Acetic acid, glacial, dehydration

Acetic acid, glacial, dehydration for use in preparation of titanium derivative of acetylacetone, 2 119... 

To prepare pure acetic acid (glacial acetic acid), the crude aqueous product is converted into the sodium salt, the latter dehydrated by fusionf and then heated with concentrated sulphuric acid anhydrous acetic acid, b.p. 118°, distils over. Only the preparation of aqueous acetic acid and of crystalline copper acetate is described below. 

Acetic Acid-Acetic Anhydride Solution. One kilogram of glacial acetic acid is dehydrated in a 3-1.. flask over phosphorus pentoxide. The supernatant liquid is then fractionally distilled in an all-glass apparatus, and the portion boiling between 118 to 118.5° is collected. This procedure is repeated until the product has a melting point of 15.6°C. corresponding to that of 99.5 per cent acetic acid.f To the pure acetic acid 10 per cent acetic anhydride is now added. This solution should be kept in a stoppered container protected from moisture. 

The bottoms from the solvent recovery (or a2eotropic dehydration column) are fed to the foremns column where acetic acid, some acryflc acid, and final traces of water are removed overhead. The overhead mixture is sent to an acetic acid purification column where a technical grade of acetic acid suitable for ester manufacture is recovered as a by-product. The bottoms from the acetic acid recovery column are recycled to the reflux to the foremns column. The bottoms from the foremns column are fed to the product column where the glacial acryflc acid of commerce is taken overhead. Bottoms from the product column are stripped to recover acryflc acid values and the high boilers are burned. The principal losses of acryflc acid in this process are to the aqueous raffinate and to the aqueous layer from the dehydration column and to dimeri2ation of acryflc acid to 3-acryloxypropionic acid. If necessary, the product column bottoms stripper may include provision for a short-contact-time cracker to crack this dimer back to acryflc acid (60). 

The acid occurs both as colorless triclinic prisms (a-form) and as monoclinic prisms ( 3-form) (8). The P-form is triboluminescent and is stable up to 137°C the a-form is stable above this temperature. Both forms dissolve in water, alcohol, diethyl ether, glacial acetic acid, anhydrous glycerol, acetone, and various aqueous mixtures of the last two solvents. Succinic acid sublimes with partial dehydration to the anhydride when heated near its melting point. 

The crude carbinol is acetylated and dehydrated by refluxing its solution in 1 1. of glacial acetic acid and 500 ml. of acetic anhydride for 1 hour. The solution is then concentrated to about 500 ml. by distillation. After cooling overnight, the crystalline 3,12-diacetoxy-5A or-cholanyldiphenylethylene is collected on a filter and washed with acetic acid. The yield is 95-105 g. (63.5-70.0%) of material melting at 154-157° (Note 5). This product is sufficiently pure to be used for the preparation of Mor-desoxycholic acid (p. 38) one crystallization from acetone gives white crystals which melt at 156-157.5° fully purified material melts at 159.5-160.5°. 

The development of the colour is carried out in the organic phase used for extraction by the addition of curcumin in glacial acetic acid and phosphoric acid as dehydrating agent. Spectrophotometric evaluation is carried out at 510nm. 

Under these conditions, the O-benzoyl derivative immediately enolizes and is O-acylated again to yield a dibenzoate. Without isolation, this product is cyclized by treatment with aqueous potassium hydroxide to yield 2-hydroxy-2,3-dihydroflavone. Dehydration to flavone is then effected by the action of glacial acetic acid containing sulfuric acid. 

As part of a programme of studies on the synthesis of mitomycins, the dione 1 was treated with sodium hydride in dry THF at room temperature. This gave an epimeric mixture of carbinolamines which was highly acid sensitive and which, on treatment with glacial acetic acid at room temperature for 5 minutes, underwent dehydration to the tricyclic indole derivative 2. 

The first step follows a modification of the well known procedure of Krej-carek and Tucker [38] yielding the monomethylamide of DTPA 27. After dehydration with glacial acetic acid the monomethylimide 28 has been obtained as an activated polycarboxylate compound. Subsequent reaction with 1,3-diaminopropane yielded the DTPA-mono(methyl-propylamino)amide Hydro-choride 29. The reaction of 29 with 28 afforded the dimeric ligand 30. 

Lemon Oil, Coldpressed, occurs as a pale to deep yellow or green-yellow liquid with the characteristic odor and taste of the outer part of fresh lemon peel. It is the volatile oil obtained by expression, without the aid of heat, from the fresh peel of the fruit of Citrus limon L. Burmann filius (Fam. Rutaceae) with or without the previous separation of the pulp and the peel. It is miscible with dehydrated alcohol and with glacial acetic acid. It may contain a suitable antioxidant. 

Fam. Rutaceae). It is miscible with dehydrated alcohol and with carbon disulfide. It is soluble in glacial acetic acid. It may contain a suitable antioxidant. 

Reference Standards. Reference standards for TLC, GC, and MS were obtained as follows. Pure abietic acid (mp 172-173 °C) was used as received. Dehydroabietic acid was prepared by oxidation of abietic acid with selenium dioxide to hydroxy abietic acid and subsequent dehydration with glacial acetic acid (11). 7-Ketodehydroabietic acid was prepared by oxidation of dehydroabietic acid with potassium permanganate and isolation of the product by way of the Girard reagent T (12). Pyroabietic acid (a mixture of dehydro- and dihydroabietic acids) was prepared by heating abietic acid with 10% palladium on charcoal to 250 °C for 1 h (13). 

Low boiling substances are removed from the chilled reactor product by distilling up to a cut point of 80 °C. These low boilers are gaseous dimethyl ether, methyl acetate, acetaldehyde, butyraldehyde, and ethyl acetate. The bottoms are flash-distilled to recover the rhodium catalyst. Flash distilled acid is azeotropically dehydrated. In the final distillation, glacial acid is obtained. Traces of iodine that may remain in the finished acid may be removed by fractional crystallization or by addition of a trace of methanol followed by distillation of the methyl iodide that forms. Somewhere in the carbonylation reaction, a minute amount of propionic acid seems to be made. It typically is found in the residues of the acetic acid finishing system and can be removed by purging the finishing column bottoms. 

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