Hydroxymethylene mechanism

The question of the mechanism of Fischer-Tropsch reaction is of considerable controversy. Three principal routes for product formation have been proposed the carbide mechanism, the hydroxymethylene mechanism, and the CO insertion mechanism. Numerous modifications were also introduced in attempts to account for some details in the complex chemistry of the process.205 207 208 211 229-233... 

In a 2-1. wide-necked Erlenmeyer flask are mixed 66.2 g. (0.525 mole) of 2-(hydroxymethylene)cyclohexanone (Note 1), 400 ml. of methylene chloride, and 106 g. (1.05 moles) of triethylamine (Note 2). The flask is cooled in an ice-salt bath at —12 to —15°, and 98.0 g. (0.500 mole) of p-toluenesulfonyl azide (Note 3) is added with vigorous mechanical stirring over a period of approximately 1 hour, at such a rate that the temperature of the reaction mixture does not rise above —5°. Stirring is continued for an additional 2 hours as the cooling bath melts. A solution of 30.8 g. (0.55 mole) of potassium hydroxide in 400 ml. of water is added, and the mixture is stirred for 15 minutes at room temperature. The resulting emulsion is placed in a 2-1. separatory funnel, the methylene chloride layer is separated after the emulsion has broken, and the aqueous alcoholic layer is... 

An important subsequent observation seemed to indicate that carbides are not reactive under Fischer-Tropsch conditions.235 When carbon was deposited on a surface by the decomposition of l4CO, labeled carbon was not incorporated into the products. This and other evidence accumulated against the carbide mechanism by the 1950s led to the formulation of other mechanisms. The hydroxymethylene or enolic mechanism191 assumes the formation via the hydrogenation of carbon monoxide [Eq. (3.13)] of a surface-bound hydroxymethylene species (2) ... 

Certain polyaryl-substituted pyrroles can be prepared by condensation of a benzoin and a benzyl aryl ketone with ammonium acetate (equation 128) (38JOC361, 71ZOR1264). The details of the mechanism are not known but one assumes enamines are involved and that the carbonyl and hydroxymethylene oxidation level of the benzoin are probably interconvertible via an enediol or related substance. A possible formulation is given in Scheme 15. 

Now it is possible to consider the mechanism of the molecular elimination process (eq. 23) in light of a new isomeric intermediate, hydroxymethylene (hCoH). In the low-temperature matrix photolysis of formaldehyde at 15 K, three sets of photochemical products were found (1) methanol and CO in solid formaldehyde (2) glycoaldehyde in a dilute Ar matrix and (3) hydroxyketene in a CO matrix (227). These observations were... 

Molecular beam photofragment translational energy spectroscopy has been used by Hepburn et to elucidate the photodissociation mechanisms of Si glyoxal. They presented evidence for predissociation of S, glyoxal in the absence of collisions and for the existence of three distinct dissociation pathM(ays. The major dissociation mechanisms were shown to lead to the formation of H2CO + CO and 2CO-I-H2, with a third minor channel producing CO 3-an isomer of H2CO, possibly hydroxymethylene. 

Compounds derived from Aldehydes and Ketones Reaction between PCI3 and Unsaturated Ketones, Mechanism of Reaction of PClj with Benzaldehyde, 1 4 Addition of Phenyldichlorophosphme, Interaction of Phosphorus Halides with Distyryl Ketone and Phenyl Cinnamylidene Methyl Ketone, Action of PCI3 on turated Aldehydes and Ketones, Interaction of Di-phenylohlorophosphine with Benzaldehyde and Benzal etophenone, Addition of Alkoxy- and Aryloxy-chlorophosphines to Carbonyl Compounds— Phosphorus Derivatives of Dimethylaniline— Derivatives of Dibenzyl-methane and Hydroxymethylene Camphor— Heterocydio Rings containing... 

The decisive role of the exo-anomeric effect in the conformational behaviour of interglycosidic linkages has been demonstrated by molecular dynamics and molecular mechanics studies on the preferred solution conformations of eight C-linked D-glucosyl disaccharides,of the C-linked disaccharide 5 together with its natural 0-linked equivalent 6, " and of the two isomeric hydroxymethylene-linked analogues of sialyl-a-(2- 3)-D-galactose. ... 

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