Alkali fusion

The technique of potassium hydroxide fusion - reaction gas chromatography has been applied to the determination of alkyl and aryl groups in polysiloxanes. The method involves the quantitative cleavage of all organic substituents bonded to silicon, producing the corresponding hydrocarbons  

After concentration of the volatile products, they are separated and determined by gas chromatography. The percent relative standard deviation of the method is 1.00% the average deviation between experimental and theoretical results is 0.5% absolute. 

Various other reagents have been used for the determination of organic snbstituents bonded to silicon in organosilicon polymers [9, 10] (Table 3.1)  

Group determined Reagent Reaction conditions Product Analysis method 

Phenyl Bromine in glacial acetic acid Boiling solution Bromobenzene Titration of excess bromine 

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Usually prepared from the corresponding sulphonic acids by alkali fusion, methylation of phenol or from the aminotoluene by treatment with nitrous acid followed by boiling. Both o- and p-cresol are used as end components in azo dyes. 

I The phenol cannot always be isolated in good yield, particularly if it contains substituent groups, owing to the destructive action of the alkali fusion upon the radical R. 

Alkali Fusion of /u-Benzenedisulfonic Acid. Even though this process like the previous one is a very ancient one, it is still the main route for the synthesis of resorcinol. It has been described in detail previously and does not seem to have drastically evolved since 1980. It involves the reaction of benzene with sulfuric acid to form y -benzenedisulfonic acid which is then converted to its disulfonate sodium salt by treatment with sodium sulfite. In a second step, this salt is heated to 350°C in the presence of sodium hydroxide yielding the sodium resorcinate and sodium sulfite. 

By the alkali fusion or hydrolysis of the appropriate aminonaphthalenesulfonic acid. 

Alkali fusion of oleic acid at about 350°C ia the Varrentrapp reaction causes double-bond isomerization to a conjugated system with the carboxylate group followed by oxidative cleavage to form palmitic acid (75). In contrast, alkaU fusion of riciaoleic acid is the commercial route to sebacic acid [111 -20-6] ... 

Alkali Fusion. Tha alkaU fusion of castor oil using sodium or potassium hydroxide in the presence of catalysts to spHt the ricinoleate molecule, results in two different products depending on reaction conditions (37,38). At lower (180—200°C) reaction temperatures using one mole of alkah, methylhexyl ketone and 10-hydroxydecanoic acid are prepared. The 10-hydroxydecanoic acid is formed in good yield when either castor oil or methyl ricinoleate [141-24-2] is fused in the presence of a high boiling unhindered primary or secondary alcohol such as 1- or 2-octanol. An increase to two moles of alkali/mole ricinoleate and a temperature of 250—275°C produces capryl alcohol [123-96-6] CgH gO, and sebacic acid [111-20-6] C QH gO, (39—41). Sebacic acid is used in the manufacture of nylon-6,10. 

Desoxybenzoln (12, r6) By the alkali fusion of desylthioglycolic acid. Behagel and Schneider, Ber. 68, ts88 (193s). 

E The writing has again been revised at the sentence level, streamlining the presentation, improving explanations, and updating a thousand small details. Several little-used reactions have been deleted (the alkali fusion of arene-sulfonic acids to give phenols, for instance), and a few new ones have been added (the Sharpless enantioselective epoxidation of alkene.s, for instance). 

Alkali fusion of the metabolite furnished p-hydroxybenzoic acid in good yield as the only isolable product. Vigorous nitric acid oxidation of M gave a high yield of picric acid. Both degradation products must have arisen from the same site, which can be represented by part structure V. While positions 3 and 5 are probably unsubstituted, the vigorous nature of the degradations allows that those at 2 and 6 could bear carbon atoms. 

Zircon Alkali fusion at 600 °C ZrSi04 + 4 NaOH —> Na2Zr03 + Na2Si03 + 2 H20 Water leaching... 

Sophisticated instrumental techniques are continually being developed and gradually replace the classical wet chemistry analytical methods. Wet chemical analysis is destructive the sample is dissolved or altered. Nowadays the analyst is highly focused on instrumental methods and chemometrics. Yet, chemical work-up methods (e.g. hydrolysis with alcoholic alkali, alkali fusion, aminolysis, and transesterification, etc.) and other wet laboratory skills should not be forgotten. 

As a starting material, tetrahydrofuran has little to recommend it except in rare cases, one of which is the preparation of fluorofurans. With cobalt(III) fluoride, tetrahydrofuran yields a mixture of polyfluoro derivatives from which alkali fusion removes HF leaving various fluorofurans including tetrafluorofuran and 2,3,4-trifluorofuran (1). Potassium tetrafluorocobaltate acts on tetrahydrofuran giving 2 as the main product and alkali fusion converts this into 2,5-difluorofuran. The fluorofurans all polymerize readily and are rather unresponsive to electrophilic reagents.17... 

The preparation of 2-naphthol by high-temperature sulphonation of naphthalene followed by alkali fusion of the resulting naphthalene-2-sulphonic acid has been mentioned previously. Further sulphonation of 2-naphthol yields several useful naphtholsulphonic acids and conditions can be chosen to make one or other of these compounds the main product. The initial product is the unstable 2-naphthol-l-sulphonic acid, which readily rearranges to 2-naphthol-6-sulphonic acid (4-36 Schaeffer s acid). Further sulphonation leads to 2-naphthol-6,8-disulphonic acid (4-37 G acid) at low temperature and 2-naphthol-3,6-disulphonic acid (4.38 R acid) at higher temperature. 

The formation of indanthrone and flavanthrone, as well as alizarin, during the alkali fusion of 2-aminoanthraquinone can be explained mechanistically on the basis of the initial loss of a proton. The resulting anionic species can be represented as a resonance hybrid and is also tautomeric (Scheme 6.12). Primary 1-hydroxylation of 2-aminoanthraquinone is probably the first step in the formation of the alizarin by-product (compare Scheme 6.8). Such an attack may initiate the formation of flavanthrone [31 ]. It is also possible to envisage the formation of all three species by a radical mechanism [32]. 

In 1904 Bally obtained a bluish violet solid by alkali fusion of benzanthrone at approximately 220 °C. Two isomeric compounds were isolated by vatting the reaction mixture and filtering off a sparingly soluble sodium salt. Oxidation of the filtrate gave a blue vat dye, violanthrone (6.75 Cl Vat Blue 20), as the main component. The less soluble residue similarly afforded a violet product, isoviolanthrone (6.76 Cl Vat Violet 10). The formation of isoviolanthrone can be suppressed by carrying out the fusion in a solvent such as naphthalene or a polyethylene glycol in the presence of sodium acetate and sodium nitrite. Dyes of this type are often referred to as dibenzanthrones. 

It was established in 1929 by Liittringhaus and Neresheimer that 4,4,-bibenzanthronyl (6.77) is an intermediate in the formation of violanthrone. Thus, compound 6.77 results when an Ullmann reaction is carried out on 4-chlorobenzanthrone the same product is obtained when benzanthrone reacts under relatively mild conditions (approximately 110 °C) with a mixture of potassium hydroxide and potassium acetate in 2-methylpropan-l-ol (isobutanol). Alkali fusion at a higher temperature then converts 4,4,-bibenzanthronyl into violanthrone. Use of aluminium chloride also leads to ring closure (Scholl reaction). 

A different route proceeds by alkali fusion of the corrspondingly substituted naphthalic acid imide. This pathway parallels the synthesis of perylene tetracarboxylic acid diimide 70 (Sec. 3.4.1.1). The method is particularly suited to aliphatic amines. 

The pigment form [16] is obtained from the leuco form, which in turn is prepared by oxidation with alkali fusion, followed by treatment with sodium hydro-gensulfite solution or sodium dithionite (vatting). 

Primary alkyl phenols have been prepared by the reduction of acyl phenols 1 by the demethylation of the corresponding ethers 12 by the diazotization of the corresponding amines 3 and by the alkali fusion of sulfonates.4 Alkyl resorcinols have been prepared by the reduction of acyl resorcinols.1 5 6 Alkyl chlororesorcinols have been prepared from the corresponding acyl chlororesorcinols by reduction.7... 

M. Kjellevold Malde, K. Bjorvatn, K. Julshamn, Determination of fluoride in food by the use of alkali fusion and fluoride ion-selective electrode, Food Chem. 73 (2001) 373-379. 

In the laboratory, phenols are predominantly prepared hy either hydrolysis of diazonium salts or alkali fusion of sulphonates. 

Alkali fusion of sulphonates Phenols can he prepared from the corresponding sulphonic acids hy fusion with alkali. 

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