Esterification dodecanoic acid

Resolution of racemic alcohols by acylation (Table 6) is as popular as that by hydrolysis. Because of the simplicity of reactions ia nonaqueous media, acylation routes are often preferred. As ia hydrolytic reactions, selectivity of esterification may depend on the stmcture of the acylatiag agent. Whereas Candida glindracea Upase-catalyzed acylation of racemic-cx-methylhenzyl alcohol [98-85-1] (59) with butyric acid has an enantiomeric value E of 20, acylation with dodecanoic acid increases the E value to 46 (16). Not only acids but also anhydrides are used as acylatiag agents. Pseudomonasfl. Upase (PFL), for example, catalyzed acylation of a-phenethanol [98-85-1] (59) with acetic anhydride ia 42% yield and 92% selectivity (74). 

The following experimental results are presented on the use of solid acid catalysts in esterification of dodecanoic acid with 2-ethylhexanol and methanol. In the next figures, conversion is defined as X [%] = 100-(1 - [Acid]fi ai / [Acid]Muai), and the amount of catalyst used is normahzed cat [%] - 100-A/cat / (A/acid + Milcohol)-Several alcohols were used to show the range of apphcability. The selectivity was assessed by testing the formation of side products in a suspension of catalyst in alcohol. Under the reaction conditions, no products were detected by GC analysis. 

Figure 33.1. Esterification of dodecanoic acid with 2-ethylhexanol (left) non-catalysed and catalysed (0.5-5 wt% SZ catalyst) reaction profiles (right).

Figure 33.2. Esterification of dodecanoic acid with methanol, using an alcohokacid ratio of 3 1 and sulfated zirconia (SZ) as catalyst.

The experimental results are presented for the esterification of dodecanoic acid (C12H24O2) with 2-ethylhexanol (CgHigO) and methanol (CH4O), in presence of solid acid catalysts (SAC). Reactions were performed using a system of six parallel reactors (Omni-Reacto Station 6100). In a typical reaction 1 eq of dodecanoic acid and 1 eq of 2-ethylhexanol were reacted at 160°C in the presence of 1 wt% SAC. Reaction progress was monitored by gas chromatography (GC). GC analysis was performed using an InterScience GC-8000 with a DB-1 capillary colunm (30 m x 0.21 mm). GC conditions isotherm at 40°C (2 ntin), ramp at 20°C min to 200°C, isotherm at 200°C (4 min). Injector and detector temperatures were set at 240°C. 

Figure 3. Stability of the sulfated zirconia catalyst in the esterification reaction of dodecanoic acid with 2-ethylhexanol - conversions given at 25, 45 and 75 minutes.

Table 8.7 Kinetic parameters for the esterification of dodecanoic acid with 2-ethylhexanol catalyzed by sulfated zirconia catalyst.

Figure 14.9 Esterification of dodecanoic acid with 2-ethylhexanol comparison of homogeneous and heterogeneous acid catalysts at 130°C (left) comparison of Amberlyst, Nafion and sulfated zirconia (SZ) at 150°C (right). The amount of solid catalyst, 3wt%, refers to the total mass of reactants [23, 24].

Partial sulfonation under mild conditions has been reported to improve the activity and selectivity for some processes [66-69], Thus, for the esterification of dodecanoic acid with 3-phenylpropan-l-ol in water, sulfonated polystyrene resins with low substitution degrees gave better results than those with higher loadings [69], It was suggested that conventional acidic ion exchange resins are too... 

The acylation of anisole with C2 - C12 acids was carried out under the same conditions as that of toluene, except a shorter reaction time (5 h). The acylated anisole formed as the major product para/ortho = 59 1 - 96 1 and no meta isomers) together with esterification products - methyl esters of carboxylic acids and phenol. No phenyl esters formed. The selectivity to esters increases from acetic to dodecanoic acid, reaching 40% for the latter. The acylation of anisole, in contrast to that of toluene, is most efficient with C2 - C6 acids, giving a 62 - 65% yield of acylated products and only 2 - 6% of methyl esters. 

During research on enzymatic acylation, Gelo-Pujic et al. [87] performed Novo-zym immobilized lipase-catalyzed esterification of 131a,b and 7 with dodecanoic acid in dry media both with microwave irradiation and with classical heating, using the same conditions of time and temperature (Scheme 12.54). Esterification of 131a by use of a focused Synthewave reactor and oil bath, both at 95 °C, afforded 132 in 95% and 55% yield, respectively. 

The immobilized Candida Antarctica lipase (Novozym 435)-catalyzed esterification of methyl a-D-glucopyranoside 65, a-glucose and a,a-trehalose 68 with dodecanoic acid 66 has been studied under microwave irradiation (see... 

In a recent work on lipase-catalyzed esterification of dodecanoic acid with glycerol in microemulsions based on different hydrocarbons as oil component, it was demonstrated that there was a clear trend toward more triglyceride and less monoglyceride with increasing hydrocarbon chain length [96]. Whereas shorter chain hydrocarbons, octane and decane. 

Using PEG-lipase from P. fragi 22.39B, a kinetic study of esterification of chiral secondary alcohols with fatty acids in transparent organic solvent was carried out [86]. PEG-lipase, of which 49% of the total amino groups in the enzyme molecule were coupled with activated PEG2, was soluble and active in hydrophobic organic solvents. The ester synthetic activity of PEG-lipase, which retained 43% of the hydrol)rtic activity of the unmodified enzyme, was 13.6 juimol/min/mg protein in benzene and 30.5 ULmol/min/mg protein in l,l,l-trichlor( thane, when dodecanol and dodecanoic acid were used as substrates. 

A secondary aromatic alcohol in (5) form, (5)-a-phenylethanol, did not serve as a substrate of the esterification by PEG-lipase. From the result obtained above, it can be concluded that PEG-lipase exhibited higher stereoselectivity for chiral secondary alcohols with a longer carbon chain or a phenyl group. In order to test the applicability of PEG-lipase to optical resolution of racemic alcohols, we conducted the esterification with PEG -lipase in 1,1,1-trichloroethane using racemic a-phenylethanol and dodecanoic acid [86]. As is shown in Fig. 13, the amount of the substrate, (R,5)-a-phenylethanol, decreased... 

Table 11 and V ax Values for Esterification of Secondary Alcohols with Dodecanoic Acid Catalyzed by PEG-Lipase from P. fluorescens in -Benzene... 

Figure 13 Time course of optical resolution of a-phenylethanol. Esterification of (jR,5)-a-phen-ylethanol with dodecanoic acid by PEG-lipase in 1,1,1-trichloroethane. (From Ref. 86.)...

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