Acetic acid, glacial, dehydration for

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

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 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. 

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. 

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). 

In the laboratory of T.-L. Ho, the total synthesis of the novel marine sesquiterpene (+)-isocyanoallopupukeanane was completed." In the endgame of the synthesis, it was necessary to install the isocyano group onto the tricyclic trisubstituted alkene substrate so that it will occupy the more substituted carbon atom (according to Markovnikov s rule). The Ritter reaction was chosen to form the required carbon-nitrogen bond. The alkene substrate was dissolved in glacial acetic acid and first excess sodium cyanide followed by concentrated sulfuric acid was added at 0 °C. The reaction mixture was stirred at ambient temperature for one day and then was subjected to aqueous work-up. The product A/-alkyl formamide was subsequently dehydrated with tosyl chloride in pyridine to give rise to the desired tertiary isocyanide which indeed was identical with the natural product. 

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