W-Butyraldehyde

Homogeneous rhodium-catalyzed hydroformylation (135,136) of propene to w-butyraldehyde (qv) was commercialized in 1976. tf-Butyraldehyde is a key intermediate in the synthesis of 2-ethylhexanol, an important plasticizer alcohol. Hydroformylation is carried out at <2 MPa (<290 psi) at 100°C. A large excess of triphenyl phosphine contributes to catalyst life and high selectivity for -butyraldehyde (>10 1) yielding few side products (137). Normally, product separation from the catalyst [Rh(P(C6HB)3)3(CO)H] [17185-29-4] is achieved by distillation. 

N-Phenylhydroxylamine (11 g., 0.10 mole)2 (Note 1) and N-phenylmaleimide (17.4 g., 0.10 mole)3 are suspended in 40 ml. of ethanol contained in a 200-ml. Erlenmeyer flask. To the mixture is added immediately (Note 2) 8.98 g. (11.2 ml., 0.124 mole) of freshly distilled w-butyraldehyde. An exothermic reaction ensues, and the mixture spontaneously heats to the boiling point. A clear slightly yellow solution results which, upon cooling, deposits an almost colorless crystalline cake. The mixture is allowed to stand in the ice box for 1 day it is then filtered through a Buchner funnel, and the crystals are washed twice with 25-ml. portions of ice-cold ethanol. The yield of air-dried product, m.p. 99-101°, is 31-32 g. (92-95%). For further purification the crude material is dissolved in 60 ml. of boiling ethanol on the steam bath, and the resulting solution is allowed to cool slowly to room temperature. If crystallization does not spontaneously begin in 5-10 minutes, it can then be induced by... 

Isopropyl orthoformate gave branched products, e.g., isobutyraldehyde, but also small amounts of normal products, e.g., w-butyraldehyde. The amount of normal product was 4-6% at 80° C and increased with rise in temperature. Piacenti et al. suggested the following mechanism ... 

Condensation of butanal has been carried out on alkaline earth metal oxides at 273 K[52 53] yielding 2-ethyl-3-hydroxy-hexanal as a main product the order of activity per unit surface area was equal to that in the case of self-condensation of acetone and in agreement with the order of basicity of the solids, namely, SrO > CaO > MgO. The authors found that for aldol condensation of w-butyraldehyde, the active sites are the surface O2 ions and the rate-determining step is the z-hydrogcn abstraction. The differences in rate-determining step and active sites in the condensation of butyraldehyde and self-condensation of the acetone were attributed to differences in acidity of the z-hydrogcn in the two molecules. CaO was slightly... 

Furukawa et al. [274] and Natta cl al. [275,276] succeeded independently in the preparation of crystalline polyacetaldehyde by using some organometallic compounds, such as diethylzinc or triethylaluminium, for the low-temperature polymerisation of acetaldehyde. Metal alkyls and metal alkoxides, e.g. aluminium isopropoxide, zinc ethoxide or ethyl orthotitanate, have also polymerised other aldehydes such as propionaldehyde and trichloroacetaldehyde to give crystalline polymers (Table 9.3) [270,275,277], A highly crystalline isotactic polymer has been obtained from the polymerisation of w-butyraldehyde with triethylaluminium or titanium tetrachloride-triethylaluminium (1 3) catalysts. Combinations of metal alkyl, e.g. diethylzinc, with water [278] or amine [279] appeared to give very efficient catalysts for aldehyde polymerisations. 

The copolymerisation of dimethylketene and acetaldehyde with diethylzinc as a catalyst produced a crystalline copolymer of alternating comonomer distribution (Table 9.3) [289], Other aldehydes such as w-butyraldehyde, i-butyraldehyde or benzaldehyde were also copolymerised with dimethylketene to produce the respective polyesters [289-318]. 

The low E factor (< 0.04) indicates that the utilization of material resources is improved more than tenfold according to Sheldon s assessment [19] production of the bulk chemical w-butyraldehyde is classified alongside the highly efficient mineral-oil refining processes. 

The preparation of 2-phenyl-3-w-propylisoxazolidine4,5-cis-dicarboxylic acid N-phenylimide from w-butyraldehyde, N-phenylhydroxylamine, and N-phenylmaleimide is new and is described by Hauck. The intermediate, C-( -propyl)-N-phenyl-nitrone, is an unstable compound and is difficult to purify. The procedure described avoids the isolation of the nitrone by adding it in situ to a suitable dipolarophile. 

BUTYRALDEHYDE or w-BUTYRALDEHYDE (123-72-8) Forms explosive mixture with air (flash point - 10°F/— 12°C). Can form explosive peroxides with air polymerization may occur. Incompatible with strong oxidizers, strong acids (with elevated temperature and pressure), caustics, amines, ammonia. 

Aldol condensations are typical base-catalyzed reactions. The reaction of w-butyraldehyde to 2-ethyl-3-hexanal at 275 °C occurs with 100 % conversion of butyraldehyde and 85 % selectivity [39] (Scheme 14.2). 

Primary alkyl hydroperoxides are decomposed in the presence of many metal salts to give mainly alcohols, aldehydes and in some cases carboxylic acids [326]. Cobalt(II) octanoate catalyzes the decomposition of w-butyl hydroperoxide in pentane at 38 °C to give -butyl alcohol (67%), oxygen (70%) and w-butyraldehyde (32%) [328], equation (215). 

From 1974 onwards, Rh-based hydroformylation became industrial. The use of a catalyst metal that is about 1000-times more expensive than cobalt was driven by several reasons. First, Rh-hydroformylation is more active and thus requires much lower process pressures (lower energy consumption in compression units) and smaller reactors. Second, Rh-hydroformylation shows a very high selectivity to the aldehyde product with only minimal hydrogenation activity being observed. This is of particular importance for propylene hydroformylation where butyl alcohol is not the principle market use. In contrast, for the desired end-use of w-butyraldehyde in the form of its aldol condensation product 2-ethylhexanol a pure aldehyde feed is required as hemiacetals (formed by reaction of aldehyde and alcohol) complicate product purification and add to operating costs. 

The reactor is a continuous stirred tank reactor that provides intense mixing of the excess aqueous phase, the organic phase (ratio aqueous/organic phase = 6), and syngas to create enough interphase for effective mass transfer. The reaction exotherm is applied in a falling film evaporator to produce w-butyraldehyde vapor to... 

It must be emphasized again that the possible dual role of biacetyl as an energy acceptor in these systems makes such conclusions tentative. Although results similar to those for the 2-pentanone-biacetyl system could be obtained for the w-butyraldehyde-biacetyl system, in the latter case... 

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