How to Predict the Ionization Statuses of a Drug in Different Parts of the Human Alimentary Canal – Part 1

pH is a logarithmic scale used to specify the acidity or basicity of aqueous solutions.


Acidic solutions (with higher concentrations of hydrogen (H+) cations) are measured to have lower pH values than basic or alkaline solutions. The neutral pH is 7. A 𝑝𝐻 meter may be used for a precise and accurate measurement of the 𝑝𝐻 of a solution.

The pH of weakly acidic chemical solutions can be estimated using the Henderson-Hasselbalch equation:

The equation relates the pH of a weak acid to the acid dissociation constant, Ka, and the ratio of the concentrations of the acid (unionized) and its conjugate base (cB, ionized).
Aspirin aka Acetylsalicylic acid (ASA) is an NSAID (non-steroidal anti-inflammatory drug) used to reduce pain, fever, and inflammation, and as an antithrombotic.

Question:

The pKa of Aspirin is 3.5. The pH of the gastric juice in human stomach is ~ 2.5 & that in the small intestine is ~ 8. Predict the ionization statuses of Aspirin in the stomach and small intestine.

Solution:



Click/tap to enlarge the image

Humbled by the Henderson-Hasselbalch equation❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

References:

‌(1)    Ncert. Chemistry : Textbook for Class XI - Part.I; National Council Of Educational Research And Training: New Delhi.

(2)    Wikipedia Contributors. pH. Wikipedia. https://en.wikipedia.org/wiki/PH.

(‌3)    Wikipedia Contributors. Henderson–Hasselbalch equation. Wikipedia. https://en.wikipedia.org/wiki/Henderson%E2%80%93Hasselbalch_equation.

‌(4)    Wikipedia. Aspirin. Wikipedia. https://en.wikipedia.org/wiki/Aspirin.

Comments

Post a Comment

Popular posts from this blog

How to Predict where an Electrophilic Aromatic Substitution May Occur in a Ring – Part 3

Image
An organic reaction in which an atom attached to an aromatic system (usually hydrogen) is substituted by an electrophile is referred to as  electrophilic aromatic substitution  ( S E Ar  or  EAS ). One of the most important  EASs  is halogenation. If Bromine water is added to Aniline, a multi-substituted product ( 2,4,6 -derivative) is obtained as Aniline is a strongly activating group (the same happens to Phenol). To generate the mono-substituted product, a protection, say, an acyl group is required. Question: Predict the major product(s) of the following reaction: Click/tap to enlarge the image Solution infographic: Click/tap to enlarge the image Motivated by EAS ❓ Let Chemaficionado know  in the comments below or at mychemistryhomework@gmail.com ❗ References: (1)      Wikipedia Contributors.  Electrophilic aromatic substitution . Wikipedia. https://en.wikipedia.org/wiki/Electrophilic_aromatic_substitution. (2)    ...
Read more

How to Carry out a Multistep Synthesis – Part 4

Image
Multistep synthesis  is the artificial execution of multiple organic chemical reactions to obtain one or more products by physical and chemical manipulations. Retrosynthetic analysis is a problem-solving approach in the organic syntheses, achieved by transforming a target molecule into simpler precursor structures regardless of any potential reactivity/interaction with reagents, and repeated until a simple or commercially available structure is reached, which can be used as a starting material to synthesize the target molecule. Question: How would you do the following transformation? Click/tap here to enlarge the image Solution infographic: Click/tap here to enlarge the image Let's keep in mind that any multistep synthesis is possible via several routes ❗Questions ❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com ❗ References: (1)      Wikipedia Contributors.  Chemical synthesis . Wikipedia. https://en.wikipedia.org/wiki/Chemi...
Read more

How to Predict where an Electrophilic Aromatic Substitution May Occur in a Ring – Part 8

Image
An organic reaction in which an atom attached to an aromatic system (usually hydrogen) is substituted by an electrophile is referred to as  electrophilic aromatic substitution  ( S E Ar  or  EAS ). One of the most important  EASs  is nitration . Let's keep in mind that the presence of an activating group on the ring may complicate nitration. Question: Predict the major product(s) of the following reactions: Click/tap to enlarge the image Solution infographic: Click/tap to enlarge the image Eerie EAS chemistry❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com ❗ References: (1)      Wikipedia Contributors.  Electrophilic aromatic substitution . Wikipedia. https://en.wikipedia.org/wiki/Electrophilic_aromatic_substitution. (2)      Brown, C.; Ford, M.  Higher Level Chemistry , 2nd ed.; Pearson Education: Harlow, Essex, 2014. ‌(3)     Electrophilic aromatic directing gro...
Read more