Acid anhydrides infrared absorptions

Infrared spectroscopy is a valuable tool for the structural analysis of acid derivatives. Ajrid chlorides, anhydrides, esters, amides, and nitriles all show characteristic infrared absorptions that can be used to identify these functional groups in unknowns. 

Aldehydes Amides Carboxylic acid anhydrides Carboxylic acids Esters Ketones and functional groups, 56 infrared absorption frequencies, 519,... 

In infrared spectra, the carbonyl group is usually indicated by a single strong and sharp absorption. However, in the case of carboxylic acid anhydrides, R—C—O—C—R, two peaks are observed even though the two carbonyl groups are chemically equivalent. 

Infrared IR spectroscopy is quite useful in identifying carboxylic acid derivatives The, carbonyl stretching vibration is very strong and its position is sensitive to the nature of IKT the carbonyl group In general electron donation from the substituent decreases the double bond character of the bond between carbon and oxygen and decreases the stretch mg frequency Two distinct absorptions are observed for the symmetric and antisym metric stretching vibrations of the anhydride function... 

Revised structures have been proposed for these compounds. The brownish-yellow acid obtained with maleic anhydride has been shown by ultraviolet, infrared, and nuclear magnetic resonance absorption measurements and oxidative degradation to have the tricyclic structure... 

N-Acetylation of Kasugamycinic Acid (9a). A solution of kasugamycinic acid (225 mg.) dissolved in 10 ml. of water was treated with acetic anhydride (0.3 ml.) under cooling sodium bicarbonate was used to keep the pH 7.2 and stirring continued for 30 minutes. The reaction product was passed through Dowex 50W-X2 (H form) and the column was washed with water. The combined filtrate was subjected to lyophilization to afford 234 mg. of a crude N-acetyl derivative. Its infrared spectrum showed strong absorptions at 1740 cm-1 characteristic of oxamic acid group. The N-acetyl derivative (178 mg.) was treated with 40 ml. 

Tetrakis(acetato)di- U-amido-diborane is a white crystalline compound which is not too sensitive to moisture. It can be stored in a nitrogen atmosphere in a refrigerator for long periods without decomposition. It is sparingly soluble in most organic solvents and slowly dissolves in glacial acetic acid and acetic anhydride. Monoclinic and triclinic crystalline forms were obtained by recrystallization from acetic anhydride and glacial acetic acid, respectively.1 The infrared spectrum recorded (Beckman i.r.-12) by the KBr pellet technique contains major absorption bands (at frequencies cm.-1) 3280(s), 3230(s), 3100(s), 1740(w,sh),... 

C=N absorptions in the infrared and the derivation of the corresponding piperazine on sodium borohydride reduction. Treatment of compound 184 with hydrochloric acid gives the aminoketone (186), and with acetic anhydride the 4-acetyl derivative (185) is obtained.383... 

Treatment of A -acetylglycine (4) with benzaldehyde in the presence of sodium acetate and acetic anhydride gave compound A, C,H NOi, which did not possess OH or NH absorption in the infrared spectrum. When compound A was heated with water it gave acid B, C, H,N03. Identify compounds A and B. 

The Infrared spectrum of the SMA copolymer labeled SMA-2, is consistent with other SMA copolymer spectra published (33). However, the absorption peaks in the range of 1700 - 1820 cm indicate that this copolymer has been partially esterified to yield a half/acid ester of maleic anhydride which should exhibit peaks in the range of 1700 - 1725 cm"l and 1735 -1750 cm (Figure 3). The small absorption bands at 1780 and 1820 cm indicate the presence of a small amount of unreacted maleic anhydride. These data appear to be consistent for those of a styrene-maleic anhydride copolymer reported by Muskat (34). The carbon, hydrogen, oxygen analyses indicate that this polymer is a half/acid ester of a 90% styrene/10% maleic anhydride copolymer wherein theoretical values of C, H and 0 are 88.89%, 7.017. and 2.58% versus values of 89.14%, 7.68% and 2.81% found for C, H and 0, respectively. The solubility parameter was found to be equal to 9.47 H. 

Only 4H-4-OXO derivatives of this heterocycle have been prepared. The infrared spectra of these compounds show a characteristic carbonyl absorption at 1780-1790 cm A variety of 2-methyl compounds have been obtained by reaction of the appropriately substituted aminopyrazinecarboxylic acids (9) with acetic anhydride, " an approach which has been described in many patents.Other anhydrides such as propionic and butyric anhydrides react to give the expected products. No reports of 2-unsubstituted compounds have appeared. 

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