Surface and interfacial tension isotherms for narrow-range distribution ALFOL 1214 alcohol oxyethylates were determined and
compared with those obtained for broad-range alcohol oxyethylates. Various adsorption parameters were estimated. The effectiveness
of surface tension reduction decreases when the length of polyoxyethylene hydrophile increases. Micellization is observed
at log cmc ranging from −4.7 to −3.3. Effects of the length and distribution of the polyoxyethylene chain on cmc are very
small. A minimum of Amin/Nav0.5 is obtained for Nav=8, where Amin and Nav denote the minimum interfacial area occupied by a statistical molecule at the saturated interface and the average degree
of oxyethylation, respectively. The interface becomes saturated at pC20=−5.61±0.35, where pC20 denotes the logarithm of concentration required to obtain the surface pressure equal to 20 mNm−1. The highest and lowest values of the surface excess at saturation and the free energy of adsorption, respectively, are obtained
for an average degree of oxyethylation equal to 8. Parameters are correlated with the average degree of oxyethylation and
the oxyethylene chain distribution parameter according to empirical second-order polynomials. Small differences in adsorption
abilities at the water/air interface are only observed for narrow- and broad-range distributed oxyethylates. The differences
become important for adsorption at the hexadecane/water interface. The lowest values of interfacial tension are obtained for
narrow-range oxyethylates with Nav=7 and 8. The Krefeld fabric detergency tests indicated that the best detergency was observed for alcohol oxyethylates with
Nav=5–7. Narrow-range oxyethylates exhibit somewhat better washing abilities than the broad-range products. No relationship between
detergency of alcohol oxyethylates and their abilities to adsorb at the water/air and water/hydrocarbon interfaces is observed. 相似文献
Nickel and potassium promoted β-Mo2C catalysts were prepared for CO hydrogenation to higher alcohols synthesis. The results revealed that β-Mo2C produced mainly hydrocarbons, but the addition of potassium resulted in a remarkable selectivity shift from hydrocarbons to alcohols over β-Mo2C. Moreover, it was found that potassium enhanced the ability of chain propagation of β-Mo2C catalyst and led to a higher selectivity to C2+OH. The addition of nickel further enhanced higher alcohols synthesis, which showed the optimum at 1/8–1/6 of Ni/Mo molar ratios. The characterization suggested that there might be a synergistic effect of potassium and nickel on β-Mo2C, which favored the alcohols synthesis. The production of alcohols appeared to be relevant to the presence of Mo4+ species, whereas the formation of hydrocarbons was closely associated with Mo2+ and/or Mo0 species on the surface of β-Mo2C-based catalysts. 相似文献
The oxidation of alcohols with tert-butylhydroperoxide (TBHP), in the presence of Mn2+ complexes immobilized in the pore channels of mesoporous hexagonal molecular sieves (HMS), were investigated. It was found that immobilized [Mn(bpy)2]2+/HMS is an efficient catalyst for the oxidation of alcohols such as benzyl alcohol, n-hexanol and cyclohexanol. The effects of reaction time, amount of Mn2+ in the catalyst, type of substrates and oxidants in this catalysis system were investigated. At optimum conditions, TBHP is more efficient oxidant with respect to H2O2. Following order has been observed for the percentage of conversions of alcohols: benzylic >1° >2°. 相似文献
Irritant and allergic reactions from cream bases observed in eczema patients are reviewed. The frequency of allergic reactions to the ingredients of vehicles in eczema patients is an indication of allergic potential for normal skin. Against this background, hypoallergenic fragrances are still very difficult to produce and a proper mixture for epicutaneous testing is lacking. Among preservatives, parabens are obviously safer and less allergenic than chlorocresol and sorbic acid. Propylene glycol (PG) is very popular for its many beneficial properties. However, it is also an irritant and a sensitiser. The exact number of allergic delayed type reactions is difficult to establish because primary irritant epicutaneous test reactions often closely resemble allergic reactions. By doing epicutaneous tests with serial dilutions of PG and by making peroral challenge tests, the number of eczema patients allergic to PG has been estimated to be as high as 1%. Glycerol is much less active in producing toxic and allergic skin reactions. Common non-ionic emulsifiers and higher fatty alcohols cause allergic contact dermatitis occasionally. The allergenic properties of these substances have not yet been examined experimentally. It seems, however, that there are only small differences between the various emulsifying agents. Les allergies et réactions de toxicité causées par les constituants des crèmes sur les sujets atteints de dermatoses 相似文献
Application of sulfamic acid as an efficient and green catalyst for the ring opening of epoxides by aliphatic and aromatic amines under solvent-free conditions is described. In this process the use of basic neutralization agent was not required due to the intrinsic zwitterionic property of sulfamic acid. The salient features of this methodology are cheaper process, easy availability of the catalyst, versatility, and the catalyst can be recovered after completion of the reaction and can be recycled without affecting the catalytic property. 相似文献
Most lipases resolve secondary alcohols in accordance with the “Kazlauskas rule” to give the R enantiomers. In a similar manner to other lipases, Candida rugosa lipase (CRL) exhibits R enantioselectivity towards heptan‐2‐ol, although the enantiomeric ratio (E) is low (E=1.6). However, unexpected enantioselectivity (i.e., S enantioselectivity, E=58) of CRL towards 4‐(tert‐butoxycarbonylamino)butan‐2‐ol, which has a similar chain length to heptan‐2‐ol, has been observed. To develop a deeper understanding of the molecular basis for this unusual enantioselectivity, we have conducted a series of molecular modeling and substrate engineering experiments. The results of these computational and experimental analyses indicated that a hydrogen bond between the Ser450 residue and the nitrogen atom of the carbamate group is critical to stabilize the transition state of the S enantiomer. 相似文献
A three‐component reaction of 3‐(tri‐n‐butylstannyl)allyl acetates, aldehydes, and triorganoboranes in the presence of a palladium‐Xantphos catalyst system predominately gave (E)‐anti‐homoallylic alcohols with high diastereoselectivity and good to high levels of alkene stereocontrol. An efficient chirality transfer was observed when an enantioenriched substrate was employed. The reaction was initiated by the formation of an allylic gem‐palladium/stannyl intermediate, which subsequently underwent allylation of the aldehyde by an allyltributyltin followed by a coupling reaction of the in‐situ‐generated (E)‐vinylpalladium acetate with the triorganoborane.
Hydrogenation of esters to alcohols with a well‐defined iron iPr2PNP pincer complex has been recently reported by us and other groups. We now introduce a novel and sterically less hindered Et2PNP congener that provides superior catalytic activity in the hydrogenation of various carboxylic acid esters and lactones compared to the known complex. Successful hydrogenation proceeds under relatively mild conditions (60 °C) with lower catalyst loadings.
This paper reports the use of an immobilised ruthenium complex in a continuous flow process for the N-alkylation of morpholine with benzyl alcohol. The ruthenium-based catalyst was supported on a phosphine bound polymer. Screening experiments were first performed in a batch reactor, with a 16 vol% mixture of morpholine and benzyl alcohol (stoichiometric molar ratio of 1:1) in toluene as the solvent. Operating at 110 °C for 24 h, it was shown that high conversions (>99%) into the desired tertiary amine could be achieved. This reaction was then shown to be viable in a continuous flow reactor, where the catalytic polymer beads were retained in the bed. Operating at 150 °C and using p-xylene as a solvent, the conversion into the desired tertiary amine was shown to be as high as 98%. This approach is clearly very promising, as it provides a greener and more atom efficient route for the production of secondary and tertiary amines in the pharmaceutical industry. 相似文献