Organic Compounds Containing Oxygen Flashcards for NEET — 22 cards

First 8 of 22 Organic Compounds Containing Oxygen flashcards

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1. Card 1 of 22

   How does the Lucas reagent ($\text{conc. HCl} + \text{anhy. ZnCl}_2$) differentiate between primary, secondary, and tertiary alcohols?

   Hint: Think about the stability of the intermediate carbocation determining the rate of substitution.

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   Answer

   Tertiary alcohols give immediate turbidity. Secondary alcohols produce turbidity within 5 minutes. Primary alcohols do not show turbidity at room temperature and only react upon heating.

2. Card 2 of 22

   What are the three core mechanistic steps in the acid-catalyzed dehydration of ethanol to ethene?

   Hint: Carbocation stability governs the ease of this reaction ($3^\circ > 2^\circ > 1^\circ$).

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   Answer

   1. Protonation of alcohol to form a stable oxonium ion. 2. Elimination of a water molecule to form a carbocation intermediate (slow, rate-determining step). 3. Deprotonation (elimination of a proton) to yield the alkene.

3. Card 3 of 22

   Compare the regioselectivity of Hydroboration-Oxidation (HBO) and Oxymercuration-Demercuration (OMDM) for hydration of unsymmetrical alkenes.

   Hint: Propene yields 1-propanol via HBO and 2-propanol via OMDM.

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   Answer

   HBO gives an addition product corresponding to Anti-Markovnikov's rule (overall addition of water without rearrangements). OMDM gives a product corresponding to Markovnikov's rule (no skeletal rearrangements).

4. Card 4 of 22

   Why is phenol significantly more acidic than ethanol?

   Hint: Stability of the conjugate base directly dictates acid strength.

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   Answer

   Phenol loses a proton to form a phenoxide ion, which is highly stabilized by the delocalization of the negative charge over the aromatic ring via resonance. The ethoxide ion lacks resonance stabilization and is destabilized by the +I effect of the ethyl group.

5. Card 5 of 22

   What products are obtained when phenol undergoes nitration with (i) dilute $\text{HNO}_3$ at $298\text{ K}$, and (ii) concentrated $\text{HNO}_3$?

   Hint: The hydroxyl group is a powerful activating group for electrophilic aromatic substitution.

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   Answer

   (i) Dilute $\text{HNO}_3$ yields a mixture of ortho-nitrophenol (volatile due to intramolecular H-bonding) and para-nitrophenol (less volatile due to intermolecular H-bonding). (ii) Concentrated $\text{HNO}_3$ yields 2,4,6-trinitrophenol (Picric acid).

6. Card 6 of 22

   Identify the active electrophile generated in the Reimer-Tiemann reaction and state the principal product obtained from phenol.

   Hint: Formed via $\alpha$-elimination of chloroform ($\text{CHCl}_3$) in the presence of $\text{NaOH}$.

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   Answer

   The active electrophile is Dichlorocarbene ($:\text{CCl}_2$). The final product obtained upon alkaline hydrolysis followed by acidification is Salicylaldehyde (2-Hydroxybenzaldehyde).

7. Card 7 of 22

   What are the chemical components and the primary product of Kolbe's reaction?

   Hint: Carbon dioxide acts as the weak electrophile in this carbon-carbon bond-forming reaction.

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   Answer

   Phenol is treated with $\text{NaOH}$ to yield sodium phenoxide, which then undergoes electrophilic attack by Carbon dioxide ($\text{CO}_2$) under pressure at high temperature, followed by acidification to produce Salicylic acid (2-Hydroxybenzoic acid).

8. Card 8 of 22

   Why is Williamson's ether synthesis highly restricted to the choice of primary alkyl halides for optimal yields?

   Hint: Alkoxide + $3^\circ$ Alkyl halide = Alkene product.

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   Answer

   The reaction proceeds via an $\text{S}_\text{N}2$ mechanism. Alkoxide ions are both strong nucleophiles and strong bases; if secondary or tertiary alkyl halides are used, steric hindrance prevents substitution, and elimination ($E2$) dominates to form an alkene.