How does DMSO affect pKa?
As a result, pKa values may be different when measured in different solvents. For example, the pKa of water is reported as 15.7 in pure water, but when dissolved in DMSO it is reported as 32. Water is much less acidic in DMSO than when it is pure. Figure AB16.
What is the pKa value of acetic acid?
Therefore, pKa was introduced as an index to express the acidity of weak acids, where pKa is defined as follows. For example, the Ka constant for acetic acid (CH3COOH) is 0.0000158 (= 10-4.8), but the pKa constant is 4.8, which is a simpler expression. In addition, the smaller the pKa value, the stronger the acid.
Does pKa change with concentration?
It is unaffected by concentration. Even a chemical ordinarily considered a base can have a pKa value because the terms “acids” and “bases” simply refer to whether a species will give up protons (acid) or remove them (base).
How does solvent affect pKa?
Some solvents may more efficiently stabilize anions that form when Bronsted acids are deprotonated. As a result, pKa values may be different when measured in different solvents. For example, the pKa of water is 14.0 in pure water, but when dissolved in DMSO it is reported as 32.
Is DMSO volatile?
Chemical and Thermal Stability of DMSO It has been reported that only 3.7% of volatile materials are produced during 72 hours at the boiling point (189°C) of DMSO. Slightly more decomposition, however, can be expected with the industrial grade material. Thus, about 5% DMSO decomposes at reflux after 24 hours.
How can pKa be changed?
The pKa of an acid can be changed by changing the surrounding temperature.
What causes pKa to shift?
Why the pKa of some amino acid side chain changes in different microenvironment? According to my chemistry knowledge, The only thing that changes an equilibrium constant of a specific reaction is a change of temperature.
How do solvents affect acidity?
The effect of the solvent is not only because of its acidity or basicity but also because of its dielectric constant and its ability to preferentially solvate and thus stabilize certain species in acid-base equilibria. A change in the solvating ability or dielectric constant can thus influence the acidity or basicity.
Which factors affect the pKa of an acid?
Therefore pKa is also a measure of how stable the conjugate base is. Put another way, strong acids have weak conjugate bases, and vice versa….
- Factor #1 – Charge.
- Factor #2 – The Role of the Atom.
- Factor #3 – Resonance.
- Factor #4 – Inductive effects.
- Factor #5 – Orbitals.
What are the recommended pKa values in water and DMSO?
As a result, recommended pKa values in water and DMSO are assigned to hydrochloric acid, hydrobromic acid, hydroiodic acid, perchloric acid and trifluoromethanesulfonic acid (triflic acid). In some cases the currently accepted pKa values were revised by more than 10 orders of magnitude J. Phys. Chem. A 2016, 120, 2591–2604
What is the solubility of active pharmaceutical ingredients in DMSO?
Solubilities of Active Pharmaceutical Ingredients in DMSO Pharmaceutical Nomenclature CAS Number Solubility g/100ml DMSO@25oC Solubility g/100g DMSO@25oC Solubility g/100ml Solution@25oC Lidocaine USP 137-58-6 163.0 148.8 59.8 Lipoic Acid, DL-alpha (DL-Thiotic Acid) 1077-28-7 311.8 284.6 74.0
What is the solubility of petroleum ether in DMSO?
Petroleum ether (DMSO soluble 0.3-0.5% in petro- leum ether) 3 Xylene Miscible Phenol >100 4 Table 2 Solubilities of Active Pharmaceutical Ingredients in DMSO
What is the pKa of acetonitrile?
pKa values of 29 bases in acetonitrile ranging from Pyridine (pKa = 12,33) to DBU (pKa = 24,13) Comparison of Brønsted acidities of neutral CH-acids in gas phase and dimethyl sulfoxide.