Organic Chemistry: Alcohols and Amines

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Questions and Answers

What is the pKA range for an alkyl alcohol (R-OH)?

9 – 13

1 – 5

10 – 11

14 – 18 (correct)

Which type of amines is generally stronger in basicity, according to the classification provided?

Tertiary amines

Aromatic amines

Secondary amines (correct)

Primary amines

What is the estimated pKB range for aromatic and heterocyclic nitrogens?

4 – 5 (correct)

3 – 4

10 – 13

1 – 4

Which group of organic weak bases is associated with the lowest pKB range?

Guanidines Signup and view all the answers

Which of the following groups is NOT included as one of the organic weak bases discussed?

Amides Signup and view all the answers

What is the relationship in basicity strength among primary, secondary, and tertiary amines?

Secondary > Tertiary > Primary Signup and view all the answers

Which of the following groups has an estimated pKA range of 12 - 13?

Guanidines Signup and view all the answers

What is the estimated pKA range for aromatic amine (Ar-NH2)?

9 - 13 Signup and view all the answers

What is the approximate pKB range for amides?

15 - 17 Signup and view all the answers

Which statement is true about the nitrogen in amide functional groups?

It cannot accept a proton. Signup and view all the answers

How are amides classified in terms of acid-base properties?

Non-electrolytes Signup and view all the answers

What type of acids are capable of donating more than one proton per molecule?

Polyprotic acids Signup and view all the answers

Which functional group is not classified as a weak base?

Amides Signup and view all the answers

Which of the following is a property of ampholytes?

They exhibit both acid and base functionality. Signup and view all the answers

In classifying amoxicillin, which functionality should be identified?

Acidic and/or basic functional groups Signup and view all the answers

What is a characteristic of monoprotic bases?

They can attach only one proton per molecule. Signup and view all the answers

What is the estimated pKA value of an aliphatic amine?

10 - 11 Signup and view all the answers

Which functional group is classified as acidic with a pKA value of 3 - 5?

Carboxylic acid Signup and view all the answers

Why are amides not classified as acids or bases?

They have no protons to donate. Signup and view all the answers

What is the estimated pKA value of phenol?

8 - 11 Signup and view all the answers

Which of the following is NOT classified as an acid or base due to being an amide?

Cefaclor Signup and view all the answers

What is the general classification of a thiol based on its pKA value?

Acidic, pKA 9 - 11 Signup and view all the answers

Which functional group is identified as basic in nature?

Aliphatic amine Signup and view all the answers

How does the pH scale represent the concentration of hydrogen ions?

Logarithmically Signup and view all the answers

What is the relationship between pH and pOH in any aqueous solution?

pH + pOH = 14 Signup and view all the answers

What occurs when a strong acid like HCl completely dissociates in water?

It produces H3O+ ions equivalent to the initial number of moles of acid. Signup and view all the answers

If the pH of a solution changes from 1 to 2, how does the concentration of H3O+ change?

The concentration decreases by a factor of 10. Signup and view all the answers

What is the pH of a 0.1% w/v HCl solution given that the molecular weight of HCl is 36.5 g/mol?

1.00 Signup and view all the answers

What equation represents the calculation of pH for a strong acid?

pH = – log[H3O+] = – log[Ca] Signup and view all the answers

For a strong base, how is pH calculated using its hydroxide concentration?

pH = 14 - - log[OH-] Signup and view all the answers

Which statement correctly describes the concentration relationship between H3O+ and OH- in an aqueous solution at neutral pH?

H3O+ = OH- Signup and view all the answers

Which method would you use to determine the pOH from a known pH?

pOH = 14 - pH Signup and view all the answers

What does a large value of KA indicate about an acid?

The acid is a strong acid that completely dissociates. Signup and view all the answers

What relationship exists between pK_A and KA for strong acids?

pK_A is small and negative. Signup and view all the answers

Which of the following is a characteristic of weak acids?

They have a much smaller KA value than strong acids. Signup and view all the answers

What is the formula for calculating pK_A from KA?

pK_A = -log(KA) Signup and view all the answers

Which acid is recognized as a strong acid?

Hydrochloric acid Signup and view all the answers

Which of the following is true about weak acids?

They have high concentrations of undissociated molecules. Signup and view all the answers

In the dissociation of a strong acid, what happens to HA?

HA completely dissociates into H+ and its conjugate base. Signup and view all the answers

Which of the following statements correctly describes strong acids?

They dissociate completely in solution. Signup and view all the answers

Study Notes

Acid-Base Properties

Alkyl alcohols (R-OH) have a pKA range of approximately 14 – 18, indicating they are not ionized in realistic pH solutions (0-14).
Organic weak bases can be categorized into five groups:
- Aliphatic and alicyclic amines
- Aromatic amines (Ar-NH2)
- Aromatic and heterocyclic nitrogens
- Amidines (R-CNH-NH2)
- Guanidines (RHN-CNH-NH2)

Basicity of Amines

General strength of basicity for amines: Secondary > Tertiary > Primary.
Estimated pKB ranges for different amines:
- Aliphatic amines: 3 – 4
- Aromatic amines: 9 – 13
- Aromatic heterocyclic nitrogens (pyridine, isoquinoline): 4 – 5
- Amidines: pKB range of 10 – 13 and pKA range of 9 - 10.

Classification of Organic Molecules

Amides have a pKB range of 15 – 17, indicating they are not ionized in typical solution pH (0-14).
Classification of organic compounds based on their acid/base functionality:
- Nonelectrolyte: No acid/base functionality.
- Monoprotic acid: Donates 1 proton/molecule.
- Polyprotic acid: Donates multiple protons/molecule.
- Monoprotic base: Accepts 1 proton/molecule.
- Polyprotic base: Accepts multiple protons/molecule.
- Ampholyte: Exhibits both acid and base functionality.

Functional Group Analysis: Examples

Amoxicillin:
- Aliphatic amine: Basic, pKA 10 - 11.
- Carboxylic acid: Acidic, pKA 3 - 5.
- Phenol: Acidic, pKA 8 - 11.
- Amide: No acid/base characteristics.
Captopril:
- Thiol: Acidic, pKA 9 - 11.
- Carboxylic acid: Acidic, pKA 3 - 5.
- Amide: No acid/base characteristics.
Cefaclor:
- Aliphatic amine: Basic, pKA 10 - 11.
- Carboxylic acid: Acidic, pKA 3 - 5.
- Amide: No acid/base characteristics.

pH Calculations

pH is calculated using the formula: pH = - log[H3O+].
pH and pOH relationship: pH + pOH = 14.
Strong acids (like HCl) and bases (like NaOH) completely dissociate in water.

Acidity Constants

KA represents the equilibrium constant for a weak acid (HA) dissociation:
- HA ⇌ H3O+ + A−
pKA can be expressed as: pKA = - log(KA).
Strong acids have large KA values indicating complete dissociation, resulting in low pKA values (often negative). Weak acids produce smaller KA values reflecting partial dissociation.

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Description

This quiz explores the basic properties of alkyl alcohols and examines the basicity of various organic amines. Understand the pKa range of alcohols and the classification of amines, focusing on their strengths in aqueous solutions. Test your knowledge on these essential organic chemistry concepts.