Industrial preparation acetic anhydride

It should be emphasised that whereas the interaction of a sodium salt and an acid chloride is a convenient general laboratory method for preparing all classes of anhydrides, acetic anhydride is prepared on a large scale by other and cheaper methods. Industrial processes are based on reactions indicated by the equations ... 

Section 20 5 Acid anhydrides may be prepared from acyl chlorides m the laboratory but the most commonly encountered ones (acetic anhydride phthahc anhydride and maleic anhydride) are industrial chemicals prepared by specialized methods... 

Although I had been aware during most of my career as a preparative chemist of a general lack of information relevant to the reactive hazards associated with the use of chemicals, the realisation that this book needed to be compiled came soon after my reading Chemistry Industry for June 6th, 1964. This issue contained an account of an unexpected laboratory explosion involving chromium trioxide and acetic anhydride, a combination which I knew to be extremely hazardous from close personal experience 16 years previously. 

Preparation of acid anhydrides Acid anhydrides are prepared from carboxylic acids by the loss of water. For example, acetic anhydride is prepared industrially by heating acetic acid to 800 °C. Other anhydrides are difficult to prepare directly from the corresponding carboxylic acids. Usually they are prepared from acid chloride and sodium carboxylate salt (see below). 

The industrial preparation of cellulose diacetate employs acetic anhydride with sulphuric acid as catalyst. The reaction is conducted at low temperature and cellulose starts to dissolve in the acetylation bath as the reaction progresses. The reaction is conducted until practically full acetylation. The homogeneous solution obtained is then hydrolysed to reduce the DS to 2.4. Precipitation in dilute acetic acid, then washing with water and finally drying produce cellulose acetate flakes. 

Summary DNAT, l,l -dinitro-3,3 -azo-1,2,4-triazole, is prepared by oxidizing 3-amino-1,2,4-triazole to 3,3 -azo-1,2,4-triazole with potassium permanganate, and then treating that intermediate with nitric acid in the presence of acetic anhydride. The precipitated product is then recovered by filtration, and then recrystallized from acetone. Commercial Industrial note Part or parts of this laboratory process may be protected by international, and/or commercial/industrial processes. Before using... 

Summary beta-HMX can be prepared by reacting hexamine with ammonium nitrate and nitric acid in the presence of excess glacial acetic acid and acetic anhydride. The rate of additions is crucial to ensure proper HMX formation. After the reaction is complete, the alpha-HMX is refluxed with water to ensure quality and purification. The resulting water insoluble product is then filtered-off, and then recrystallized from acetone to produce excellent crystals of beta-HMX. Commercial Industrial note For related, or similar information, see Serial No. 696,888, November 15th, 1957, by The United States Army, to Jean P. Picard, Morristown, NJ. Part or parts of this laboratory process may be protected by international, and/or commercial/industrial processes. Before using this process to legally manufacture the mentioned explosive, with intent to sell, consult any protected commercial or industrial processes related to, similar to, or additional to, the process discussed in this procedure. This process may be used to legally prepare the mentioned explosive for laboratory, educational, or research purposes. 

Allene carboxylic acids have been cyclized to butenolides with copper(II) chloride. Allene esters were converted to butenolides by treatment with acetic acid and LiBr. Cyclic carbonates can be prepared from allene alcohols using carbon dioxide and a palladium catalyst, and the reaction was accompanied by ary-lation when iodobenzene was added. Diene carboxylic acids have been cyclized using acetic acid and a palladium catalyst to form lactones that have an allylic acetate elsewhere in the molecule. With ketenes, carboxylic acids give anhydrides and acetic anhydride is prepared industrially in this manner [CH2=C=0 + MeC02H (MeC=0)20]. 

Compounds containing the acetyl group are often prepared from acetic anhydride it is cheap, readily available, less volatile and more easily handled than acetyl chloride, and it does not form corrosive hydrogen chloride. It is widely used industrially for the esterification of the polyhydroxy compounds known as carbohydrates, especially cellulose (Chap. 35). 

Simple nitrofurans are also difficult to prepare. 2-Nitrofuran can be obtained from furan228 or 2,5-furandicarboxylic acid229 in acetic anhydride and nitric acid (d 1.51), though in the latter case the yield is only ca. 5%. Here too methyl substituents facilitate the reaction 3-3.5 g of 2-methyl-5-nitrofuran were obtained from 10 g of 2-methylfuran under similar conditions to those cited.230 The industrially important 5-nitro-2-furaldehyde can be prepared in 40-45% yield by direct nitration of 2-furaldehyde or its diacetate.231... 

Acetic acid is the main impurity in acetic anhydride, which is prepared industrially from acetaldehyde or from acetic acid and ketene. The acid can be removed by fractionation, and residual amounts thereof by prolonged boiling with magnesium turnings.33... 

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