Introduction

Anhydrides are organic compounds having two acyl groups bonded to the same oxygen atom. Acid anhydride is usually formed by the contraction of two monoacid molecules or one diacid molecule, which is the main source of active acyl groups, and its related reactions are similar to those of acid halides. Presently, acid anhydrides widely used in industrial production and scientific research mainly include acetic anhydride, succinic anhydride, maleic anhydride and phthalic anhydride.

• Acetic Anhydride

Acetic anhydride (AA) is a colorless and transparent organic compound with the chemical formula C₄H₆O₃, which reacts with water to produce acetic acid and ethanol to produce ethyl acetate. AA is an important acetylating reagent and has a wide range of applications in the manufacture of cellulose acetate, acetate plastics and non-combustible motion picture films. In particular, the heterogeneous catalysis of nerol and AA to synthesize neryl acetate, which is widely used in solvents, lubricating oils, medicines and flavors, plays an important role in the field of fine chemicals (Fig. 1).

Fig. 1. Preparation of neryl acetate by acetic anhydride (Journal of Industrial and Engineering Chemistry. 2022, 105: 121-131).

• Succinic Anhydride

Succinic anhydride (SA), with the chemical formula C₄H₄O₃, is an important organic synthesis intermediate and fine chemical raw material, which is widely used in the synthesis of food, coatings, medicine, pesticides, plastics, resin materials and other fields. Succinic anhydride can also be used as a standard reagent for analytical chemical acid-base titrations. In addition, agar with succinic anhydride modification achieved a breakthrough in gel performance, and its swelling rate, freeze-thaw stability, gel strength and gel transparency were greatly improved (Fig. 2).

Fig. 2. Preparation of agar through modification with succinic anhydride (Food Chemistry. 2022, 381: 132164).

• Maleic Anhydride

Maleic anhydride (MA) is in the form of white needle-like crystals, soluble in water to form maleic acid, and easily soluble in alcohol, ether and acetone. MA is produced by oxidation of benzene or butane or conversion of biomass platform compounds such as furfural and butanol. MA is the third largest organic acid anhydride after acetic anhydride and phthalic anhydride. It is mainly used in the production of unsaturated polyester resins, lubricant additives, pharmaceutical intermediates, organic chemical intermediates, food additives and pesticides. Meanwhile, MA as a polymer exhibits excellent activity against various pathogenic bacteria, fungi and drug-resistant bacteria (Fig. 3).

Fig. 3. Maleic anhydride exhibits excellent activity against various pathogenic bacteria (Chemical Engineering Science. 2022, 251: 117480).

• Phthalic Anhydride

Phthalic anhydride (PHA) is an important chemical raw material obtained from a mixture of naphthalene, naphthalene and o-xylene. PHA can be used as an intermediate for organic compounds, including plasticizers, alkyd resins, unsaturated polyester resins, dyes and pigments, pharmaceuticals, food additives, and pesticides. In particular, 2-ethylanthraquinone synthesized from phthalic anhydride has been widely used in the fields of pharmaceuticals, dyes, and electrochemistry due to its broad anti-inflammatory and antitumor pharmacological activities (Fig. 4).

Fig. 4. Preparation of 2-ethylanthraquinone of the polymeric micelles (Chemical Engineering Science. 2022, 251: 117480).

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References

1. Zeferino, R.C.F. et al. Neryl acetate synthesis from nerol esterification with acetic anhydride by heterogeneous catalysis using ion exchange resin. Journal of Industrial and Engineering Chemistry. 2022, 105: 121-131.
2. Xiao, Q. et al. Gel properties transition from mono-succinylation to cross-linking of agar by attemperation with succinic anhydride. Food Chemistry. 2022, 381: 132164.
3. Nagaraja, A. et al. A review on various maleic anhydride antimicrobial polymers. Journal of Microbiological Methods. 2019, 163: 105650.
4. Ji, C. et al. One-pot synthesis of 2-ethylanthraquinone from phthalic anhydride and ethylbenzene over a Sc-modified Hβ catalyst. Chemical Engineering Science. 2022, 251: 117480.