Acid derivatives, acylation

FIGURE 20.1 Structure, reactivity, and carbonyl-group stabilization in carboxylic acid derivatives. Acyl chlorides are the most reactive, amides the least reactive. Acyl chlorides have the least stabilized carbonyl group, amides the most. Conversion of one class of compounds to another is feasible only in the direction that leads to a more stabilized carbonyl group that is, from more reactive to less reactive. 

Much better leaving groups are encountered in carboxylic acid derivatives. Acyl halides possess... 

As one of the most reactive groups of carboxylic acid derivatives, acyl halides are very useful substrates for the preparation of the other classes of derivatives. For example, anhydrides may be synthesized by the reaction of carboxylic acid salts with an acyl halide. In this reaction, the carboxylate anion acts as the nucleophile, eventually displacing the halide leaving group. 

A number of tetramic acid derivatives acylated with a liposaccharide unit have recently been discovered in marine sponges. The first example was uncovered in the sponge Ancorina sp using a bioassay to detect inhibition of blastulation in starfish embryos. The structure of the compound (27), named ancorinoside A, was determined by spectroscopic techniques... 

The major use for acyl chlorides is as starting materials for the preparation of the other carboxylic acid derivatives. Acyl fluorides, bromides, and iodides could potentially be employed to prepare the other derivatives also. However, because they offer no advantages over the acyl chlorides, they are seldom used. 

Ammonia and amines react with partially or fully activated carboxylic acid derivatives (acylating reagents) like acid anhydrides, acid halides, ammonium salts of monoesters, monoamides with heating, diesters under basic conditions and dinitriles after partial hydrolysis. ... 

U.S. 5981450 (2000) Fabry et al. (Henkel) Monoglyceride (ether) sulfate amino acid derivatives (acyl gluamates, vegetable protein hydrolyzates, or vegetable protein fatty acid condensates) Mild detergent mixtures... 

Several syntheses have been reported implementing this strategy for preparing useful quantities of (i )-malic acid derivatives. Acylation of dimethyl (i )-tartrate (889) affords 890. Conversion of the 3-hydroxyl to chloride followed by dehalogenation with tri- -butyltin hydride furnishes the 0-acetyl (i )-malate (892). Acidic hydrolysis of the acetyl group gives dimethyl (i )-malate itself (203) (Scheme 130) [197]. 

Among the various carboxylic acid derivatives, acyl chlorides are especially useful because they are readily converted to acid anhydrides, esters, and amides by nucleophilic acyl substitution (Table 19.1). Yields are high and the reaction rates are much... 

The malonic ester synthesis might seem like an arcane technique that only an organic chemist would use. Still, it is much like the method that cells use to synthesize the long-chain fatty acids found in fats, oils, waxes, and cell membranes. Figure 22-4 outlines the steps that take place in the lengthening of a fatty acid chain by two carbon atoms at a time. The growing acid derivative (acyl-CoA) is activated as its thioester with coenzyme A (structure on page 1027). A malonic ester acylation adds two of the three carbons of malonic acid (as malonyl-CoA), with the third carbon lost in the decarboxylation. A )8-ketoester results. Reduction of the ketone, followed by dehydration and reduction of... 

Two major groups of phenols exist that are formed by the sequential addition of C2 units to a growing chain. Acetyl-CoA is generally used as the primer in fungal systems, whereas a shikimic acid-derived acyl-CoA is required for flavonoid synthesis in higher plants. Flavonoids are multiringed phenols found most commonly in flowers and fruit, where they are responsible for the color. 

Acyl halides are among the most reactive of carboxylic acid derivatives. Acyl chlorides are more common and less expensive than bromides or iodides. They can be prepared from acids by reaction with thionyl chloride. 

Amines are nitrogen nucleophiles. They react with the carbonyl group of carboxylic acid derivatives (acyl halides, anhydrides, and esters) by nucleophilic acyl substitution (Sec. 10.11). 

Carboxylic Acid Derivatives Acyl Halides and Anhydrides CHAPTER 19... 

CARBOXYLIC ACID DERIVATIVES ACYL HALIDES AND ANHYDRIDES... 

Carbonyl stretching frequencies in the IR spectra are diagnostic of the carboxylic acid derivatives Acyl chlorides absorb at 1790-1815 cm , anhydrides at 1740-1790 and 1800-1850 cm , esters at 1735-1750 cm and amides at 1650-1690 cm . ... 

The Corrositex can be used to assess corrosivity of seven categories of chemicals acids, acid derivatives, acyl halides, alkylamines/polyalkylamines, bases, chlorosilanes, metal halides and oxyhalides. Therefore, if the test substance is found to be corrosive it can be assigned packing group criteria according to the US DOT regulations. 

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