Organic Chemistry: Functional Groups & Equations
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Organic Chemistry: Functional Groups & Equations

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Questions and Answers

At a pH of 8.0, what is the percentage of the ionized form of the acid?

  • 80%
  • 100%
  • 20%
  • 50% (correct)

    • What is the pH level at which the ionized form of the acid is at 20%?

  • 8.0
  • 5.5
  • 2.0
  • 7.4 (correct)

    • At a pH of 5.5, what proportion of the acid is in the ionized form?

  • 50%
  • 0.3%
  • 10%
  • 99.7% (correct)

    • At what pH will an acid be completely in its unionized form (100%)?

    <p>2.0</p> Signup and view all the answers

    When pH is increased from 5.5 to 7.4, how does the proportion of the ionized form change?

    <p>Increases to 80%</p> Signup and view all the answers

    If the pH is 8.0 and the concentration of the acid form is represented as [HA], what is the representation of the ionized form?

    <p>[A-] = 1</p> Signup and view all the answers

    What is the total addition of [A-] and [HA] at a pH of 8.0?

    <p>2</p> Signup and view all the answers

    At pH levels lower than 5.5, how does the ionized form behave?

    <p>Decreases significantly</p> Signup and view all the answers

    Which factor does not directly affect the acidity of a functional group?

    <p>Chirality</p> Signup and view all the answers

    What does the Henderson-Hasselbalch equation primarily describe?

    <p>The relationship between pH and ionization</p> Signup and view all the answers

    Which of the following describes the solubility effects of functional groups in drugs?

    <p>They influence both water and lipid solubility.</p> Signup and view all the answers

    In the context of functional groups, what is meant by steric effects?

    <p>The physical size and shape of molecules affecting reactivity</p> Signup and view all the answers

    What is the primary reason for drug chirality to be significant in medicinal chemistry?

    <p>It can lead to drugs having different biological activities.</p> Signup and view all the answers

    Which aspect of a functional group primarily influences its solubility in water?

    <p>Acid-base properties</p> Signup and view all the answers

    What is the effect of resonance on the properties of functional groups in medicinal chemistry?

    <p>It stabilizes the ionized form of weak acids.</p> Signup and view all the answers

    When considering acid-base properties, what would a higher pKa value imply about a weak acid?

    <p>It is less likely to ionize in solution.</p> Signup and view all the answers

    What term describes molecules with the same molecular formula but different spatial arrangements?

    <p>Stereoisomers</p> Signup and view all the answers

    Which type of stereoisomer consists of non-superimposable mirror images?

    <p>Enantiomers</p> Signup and view all the answers

    In R/S configuration, which step involves assigning priorities to the ligands?

    <p>Step 1</p> Signup and view all the answers

    What is the lowest possible priority ligand in the R/S configuration method?

    <p>Hydrogen</p> Signup and view all the answers

    Which of the following statements is true regarding diastereomers?

    <p>They have more than one chiral center.</p> Signup and view all the answers

    In terms of geometric isomers, what does the E/Z nomenclature refer to?

    <p>Different arrangements of alkene substituents</p> Signup and view all the answers

    If the arrangement of ligands 1 to 3 is counterclockwise, what configuration should be assigned?

    <p>S</p> Signup and view all the answers

    Which of the following statements is correct about the enantiomer of Ibuprofen?

    <p>Only the S enantiomer has analgesic properties.</p> Signup and view all the answers

    What happens to Ecstasy in the alkaline environment of the small intestine?

    <p>It becomes nonpolar and diffuses into the blood.</p> Signup and view all the answers

    In the stomach, which type of drug is more likely to be absorbed?

    <p>Weak acids.</p> Signup and view all the answers

    What is the implication of a drug's pKa when the surrounding pH is above the pKa for acidic drugs?

    <p>The drug will mostly remain in the ionized form.</p> Signup and view all the answers

    How does chirality affect a molecule with 'n' asymmetric carbons?

    <p>It gives rise to 2n optical isomers.</p> Signup and view all the answers

    What determines whether weak bases are mostly ionized or un-ionized?

    <p>The pH relative to the pKa of the bases.</p> Signup and view all the answers

    In terms of electronic effects in drug molecules, which property is NOT typically considered?

    <p>Thermal conductivity.</p> Signup and view all the answers

    What is a primary characteristic of a chirality in molecules?

    <p>Orientation of functional groups in three-dimensional space.</p> Signup and view all the answers

    Which statement about drug molecules and their absorption is false?

    <p>Only nonpolar drugs can diffuse through lipid membranes.</p> Signup and view all the answers

    What is the correct stereochemical designation for a molecule with the priority order of substituents I > Br > F and H in the back?

    <p>S</p> Signup and view all the answers

    Which of the following best describes the relationship between enantiomers?

    <p>They have identical connections but differ in spatial orientation.</p> Signup and view all the answers

    What does the Easson-Stedman hypothesis suggest about interactions with receptors?

    <p>A minimum of three intermolecular interactions is required.</p> Signup and view all the answers

    If a drug exhibits dextrorotatory properties, how would this be denoted in optical rotation notation?

    <p>(+)</p> Signup and view all the answers

    In which scenario is a molecular compound considered achiral?

    <p>When all substituents can be superimposed.</p> Signup and view all the answers

    How is the relationship between optical rotation and R, S designation characterized?

    <p>They are unrelated aspects of stereochemistry.</p> Signup and view all the answers

    What characterizes a racemate in stereochemistry?

    <p>An equal mixture of two enantiomers.</p> Signup and view all the answers

    Which of the following statements is true regarding amino acids?

    <p>Amino acids are predominantly found in their L-form.</p> Signup and view all the answers

    Study Notes

    Functional Groups (FG)

    • A specific part of a compound or drug that dictates the compound's behavior and properties, thereby influencing biological response
    • Chemical properties of FG:
      • Electronic effects - Resonance and Inductive effect
      • Steric Effects
      • Acid-base properties
      • Chirality
      • Solubility Effects: Water and Lipid Solubility, Salt Formation

    Henderson-Hasselbach equation

    • First described by Lawrence Henderson in 1908 and modified by Karl Hasselbach in 1916
    • Used to calculate the pH of a solution of a weak acid or weak base
    • Describes the relationship between the pH of a solution, the pKa of the acid (or base) and the ratio of the concentrations of the acidic (or basic) form and its conjugate base (or acid) form

    3. Acid-Base Properties

    • Weak Acids: HA ↔ H+ + A-
      • HA: Acid
      • A-: Conjugate Base
      • Equation: pKa = pH + log([acid]/[conjugate base])
    • Weak Bases: B:H ↔ H+ + B:
      • B:H: Conjugated Acid (Protonated Form)
      • B: Base (Unprotonated form)
      • Equation: pH = pKa + log([base]/[conjugate acid])
      • Equation: pH = pKa + log([un-ionized]/[ionized])

    Importance of Ionization Example: Amobarbital

    • Calculation of % ionization of amobarbital at pH 2.0, pH 8.0, and pH 7.4
    • At pH 8.0, equal amounts of acid and conjugate base exist
    • At pH 7.4, ~20% of molecules are in the ionized form, leaving ~80% in the unionized form
    • At pH 5.5, the acid form predominates (~99.7% unionized)
    • At pH 2.0, amobarbital is in the unionized form (~100%)

    General Rules for Ionization

    • Weak Acids:
      • When pH < pKa, acids are more likely to be in the un-ionized (HA) form. The un-ionized form can diffuse through lipid membranes.
    • Weak Bases:
      • When pH < pKa, bases are more likely to be in the ionized (BH+) form. The ionized form will not diffuse through a lipid membrane.

    Absorption

    • Stomach (pH 2): Most acids will diffuse through the membrane (absorb), but bases will not.
    • Small Intestine (pH 4.8-8.2): Most acids will not absorb, but most bases will.

    Chirality

    • Stereochemistry - The orientation of functional groups in three-dimensional space
    • Asymmetric carbon (chiral carbon) - a carbon atom bound to four different substituents
    • A molecule with "n" asymmetric carbons will have 2^n optical isomers
    • The spatial arrangement of a molecule affects its reactivity in chemical reactions, as well as its biological and physical properties.

    Stereoisomers

    • Molecules with the same molecular formula but differing in the arrangement of their atoms in space
    • Different types: enantiomers, diastereomers, geometric isomers
    • Enantiomers: Non-superimposable mirror images of each other.
      • Example: Ibuprofen - Only the S enantiomer has analgesic properties
    • Diastereomers: Non-superimposable, non-mirror images. Isomers with more than one chiral center.
    • Geometric isomers: E/Z alkene isomers - Diastereomers, which are a result of restricted rotation about a double bond

    Absolute Configuration (R/S Convention)

    • Description of the order of ligands in space
    • R (rectus, right): Clockwise arrangement
    • S (sinister, left): Counterclockwise arrangement
    • Determined by the priority of the substituents around the stereogenic center. Higher atomic numbers indicate a higher priority

    Easson-Stedman Hypothesis

    • Postulated that drug receptor interactions require at least three-point fit for optimal binding (minimum of 3 intermolecular interactions)
    • Explains why some enantiomers are more potent than others: The less potent enantiomer may interact with fewer sites on the receptor.

    Optical Rotation & Key Points

    • Optical Rotation: Measure of the angle of rotation of plane-polarized light by a chiral compound
      • (+) = d (dextrorotatory)
      • (-) = l (levorotatory)
    • Optical rotation does not correlate to the R,S designation. The R and S designations are based on the spatial arrangement of the ligands and the R/S convention.
    • Enantiomeric: Not superimposable
    • Racemate: An equal mixture of two enantiomers
    • Amino acids: Chiral molecules (all L isomers)
    • Proteins: Chiral molecules - The interaction of chiral proteins (receptors) with different enantiomers of a chiral drug may involve different binding sites.

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    Description

    Explore the key concepts of functional groups and their impact on chemical behavior in this quiz. You'll also delve into the Henderson-Hasselbalch equation, crucial for understanding pH in weak acid and base solutions. Test your knowledge on acid-base properties and their applications.

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