Halides anhydrides, structure

Unlike any of the other acetylated glycosyl halides, the fluorides may be deacetylated without lo.ss or tsomerization of the halide function. This unique reaction can be effected either with alcoholic ammonia or with a catalytic amount of sodium methoxide in alcohol. In some instances, however, depending on the concentration of base and on the configuration and type of substitution at the carbon atom next to the glycosidic center, side-reactions occur that lead to glycoside or anhydride structures. ... 

Nomenclature for carboxylic acids and dicarboxylic acids. Structure and nomenclature for acid halides, anhydrides, esters, and amides. 

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. 

While metallocenes are usually acetylated with acid halides, acid anhydrides, or carboxylic acids, a number of other acylating agents have been reported. The reaction of ferrocene with various isocyanates and aluminum chlorides leads to N-substituted ferrocenecarboxamides (IX) (89). Use of ruthenocene in place of ferrocene leads to analogous results (88). The preparation of V-phenyl-ferrocenecarboxamide from phenyl isocyanate in this manner has been used as a proof of structure for the product obtained from the Beckmann rearrangement of benzoylferrocene oxime (124). 

Acyl and sulfonyl halides and anhydrides react instantaneously with pyridine to form quaternary salts which are excellent acylating and sulfonylating agents. The familiar use of pyridine as a solvent in such reactions reflects this. While usually used in situ, stable A-acylpyridinium and N-acylisoquinolinium salts, e.g. (63), have been isolated and their structures confirmed by single crystal... 

Structures 24 are conveniently thought of as derivatives of carboxylic acids, and include acids, esters, anhydrides, acyl halides, and amides. These structures (and others less commonly encountered) can be readily interconverted, either directly or indirectly the number of different reactions is therefore large.109 Because these processes occupy an important place in organic chemistry and because carboxylic acid derivatives are of central importance in biochemical systems and therefore of considerable interest in the study of enzyme action, they have been the subject of intensive investigation.110 We shall outline briefly the main features, and in order to give an idea of the kinds of mechanistic questions involved, we consider ester hydrolysis in somewhat greater detail. 

Given the IUPAC name of a carboxylic acid, salt, ester, amide, acyl halide, or anhydride, write its structural formula, and given the structure, write the name. 

The l,4-diacyl-3-acylamino-5-phenyl-4,5-dihydro-1H-1,2,4-triazole (99) was generated by the ring-closure of a guanidinylhydrazone with acetic anhydride in ca. 80% yield. The structure of the triazole was confirmed by spectroscopy and x-ray analysis [95M733], The N-benzyl triazoline (100) was prepared by reaction of N-benzylidinebenzylamine with a hydrazonyl halide with K,CO, in benzene, followed by 2 eq of Et,N for 1 h, in 75% yield [95ZOB308]. 

On activation of Dane s salt by an acyl halide to give a mixed anhydride, N-acylation is prevented by the enaminone moiety. The product of cyclocondensation can be hydrolysed, losing the enaminone group to yield a free aminoazetinone. Such /Mactam derivatives are of great interest due to the structural analogy to aminopenicillins and cephalosporins. 

The iV-acylated derivatives of maleic hydrazide, prepared from open-chain compounds, have been found to differ from acylated products obtained from maleic hydrazide acylations. Acylation of 4- or 5-substituted maleic hydrazides should permit the existence of two 0-acylated isomers. So far, only one isomer of unknown structure has been isolated from benzoylation of the 4-methyl analog. Maleic hydrazide and its 2-substituted analogs are 0-acylated with acetic anhydride, acyl halides, and 0,0-dialkylphosphorochlor-... 

The nitryl halides (C2 symmetry) are planar in analogy to the isoelectronic COs. The gas phase and solid-state structures for CINO2 both show covalently bound molecules (see Table 40). In contrast to the nitrosyl hahdes, the halogen-nitrogen bond distances in the gas phase and in the solid state are similar. The nitryl halides NO2F and NO2CI are the mixed anhydrides of nitric acid and hydrofluoric or hydrochloric acid, respectively. 

Applications The Karl Fischer reagent can be applied directly to the determination of water in a variety of organic compoimds, including saturated or unsaturated hydrocarbons, alcohols, halides, acids, acid anhydrides, esters, ethers, amines, amides, nitroso and nitro compounds, sulfides, hydroperoxides, and dialkyl peroxides. The use of sodium tartrate dihydrate for standardization of the response of the Karl Fischer reagent has been shown to lead to a small error because of occlusion of about 2% (relative) water in the crystal structure. 

---