Acid anhydride structure

Phosphoric acid molecules can form acid-anhydride bonds with each other. It is therefore possible for two nucleotides to be linked via the phosphate residues. This gives rise to dinucleotides with a phosphoric acid-anhydride structure. This group includes the coenzymes NAD(P) " and CoA, as well as the flavin derivative FAD (1 see p. 104). 

The structure of acid anhydrides has been found to impart a significant effect on the practical handling properties of the system such as gelation rate, exotherms, cure rate, etc, as well as on the ultimate physical, chemical and electrical properties of the cured film. The most significant changes which take place as a result of variations in the acid anhydride structure are changes in the heat distortion temperature and thermal stability of the cured films. 

Step 2 Structurally O acylisoureas resemble carboxylic acid anhydrides and are powerful acylatmg agents In the reaction s second stage the amine adds to the carbonyl group of the O acylisourea to give a tetrahedral intermediate... 

Properties and Structure. Phosphoms(V) oxide, the extremely hygroscopic acid anhydride of the phosphoric acids, exists in several forms but is often referred to by its empirical formula, P2O3. Three crystalline polymorphs, two distinct Hquids, and several amorphous or glassy soHds are recogni2ed. Some properties of the various forms of phosphoric oxide are Hsted in Table 10. 

Table 2. Structure and Properties of Aromatic Diamines and Acid Anhydrides Used in Epoxy-Matrix Resins...

By virtue of their fused /3-lactam-thiazolidine ring structure, the penicillins behave as acylating agents of a reactivity comparable to carboxylic acid anhydrides (see Section 5.11.2.1). This reactivity is responsible for many of the properties of the penicillins, e.g. difficult isolation due to hydrolytic instability (B-49MI51102), antibacterial activity due to irreversible transpeptidase inhibition (Section 5.11.5.1), and antigen formation via reaction with protein molecules. 

The chemistry of carboxylic acids is the central theme of this chapter. The importance of carboxylic acids is magnified when we realize that they are the parent compounds of a large group of derivatives that includes acyl chlorides, acid anhydrides, esters, and amides. Those classes of compounds will be discussed in Chapter 20. Together, this chapter and the next tell the story of some of the most fundamental structural types and functional group transfonnations in organic and biological chemistry. 

Phenylaceturic acid cychzes in acetic anhydride to give 2-benzyli-dene-3-acetyl-5-oxazolidinone (70) the previously proposed anhydride structure 71 was shown to be incorrect. Compound 70 reacts... 

Acids, anhydrides, and esters are considered together because of their structural similarities and common characteristics on catalytic hydrogenation. None is reduced easily and often vigorous conditions are required. 

Closely related to the carboxylic acids and nitriles discussed in the previous chapter are the carboxylic acid derivatives, compounds in which an acyl group is bonded to an electronegative atom or substituent that can net as a leaving group in a substitution reaction. Many kinds of acid derivatives are known, but we ll be concerned primarily with four of the more common ones acid halides, acid anhydrides, esters, and amides. Esters and amides are common in both laboratory and biological chemistry, while acid halides and acid anhydrides are used only in the laboratory. Thioesters and acyl phosphates are encountered primarily in biological chemistry. Note the structural similarity between acid anhydrides and acy) phosphates. 

Phosphine(s), chirality of, 314 Phosphite, DNA synthesis and, 1115 oxidation of, 1116 Phospholipid, 1066-1067 classification of, 1066 Phosphopantetheine, coenzyme A from. 817 structure of, 1127 Phosphoramidite, DNA synthesis and, 1115 Phosphoranc, 720 Phosphoric acid, pKa of, 51 Phosphoric acid anhydride, 1127 Phosphorus, hybridization of, 20 Phosphorus oxychloride, alcohol dehydration with. 620-622 Phosphorus tribromide, reaction with alcohols. 344. 618 Photochemical reaction, 1181 Photolithography, 505-506 resists for, 505-506 Photon, 419 energy- of. 420 Photosynthesis, 973-974 Phthalic acid, structure of, 753 Phthalimide, Gabriel amine synthesis and, 929... 

Pyrrole is one of the most prominent heterocycles, having been known for more than 150 years, and it is the structural skeleton of several natural products, synthetic pharmaceuticals, and electrically conducting materials. A simple access to the pyrrole ring system involves the conversion of cyclic anhydrides into five-membered imides. Mortoni and coworkers have described the conversion of 2-methylquinoline-3,4-dicarboxylic acid anhydride to a quinoline-3,4-dicarboximide library by treatment of the anhydride with a diverse set of primary amines under microwave conditions (Scheme 6.180) [341]. The authors studied a range of different conditions, including dry media protocols (see Section 4.1) whereby the starting materials were adsorbed onto an inorganic support and then irradiated with microwaves. For the transforma-... 

The anhydride of ethane- 1,2-disulfinic acid has structure [31b] (Mueller and Dines, 1969). In this instance the strain associated with the four-membered ring in [31a], which is absent in the five-membered sulfinic anhydride, is sufficient to ... 

While the anhydride of butane-1-sulfinic acid has the usual sulfinyl sulfone structure ([30a], R = n-Bu), the anhydride of 2-methylpropane-2-sulfinic acid has the sulfinic anhydride structure ([30b], R = t-Bu) Kice and Ikura, 1968). Presumably there is some steric interference between the bulky t-butyl groups in [30a] which is absent in [30b] where, because of the oxygen bridge, they are now further away from each other. However, since it seems unlikely that the... 

An electrochemical explanation of the basic reaction was suggested by P rumkin 17), while Shilov et al. 22, 23) claimed surface oxides of definite structure to be the only cause of either acidic or basic reaction. Shilov formulated the acidic surface oxides as carboxylic acid anhydrides bound to the edges of the carbon layers. 

The tropolone alkaloid of Liliaceae species, colchicine, is transformed by acetylation, alkaline cyclization, and dehydration into the tetracyclic pyrrolotropone acetyl anhydrocolchicine [77TL2977 83AX(C)1709]. When the dicarboxylic acid anhydride groups of puberulonic and stipitatonic acids (metabolites of Penicillium species) condense with o-phenylenediamine, another tetracyclic pyrrolotropone structure is formed (51JCS1139 59JCS2847). 

A feature of phosphoric acid is that it forms a series of poiymeric anhydrides that resembie carboxyiic acid anhydrides in structure and reactivity. Diphosphoric acid (formeriy caiied pyrophosphoric... 

An enzymatic reaction intermediate formed by phospho-ryl transfer to a carboxyl group on an enzyme. Acyl-phosphates are structurally analogous to acid anhydrides (R—CO —O —CO—R ), and they are thermodynamically less stable than either of the two phosphoanhydride bonds in ATP. This is evident by the fact that the acetate kinase reaction (ADP + acetyl-phosphate = ATP + acetate) favors ATP formation with an equilibrium constant of about 3,000. Acetyl-phosphate can be chemically synthesized by reacting orthophosphate with acetic anhydride. 

In Chapter 9 you see the basic structure of each of the carboxylic acids and Ccirboxylic acid derivatives. In this chapter we focus on the carboxylic acids and related compounds, such as esters, acyl chlorides, and acid anhydrides, and we also include some information on amides (see Chapter 13 for an additional examination of cimides). Before you can get into synthesis and reactions, though, you need to understand the structure and nomenclature of these compounds. 

While lactams are often polymerized by anionic ROPs, A-carboxyl-alpha-amino acid anhydrides, called Leuchs anhydrides, can be polymerized by either cationic or anionic techniques (structure 5.29). These polypeptide products, which are called nylon-2 products. 

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