Determination of complex association constants from gas chromatograhic data

Abstract The equilibrium constants for hydrogen bonding of a series of β-substituted alcohols with a number of monofunctional hexadecyl derivatives and dioctyl compounds have been measured by gas chromatography. For ethanol, propanol and butanol, the enthalpy and standard entropy of hydrogen bonding have also been determined. An analysis is presented on the precision and the accuracy of the data. The acceptor strengths of the proton acceptors are compared on the basis of the enthalpies and standard entropies of hydrogen bonding, and a comparison is made of the enthalpies of inter- and intra-molecular hydrogen bonding with the same proton-acceptor group. The influence of the substituents in the alcohols on the values of the association constants is investigated; evidence is presented for a mesomeric substituent effect, probably caused by intra-molecular hydrogen bonding in the substituted alcohols. It is shown that the effect of intra-molecular interaction of two substituents on partition equilibria is, formally, full analogous to the effect of intra-molecular interaction between a substituent and the reaction centre on chemical equilibria. By using the mathematical technique of factor analysis, it is shown that the factors governing substituent effects on both types of equilibria are closely related

Ligament reconstruction in thumb carpometacarpal joint instability: A systematic review

Summary: In thumb carpometacarpal (CMC) instability, laxity of the ligaments surrounding the joint leads to pain and weakness in grip and pinch strength, which predisposes the patient to developing CMC joint arthritis. Recent advancements in joint anatomy and kinematics have led to the development of various surgical reconstructive procedures. This systematic review outlines the available ligament reconstruction techniques and their efficacy in treating nontraumatic and nonarthritic CMC instability. Additionally, we aimed to provide evidence which specific ligament reconstruction technique demonstrates the best results. Four databases (Embase, MEDLINE, Web of Science, and Cochrane Central) were searched for studies that reported on surgical techniques and their clinical outcomes in patients with nontraumatic and nonarthritic CMC instability. Twelve studies were analyzed for qualitative review, including nine different surgical ligament reconstruction techniques involving two hundred and thirty thumbs. All but one of the reported techniques improved postoperative pain scores and showed substantial improvement in pinch and grip strength. Complication rates varied between 0% and 25%. The included studies showed that ligament reconstruction effectively alleviated the patients’ complaints regarding pain and instability, resulting in overall high patient satisfaction. Nevertheless, drawing definitive conclusions regarding the superiority of any ligament reconstruction technique remains challenging owing to the limited availability of homogeneous data in the current literature