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Evaluation of Thiol Raman Activities and pKa Values Using Internally Referenced Raman-Based pH Titration
Analytical Chemistry ( IF 6.7 ) Pub Date : 2016-03-18 00:00:00 , DOI: 10.1021/acs.analchem.5b04241
Nuwanthi Suwandaratne 1 , Juan Hu 2 , Kumudu Siriwardana 1 , Manuel Gadogbe 1 , Dongmao Zhang 1
Affiliation  

Thiols, including organothiol and thiol-containing biomolecules, are among the most important classes of chemicals that are used broadly in organic synthesis, biological chemistry, and nanosciences. Thiol pKa values are key indicators of thiol reactivity and functionality. Reported herein is an internally referenced Raman-based pH titration method that enables reliable quantification of thiol pKa values for both mono- and dithiols in water. The degree of thiol ionization is monitored directly using the peak intensity of the S–H stretching feature in the 2600 cm–1 region relative to an internal reference peak as a function of the titration solution’s pH. The thiol pKa values and Raman activity relative to its internal reference were then determined by curve fitting the experimental data with equations derived on the basis of the Henderson–Hasselbalch equation. Using this Raman titration method, we determined for the first time the first and second thiol pKa values for 1,2-benzenedithiol in water. This Raman-based method is convenient to implement, and its underlying theory is easy to follow. It should therefore have broad application for thiol pKa determinations and verification.

中文翻译:

使用内部参照的基于拉曼的pH滴定法评估硫醇拉曼活性和p K a

硫醇,包括有机硫醇和含硫醇的生物分子,是最重要的一类化学物质,广泛用于有机合成,生物化学和纳米科学中。硫醇p K a值是硫醇反应性和官能度的关键指标。本文报道的是内部引用的基于拉曼的pH滴定方法,该方法能够可靠地定量水中一硫醇和二硫醇的硫醇p K a值。硫醇离子化的程度可以直接使用2600 cm –1区域中S–H拉伸特征的峰强度(相对于内部参比峰)进行监测,该峰强度是滴定溶液pH的函数。硫醇p K a然后,通过将实验数据与基于Henderson-Hasselbalch方程得出的方程进行曲线拟合,来确定相对于其内部参考的Rb值和拉曼活性。使用这种拉曼滴定法,我们首次确定了水中1,2-苯二硫醇的第一和第二硫醇p K a值。这种基于拉曼的方法易于实现,其基础理论也易于遵循。因此,它应在硫醇基测定和验证中具有广泛的应用。
更新日期:2016-03-18
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