With boric anhydride reaction

Diphenylamine can also be produced by passing the vapors of aniline over a catalyst such as alumina, or alumina impregnated with ammonium fluoride (17). The reaction is carried out at 480°C and about 700 kPa (7 atm). Conversion per pass, expressed as parts diphenylamine per 100 parts of reactor effluent, is low (18—22%), and the unconverted aniline must be recycled. Other catalysts disclosed for the vapor-phase process are alumina modified with boron trifluoride (18), and alumina activated with boric acid or boric anhydride (19). 

Rapid procedure Dry over anhydrous K2CO3 for 24h, followed by further drying for 24h over 3A molecular sieves or boric anhydride, followed by distn. Alternatively, stir over P2O5 (5% w/v) for 24h then distil. However this last method is not suitable for use in reactions with very acid sensitive compounds. 

On the other hand, the reaction of 3-,sec-aminophenols (71) with phthalic anhydride does not give the corresponding keto acids (72). The keto acids (72) having a secondary amino group at 4-position are prepared by the reaction of 3-sec-aminophenols (71) with phthalimide at 150-220°C in the presence of boric acid, followed by hydrolysis of the intermediate carboxamide with aqueous sodium hydroxide (Eq. 3). 

Borate. Dehydration is the first reaction occurring on heating the borate as in the case of the phosphate but at a much lower temperature (130-270 C, step 1 Figure 17). Boric acid heated alone in the same conditions in TG, eliminates water between 80-300 C in two main overlapping steps with maximum rate at 170 and 190 C corresponding to formation of metaboric acid and boric anhydride respectively ... 

Of practical interest are the last two techniques for producing trialkylbo-rates. It should be noted however, that the industrial reaction of boric anhydride with alcohols is fraught with difficulties. E.g., when powderlike boric anhydride is introduced into alcohol, clumps should be broken lest they kill the reaction. If boric anhydride is used in the form of pieces, the reaction should be conducted under an increased pressure and alcohol should be dehydrated beforehand. Thus, the most technological method is to obtain trialkyl(aryl)borates by the interaction of boric acid with alcohols. 

Similarly to trimethylborate, the reaction of a corresponding alcohol with boric acid or boric anhydride yields other trialkylborates triethyl-, tri-n-propyl-, tri-n-butyl-, tri-sec-butyl-, tri-tret-butyl-, tri-n-pentyl-, triisopen-... 

Mono- or diacyl derivatives that undergo cyclization to benzoxazoles on heating or under the influence of dehydrating agents are formed as intermediates in this reaction [134, 452, 453, 459, 461 173], Phosphorus oxychloride [453, 457], boric anhydride [455, 461, 462], or polyphosphoric acid [134, 471] are used as condensing agents. In particular, 2-hydroxy-5-nitrobenzoxazole, used for the synthesis of antivirus medicines, has been obtained by the reaction of condensation of 4-nitro-2-aminophenol with (NH2)2CO in pyridine [474],... 

Pavolini (118) who prepared curcumin by condensation of acetylacetone with vanilline. He observed that Knoevenagel condensation, one of the main side reactions, could be suppressed by adding boric oxide. This method was further developed by Pabon (119) who first prepared a complex from acetylacetone and boric anhydride and reacted the product with vanilline in the presence of triisopropyl borate and butylamine. Yields calculated on vanilline were thus improved from 10% to 80%. Besides several other indutrial applications (120-123) the method was also used for the synthesis of dihydroyashabushiketol (6) (11) and the tetramethylether of oregonin (11) (14). By selective alkylation of acetylacetone at C-3 Pedersen and associates exploited the above method for the preparation of a series of non-natural diaiylheptanoids substituted at C-4 (124). 

BORIC ACID (10043-35-3) BH3O3 Aqueous boric acid is a weak acid incompatible with alkali carbonates hydroxides strong reducing agents, including metal hydrides, nitrides, sulfides, and alkali metals. Violent reaction with potassium metal. Contact with acetic anhydride forms a heat-sensitive explosive. On small fires, use water fog. 

Thionyl chloride, as well as other inorganic acid chlorides, reacts with polyols to form mixed esters (see under Sulfate esters. Chapter III). In the presence of pyridine, partial chlorohydrin formation may occur (95), Selenium oxychloride forms a selenite ester upon reaction with mannitol (96), Phosphorus pentachloride yields unsaturated chlorohydrins of mannitol and galactitol which have the composition CeHeCU (97), Extremely interesting are the so-called complexes of alditols with various inorganic polybasic acids, their salts, or anhydrides in aqueous solutions. Complexes with boric, molybdic, tungstic, and other acids, as well as the oxides of antimony and arsenic, have been reported. It is believed that these complexes are true esters with one or more moles of alditol, a chelate type of structure being involved at some point. For the hexitols a compound with boric acid such as the following is postulated (98),... 

Petoxycatboxyhc acids also have been prepared by the reaction of acid chlorides, anhydrides, or boric-catboxyhc anhydrides with hydrogen or sodium peroxide. These reactions ate carried out at low temperature and with excess peroxide to avoid the formation of diacyl peroxides (44,168,181,184). 

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

It is proposed that the boric acid reacts with the carboxylic acid to form a mixed anhydride as the actual acylating agent.913 Upon reaction with an amine, this intermediate forms the desired carboxamide and regenerates the catalytically active boric acid. 

Although anthraquinone is the starting point for the preparation of many derivatives, involving substitution and replacement reactions, certain compounds are obtained directly by varying the components in the above synthesis. Thus, for example, replacement of benzene with methylbenzene (toluene) leads to the formation of 2-methylanthraquinone. A particularly important variation on the phthalic anhydride route is the synthesis of 1,4-dihydroxyanthraquinone (6.6 quinizarin) using 4-chlorophenol with sulphuric acid and boric acid as catalyst (Scheme 6.3). The absence of aluminium chloride permits hydrolysis of the chloro substituent to take place. 

The first commercial copper phthalocyanine synthesis, a baking process, involved melting phthalic anhydride with urea at 150°C in the presence of boric acid. Cop-per(II)chloride was then added and the temperature increased to approximately 200°C until the copper phthalocyanine production was completed. The reaction mixture was cooled and the crude product milled. After being washed, first with dilute sodium hydroxide solution and then with dilute sulfuric acid, the material was filtered off and dried. The crude copper phthalocyanine obtained was then... 

Preparation and Properties. Spill 5 g of pure boric acid into an iron crucible (better use a platinum crucible why ). Cover the crucible with its lid and roast it in a muffle furnace at 800 °C up to complete removal of the water. What reactions occur To extract the boric acid anhydride, immerse the bottom part of the red-hot crucible into cold water. Transfer the extracted substance into a bottle with a good stopper. 

Treat a part of the boric acid anhydride in a test tube with water and determine the pH of the solution. Write the equations of the reactions. 

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