Gattermann

Gattermann-Koch reaction Formylation of an aromatic hydrocarbon to yield the corresponding aldehyde by treatment with CO, HCl and AICI3 at atmospheric pressure CuCl is also required. The reaction resembles a Friedel-Crafts acylation since methanoyl chloride, HCOCl, is probably involved. 

Gattermann s reaction A variation of the Sandmeyer reaction copper powder and hydrogen halide are allowed to react with the diazonium salt solution and halogen is introduced into the aromatic nucleus in place of an amino group. 

Hoesch synthesis A variation of the Gattermann synthesis of hydroxy-aldehydes, this reaction has been widely applied to the synthesis of anthocyanidins. It consists of the condensation of polyhydric phenols with nitriles by the action of hydrochloric acid (with or without ZnCl2 as a catalyst). This gives an iminehydrochloride which on hydrolysis with water gives the hydroxy-ketone. 

Zinc cyanide. Solutions of the reactants are prepared by dis solving 100 g. of technical sodium cyanide (97-98 per cent. NaCN) in 125 ml. of water and 150 g. of anhydrous zinc chloride in the minimum volume of 50 per cent, alcohol (1). The sodium cyanide solution is added rapidly, with agitation, to the zinc chloride solution. The precipitated zinc cyanide is filtered off at the pump, drained well, washed with alcohol and then with ether. It is dried in a desiccator or in an air bath at 50°, and preserved in a tightly stoppered bottle. The yield is almost quantitative and the zinc cyanide has a purity of 95-98 per cent. (2). It has been stated that highly purified zinc cyanide does not react in the Adams modification of the Gattermann reaction (compare Section IV,12l). The product, prepared by the above method is, however, highly satisfactory. Commercial zinc cyanide may also be used. 

Gattermann (1890) found that the preparation of the cuprous halide may be avoided by making use of the fact that finely-divided copper (e.g., freshly-precipitated or reduced by hydrogen or copper bronze) acts catal3d.ically in the decomposition of solutions of diazonium salts, for example ... 

The yields by the Gattermann reaction are usually not as high as those by Sandmeyer s method. Copper powder is also employed in the preparation of sulphinlc acids, for example ... 

By passing a mixture of carbon monoxide and hydrogen chloride into the aromatic hydrocarbon in the presence of a mixture of cuprous chloride and aluminium chloride which acts as a catalyst (Gattermann - Koch reaction). The mixture of gases probably reacts as the equivalent of the unisolated acid chloride of formic acid (formyl chloride) ... 

The Gattermann-Koch formylatioii was found unsuited to the preparation of aldehydes from phenols and phenol ethers such aldehydes may be obtained by Gatteimann s aldehyde reaction. 

By interaction of hydrogen cyanide and hydrogen chloride with an anxnatic compound (hydrocarbon, phenol or phenol ether) in the presence of aluminium chloride (or zinc chloride). This is known as the Gattermann... 

This reaction, applicable only to the preparation of hydroxy-aldehydee, is alternative to the Gattermann aldehyde reaction (or the Adams modification of it) given under 4. The yields are usually smaller, but a large quantity of the phenol may be recovered. The following mechanism is consistent with the known facts ... 

By the condensation of a nitrile with a phenol or phenol ether in the presence of zinc chloride and hydrogen chloride a hydroxyaryl- or alkoxyaryl-ketone is produced. The procedure is termed the Hoesch reaction and is clearly an extension of the Gattermann aldehyde reaction (Section IV,121). The reaction gives the best results with polyhydric phenols and their ethers with simple monohydric phenols the imino ester hydrochloride is frequently the sole product for example ... 

Gabriel synthesis Gattermaim aldehyde reaction Gattermann reaction Gattermann-Kocll reaction Gomberg-Hey reaction Grignard reaction... 

For aromatic hydrocarbons some very efficient formytation and acylation procedures are known (e.g. Friedel-Crafts, Vilsmeier, Gattermann-Koch), They are treated in introductory text books. 

Hydroxy-4-methylthiazole failed to react when submitted to Friedel-Crafts benzoylation conditions (349) on the other hand, it reacted normally in Gattermann and in Reimer-Tiemann formylation reactions, affording the 5-formyl derivative (348). 4-Methylthiazole is insufficiently activated and fails to react under the same conditions. 2,4-Dimethylthiazole undergoes perfluoroalkylation when heated at 200° for 8 hr in a sealed tube with perfluoropropyl iodide and sodium acetate (116) (358). 

FUELS, SYNTHETIC - LIQUID FUELS] (Vol 12) Gattermann-Koch reaction... 

In the presence of aluminum chloride and a small amount of cuprous haUde, a mixture of hydrogen chloride and carbon monoxide serves as a formyl a ting agent of aromatics (Gattermann-Koch reaction) (107) ... 

The Gattermann-Koch synthesis is suitable for the preparation of simple aromatic aldehydes from ben2ene and its substituted derivatives, as well as from polycychc aromatics. The para isomers are produced preferentially. Aromatics with meta-directing substituents cannot be formylated (108). 

Friedel-Crafts acylation using nittiles (other than HCN) and HCI is an extension of the Gattermann reaction, and is called the Houben-Hoesch reaction (120—122). These reactions give ketones and are usually appHcable to only activated aromatics, such as phenols and phenoHc ethers. The protonated nittile, ie, the nitrilium ion, acts as the electrophilic species in these reactions. Nonactivated ben2ene can also be acylated with the nittiles under superacidic conditions 95% trifluoromethanesulfonic acid containing 5% SbF (Hg > —18) (119). A dicationic diprotonated nittile intermediate was suggested for these reactions, based on the fact that the reactions do not proceed under less acidic conditions. The significance of dicationic superelectrophiles in Friedel-Crafts reactions has been discussed (123,124). 

The Gattermann-Koch reaction when appHed to alkenes or alkanes gives ketones or acids but not aldehydes. However, the Vilsmeier aldehyde synthesis can be appHed to aUphatic compounds. For example, 1,2-diaLkoxyethylenes react with /V-methy1foTmani1ide and POCl to give alkoxymalondialdehydes ... 

SANDMEYER GATTERMANN AramaUcsubstitution Substitution of an annine group via the diazonkim sait by nudeophiies such as Ci, Br, i, CN R-S, HO, soma via cuprous salt catalysis. 

Zinc cyanide [557-21-1] M 117.4, m 800"(dec), d 1.852. It is a POISONOUS white powder which becomes black on standing if Mg(OH)2 and carbonate are not removed in the preparation. Thus wash well with H2O, then well with EtOH, Et20 and dry in air at 50°. Analyse by titrating the cyanide with standard AgN03. Other likely impurities are ZnCl2, MgCl2 and traces of basic zinc cyanide the first two salts can be washed out. It is soluble in aq KCN solns. However, if purified in this way Zn(CN)2 is not reactive in the Gattermann synthesis. For this the salt should contain at least 0.33 mols of KCl or NaCl which will allow the reaction to proceed faster. [J Am Chem Soc 45 2375 1923, 60 1699 1938-, Org Synth Coll Vol III 549 1955.]... 

A Tube Furnace.—Various forms of furnace are used. Those which are heated on the principle of the Lothar Meyer hot-air furnace by a number of pin-hole gas jets are easily regulated, and can be raised to a high temperature. The Gattermann furnace, shown in the diagram (Fig. 20), is a very convenient form. 

Gattermann s Method.— Accoiding to this method the diazonium bromide is first picparcd and then decomposed by finely divided metallic copper. The 50 grams /-toluidine is dissohed in 200 c.c. liydrobromic acid previously diluted with too c.c. water and diazoliscd in the usual way. To this solution... 

Some of the cuprous chloride compounds of the diazonium salts have been isolated and analysed, and coirespond to the formula CoH.-.NjCl.CuoCIo (Hantzsch). The formation of a crystalline copper compound is rendeied very evident in the present preparation.. A modification of Sandmeyer s reaction IS the introduction of precipitated metallic copper in place of the cuprous salt (Gattermann). 

The majority of aromatic sulphonic acids aie very soluble in water, and are difficult to obtain in the crystalline form On the other hand, the sodium or potassium salts generally ciystal-lise well, and it is customary to prepare them by pouiing the sulphonic acid directly after sulphonation into a strong solution of sodium or potassium chloride (Gattermann). 

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