Functional Groups in Chemistry
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Questions and Answers

At a pH of 8.0, what percentage of the molecules are in the ionized form?

  • 80%
  • 70%
  • 20%
  • 50% (correct)

    • What is the percentage of the conjugate base at a pH of 7.4?

  • 40%
  • 30%
  • 20% (correct)
  • 25%

    • At what pH does the acid form predominate by 99.7%?

  • 7.0
  • 6.5
  • 6.0
  • 5.5 (correct)

    • At pH 2.0, what is the form of amobarbital?

    <p>100% unionized</p> Signup and view all the answers

    If the pKa of a compound is 8.0, what is the ratio of [A-] to [HA] at pH 8.0?

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

    What is the effect of a decrease in pH on the ionization of an acid?

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

    When the pH is 6 log units below the pKa, how much of the acid is in the ionized form?

    <p>99.7%</p> Signup and view all the answers

    At a pH of 7.4 with [A-] at 0.25, what is the total concentration of [A-] and [HA] combined?

    <p>1.25</p> Signup and view all the answers

    Which property is NOT a chemical property of functional groups?

    <p>Thermal Stability</p> Signup and view all the answers

    Which equation is used to relate the pH, pKa, and ionization of weak acids?

    <p>pKa = pH + log([acid]/[conjugate base])</p> Signup and view all the answers

    Which effect describes the influence of molecular shape on the behavior of drugs?

    <p>Steric Effects</p> Signup and view all the answers

    How do functional groups primarily influence the solubility of drugs?

    <p>Through their ability to form salts</p> Signup and view all the answers

    Which of the following is a characteristic of chirality in drugs?

    <p>Only one form is biologically active</p> Signup and view all the answers

    What is the primary factor in the acidity of a functional group?

    <p>The presence of electronegative atoms</p> Signup and view all the answers

    What term describes the ability of a compound to exist in both protonated and unprotonated forms?

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

    In the context of drug formulation, why is it essential to understand salt formation?

    <p>It influences drug stability and solubility</p> Signup and view all the answers

    At a pH of 2.0, what is the main form of phenylpropanolamine found?

    <p>More than 99% ionized</p> Signup and view all the answers

    What happens to the ionization of phenylpropanolamine as the pH increases from 2.0 to 5.5?

    <p>It becomes less ionized</p> Signup and view all the answers

    Why is a weak base like Ecstasy difficult to absorb in the stomach?

    <p>It becomes charged, preventing crossing of membranes</p> Signup and view all the answers

    How does urine alkalinization affect the excretion of acetylsalicylic acid?

    <p>It increases the proportion in ionized state significantly</p> Signup and view all the answers

    What is the primary influence of pH on the state of a drug in the stomach?

    <p>Lower pH increases charged drug forms</p> Signup and view all the answers

    What effect does increasing urine pH above the pKa of certain drugs have?

    <p>Significantly increases the ionized form of the drug</p> Signup and view all the answers

    What percentage of phenylpropanolamine is ionized at pH 5.5?

    <p>99.9%</p> Signup and view all the answers

    What is the primary purpose of urine alkalinization in medical treatment?

    <p>To facilitate drug excretion</p> Signup and view all the answers

    What are stereoisomers?

    <p>Molecules with the same molecular formula but differing in the arrangement of their atoms in space.</p> Signup and view all the answers

    Which type of stereoisomer is characterized by non-superimposable mirror images?

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

    What distinguishes diastereomers from enantiomers?

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

    In the R/S system of assigning absolute configuration, what does a clockwise arrangement signify?

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

    Which substituent would take precedence according to the Cahn-Ingold-Prelog rules?

    <p>A carbon atom bonded to one chlorine</p> Signup and view all the answers

    What is the common characteristic of geometric isomers?

    <p>They differ in arrangement due to restricted rotation.</p> Signup and view all the answers

    Which of the following statements about enantiomers is true?

    <p>Only one enantiomer is biologically active for a given function.</p> Signup and view all the answers

    When assigning priorities based on atomic numbers, which atom would receive the lowest priority?

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

    Which is true about the S-(+)-isomer of dexchlorpheniramine?

    <p>It is 200 times more potent than the R-(-)-isomer.</p> Signup and view all the answers

    What side effect is associated with the R isomer of fluoxetine?

    <p>Significant cardiac side effects</p> Signup and view all the answers

    What was the main issue caused by the (S)-isomer of thalidomide?

    <p>Birth defects in newborns</p> Signup and view all the answers

    What distinguishes the (+)-isomer of picenadol from its (-)-isomer?

    <p>The (+)-isomer is an agonist, the (-)-isomer is an antagonist.</p> Signup and view all the answers

    Which statement is accurate regarding enantiomers in pharmacology?

    <p>One enantiomer can have completely opposite therapeutic effects.</p> Signup and view all the answers

    What fraction of drugs is commonly sold as racemic mixtures?

    <p>About one-third</p> Signup and view all the answers

    What potential benefit exists in the racemic sales of nebivolol?

    <p>Each isomer achieves a unique therapeutic effect.</p> Signup and view all the answers

    What is a significant concern regarding enantiomeric impurities in pharmaceuticals?

    <p>They may cause unwanted side effects.</p> Signup and view all the answers

    Which factor primarily determines the electronic effect of functional groups in drugs?

    <p>Inductive and resonance effects</p> Signup and view all the answers

    How does chirality affect the activity of a drug?

    <p>It can lead to different therapeutic effects</p> Signup and view all the answers

    In the Henderson-Hasselbalch equation, what does a high pKa value indicate about the acid in question?

    <p>It is mostly in its un-ionized form at higher pH</p> Signup and view all the answers

    Which property is most affected by the steric effects of a functional group?

    <p>The drug's binding affinity to receptors</p> Signup and view all the answers

    What does the percent ionization of an acid at a specific pH indicate?

    <p>The degree of ionization and thus its absorption potential</p> Signup and view all the answers

    What role do salt formations play in the solubility of drugs?

    <p>They enhance the aqueous solubility of weak acids and bases</p> Signup and view all the answers

    At a pH of 5.5, how much of the molecules are in the unionized form?

    <p>99.7%</p> Signup and view all the answers

    Which of the following statements best describes an inductive effect?

    <p>A temporary shift of electrons due to electronegativity differences</p> Signup and view all the answers

    What is the percentage of molecules in the ionized form at pH 7.4?

    <p>20%</p> Signup and view all the answers

    What is the relationship between pH and the ionization state of a weak base?

    <p>As pH increases, more weak base becomes unprotonated</p> Signup and view all the answers

    If the pKa of a compound is 8.0, how does a pH of 2.0 affect the ionization?

    <p>100% in acid form</p> Signup and view all the answers

    At pH 8.0, what is the ratio of ionized form to total concentration?

    <p>1:2</p> Signup and view all the answers

    What does the equation % [A-] = [A-] / ([A-] + [HA]) * 100 reveal about the ionization behavior?

    <p>It indicates the fraction of molecules that are ionized.</p> Signup and view all the answers

    What is indicated by a pH of 6 log units below the pKa of amobarbital?

    <p>Total conversion to the unionized acid form.</p> Signup and view all the answers

    At a pH of 7.4, what percentage of molecules are in the acid form?

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

    What is the relationship between pH and the ionization of weak acids?

    <p>Lower pH increases acid ionization.</p> Signup and view all the answers

    What primarily allows Ecstasy to diffuse across the biological membrane into the blood capillaries in the small intestine?

    <p>It loses a proton and becomes nonpolar.</p> Signup and view all the answers

    At what pH range do most bases absorb well in the small intestine?

    <p>Between 4.8-8.2</p> Signup and view all the answers

    What occurs to weak acids when the pH is below their pKa?

    <p>They are mostly in the un-ionized form.</p> Signup and view all the answers

    Which of the following statements about the ionization of weak bases is accurate?

    <p>Weak bases are mostly un-ionized when the pH is below their pKa.</p> Signup and view all the answers

    How does the presence of asymmetric carbon in a molecule affect its optical isomers?

    <p>Two asymmetric carbons generate 4 isomers.</p> Signup and view all the answers

    What is indicated by a pH significantly lower than the pKa for acidic drugs?

    <p>The drug is predominantly in the un-ionized form.</p> Signup and view all the answers

    Which combined effect does chirality have on drug molecules?

    <p>It influences the drug's binding affinity and action.</p> Signup and view all the answers

    What does the Henderson-Hasselbalch equation help calculate regarding drug molecules?

    <p>The percentage of ionization of drugs at various pH levels.</p> Signup and view all the answers

    Which is true about the biological activity of the S-(+)-isomer of dexchlorpheniramine compared to its R-(-)-isomer?

    <p>The S-(+)-isomer is 200 times more potent than the R-(-)-isomer.</p> Signup and view all the answers

    What distinguishes the cardiac side effects of the R isomer of fluoxetine from the S isomer?

    <p>The R isomer has small but significant cardiac side effects.</p> Signup and view all the answers

    Why did the S-isomer of thalidomide cause significant health issues during its use?

    <p>It was responsible for severe birth defects.</p> Signup and view all the answers

    In the context of enantiomers, which statement about the experimental narcotic analgesic picenadol is correct?

    <p>The (-)-isomer is a narcotic antagonist.</p> Signup and view all the answers

    How does the therapeutic effect of the enantiomers of dextropropoxyphene differ?

    <p>2R, 3S-(+)-dextropropoxyphene is the analgesic variant.</p> Signup and view all the answers

    What is a characteristic of racemic mixtures in pharmaceuticals?

    <p>About a third of drugs are sold as racemic mixtures.</p> Signup and view all the answers

    What is a potential benefit of combining the isomers in nebivolol?

    <p>It takes advantage of synergistic pharmacological activities.</p> Signup and view all the answers

    Which statement about enantiomers in drug development is accurate?

    <p>It can be costly to separate enantiomeric impurities.</p> Signup and view all the answers

    Which of the following statements is true regarding the R and S configurations of chiral molecules?

    <p>Switching the position of the lowest priority group affects the designation of R or S.</p> Signup and view all the answers

    What effect does optical rotation have on the designation of compounds as R or S?

    <p>Optical rotation indicates how a compound interacts with plane-polarized light, independent of R or S.</p> Signup and view all the answers

    According to the Easson-Stedman hypothesis, what is required for a drug to interact effectively with its receptor?

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

    What characterizes a racemate in the context of chiral compounds?

    <p>A racemate is an equal mixture of two enantiomers.</p> Signup and view all the answers

    Based on the information provided, which statement applies to amino acids and proteins?

    <p>Amino acids are chiral molecules, and proteins also exhibit chirality.</p> Signup and view all the answers

    Which of the following statements is false regarding chiral drugs and their enantiomers?

    <p>Chiral drugs always display the same potency regardless of their enantiomeric form.</p> Signup and view all the answers

    In terms of prioritization using the Cahn-Ingold-Prelog rules, which substituent will receive the lowest priority?

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

    Which characteristic correctly distinguishes between dextrorotatory and levorotatory compounds?

    <p>Dextrorotatory compounds rotate plane-polarized light to the right, while levorotatory rotates it to the left.</p> Signup and view all the answers

    Study Notes

    Functional Groups

    • Functional groups (FGs) are parts of a compound/drug that provide specific properties and behaviors.
    • FGs enable a compound/drug to produce a biological response.
    • The chemical properties of FGs include electronic effects, steric effects, acid-base properties, chirality, and solubility.

    Electronic Effects

    • Electronic effects refer to the influence of electron distribution within a molecule.
    • Resonance effects occur when electrons are delocalized across multiple atoms, affecting chemical reactivity.
    • Inductive effects occur when electron density shifts due to electronegative atoms or groups in the molecule.

    Steric Effects

    • Steric effects are based on the physical size and shape of molecules and functional groups.
    • Large groups can hinder or prevent reactions due to steric hindrance.

    Acid-Base Properties

    • The Henderson-Hasselbach equation describes the relationship between the pH of a solution and the ionization state of weak acids and bases.
    • For weak acids (HA): pKa = pH + log ([conjugate base]/[acid])
    • For weak bases (B:H): pH = pKa + log ([base]/[conjugate acid])
    • The percentage of ionization can be calculated using the Henderson-Hasselbach equation and the pKa of the compound.

    Chirality

    • Molecules with the same molecular formula but different spatial arrangements of atoms are called stereoisomers.
    • Stereoisomers can have different biological properties.
    • Enantiomers are non-superimposable mirror image isomers.
    • Diastereomers are non-superimposable, non-mirror image isomers with more than one chiral center.
    • Geometric isomers are diastereomers with different arrangements of groups around a double bond (E/Z isomers).

    Separation of Enantiomers

    • About a third of drugs are sold as racemic mixtures, meaning they contain equal amounts of both enantiomers.
    • The separation of enantiomers can be expensive, but it is important because one enantiomer might be inactive or responsible for side effects.

    Enantiomers and Biological Activity

    • Enantiomers can have different biological activities.
    • The S-(+)-isomer of antihistamine dexchlorpheniramine is 200 times more potent than the R-(-)-isomer.
    • Both isomers of fluoxetine (Prozac) are equally potent as selective serotonin reuptake inhibitors (SSRIs), but the R isomer has some cardiac side effects.
    • The S isomer of fluoxetine is effective for the anti-migraine effect.

    Thalidomide

    • Thalidomide was a drug marketed as a sedative but later found to cause severe birth defects.
    • The (S)-isomer of thalidomide was responsible for the birth defects, while the (R)-isomer was converted to the (S)-isomer in vivo.

    Importance of Chirality in Drug Design

    • Chiral drugs can have different pharmacokinetic and pharmacodynamic properties.
    • This leads to different therapeutic effects, side effects, and toxicity profiles.
    • It is crucial to consider chirality in drug design and development.

    Drug Trapping

    • The pH of a drug's environment can influence its ionization state.
    • Ionized forms of drugs are generally less permeable to cell membranes, leading to drug trapping in specific compartments.
    • For example, morphine is highly ionized in the stomach, preventing its absorption into the bloodstream.

    Urinary Alkalinization

    • Urinary alkalinization is a treatment regimen that increases the excretion of acidic drugs by increasing the pH of urine.
    • This is useful for eliminating drugs like acetylsalicylic acid (aspirin).
    • Drugs like mecoprop, methotrexate, phenobarbital, and salicylate can be eliminated more effectively by alkalinizing the urine.

    Acid, Base, and Absorption

    • Ecstasy (MDMA) is a weak base. In the stomach, it is protonated (has a positive charge), making it difficult to cross cell membranes and get absorbed into the bloodstream.

    Functional Groups

    • Functional groups are parts of a compound that allow it to produce a biological response
    • Key chemical properties of FGs:
      • Electronic effects: Resonance and Inductive Effect
      • Steric effects
      • Acid-base properties
      • Chirality
      • Solubility effects: Water and lipid solubility, salt formation

    Henderson-Hasselbalch Equation

    • Describes the relationship between the pH of a solution and the ionization of a weak acid or base
    • For weak acids: pH = pKa + log([conjugate base]/[acid])
    • For weak bases: pH = pKa + log([base]/[conjugate acid])
    • When pH is below the pKa, acids are more likely to be in the un-ionized (HA) form
    • When pH is above the pKa, bases are more likely to be in the un-ionized (B) form
    • For weak acids:
      • pH above pKa, mostly ionized
      • pH below pKa, mostly unionized
    • For weak bases:
      • pH above pKa, mostly unionized
      • pH below pKa, mostly ionized

    Chirality

    • The orientation of functional groups in three-dimensional space
    • An asymmetric carbon (chiral carbon) is attached to four different substituents
    • A molecule with "n" asymmetric carbons will have 2^n optical isomers
    • Stereoisomers are not superimposable mirror images
    • Enantiomers rotate plane-polarized light in opposite directions
    • (+) = d = dextrorotatory
    • (-) = l = levorotatory

    Stereochemistry and Biologic Activity

    • The Easson-Stedman Hypothesis states that interactions require a minimum of a three-point fit to the receptor
    • The enantiomer with a better fit to the receptor will be more potent
    • Enantiomers can have different biological activities, including:
      • One enantiomer more potent than the other
      • Both isomers biologically active, but only one contributes to toxicity
      • One isomer contributing to side effects and toxicity
      • Enantiomers having different therapeutic activities
      • Enantiomers having opposite effects
      • Enantiomers having synergistic pharmacological activities

    Separation of Enantiomers

    • About a third of drugs are sold as racemic mixtures, even though one enantiomer may be inactive or contribute to side effects
    • It can be expensive to separate enantiomeric impurities

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    Description

    This quiz explores the key concepts of functional groups, including their properties and behaviors in chemistry and pharmacology. Test your understanding of electronic effects, steric effects, and acid-base properties as they relate to compounds and drugs. Dive into the specifics of how these groups influence biological responses.

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