Caprylate esters

The chemical catalysis (i.e. the decrease of the activation energy of the particular hydrolysis of the caprylic ester) may in fact be positive or negative, but it is probably negligible with respect to the physical catalysis (increase of the active surface where the hydrolysis takes place). Lack of understanding of this concept has led to confiision and to the search of complicated mechanism to explain micellar autocatalysis. The same type of argument holds of course for vesicles. 

Definition Sodium salt of the capryl ester of lactyl lactate... 

Dodge has isolated a small quantity of an aldehyde, which appears to be decyl aldehyde. Brooks has identified methyl-heptenone, nonyl aldehyde, linalol, acetic and caprylic esters, a phenol (chavicol ), and a -sesqmterpene alcohol having the characteristic odour of the oil. This body C Hj,0, which has been termed zingiberol, boils at 154 to 157 at 14 5 mm. pressure. 

Figure 1.5 Binary phase diagrams of diglycerol esters of fatty acids in water (a) caprylate ester (CIO), (b) laurate ester (C12), (c) myristate (C14), (d) palmitate (C16) (La=lamellar liquid crystals, W=excess water, II = two-liquid phase region, Om = isotropic reverse micellar solution, S = solid).

Ethyl Caprylate.—This ester is an oil reminding one of the secondary products of fermentation. It boils with decomposition at 275° to 290°, and has the formula CH3(CH2) COOC2H5. 

Calcium hydride (CaH2), 12 Caprylic acid, 4,7-dioxo-, methyl ester [Octanoic acid, 4,7-dioxo-, methyl... 

The same procedure was used in the prepn of esters of other acids, such as caprylic and heptyhc... 

Completely negative results on the formation of liver glycogen were obtained when the sodium salts of caproic or caprylic acid61 60 were fed, as well as after the administration of the ethyl esters of caproic, caprylic, capric, myristic or oleic acids or methyl laurate.81 Caproic acid was found to be ineffective as a D-glucose-former in the phlorizinized dog.89... 

This procedure has been used successfully for many years in the preparation of ethyl laurate, caprylate, and myristate by the alcoholysis of cocoanut oil (1 kg.) in ethanol (1900 g.) with hydrogen chloride (50 g.) as a catalyst.3 The method differs slightly from the one described above. The alcoholysis is complete after fifteen or twenty hours, and the solution is then neutralized to methyl orange with barium carbonate. The mixture is added to an equal volume of a saturated sodium chloride solution, whereupon 1100-1300 g. of the mixture of crude ethyl esters separates. This mixture of esters is washed with water and fractionated as described above. The yields are approximately 50 g. of ethyl caprylate, 350 g. of ethyl laurate, and 60 g. of ethyl myristate from 1000 g. of cocoanut oil. 

Vinyl caproate, caprylate, pelargonate, caprate, myristate, pahnitate, stearate, 10-hendecenoate (undecylenate) and oleate can be prepared in a similar manner, except that in the preparation of the pahnitate and stearate the fatty acids are added to a solution of mercuric acetate and sulfuric acid in vinyl acetate. Vinyl stearate is not redistilled, but the once-distilled product is recrystallized from acetone at 0° (3 ml. of acetone per gram of vinyl stearate). The amount of mercuric acetate employed was 2%, and the amount of 100% sulfuric acid was 0.3-0.4%, of the weight of the stearic acid. Average yields and properties of these vinyl esters are given in the table. 

Among the compounds commonly determined in research laboratories are diacetyl, 2,3-butandiol, glycerol, citramalic acid, amino acids (especially proline), histamine, ammonia, succinic acid, phosphate, ash, alkalinity of the ash, ethyl, acetate, methyl anthranilate, total volatile esters, higher alcohols (both total and individually) phenolic compounds, etc. An elegant method for determining ethyl esters, capronate, caprylate, caprinate, and laurate using carbon disulfide extraction and GLC has been published (123). 

The ethyl esters of caprylic, capric, and lauric acids are not included in Figure 6. However, they should all fall to the left of the curve for ethyl valerate and exhibit a somewhat steeper volatility gradient. 

Other acids (often as esters) have been found in fermented molasses. Usually these substances are products of bacteriological action and they are not normal constituents of unfermented molasses. Bauer" oil from the yeast fermentation of Cuban blackstrap consists chiefly of the ethyl esters of capric, lauric, myristic and palmitic acids.122 The fat from the scums of hot-room Louisiana molasses contained hexanoic (caproic) and octanoic (caprylic) acids.10 The occurrence of such volatile acids as propionic,128 butyric128 124 and valeric acids124 requires more adequate establishment. 

Fig. 3. Effect of acid chain length on ester synthesis catalyzed by POS-PVA lipase Reactions were carried out at 37°C for 24 h using n-butanol. C4, Butyric acid C8, caprylic acid 02, lauric acid 06, palmitic acid.

Reaction rates by POS-PVA lipase gradually increased from C4 to C8, reached a plateau between C8 and 02, and then an activity decrease was observed, probably owing to a substrate-size feature limitation. From this set of results, caprylic acid (C8) maybe considered the best acyl donor for the synthesis of butyl esters in heptane by POS-PVA lipase. 

Recently an effect of PEG glyceryl fatty acid esters such as PEG-8 glyceryl caprylate/caprate (commercially known as Labrasol) on the transport of a P-glycoprotein substrate has been reported. In in situ absorption studies, Labrasol (0.1 % (v/v)) significantly enhanced the intestinal absorption of rhodamine... 

Luisi has shown that membrane material itself can be formed autocatalytically in an experiment to investigate the base catalysed ester hydrolysis of hydrophobic ethylcaprylate [27], Hydrolysis occured initially at the aqueous-organic interface where the products were micelle-forming sodium caprylate and ethanol. Once the critical micelle concentration, or cmc, was reached an exponential increase in hydrolysis was observed. The rate of hydrolysis in this second phase was almost 1000 times greater than in the initial phase suggesting that a catalytic mechanism had been activated. Luisi and co-workers hypothesized that once the cmc had been reached hydrolysis occurred within the micelles and, as the reactants were then constrained within a more hydrophobic environment, the increased rate was due to autocatalysis. Below pH 7 the micelles reorganized into unstable vesicles, in the order of 150 nm across as verified by freeze-fracture electron microscopy. 

Salicyl esters acetate (C2) propionate (C3) butyrate (C4) caproate (Ce) caprylate (Cg) caprate (Cio) isovalerate (branched C5)... 

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