Isophorone from condensation

The reaction mechanism is shown in Figure 4 and is adapted from work by Fiego et al. [9] on the acid catalysed condensation of acetone by basic molecular sieves. The scheme has been modified to include the hydrogenation of mesityl oxide to MIBK. The scheme begins with the self-condensation of acetone to form diacetone alcohol as the primary product. The dehydration of DAA forms mesityl oxide, which undergoes addition of an addition acetone to form phorone that then can cyclise, via a 1,6-Michael addition to produce isophorone. Alternatively, the mesityl oxide can hydrogenate to form MIBK. 

Clearly there is a switch from MO to MIBK when hydrogen was made the carrier gas. The yield of isophorone dropped as at this temperature the hydrogenation intercepted the MO before it could undergo another aldol condensation. At 673 K the aldol condensation reaction became kinetically more competitive with the hydrogenation reaction. 

The potential for M02N to function as a base catalyst has been demonstrated by Bej and Thompson in a study of acetone condensation. Isophorone, which is known to be produced from a base catalysed pathway, was a product... 

The hydrogenated resin of acetophenone and formaldehyde (400 g, Mn 1000 Da) was condensed with isophorone diisocyanate (90 g) in the presence of 0.2% (on resin) 2,6-bis(f-butyl)-4-methylphenol and 0.1% of dibutyltin dilaurate (on resin) in 40% dilution with acetone. The mixture was refluxed until an NCO number of less than 0.1% was reached. The product was then isolated and had a melting range of from 171 to 176°C after the removal of acetone. 

Aldol condensations of monoketones can lead to trimeric products if the reaction is carried out under more vigorous conditions. The prototypical example of this behavior is acetone, which can give rise to mesityl ketone (7), phorone (8) and isophorone (9 equation 30). An example is seen in the treatment of acetone with aluminum tri-r-butoxide in toluene (equation 31). Isophorone is frequently obtained as a by-product in base treatment of acetone it may be formed from the phorone enolate by an electrocycli-zation mechanism (equation 32). 

Two new alkaloids have been isolated from Burley tobacco Nicotiana tabacum L.) condensate, and their structures elucidated mainly on mass and n.m.r. spectral evidence. Structure (38) has been assigned to one and confirmed by two syntheses, one of which involves the exhaustive aeetylation of isophorone (39) with aeetie anhydride-perchlorie acid to the pyrylium salt (40). Ammonolysis of the salt yielded the alkaloid (38). The second alkaloid, formulated as (41), was synthesized from 5,5-dimethyl-2-cyclopenten-l-one (42) via Michael addition of ethyl acetoacetate to give, after hydrolysis and decarboxylation, (43). Regioselective acetalization then... 

At high-temperature conditions, the product distributions of typical decar-boxylative and aldol condensations vary with temperature, time on stream, and catalyst age. Several ketone isomers can be produced. With acetic acid, e.g., C5-C7 (e.g., methylhexanone, pentan-2-one, 3,3 -dimethylbutan-2-one) ketones and alkylphenols arise from acetone aldolization. An important cyclic product in low temperature acetone aldolization is isophorone (2-cyclohexen-l-one, 3,5,5 -trimethyl), formed by the aldol condensation of acetone with mesityl oxide, followed by 1,6-Michael addition. In reactions with acetic acid, we have observed 2-cyclohexen-l-one, 3,5-dimethyl, which is probably a cracking product of isophorone, and small amounts of isophorone itself. Cracking to produce... 

All PdPn x(a) catalysts showed activity and selectivity for the synthesis reaction of MIBK from acetone (Table 1). The conversion increased with the Pd content, while the selectivity toward MIBK reached a maximum for catalysts with Pd loading in the range 0.2-0.5 wt-%. Indeed, at lower Pd loading, when the basic function of the support prevailed on the hydrogenating ability, condensation reactions took place condensation of acetone with mesityl oxide to phorone, isophorone and trimethyl-cyclohexanone, and condensation of MIBK with acetone or its self condensation to diisobutyl ketone (DIBK) or trimethyl nonanone (NONA), respectively (Figure 6). 

Self-condensation of acetone was carried out at 473 K and 100 kPa in a flow system with a differential fixed-bed reactor. Acetone was vaporized in H2 (H2/acetone =12) before entering the reaction zone. The standard contact time (6fc) was 0.84 g of cat h/g of acetone. Main reaction products were mesityl oxides (MO s), isophorone (IP) and mesitylene (MES). Traces of phorone and light hydrocarbons were also identified. The coke formed on the catalysts was characterized after reaction, ex-situ, in a temperature-programmed oxidation (TPO) unit. The TPO experiments were carried out in a microreactor loaded with 50 mg of catalyst and using a 3 % O2/N2 carrier gas. Sample temperature was increased linearly from room temperature to 973 K at 10 K/min. The reactor exit gases were fed into a methanator operating at 673 K to convert CO in methane and then analyzed by flame ionization detector. 

Acetone aldol condensation proceeds on either acidic or basic catalysts. On basic catalysts, the reaction products are mainly a,P-unsaturated ketones [5] whereas on acidic materials formation of aromatics and olefins is favored [6]. In our catalytic tests, the main reaction products were mesityl oxides (MO s) and isophorone (IP). MO is formed from the initial selfcondensation of acetone whereas IP is a secondary product arising from the consecutive aldol condensation between MO and acetone. Over all the samples the reaction rate diminished as a function of time-on-stream as shown in Fig. 1 for the MgjAlOx sample which lost about 60 % of its initial activity after 10 h-run. Initial reaction rates (r ) and product selectivities (S j) were calculated by extrapolating the reaction rates vs. time curves to zero. 

Oxy-bis(iV-(4-phenylene)-trimellitic imide) is the product of condensation of trimellitic acid anhydride and 4,4 -diaminodiphenyl ether. Analogous bisimides can be prepared from trimellitic acid anhydride and MDI, 4,4 -diaminodiphenylmethane, or isophorone diamine. 

The copolymer (Fig. 14.4) is prepared from l,l-bis(4-hydroxyphenyl)-3,3, 5-trimethylcyclohexane (1) and bisphenol A. The cyclohexane containing bisphenol (1) is prepared by the condensation of phenol with 3,3,5-trimethylcyclohexanone and an acidic catalyst. The cyclohexanone can be prepared by the selective hydrogenation of isophorone [113, 114]. The Tg of the copolymers can be varied from 150°C (e.g., BPAhomopolymer) to 240°C [e.g., homopolymer of l,l-bis(4-hydroxyphenyl)-3,3,5-trimethylcydohexane]. And the resins can be prepared by either melt or interfacial processes. For increased ductility, terpolymers have been reported with a sUoxane block [115]. For applications requiring low moisture absorption, the bisphenol (1) has been polymerized with bisphenol M (see the section New Copolymers for Optical Storage Media ). 

Condensation (f) Preparation of polyurethanes via miniemulsion from isophorone diisocyanate and bisphenol A or dodecane diol in aqueous media 129... 

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