Acetyl Chloride dehydrating agent

Acetyl peroxide, 164, 245, 295, 338 Acetyltriallyl citrate, MA copolymerization, 297 2-Acetyl-2,5,6-trimethyl-2,3-dihydropyran, 322 Acid chlorides, dehydrating agent, 86, 89 Acids, organic, dissociation constants, 74, 75 Acridine, 131... 

Some cyclic anhydrides are made simply by heating the corresponding diacid. A dehydrating agent, such as acetyl chloride or acetic anhydride, is occasionally added to accelerate this reaction. Because five- and six-membered cyclic anhydrides are particularly stable, the equilibrium favors the cyclic products. 

The j8-hydroxy esters obtained by Reformatzki syntheses are very readily dehydrated, so that water is often lost on distillation and hydrolysis then dehydration is completed by heating with acetic anhydride, acetyl chloride, potassium hydrogen sulfate, formic acid, or sulfuric acid. Depending on the nature of the substituents present on the /9-carbon atom, the products are oc,P- or /9,y-unsaturated acids or mixtures of both.43 In a few exceptional cases <%,/ - or /9,y-unsaturated acids can be obtained at will from /9-hydroxy acids by choice of a suitable dehydrating agent an example of this is (1-hydroxy-cyclohexyl)acetic acid (1) which, according to Wallach,44 is converted by potassium hydrogen sulfate or phosphorus(v) oxide into (1-cyclohexenyl)-acetic acid (2) but by acetic anhydride into the isomer, cyclohexylideneacetic acid (3) ... 

Cyclic anhydrides are more easily prepared if the dicarboxylic acid is heated in the presence of acetyl chloride or acetic anhydride or if it is treated with a strong dehydrating agent such as P2O5. 

Under less vigorous conditions the acyclic monoamide (—amic acid) is formed and this can usually be converted into the cyclic imide by treatment with a mild dehydrating agent such as acetyl or thionyl chloride [77]. Alternatively, the reactants may be refluxed with triethylamine in benzene or toluene and the water formed in the reaction removed by azeotropic distillation [78]. The phthaloyl group has also been introduced into a-amino acids by heating with 0-carbethoxy-thiobenzoic acid in JV,JV-dimethylformamide at 80° [79], or at room temperature with JV-ethoxycarbonylphthalimide in the presence of sodium hydroxide [80]. 

---