Alcohols, Carboxylic Acids, and Acid Derivatives (5D) - Chem & Physics

1. What is the general formula for an amide functional group?

   $\text{R-CONH}_2$ (or $\text{R-CONR'}_2$). Amides have a carbonyl group bonded to a nitrogen atom, which may be substituted with hydrogens or alkyl groups.

2. Identify the product when a carboxylic acid reacts with an alcohol under acid catalysis.

   Ester (Fischer esterification). Acid catalysis protonates the carbonyl, enabling nucleophilic attack by alcohol and water elimination to form the ester.

3. Which leaving group is better in acyl substitution: $\text{Cl}^-$ or $\text{RO}^-$?

   $\text{Cl}^-$. Chloride is a weaker base and better leaving group than alkoxide in acyl substitution reactions.

4. Identify the oxidation product of a primary alcohol under strong oxidation conditions.

   Carboxylic acid. Strong oxidants fully oxidize primary alcohols to carboxylic acids by adding an oxygen and removing hydrogens.

5. What is the general formula for an acid chloride (acyl chloride)?

   $\text{R-COCl}$. Acid chlorides feature a carbonyl group bonded to a chlorine atom, with R as the alkyl substituent.

6. Which is more acidic: a typical carboxylic acid or a typical alcohol?

   Carboxylic acid. Carboxylic acids have lower pKa values due to resonance stabilization of their conjugate bases compared to alcohols.

7. What structural feature makes an alcohol capable of hydrogen bonding with water?

   Polar $\text{O-H}$ bond (H-bond donor and acceptor). The electronegativity difference in the O-H bond creates polarity, enabling alcohols to donate and accept hydrogen bonds with water molecules.

8. Which acid derivative is least reactive toward nucleophilic acyl substitution?

   Amide. Amides possess a poor leaving group due to nitrogen's resonance donation, reducing reactivity in substitution reactions.

9. What is the general formula for an ester functional group?

   $\text{R-COOR'}$. Esters comprise a carbonyl group attached to an alkoxy group, where R and R' are alkyl chains.

10. What is the standard reactivity order of acid derivatives toward nucleophilic acyl substitution?

    Acid chloride $>$ anhydride $>$ ester $\approx$ thioester $>$ amide. Reactivity decreases with poorer leaving groups and increased resonance stabilization from the heteroatom.

11. What is the general formula for a carboxylic acid functional group?

    $\text{R-COOH}$. Carboxylic acids contain a carbonyl and hydroxyl group on the same carbon, represented with R as the alkyl chain.

12. What is the general formula for an alcohol functional group attached to an alkyl chain?

    $\text{R-OH}$. Alcohols feature a hydroxyl group bonded to a carbon atom in an alkyl chain, denoted by R representing the alkyl substituent.

13. Which functional group is formed when an acid derivative reacts with an amine via acyl substitution?

    Amide. Amines function as nucleophiles, attacking the carbonyl and expelling the leaving group to produce amides.

14. Which functional group is formed when an acid derivative reacts with an alcohol via acyl substitution?

    Ester. Alcohols serve as nucleophiles in acyl substitution, displacing the leaving group to yield esters.

15. What is the general formula for an acid anhydride functional group?

    $\text{R-CO-O-CO-R}$. Acid anhydrides consist of two acyl groups linked by an oxygen atom, often represented symmetrically for simplicity.

16. What resonance feature stabilizes the carboxylate anion and increases acidity?

    Negative charge delocalized over two oxygens. Resonance in the carboxylate ion distributes the negative charge across two oxygen atoms, enhancing stability and acidity.

17. What is the approximate $pK_a$ range for most simple carboxylic acids?

    $pK_a \approx 4$ to $5$. The pKa reflects the strength of carboxylic acids, influenced by resonance stabilization of the conjugate base.

18. What is the general formula for a carboxylate derivative called a thioester?

    $\text{R-COSR'}$. Thioesters replace the oxygen in esters with sulfur, linking the carbonyl to a thioalkyl group.

19. Identify the oxidation product of a secondary alcohol under typical oxidation conditions.

    Ketone. Secondary alcohols lose two hydrogens during oxidation, forming ketones due to the carbon's attachment to two alkyl groups.

20. What is the conjugate base of a carboxylic acid called?

    Carboxylate ($\text{R-COO}^-$). Deprotonation of the carboxylic acid's hydroxyl group yields the carboxylate anion, stabilized by resonance.

21. Identify the oxidation product of a primary alcohol under mild oxidation conditions.

    Aldehyde. Mild oxidants selectively convert primary alcohols to aldehydes by removing two hydrogens without further oxidation.

22. Which acid derivative is most reactive toward nucleophilic acyl substitution?

    Acid chloride. Acid chlorides have the best leaving group, chloride, making them highly susceptible to nucleophilic attack.

23. What is the approximate $pK_a$ range for most simple alcohols?

    $pK_a \approx 16$ to $18$. Alcohols have higher pKa values because their conjugate bases lack resonance stabilization, making them weaker acids.

24. Identify the nucleophile that converts an acid chloride into an amide in one step.

    Ammonia or an amine ($\text{NH}_3$ or $\text{RNH}_2$). Amines or ammonia act as nucleophiles, attacking the carbonyl and displacing chloride to form the amide bond.

25. What is the oxidation outcome for a tertiary alcohol under typical oxidation conditions?

    No oxidation (unless C-C bond cleavage occurs). Tertiary alcohols lack the necessary hydrogen on the carbinol carbon for typical oxidation, preventing reaction unless bonds break.

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