Organic Compounds Containing Halogens Flashcards for NEET — 20 cards

First 8 of 20 Organic Compounds Containing Halogens flashcards

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1. Card 1 of 20

   What is the correct order of dipole moment for halomethanes ($CH_3X$) where X = F, Cl, Br, I?

   Hint: Dipole moment = charge $\times$ distance. Fluorine's tiny size is the catch.

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   Answer

   $CH_3Cl > CH_3F > CH_3Br > CH_3I$. Note the anomaly: $CH_3Cl$ has a higher dipole moment than $CH_3F$ because the larger C-Cl bond length outweighs the higher electronegativity of Fluorine.

2. Card 2 of 20

   Why is Thionyl Chloride ($SOCl_2$) preferred over $PX_3$ or $PX_5$ for preparing alkyl chlorides from alcohols?

   Hint: Think about the physical state of the byproducts.

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   Answer

   The reaction produces alkyl chloride along with gases ($SO_2$ and $HCl$). Since the byproducts are escapable gases, the reaction yields pure alkyl chloride without the need for complex separation.

3. Card 3 of 20

   Identify the reaction and its purpose: $R-X + NaI \xrightarrow{\text{dry acetone}} R-I + NaX$ (where X = Cl, Br).

   Hint: NaI is soluble in dry acetone, but NaCl and NaBr precipitate out.

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   Answer

   This is the Finkelstein reaction. It is a halogen exchange method specifically used for the preparation of Alkyl Iodides.

4. Card 4 of 20

   Which reaction is best suited for synthesizing Alkyl Fluorides, and what reagents are used?

   Hint: Exchange with a transition/heavy metal fluoride.

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   Answer

   Swarts Reaction. It involves heating an alkyl chloride/bromide in the presence of heavy metal fluorides such as $AgF$, $Hg_2F_2$, $CoF_3$, or $SbF_3$.

5. Card 5 of 20

   How do the reagents differ between the Sandmeyer and Gattermann reactions for synthesizing haloarenes?

   Hint: Sandmeyer = Cuprous salt; Gattermann = Copper powder.

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   Answer

   Both start with a diazonium salt. Sandmeyer: Uses Cuprous halides dissolved in corresponding acid ($Cu_2Cl_2/HCl$ or $Cu_2Br_2/HBr$). Gattermann: Uses Copper powder in the presence of corresponding acid ($Cu/HCl$ or $Cu/HBr$).

6. Card 6 of 20

   How does the boiling point vary among isomeric haloalkanes?

   Hint: Spheres have the smallest surface area for a given volume.

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   Answer

   The boiling point decreases with an increase in branching. Branching makes the molecule more spherical, decreasing the surface area of contact, which weakens the intermolecular van der Waals forces.

7. Card 7 of 20

   What is the reactivity order of alkyl halides towards $S_N2$ mechanism? Explain the stereochemical outcome with a diagram.

   Hint: Less crowding = faster reaction.

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   Answer

   Stereochemical outcome: Complete Walden Inversion (like an umbrella turning inside out).

8. Card 8 of 20

   What is the reactivity order of alkyl halides towards $S_N1$ mechanism, and what is the stereochemical outcome?

   Hint: Two-step reaction; intermediate is a planar carbocation.

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   Answer

   $3^\circ > 2^\circ > 1^\circ$. The reactivity is governed by the stability of the carbocation intermediate. The stereochemical outcome is racemization (a mixture of retention and inversion of configuration) because the nucleophile can attack the planar carbocation from either side.