Cyclohexanoate esters

In the absence of ultrasound, the results show a substantial amount (49 %) of the dimer bicyclohexyl from the one-electron pathway, together with cyclohexylmethyl-ether, cyclohexanol and other products from the two-electron pathway (approx. 30%). The methyl cyclohexanoate ester (17%) can be thought to arise from the acid catalysed chemical esterification of the starting material with the solvent methanol. (As a result of the high current densities needed, (parasitic) discharge of the solvent methanol produces a large quantity of protons around the anode as a competitive reaction [54].)... 

It is also noted that the formation of methyl cyclohexanoate ester is less in the presence of ultrasound, suggesting enhanced adsorption of carboxylate with concomitant suppression of solvent discharge. This has precedent since ultrasound is thought to enhance adsorption phenomena in some dissolving-metal chemical reactions [58]. 

A series of comparative experiments using either phthalate esters or cyclohexanoic esters have been presented (15). For example. 

Scheme 2.14 Transition-state models for the deprotonation of cyclohexanoic ester 54 with LDA in different solvents and cosolvents.

Use of esters of cyclohexanone polycarboxylic acids, such as di-(2-ethyl-hexyl) cyclohexanoic acid ester, enables production of materials having comparable mechanical properties with less PVC. It also increases UV stability, improves low temperature properties, and reduces smoke on burning. Highly flexible and semi-rigid goods can be manufactured with these plasticizers. This film is specially suitable for production of blood bags. 

DOP - di-(2-ethylhexyl) phthalate, DEHCH - Cg alcohol ester of cyclohexanoic acid, DDSIP -diisononyl phthalate, DINCH - diisononyl ester of cyclohexanoic acid, DIDP - diisodecyl phthalate, DfDCH - Cjo alcohol ester of cyclohexanoic acicf (PVC 100, plasticizer 50, CaCOj 10, LZB 320 2) (PVC 100, plasticizer DOP 50, DEHCH 50, DINP 53, DINCH 54.5, DIDP 55, DIDCH 57.5, LZB 722 2, ESBO 0.5)... 

As shown in Scheme 2.8, the racemic starting acetate (A/B) is hydrolyzed to give alcohols (P/Q) in an organic medium containing a minimum amount of water, which in turn, by the action of the same lipase, are re-esterified with cyclohexanoic acid present in the mixture. Thus, the alcohol moiety of the substrate has to enter the active site of the lipase twice during the course of its transformation into the final product ester (R/S). An apparent selectivity of = 4(X) was achieved in this way, whereas the corresponding isolated single-step resolutions of this process were 1 = 8 for the hydrolysis of acetate A/B, and 2 = 97 for the esterification of alcohol P/Q with cyclohexanoic acid. 

Citrates are fast-fusing plasticizers, especially when compared to many of the phthalate alternatives. Unfortunately citrates are not as permanent because of high volatility losses, and the finished PVC products do not remain as flexible for as long as those prepared from more permanent plasticizers. Citrates are often used in blends with the harder-to-process terephthalate or cyclohexanoate plasticizers, but in these applications, because of costs, dibenzoate plasticizers may be preferred. Citrate esters also find uses with other plastics such as acrylics, cellulosic polymers, and vinyl acetate. Acetylated tributyl citrate (ATBC) does have a number of food contact and medical approvals and is commonly found in toys, often in combination with DEHTP or DC9CH. 

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