Complete the following reactions and draw the structure of the major product(s) formed:

(i) 2XeF₆ + SiO₂ → ____ 50 °C

(ii) NH₄NO₃ → ____ + ____ 520 K

(iii) N₂O + NaNH₂ → ____ 470 K

(iv) 2B₂H₆ + 6NH₃ → ____ + ____ 180°C

(v) 6SCl₂ + 16NH₃ → ____ +

Question

Complete the following reactions and draw the structure of the major product(s) formed:

(i) 2XeF₆ + SiO₂ → ____ 50 °C

(ii) NH₄NO₃ → ____ + ____ 520 K

(iii) N₂O + NaNH₂ → ____ 470 K

(iv) 2B₂H₆ + 6NH₃ → ____ + ____ 180°C

(v) 6SCl₂ + 16NH₃ → ____ + ____ + ____

Draw all possible stereoisomers for [Co(CN)₂(H₂O)₂(NH₃)₂]⁺ complex ion.

Write the IUPAC nomenclature of the following complexes:

(i) [Cr(H₂O)₄Cl₂]Cl

(ii) [Co(en)₃][Fe(CN)₆]

(iii) Na[Cr(H₂O)₂(ox)₂]

(iv) [Pd(CO)₂(H₂O)Cl]⁺

(v) Na₄[(H₂O)₄V(μ-OH)₂V(H₂O)₄]

Explain the structural and other features of rubredoxin. How does it differ from ferredoxins?

Predict the number of framework bonding electrons and the structure of the following boranes:

(i) B₇H₇²⁻ (ii) B₁₁H₁₃²⁻ (iii) B₂H₇⁻

UPSC Answer Check · Accepted Answer

Begin by completing all five inorganic reactions with correct products and conditions, then systematically draw all stereoisomers of the cobalt complex showing optical and geometrical isomerism. Write precise IUPAC names for all five coordination compounds, paying special attention to bridging ligands and oxidation states. Explain rubredoxin's Fe-S₄ tetrahedral structure and contrast it with 2Fe-2S and 4Fe-4S ferredoxin clusters. Finally, apply Wade-Mingos rules to predict borane structures with correct styx numbers and polyhedral shapes.
- Reaction (i): 2XeF₆ + SiO₂ → 2XeOF₄ + SiF₄ at 50°C; xenon oxyfluoride formation
- Reaction (ii): NH₄NO₃ → N₂O + 2H₂O at 520K; ammonium nitrate decomposition to nitrous oxide
- Reaction (iii): N₂O + NaNH₂ → NaN₃ + H₂O at 470K; azide synthesis from nitrous oxide
- Reaction (iv): 2B₂H₆ + 6NH₃ → 2[BH₂(NH₃)₂]⁺[BH₄]⁻ at 180°C; ionic product formation
- Reaction (v): 6SCl₂ + 16NH₃ → S₄N₄ + S₅N₂ + 12NH₄Cl; sulfur-nitrogen heterocycle formation
- Stereoisomers of [Co(CN)₂(H₂O)₂(NH₃)₂]⁺: draw all five geometrical isomers (cis-cis, cis-trans, trans-cis, trans-trans, and mer/fac distinctions) and identify optical activity where applicable
- IUPAC nomenclature: tetraaquadichloridochromium(III) chloride; tris(ethane-1,2-diamine)cobalt(III) hexacyanoferrate(III); sodium bis(oxalato)diaquachromate(III); dicarbonylaquachloridopalladium(II); sodium μ-hydroxido-bis[tetraaquavanadium(II)]
- Rubredoxin: single Fe with four cysteine sulfur ligands in tetrahedral geometry; ferredoxins contain Fe-S clusters with bridging sulfide; rubredoxin has higher redox potential and simpler electron transfer
- Borane structures: B₇H₇²⁻ (nido, 16 framework electrons, pentagonal bipyramid); B₁₁H₁₃²⁻ (nido, 26 framework electrons, octadecahedron fragment); B₂H₇⁻ (arachno, 8 framework electrons, pentagonal bipyramid fragment)

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	20%	10	Correctly identifies all reaction products with proper oxidation states; accurately distinguishes rubredoxin (FeS₄, no inorganic sulfide) from ferredoxins (Fe-S clusters with bridging sulfide); applies Wade-Mingos rules correctly for borane classification (closo/nido/arachno)	Identifies most products correctly but confuses similar compounds (e.g., XeOF₄ vs XeO₂F₂); basic distinction between rubredoxin and ferredoxin but misses cluster details; some errors in borane electron counting	Major errors in product identification; confuses rubredoxin with ferredoxin completely; fails to apply Wade-Mingos rules or makes fundamental errors in framework electron calculation
Mechanism / equation	20%	10	All five reactions balanced with correct stoichiometry; conditions (temperature, pressure where relevant) specified; ionic nature of product in reaction (iv) clearly indicated; ammonium chloride byproduct in (v) included	Most reactions correctly written but some balancing errors; missing or incorrect conditions; incomplete products (e.g., missing H₂O in azide synthesis)	Multiple unbalanced equations; incorrect reactants or products; omission of critical conditions leading to wrong products
Numerical accuracy	15%	7.5	Correct framework electron counts: B₇H₇²⁻ = 2×7 + 2 = 16 electrons (nido); B₁₁H₁₃²⁻ = 2×11 + 4 = 26 electrons (nido); B₂H₇⁻ = 2×2 + 4 = 8 electrons (arachno); correct oxidation states for all metals in complexes	Correct electron counting for simpler boranes but errors with charged species; some oxidation state errors in complex nomenclature	Fundamental errors in electron counting formula (should be BₙHₙ⁴⁻ for closo, adjust for nido/arachno); consistent oxidation state errors
Diagram / structure	25%	12.5	All five stereoisomers of [Co(CN)₂(H₂O)₂(NH₃)₂]⁺ drawn with correct geometry (octahedral), showing cis/trans relationships clearly, identifying enantiomeric pairs where applicable; clear 3D wedge-dash representations; borane structures show correct polyhedral fragments	Draws 3-4 stereoisomers correctly but misses some geometrical isomers or optical isomer relationships; 2D representations without stereochemical detail; basic borane sketches	Only 1-2 stereoisomers attempted; incorrect geometry (square planar instead of octahedral); no attempt at borane structures or completely wrong shapes
Application context	20%	10	Connects azide synthesis to industrial/hydrazoic acid applications; notes rubredoxin's role in electron transfer in Clostridium and sulfur-reducing bacteria; mentions ferredoxins in photosynthesis (ferredoxin-NADP⁺ reductase); relates borane structures to carborane and medicinal applications	Brief mention of biological significance without elaboration; generic statements about borane applications; misses Indian context (e.g., CSIR-NCL work on boranes)	No biological or industrial context provided; fails to distinguish practical significance of different Fe-S proteins; no application mentioned for boranes

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