Molecular Apparatus for Automatic Titrations

{[1.1.1]Cryptand/Imidazole}: A Prototype Composite Kinetic Molecular Device for Automatic NMR Variable pH Reaction Monitoring

“…This is classified as a composite KMD [1] because it is formed by two devices working in the same environment. More specifically, the KMD is of a cooperative type because the components perform their functions (that is, varying the pH and measuring it) without interacting with each other [Scheme 1, Eqs.…”

“…inside a reaction vessel making it possible to carry out variable-parameter kinetic experiments [8] without using physical devices (electronic temperature programmer, mechanical autoburette, etc.). [1.1.1]Cryptand, for instance, is capable of changing almost linearly with time the pH of a solution [1,2,9] (2-3 pH units in the range 4-11) and thus made it possible to carry out, in a single run, a spectrophotometric variable-pH kinetic experiment in which the pH-rate profile of the hydrolysis of aspirin was obtained. In a similar timedependent linear fashion, acetic anhydride is capable of changing the temperature of a solution [10] and as a result it was possible to carry out a spectrophotometric variable-temperature kinetic experiment to obtain, in a single run, the activation parameters of the cis-to-trans isomerisation of the…”

“…For this reason, the search for chemical devices able to replace the physical ones has recently become very active. Herein, a molecular apparatus, [1] consisting of a molecular titrator and a molecular pH-meter ([1.1.1]cryptand [2,[3][4][5] (4,10,15-trioxa-1,7-diazabicycloA C H T U N G T R E N N U N G [5.5.5]-heptadecane) and imidazole, [6] respectively) is proposed as a useful chemical device for the 1 H NMR automatic monitoring of variable-pH experiments and, as a case-study, the automatic pK a determination of an organometallic compound is reported. To the best of our knowledge, this is an unprecedented [7] type of 1 H NMR investigation.…”

“…A similar device {[1.1.1]cryptand/bromothymol blue} was used as a molecular apparatus to carry out the spectrophotometric titration of the nimesulide molecule to obtain its pK a . [1] [a] Prof. G. Alibrandi We chose as a model reaction the titration of the water-soluble organometallic complex…”

“…Kinetic molecular devices (KMD) were defined as "devices able to perform a specific task at a molecular level by using the kinetics in which they are involved". [1] Variable-parameter kinetic molecular devices (VPa-KMD) are able to change gradually the value of an environmental parameter (T, pH, I, etc.) inside a reaction vessel making it possible to carry out variable-parameter kinetic experiments [8] without using physical devices (electronic temperature programmer, mechanical autoburette, etc.).…”