Alcohols chain length

Alcohol Chain length Approximate % of wool-wax alcohols... 

Fatty alcohol Chain length Degree of saturation Purity... 

These systems were referred to by Clausse t a (21) as Type U systems. On the other hand, with cofurfactants with chain length Cg to Cy (Figur 3 e-g), the Winsor IV domain is split into two disjointed areas that are separated by a composition zone over which viscous turbid and birifringent media are encountered. This second class of systems was referred as Type S systems (24). It can also be seen that the Winsor IV domain reaches its maximum extension at reducing in size below and above C. Moreover, at C, one observes a small monophasic region near the W apex (probably o/w microemulsion of the Schulman s type) which vanishes as the alcohol chain length is increased to Cg. 

Further information on the dependence of structure of microemulsions formed on the alcohol chain length was obtained from measurement of self diffusion coefficient of all the constitutents using NMR techniques (29-34). For microemulsions consisting of water, hydrocarbon, an anionic surfactant and a short chain alcohol and C ) the self diffusion... 

Hyde et al. (24) found that the peak apparent viscosity of lamellar liquid crystal fell by about two orders of magnitude as alcohol chain length was reduced from 15 to five in water-alcohol-Teepol systems. However, the complete picture of how various types of amphiphilic compounds and their mixtures influence viscosity is not available. In particular, it is not known under what conditions fairly low viscosities of liquid crystals can be achieved although Hallstrom and Friberg (22) report viscosities of about 0.2 poise for some compositions in the water— monocaprylin-tricaprylin system. As indicated previously, low viscosities increase the possibilities for occurrence of hydrodynamic instabilities involving cellular convection. 

C4-C16), alcohol chain length (C4-C8), and alcohol structure (e.g., primary or secondary) were studied. 

Fig. 4. Effect of alcohol chain length on ester synthesis catalyzed by POS-P VA lipase. Reactions were performed at 37°C for 24 h using caprylic acid as acyl donor.

The influence of alcohol chain length was studied by using substrate containing caprylic acid and the required alcohol (C4 to C6 and C8) at a fixed molar ratio (1.5) and 50 mg/mL of POS-PVA lipase. The results of acid molar conversion after 24 h are displayed in Fig. 4. The carbon chain significantly influenced esterification performance. As the length of the alcohol carbonic chain increased, lower molar conversion was detected. The highest value (70%) was attained for butanol and the lowest (40%) for octanol. 

Comparison of Figs. 3 and 4 reveals that alcohol chain length exerted more influence on ester yield than the acid carbon size. For alcohol size varying from C5 to C8, conversion was lower than 40%, and for acid size from C4 to Cl6, similar esterification yields (60-80%) were found. These results may reflect both the intrinsic selectivity of the enzyme and different accessibility of substrates to enzyme active site (22). 

Eccleston GM. Structure and rheology of cetomacrogol creams The influence of alcohol chain length and homologue composition. Pharm Pharmacol 1997 29 157-162. 

The rigidity and strength of networks prepared with cetostearyl alcohol and alkyltrimethyl-ammonium bromides (Cj2-Cjg) increase as the alkyl chain length increases. The rheological stability of ternary systems is markedly dependent on the alcohol chain length networks prepared with ionic or nonionic surfactants and pure cetyl or pure stearyl alcohol are weaker than those prepared with cetostearyl alcohol. In particular, emulsions prepared with stearyl alcohol are mobile and eventually separate. 

In previous papers, the experimental values of B for several (jj/o microemulsions have been measured. As already pointed out, these values are function of both the radius of the micelles and the alcohol chain length (9-10). The attractive interactions between micelles increase as the micellar radius increases and as the alcohol chain length is shorter. We have proposed an interaction potential between w/o micelles which allows to account for the scattering results (10). This potential V(r) results from the possibility of penetration of the micelles. V(r) is proportional to the volume of interpenetration of micelles. The penetration is limited by the molecules of alcohol located inside the interfacial film, r is the distance between two micelles. 

But in our interpretation the comparison with the experimental behavior is quantitative and the calculation of the demixing line is based on the experimental dependence of the interactions upon micellar radius or alcohol chain length. We can notice that calculations made by Safran et al. lead the authors to suppose interactions increasing with the radius what is experimentally well established. 

The goal of the present work is to obtain a consistent structural model for a microemulsion system. In particular, we are interested in carrying this model down to the molecular level so that the intermolecular effects which are responsible for the stability of these systems can be elucidated. We have studied the system consisting of water, SLS and MMA with and without n-hexanol or n-pentanol. We have determined the phase boundaries of the isotropic microemulsion and Lj phases and determined how these are affected by surfactant concentration and alcohol chain length. Measurements were also made of the vapor pressure of MMA over these systems to determine the concentration of MMA in the water surrounding the microemulsion droplets. From these data, the energetics of transfer of the MMA from aqueous to micellar solution were determined. Finally, a 1,C NMR chemical shielding study was performed to find how the MMA and the alcohol were distributed within the microemulsion. 

In addition to mixed emulsifier concentration and the droplet size, micro- and miniemulsions differ in the fatty alcohol chain length used. Stable miniemulsions can only be prepared with a fatty alcohol chain length of at least 12 carbon atoms compared to the shorter chain lengths used for most microemulsions. Also, the order... 

The results for the effect on interfacial tension of the fatty alcohol chain length are given in Table I for 1 1 molar ratio mixed emulsifier solutions. 

Table I. The Effect of Fatty Alcohol Chain Length on Interfacial Tension at 65°C between Styrene and Aqueous Mixed Emulsifier Solutions, based on lOmM SLS and a Molar Ratio...

The interfacial tension values increase from A.l dynes/cm for SLS/ decanol to 8.3 dynes/cm for SLS/octadecanol. Conductometric titration results have indicated that all of these mixed emulsifier systems, except the one with decanol, should give a relatively stable emulsion (22,23). Interestingly, the SLS/decanol mixed emulsifier solution was the only case in which the presence of the fatty alcohol reduced the interfacial tension with styrene to below the value measured for SLS alone. Studies are in progress to investigate this phenomenon and to determine the effect of alcohol chain length on miniemulsion stability. 

The interfacial tensions between styrene and mixed emulsifier solutions increased with increasing fatty alcohol chain length at a constant molar ratio. 

This point was confirmed recently by studying the reverse reaction with hemiester copolymers of various alcohol chain lengths. The reverse reaction is directly governed by the steric hindrance introduced by alcohol chain length and/or nature (30). 

The work from Sheldon s group [10] was the first to present the use of ionic liquids in the enzymatic synthesis of esters. Since then, there have been many reports on biosynthesis of esters in ionic liquids. De los Rios et al. [64,65] synthesised a wide range of aliphatic organic esters, commonly used in the perfumery, flavour and pharmaceutical industries, by transesteriflcation from vinyl esters and alcohols catalysed by free CaLB in different 1,3-dialkylimidazolium-based ILs (Fig. 7.2). They analysed the effects of the alkyl chain lengths of the acyl donor and the alcohol. The optimum (C6 for acyl donor and C4 for alcohol) chain lengths were found because the activity decreased with further increase in alkyl chain length. The authors attributed the enzyme behaviour to a substrate modulation mainly due to the different affinity of the lipase towards the different substrates and steric hindrance and denaturalisation by small alcohol molecules. 

The entropies of transfer are positive at 298.15 K. Neither the enthalpy nor the entropy of transfer appears to be a linear function of the number of carbon atoms. The methylene group contribution is not constant, but depends on the alcohol chain length. DeLisi and Milioto have tried to explain this by taking the size of the solute into consideration. The solubilization of additives in the micelles thus involves a micellar rearrangement to accommodate the alkyl chain. In principle, short-chain alcohols, mostly accommodated in the palisade layer, need less rearrangement of the micelle than the longer-chain alcohols that will require a cavity suitable to accommodate part of the alkyl chain. 

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