Single-phase titration with

These new methods for determining the partition coefficients of ionized species are still e3q>erimenta1, but they are presented in a spirit that they may stimulate thinking and further refinement. Single-phase titrations with HCl in octanol have only recently been run. A possible concentration dependency of pKa in the single-phase titrations has been suggested by a referee and will be looked for. Further refinement of the two-phase titrations may incorporate ion-pair association constants. 

Single-phase titration with sodium tetraphenylborate... 

Despite affecting conversion, mass transfer is known to impact enantio- and regioselectivity for many reactions [63]. For this reason, conventional micro-titration apparatus, typically employed in combinatorial chemistry of single-phase reactions, also often suffer from insufficient mixing when dealing with multi-phases [63, 66]. 

C. Each Figure shows titration data for compositions inside of the miscibility gap (where the "curve" is linear), as well as enthalpies in a single-phase region. Data from the literature are also shown for comparison with the present results (13-161. Table I shows values of the compositions of the aqueous and amphiphilic phases for n-butanol/water at 30.0 and 55.0 °C and for n-butoxyethanol/water at... 

The polyhedral boranes and carboranes discussed above may be regarded as boron clusters in which the single external orbital of each vertex atom helps to bind an external hydrogen or other monovalent atom or group. Post-transition main group elements are known to form clusters without external ligands bound to the vertex atoms. Such species are called bare metal clusters for convenience. Anionic bare metal clusters were first observed by Zintl and co-workers in the 1930s [2-5], The first evidence for anionic clusters of post-transition metals such as tin, lead, antimony, and bismuth was obtained by potentiometric titrations with alkali metals in liquid ammonia. Consequently, such anionic post-transition metal clusters are often called Zintl phases. 

To elucidate the use of TMS systems for the isomerizing hydroformylation, PC was chosen as the solvent for the rhodium catalyst, because the best selectivity to n-nonanal of 95% with a conversion on trans-4-octene of also 95% was achieved in this solvent under single-phase conditions. Dodecane was used as a non-polar solvent for the extraction of the product and p-xylene served as the mediator between the catalyst and the product phase [24]. Appropriate operation points for the reaction within this solvent system were determined by cloud titrations. 

Titration with an anionic surfactant At low pH, long-chain amine oxides and the free amines can be determined by titration with an anionic surfactant or tetraphenylborate, using either the two-phase indicator method or the single-phase ion selective electrode method, as described in Chapter 16. The free amine can be separated from the aqueous sample solution by extraction at pH 10.5-12.0 with petroleum ether. The amine content is then determined by stripping off the petroleum ether, dissolving the residue in water, and titrating at pH 2 with an anionic. The amine oxide content is determined by difference (153). 

Cationics may be titrated with tetraphenylborate in a single aqueous phase using 2,7-dichlorofluorescein as indicator (101). Dichlorofluorescein forms a complex with quaternary compounds, which dissociates, with a color change from pink to yellow, when the end point of the titration is reached. Since this is a precipitation reaction, alcohols and other water-miscible organic solvents must be avoided since they partially dissolve the precipitate and spoil the end point. By adjustment of pH as described above, the procedure may be used for the determination of amines other than quaternaries. 

Often the experimentalist will have an approximate idea of the location of a phase boundary from data taken at other temperatures or from measurements on closely related compounds. In such cases, a reasonably accurate guess about the location of the phase boundary may allow one to choose a starting composition that crosses the boundary with only a single titration. This can be considerably more efficient than starting with a neat compound and performing titrations over successive compositional ranges until the phase boundary is found. 

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