21. Draw and Name 2 constitutional isomers for C2H5NO (Amides group).

21. Constitutional Isomers for C₂H₅NO (Amide Group)

The molecular formula C₂H₅NO indicates that we are dealing with an amide group derived from a two-carbon structure. The two constitutional isomers for C₂H₅NO, specifically in the context of amides, are:

1. Ethylamide (N-ethylacetamide): This is the simplest amide, where the amide nitrogen is bonded to an ethyl group (–C₂H₅) and directly bonded to a carbonyl group (CO), making it:
   • Structure:

       O
       ||
       C
      / \
     

   H2N H | C | H

2. Acetamide (Ethanamide): In this isomer, the amide nitrogen is bonded to a methyl group and an ethyl group. The structure looks like this:
   • Structure:

       O
       ||
       C
      / \
     

   NH2 C | H

22. Solubility of Amine Groups (Primary, Secondary, and Tertiary Amides)

• Primary Amides (RCONH₂): Generally have good solubility in water due to their ability to form hydrogen bonds with water molecules. The presence of the amine group (-NH₂) allows for strong hydrogen bonding.

• Secondary Amides (RCONHR'): Also tend to be soluble in water, though they may have somewhat lower solubility compared to primary amides. They can still participate in hydrogen bonding effectively, though they may have increased hydrophobic character due to the presence of additional alkyl groups (R').

• Tertiary Amides (RCONR'R"): These amides might have reduced water solubility compared to primary and secondary amides due to the absence of a hydrogen atom directly bonded to the nitrogen, which limits hydrogen bonding capability. However, larger or polar substituents may enhance solubility in some cases.

In general, the trend is that primary and secondary amides are more soluble in water than tertiary amides, with solubility decreasing with increasing alkyl branching or size.

23. Complete the following reaction (Reactants and Products) by chemical structures.
(Complete Line, structural or condensed is acceptable)
(A) Butan-2-ol + hydrobromic acid →
(B) N-propyl methanamide + water → (H2SO4 with triangle symbol on the arrow)
(C) 2-ethoxy-2-iodo butanoic acid + ethanol →
(D) Pentan- 2-ol + [O] →
(E) 3 - fluoro pent-2-one + [H ] →

Below are the complete reactions, including reactants and products, in line or condensed structural form.

(A) Butan-2-ol + Hydrobromic Acid →

Reactants:

• Butan-2-ol: \[ \text{CH}_3\text{C(OH)(CH}_3)\text{CH}_2\text{CH}_3 \]
• Hydrobromic Acid: \(\text{HBr}\)

Reaction: Butan-2-ol reacts with HBr, undergoing an acid-catalyzed dehydration to form butyl bromide.

Products:

• 2-Bromobutane: \[ \text{CH}_3\text{C(Br)(CH}_3)\text{CH}_2\text{CH}_3 \]
• Water is also produced.

The balanced reaction can be represented as: \[ \text{CH}_3\text{C(OH)(CH}_3)\text{CH}_2\text{CH}_3 + \text{HBr} \rightarrow \text{CH}_3\text{C(Br)(CH}_3)\text{CH}_2\text{CH}_3 + \text{H}_2\text{O} \]

(B) N-Propyl Methanamide + Water → (H₂SO₄ with triangle symbol on the arrow)

Reactants:

• N-Propyl methanamide: \[ \text{C}_3\text{H}_7\text{C(O)NH}_2 \]
• Water: \[\text{H}_2\text{O}\]

Reaction: The presence of heat (indicated by the triangle) and H₂SO₄ suggests that the amide undergoes hydrolysis.

Products:

• Propylamine: \[ \text{C}_3\text{H}_7\text{NH}_2 \]
• Methanoic acid or formic acid: \[ \text{HCOOH} \]

The reaction can be summarized as: \[ \text{C}_3\text{H}_7\text{C(O)NH}_2 + \text{H}_2\text{O} \xrightarrow{\text{H}_2\text{SO}_4, \Delta} \text{C}_3\text{H}_7\text{NH}_2 + \text{HCOOH} \]

(C) 2-Ethoxy-2-iodo Butanoic Acid + Ethanol →

Reactants:

• 2-Ethoxy-2-iodo butanoic acid: \[ \text{C}_3\text{H}_7\text{OI} \text{ (with the ethoxy group)} \]
• Ethanol: \[\text{C}_2\text{H}_5\text{OH}\]

Reaction: In the presence of ethanol, the iodo substituent can lead to a substitution reaction.

Products:

• Ethyl ester of butanoic acid and iodoethane: \[ \text{C}_4\text{H}_9\text{COOC}_2\text{H}_5 + \text{HI} \]

The full reaction can be represented as: \[ \text{C}_3\text{H}_7\text{OI} + \text{C}_2\text{H}_5\text{OH} \rightarrow \text{C}_4\text{H}_9\text{COOC}_2\text{H}_5 + \text{HI} \]

(D) Pentan-2-ol + [O] →

Reactants:

• Pentan-2-ol: \( \text{CH}_3\text{CH}(\text{OH})\text{CH}_2\text{CH}_2\text{CH}_3 \)

Reaction: Oxidation of the alcohol occurs, converting it to a ketone.

Products:

• Pentan-2-one: \[ \text{CH}_3\text{C(=O)(CH}_2\text{CH}_2\text{CH}_3) \]

The balanced reaction is represented as: \[ \text{CH}_3\text{CH}(\text{OH})\text{CH}_2\text{CH}_2\text{CH}_3 + [O] \rightarrow \text{CH}_3\text{C(=O)(CH}_2\text{CH}_2\text{CH}_3) + \text{H}_2\text{O} \]

(E) 3-Fluoro Pent-2-one + [H] →

Reactants:

• 3-Fluoro pent-2-one: \[ \text{C}_3\text{HF} \text{C(=O)C}_2\text{H}_5 \]

Reaction: Reduction of the ketone yields the corresponding alcohol.

Products:

• 3-Fluoro pentan-2-ol: \[ \text{CH}_3\text{CHF}\text{C(OH)(CH}_2\text{CH}_3) \]

The full reaction can be represented as: \[ \text{C}_3\text{HF}\text{C(=O)C}_2\text{H}_5 + [H] \rightarrow \text{C}_3\text{H}_7\text{F}\text{C(OH)(CH}_2\text{CH}_3) \]

These reactions provide the structural representation of each chemical transformation based on the specified reactants and products. If you need more detailed structures or specific details regarding any of the reactions, please let me know!

For this question (C) 2-Ethoxy-2-iodo Butanoic Acid + Ethanol →
is there no reaction without catalyst or specific conditions?

You are correct to point out that conditions and catalysts significantly influence the likelihood of a reaction occurring. In the case of the reaction between 2-ethoxy-2-iodo butanoic acid and ethanol, simply mixing these two compounds without a catalyst or specific conditions may not lead to a significant reaction.

Clarification on Reaction Conditions

Reaction Scenario: For the reaction to effectively occur between 2-ethoxy-2-iodo butanoic acid and ethanol, specific conditions such as heating or the presence of a catalyst would typically be required.

• Nature of the Reactants: 2-Ethoxy-2-iodo butanoic acid is relatively stable under normal conditions, and the ether group present may not promote a reaction under mild conditions simply when mixed with ethanol.

• Potential Reaction: If a reaction were to occur, it could involve nucleophilic substitution where the ethanol acts as a nucleophile. However, for this to happen efficiently, conditions such as acidic or basic catalysts, heat, or even a solvent that enhances nucleophilicity may be necessary.

Conclusion

Under standard conditions (room temperature and without catalyst), a reaction between 2-ethoxy-2-iodo butanoic acid and ethanol is unlikely to take place significantly due to the stability of the reactants and lack of driving forces (like high temperatures or a strong acid/base catalyst).

For theoretical or practical purposes, please specify conditions under which a reaction might proceed, or if you're exploring a specific pathway, that could be discussed! Thank you for the clarification.