (dehydroxylated at 573 and 973 K) at room temperature and 178–183 K. Surface acetate and acetic acid anhydride species were produced by the interaction of ketene with hydroxy groups. Silica pretreated at the higher temperature showed a lower reactivity towards ketene chemisorption and in particular towards acid anhydride formation. Adjacent hydroxy groups were mainly responsible for ketene chemisorption. Physisorbed ketene was observed at 178–183 K, while chemisorption products were considerably reduced compared with the experiments at room temperature.

Enantioselective construction of a quaternary stereogenic centre via tandem acid anhydride formation–intramolecular Michael reaction

A novel method for the enantioselective construction of a quaternary stereogenic centre by tandem acid anhydride formation–intramolecular Michael reaction has been developed; a synthetic intermediate 16 for Hunteria and Aspidosperma indole alkaloids has been prepared by the application of this procedure.

Catalyst effects found in thermal and mass spectrometric analyses of polycarboxylic acids used as durable press reactants for cotton

AbstractEffective polycarboxylic acids (PCAs) crosslink cotton cellulose by an ester linkage and smooth‐drying fabrics are produced. The presence of a catalyst improves the crosslinking reaction. A series of seven PCAs was examined by thermal analytical (TA) and mass spectrometric (MS) techniques. The focus of this research was to discover if catalyst effects were measurable by TA and MS and to seek additional support for a proposed mechanism of cellulose/organic acid reactivity via acid anhydride formation. Thermal analyses consisted of differential scanning calorimetric (DSC) and thermogravimetric (TG) procedures. MS analyses, using the electron impact mode, were performed by direct probe sample insertion. Observed catalyst effects included shifts in peak positions to lower temperature/time, and were noticeable primarily in MS‐reconstructed ion current chromatograms and DSC thermograms. Two TG parameters, the amount of residue produced and the rates of weight loss, offer ways to predict the effectiveness of a PCA with respect to smooth‐drying character. The presence of the catalyst influenced both measurements in desirable directions. Finally, the catalyst did not alter TG water loss data that support the proposed mechanism of reaction with cellulose via an anhydride intermediate.

ポリアミド酸ラテックスの銅板上への電着によりつくられたフィルムのポルフィリンによる熱安定化

Poly(amic acid) latex was electro-deposited and cured on copper plate. Formation of acid anhydride in the sample was shown by its infrared spectrum but the sample had low heat stability. It was found that O.11 mol/monomer unit of Cu2+ ion were contained in the poly (amic acid) film deposited on copper plate and the Cu2+ ion was considered to act as a catal yst of the formation of acid anhydride in curing. Addition of octaethylporphyrin into t he latex reduced the quantity of Cu2+ ion in the deposited film even by acid treatment of sample and improved the heat stability of the cured film.

Application of Chemical Reactions on Thin-layer Chromatoplates. IV. Triterpenes

Abstract Some specific reactions of triterpenoids had been performed on thin-layer chromatoplates. The reactions conducted were: oxidation with oxygen in K-t-butoxide, benzilic acid rearrangement, decarboxylation with lead tetraacetate, Wolff-Kischner reduction, reduction with sodium borohydride, reduction with lithium aluminium hydride, oxidation with chromium trioxide in pyridine and in acetic acid, oxidation with manganese dioxide in chloroform, methylene chloride and isopropyl alcohol, insertion of an oxygen atom in ring A of triterpenoids by the formation of acid anhydride and reduction by a modified Clemmensen method.

各種の高分子カルボン酸の酸無水物形成

各種の高分子カルボン酸の酸無水物形成