Koch reaction

Strong mineral acids under forcing reaction conditions catalyze the addition of carbon monoxide and water to alkenes to form carboxylic acids 96 97 

The reaction is also called hydrocarboxylation. According to a later modification, the alkene first reacts with carbon monoxide in the presence of the acid to form an acyl cation, which then is hydrolyzed with water to give the carboxylic acid.97 The advantage of this two-step synthesis is that it requires only medium pressure (100 atm). Aqueous HF (85-95%) gave good results in the carboxylation of alkenes and cycloalkenes.98 Phosphoric acid is also effective in the carboxylation of terminal alkenes and isobutylene, but it causes substantial oligomerization as well.99 100 Neocarboxylic acids are manufactured industrially with this process (see Section 7.2.4). The addition may also be performed with formic acid as the source of CO (Koch-Haaf reaction).101 102 The mechanism involves carbocation formation via protonation of the alkene97 103 [Eq. (7.10)]. It then reacts with carbon monoxide 

Superacid systems, such as HF—BF3 and CF3S03H, allow further improvement of the Koch reaction.109 Triflic acid proved to be far superior to 95% H2S04 at atmospheric pressure.110 This was attributed to the higher acidity of triflic acid and the higher solubility of CO in this acid. FS03H—SbF5 combined with Cu(I) is also effective.111 

Alcohols instead of olefins can also be used in these reactions. Although secondary and tertiary alcohols react preferentially in the presence of H2S04,112 SbCl5—S02,113 and acids with Cu(I) or Ag(I) ions,105 107 108 114 even methanol was shown under superacidic conditions to give acetic acid.115 

The preparation of acetic acid represents a special case. Olah and coworkers as well as Hogeveen and coworkers have demonstrated that CO can react with methane under superacidic conditions, giving the acetyl cation and by subsequent quenching acetic acid or its derivatives (see Section 7.2.3). Monosubstituted methanes, such as methyl alcohol (or dimethyl ether), can be carbonylated to acetic acid.115 Similarly, methyl halides undergo acid-catalyzed carbonylation.115,116 Whereas the acid-catalyzed reactions can be considered as analogs of the Koch reaction, an efficient Rh-catalyzed carbonylation of methyl alcohol in the presence of iodine (thus in situ forming methyl iodide) was developed by Monsanto and became the dominant industrial process (see Section 7.2.4). 

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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. 

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) ... 

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

The formyl cation, HCO, is also likely to be an intermediate in the modification of the Koch reaction whereby formic acid reacts with olefins to give carboxyhc acids (20) ... 

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 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 ... 

Propylene-Based Routes. The strong acid-catalyzed carbonylation of propylene [115-07-1] to isobutyric acid (Koch reaction) followed by oxidative dehydration to methacrylic acid has been extensively studied since the 1960s. The principal side reaction in the Koch reaction is the formation of oligomers of propylene. Increasing yields of methacrylic acid in the oxydehydration step is the current focus of research. Isobutyric acid may also be obtained via the oxidation of isobutyraldehyde, which is available from the hydroformylation of propylene. The -butyraldehyde isomer that is formed in the hydroformylation must be separated. 

Koch Ro- ction. C-6-neoacids are readily available from amyl alcohols by the Koch reaction. Greater than 95% 2,2-dimethylbutyric acid [595-37-9] was obtained from 2-methyl-1-butene at 304 kPa (3 atm) CO and 35°C for 1 h with cupric oxide and sulfuric acid catalyst (31). Likewise,... 

Reduction of Acids. Patents claim catalysts for the hydrogenation of neoacids in the vapor-phase to the neoalcohols in good yields. For example, neopentyl alcohol has been prepared by passing pivaUc acid (obtained by the Koch reaction of isobutylene) over a Cu0/Zn0/Al202 catalyst at... 

Carbonylation, or the Koch reaction, can be represented by the same equation as for hydrocarboxylation. The catalyst is H2SO4. A mixture of C-19 dicarboxyhc acids results due to extensive isomerization of the double bond. Methyl-branched isomers are formed by rearrangement of the intermediate carbonium ions. Reaction of oleic acid with carbon monoxide at 4.6 MPa (45 atm) using 97% sulfuric acid gives an 83% yield of the C-19 dicarboxyhc acid (82). Further optimization of the reaction has been reported along with physical data of the various C-19 dibasic acids produced. The mixture of C-19 acids was found to contain approximately 25% secondary carboxyl and 75% tertiary carboxyl groups. As expected, the tertiary carboxyl was found to be very difficult to esterify (80,83). 

Another formylation reaction, which is named after Gattermann, is the Gatter-mann-Koch reaction. This is the reaction of an aromatic substrate with carbon monoxide and hydrogen chloride (gas) in the presence of a Lewis acid catalyst. Similar to the Gattermann reaction, the electrophilic agent 9 is generated, which then reacts with the aromatic substrate in an electrophilic aromatic substitution reaction to yield the formylated aromatic compound 10 ... 

In the Gatteinicin-Koch reaction, a formyl group (-CHO) is introduced directly onto a benzene ring. For example, reaction of toluene wjfh CO and HCJ in the presence of mixed CUCI/AICI3 gives p-methylbenzaldehyde. Propose a mechanism. 

Gasoline, manufacture of, 99-100 octane number of, 100 Gatterman-Koch reaction. 596 Gauche conformation, 95 butane and, 95-96 steric strain in, 96... 

When aqueous solutions of aromatic and heteroaromatic diazonium salts are treated with cuprous chloride, -bromide, or -cyanide, the corresponding aromatic chlorides, bromides, or cyanides are formed, respectively. In many cases the anions mentioned must be present in excess. This reaction, the Sandmeyer reaction, was discovered by Sandmeyer in 1884. A variant carried out with copper powder and HBr or HC1 was for many years called the Gattermann reaction (Gattermann, 1890). As it is often confused with the Gattermann-Koch reaction (ArH + CO + HC1 ArCHO), and as it is mechanistically not significantly different from Sandmeyer s procedure, the name Gattermann reaction should be avoided. 

Gattermann-Koch reaction 230 Gattermann reaction 230 General acid/base catalysis, see Bronsted catalysis... 

The reaction between carbonium ions and carbon monoxide affording oxocarbonium ions (acyl cations) is a key step in the well-known Koch reaction for making carboxylic acids from alkenes, carbon monoxide and water ... 

The Koch reaction comprises the following reversible steps (2)-(5) ... 

The two main reasons for studying the reversible reaction (3) were (a) to complete the picture of the Koch reaction in terms of quantitative information and (b) to set up a scale of reactivity towards a neutral nucleophile for carbonium ions of different structure. The first item is important from a practical point of view because there are reactions competing with the carbonylation step (3), which can be divided into intramolecular and intermolecular processes. Rearrangement of the intermediate alkylcarbonium ion, e.g. 

Another method, formylation with CO and HCl in the presence of AICI3 and CuCl (the Gatterman-Koch reaction), is limited to benzene and alkylbenzenes. ... 

The decarbonylation of aromatic aldehydes with sulfuric acid" is the reverse of the Gatterman-Koch reaction (11-16). It has been carried out with trialkyl- and trialkoxybenzaldehydes. The reaction takes place by the ordinary arenium ion mechanism the attacking species is H and the leaving group is HCO, which can lose a proton to give CO or combine with OH from the water solvent to give formic acid." Aromatic aldehydes have also been decarbonylated with basic catalysts." When basic catalysts are used, the mechanism is probably similar to the SeI process of 11-38. See also 14-39. 

Shell has claimed that the Koch reaction to make Koch neo-acids can be carried out with a CIER, instead of concentrated sulphuric acid (Eqn. (8)). 

Gabriel synthesis Gattermann aldehyde reaction Gattermann reaction Gattermann-Koch reaction Gomberg-Hey reaction Grignard reaction... 

Formylation may be carried out by use of CO, HC1, and A1C13 (the Gattermann-Koch reaction) it is doubtful whether HCOC1 is... 

Koch-Haaf reaction, acylium ions, 42 160 Koch reaction, 34 126 Kolbel-Engelhardt reaction, 31 59 Kolbe reaction, 40 160-161 chemical identity of adsorbed intermediates, 38 18-19... 

This reaction is known as Gatterman-Koch reaction. 

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