By the Koch reaction

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... 

Koch Reacdon. C-6-neoacids are readily available from amji alcohols by the Koch reaction. Greater than 95% 2,2-dimethylbutyric acid [595-37-9] was obtained from 2-meth5i-1-butene at 304 kPa (3 atm) CO and 35°C for 1 h with cupric oxide and sulfuric acid catalyst (31). Likewise, 2,2-dimethylbutyric acid can be obtained in high yidd (75—80%) from 1- or 2-pentanol or neopentyl alcohol from the Koch-Haaf reaction (32,33). tert-Amy. alcohol gives a mixture of trimethyl acetic acid [75-98-9] (pivalic acid), 2,2-dimeth5ibutyric acid, C-7 acids, and C-11 acids under similar Koch-Haaf conditions (33). 

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. 

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). 

By in situ MAS NMR spectroscopy, the Koch reaction was also observed upon co-adsorption of butyl alcohols (tert-butyl, isobutyl, and -butyl) and carbon monoxide or of olefins (Ao-butylene and 1-octene), carbon monoxide, and water on HZSM-5 (Ksi/ Ai — 49) under mild conditions (87,88). Under the same conditions, but in the absence of water (89), it was shown that ethylene, isobutylene, and 1-octene undergo the Friedel-Crafts acylation (90) to form unsaturated ketones and stable cyclic five-membered ring carboxonium ions instead of carboxylic acids. Carbonylation of benzene by the direct reaction of benzene and carbon monoxide on solid catalysts was reported by Clingenpeel et al. (91,92). By C MAS NMR spectroscopy, the formation of benzoic acid (178 ppm) and benzaldehyde (206 ppm) was observed on zeolite HY (91), AlC -doped HY (91), and sulfated zirconia (SZA) (92). 

The acid-catalyzed hydrocarboxylation of olefins (the Koch reaction) can be performed in a number of ways.565 In one method, the olefin is treated with carbon monoxide and water at 100 to 350°C and 500 to 1000 atm pressure with a mineral-acid catalyst. However, the reaction can also be performed under milder conditions. If the olefin is first treated with CO and catalyst and then water added, the reaction can be accomplished at 0 to 50°C and 1 to 100 atm. If formic acid is used as the source of both the CO and the water, the reaction can be carried out at room temperature and atmospheric pressure.566 The formic acid procedure is called the Koch-Haaf reaction (the Koch-Haaf reaction can also be applied to alcohols, see 0-103). Nearly all olefins can be hydrocarboxylated by one or more of these procedures. However, conjugated dienes are polymerized instead. 

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). 

Just as protocatechuic aldehyde may be synthesized by the Reimer-Tiemann or Gattermann-Koch reactions from the -di-phenol pyro-catechinol, so vanillin may be made by the same reactions from the mono-methyl ether of pyrocatechinol, Le.f guaiacol (p. 621). 

Olah et al. have developed direct carbonylation of isoalkanes that lead to ketones in high conversion and high selectivity under HFiBFs catalysis. The chemistry is unlike the Koch reaction and involves activated formyl cation inserting directly into the C-H a-bond of isoalkanes, followed by strong acid-catalyzed rearrangement. 

Improvements in the Koch reaction were achieved by applying superacid systems as the acid catalyst (63). Triflic acid is especially useful because of its high acidity and the higher solubility of CO. Under superacidic conditions using HF-SbFs, alcohols, preferably secondary and tertiaiy alcohols, can be substituted for alkenes. Moreover, CO can react with monosubstituted methanes (methyl alcohol, dimethyl ether, methyl halides) to yield acetic acid or its derivatives. 

The carbonylation reaction on the present system is most likely interpreted to be the carbonylation of methyl carbenium ion, as postulated for the Koch reaction (11). Copper(II) ion that was incorporated into the zeolites by ion exchange accelerates the carbonylation. The copper ion did not change the product pattern. The copper(II) ion on the zeolite might be reduced by methanol or carbon monoxide to copper(I) ion under reaction conditions. The copper(I) ion has been known to react easily with carbon monoxide to form Cu(CO)n (S < n < 4), which is an active carbonylation reagent for formaldehyde, n-olefins, and alcohols (85). 

To a large extent the Koch reaction is accompanied by double bond isomerizations and isomerization of the carbon skeleton with migration of alkyl groups, which is thought to occur through the carbonium ions (see e.g. scheme page 125). 

The same holds for the synthesis of unsaturated y-lactones starting from unsaturated aldehydes. Thus, the formation of an unsaturated yl ctone which was reported by Himmele [802] to occur when 2-ethylhexene-l-al was reacted with CO in the presence of 96 % H2SO4 at 200 atm and 60 °C in 70.5 % yield, might also follow either the mechanism of the Koch reaction or the ring closure mechanism. 

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) ... 

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. 

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. 

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

The range of the reaction was extended by the elegant aldehyde synthesis of Gattermann and Koch. If a mixture of carbon monoxide and hydrogen chloride is allowed to act in the presence of aluminium chloride (and cuprous chloride) on toluene (benzene is less suitable), the reaction occurs which might he expected with formyl chloride if this substance were capable of existence. 

Second, partial decomposition of an aryl thiolsulfinate specifically labeled (35S) at the sulfinyl sulfur indicates (a) some incorporation of label in ArSSAr, which would not be expected if (75) were the only path for formation of disulfide (b) a significantly unequal distribution of label beween the two sulfurs of ArS02SAr [in its simple form (76) predicts both sulfurs should be equally labeled] (c) some incorporation of label into the sulfenyl sulfur of the recovered unreacted thiolsulfinate. The specific reactions responsible for these variations of the 35S-distribution from the pattern predicted by (74)-(76) cannot be pinpointed with certainty, although Koch et al. (1970) considered that a homolytic decomposition (80) of sulfenyl sulfinate [20], competitive with its... 

The first one is the reaction of oxygen with a clean Si surface, or the initial stage of oxidation of the Si surface. On the Si(lll)-7 X 7 surface, the reaction activity and the local reaction mechanism are now understood at the atom-by-atom level (Avouris and Lyo, 1990 Avouris, Lyo, and Bozso, 1991 Pelz and Koch, 1991). Two different early products of oxidation and their site selectivity are identified with STM and STS. 

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