Carboxylic bases

Alkanesulfonates are the petrochemically derived sulfur analogs of soaps, which are alkane carboxylates based on renewable resources. The main difference between alkanesulfonates and soaps is, however, that alkanesulfonates consist of a rather complex mixture of homologs with different carbon chain lengths and isomers with an almost statistical distribution of the functional group along the hydrophobic carbon chain (Fig. 1), whereas soap is a mixture of homologs of alkane 1-carboxylates with an even number of carbon atoms. 

Already in 1943 M. Schuler [2] described the comparison of the surface-active properties of sodium palmitate with several ether carboxylates based on a constant amount of C atoms. The results showed that with more O bridges the optimal surface activity and emulsifying properties can be achieved at lower temperature, with the detergent properties decreasing and solubility increasing. 

In a patent survey [76] about shampoos over the period 1968-1978 the so-called cryptoanionic alkyl ether carboxylate based on tridecyl alcohol with 6.5 mol EO has been mentioned for a conditioning shampoo in combination with an amphoteric and cationic surfactant [77]. Because of the low interference with cationic surfactants no negative effect on the conditioning properties has been found [78]. 

Nontoxic effect on the skin flora was found by Schafer, which means that these amidether carboxylates can be well used in products which remain on the skin for a longer period [80]. A laurylamidether carboxylate based on digly-colamine has been described for the use in syndet soap with high mildness and good foaming effect [36]. 

The reaction product with monoethanolamine acts as a thickening agent [41,101] and with alcohols as an emollient [40]. Also reaction products with amino acids and oligo- or polypeptides for use in cosmetic formulations are known [43]. Sorbitan esters from ether carboxylates are described as emulsifiers or mild surfactants in cosmetic formulations [39] and alkyl ether carboxylic acid taurides as nonirritant anionic surfactants for cosmetic cleaners in particular [44]. Using unsaturated ether carboxylates it is possible to make viscous formulations based on combinations of unsaturated and saturated ether carboxylates [111]. Highly purified alkyl ether carboxylates based on alcohol ethoxylates with low free alcohol content have also been described [112]. 

For example, compared to alkylbenzenesulfonate the lauryl ether carboxylate based on C12-C14 alcohol and 4.5 mol EO shows good wetting, lime soap... 

For safety assessment of surfactants a CESIO Committee has published a proposal for the labeling of surfactants [254]. The conclusions for ether carboxylates based on the then-available Figures are given in Table 16. 

Carboxylate-based brine solution, 9 33 Carboxylated acrylic polymers, in water-based inks, 14 326 Carboxylation, 9 282 Carboxyl cure sites, in ethylene-acrylic elastomers, 10 698... 

An interesting question then arises as to why the dynamics of proton transfer for the benzophenone-i V, /V-dimethylaniline contact radical IP falls within the nonadiabatic regime while that for the napthol photoacids-carboxylic base pairs in water falls in the adiabatic regime given that both systems are intermolecular. For the benzophenone-A, A-dimethylaniline contact radical IP, the presumed structure of the complex is that of a 7t-stacked system that constrains the distance between the two heavy atoms involved in the proton transfer, C and O, to a distance of 3.3A (Scheme 2.10) [20]. Conversely, for the napthol photoacids-carboxylic base pairs no such constraints are imposed so that there can be close approach of the two heavy atoms. The distance associated with the crossover between nonadiabatic and adiabatic proton transfer has yet to be clearly defined and will be system specific. However, from model calculations, distances in excess of 2.5 A appear to lead to the realm of nonadiabatic proton transfer. Thus, a factor determining whether a bimolecular proton-transfer process falls within the adiabatic or nonadiabatic regimes lies in the rate expression Eq. (6) where 4>(R), the distribution function for molecular species with distance, and k(R), the rate constant as a function of distance, determine the mode of transfer. 

In recent years, there have been many significant advances in our models for the dynamics for proton transfer. However, only a limited number of experimental studies have served to probe the validity of these models for bimolecular systems. The proton-transfer process within the benzophenone-AL A -di methyl aniline contact radical IP appears to be the first molecular system that clearly illustrates non-adiabatic proton transfer at ambient temperatures in the condensed phase. The studies of Pines and Fleming on napthol photoacids-carboxylic base pairs appear to provide evidence for adiabatic proton transfer. Clearly, from an experimental perspective, the examination of the predictions of the various theoretical models is still in the very early stages of development. 

Matter, H., Schudok, M., Schwab, W., Thorwart, W., Barrier, D., Billen, G., Haase, B., Neises, B., Weithmann, K., WOLLMANN, T. Tetrahydroisoquinoline-3-carboxylate based matrix-metalloproteinase inhibitors design, synthesis and structure-activity relationship. Bioorg. Med. Chem. 2002, 10(11), 3529-3544. 

Tetrahydroisoquinoline-3-carboxylate based matrix metalloproteinase inhibitors design, synthesis and structure-activity relationship. Bioorg. Med. Chem. 2002, 10, 3529-3544. 

In order to prepare ligands forming complexes of a predominant h-cis confignration like in ferrichrome, rather than a A-configuration, tris-carboxylate-based templates were selected as a template whose three arms were extended by attachment of amino acids via their amino termini rather than via their carboxy termini. 

Recent Scientific and Technological Developments in Electrochemical Carboxylation Based on Carbon Dioxide... 

The high activity of Nd-based catalysts was reported by Shen et al. in 1980 [92], In this publication, the polymerization activity of the whole lanthanide series was studied. Ln halogen-based binary catalyst systems (LnCb/EtOH/AlEts or LnCl3 (TBPU/Al Bua), as well as Ln-carboxylate-based ternary catalyst systems (Ln(naphthenate)3/AlIBu3/EASC) were used. The activity profile for the entire series of lanthanides is depicted in Fig. 2. Two years later, Monakov et al. confirmed in a similar study that Nd is the most active Ln element [93,94]. 

A recent effort to increase the activity of NdCl3-based system comprises the use of NdCb nanoparticles. Kwag et al. succeeded in the preparation of nanosized NdCU 1.5 THF (particle size > 92 nm). The nanosized NdCl3 was prepared in THF medium by dissolution of anhydrous NdC. Nanosized NdCl3 particles were obtained in a colloidal formation step during which THF is slowly replaced by cyclohexane upon addition [ 132], Catalyst activity is inversely proportional to the size of the NdCU nanoparticles. The activation of NdCl3 nanoparticles with DIBAH/TIBA results in catalyst activities which match the activities of standard Nd-carboxylate-based ternary sys-... 

Numerous studies on Nd-carboxylate-based catalyst systems address hydrocarbon solubility, catalyst activity, stereospecificity and control of molar mass [49,89, 111, 141,156-183]6. 

Various cocatalysts are used in Nd-carboxylate-based systems. Most commercially available aluminum alkyls were studied in detail AlMe3 (TMA) [ 174, 184-186], AlEt3 (TEA) [159,187], APBu3 (TIBA) [175,179,188] and A10ct3 [ 189,190]. One of the most referenced cocatalysts is Al Bu2H (DIBAH), e.g. in [178,179,187,191]. Some of the aluminum alkyl cocatalysts were studied comparatively [49,174,179,189,190,192,193]. Some of these studies report results and trends which seem to be contradictory. Since there are so many factors which have an influence on polymerization characteristics and on polymer properties, the discrepancies between the results of different research groups in many cases can be reconciled on the basis of different experimental conditions. 

Table 3 gives a representative selection of studies on Nd(III)-carboxylate-based catalyst systems. 

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